Patent Application
20130026935
1. Field of the Invention
Exemplary embodiments of the present invention relate to a Light-Emitting Diode (LED) luminescence apparatus using Alternating Current (AC) power and, more particularly, to an LED luminescence apparatus that is capable of improving power factor and Total Harmonics Distortion (THD) and effectively dealing with the distortion and commercial AC voltage and variation in the magnitude thereof. Exemplary embodiments of the present invention also relate to an LED luminescence apparatus equipped with a driving circuit, which defines the characteristic range of total LED driving voltage (Vf) and uses LEDs having a plurality of driving voltages, thus decreasing a flicker phenomenon and increasing the quantity of light while minimizing an interval in which the LEDs are turned off.
2. Discussion of the Background
The conventional LED luminescence apparatus using AC power 1 is configured to provide unidirectional ripple voltage, output from a rectification circuit 2 that is implemented using a bridge circuit, to high voltage LEDs 3-1 to 3-4 via a resistor 4.
In such a conventional LED luminescence apparatus using AC power, LED driving current provided to the LEDs may not have a complete sinusoidal wave form and there may be a phase difference between the LED driving current and AC voltage, and therefore a problem may arise in that electrical characteristics, including power factor and THD, do not fulfill requirements for LED lighting.
In order to solve this problem, there is a method of reducing LED driving voltage (forward voltage: Vf). However, since the driving efficiency and light output characteristics of high-voltage driven LEDs may be determined depending on the driving voltage Vf of the LEDs, the simple reduction in the driving voltage Vf of the LEDs may cause the problem of not fulfilling the power factor and the THD that are presented in the LED lighting standard.
Furthermore, commercial AC power may not provide AC voltage in ideal sinusoidal wave form. That is, the problem of the magnitude of commercial AC voltage being higher or lower than that of a reference voltage in ideal sinusoidal wave form arises, and the waveform thereof may be distorted by harmonics.
When the instantaneous voltage of an input voltage exceeds the driving voltage Vf of the LEDs, a driving current flows in proportion to the input voltage. As shown in FIG. 2A and
Further, in order to drive LEDs using AC power, various circuits such as a rectification circuit, a power supply circuit, a voltage detection circuit, a pulse generation circuit, a switch circuit, and a current control circuit may be required.
Exemplary embodiments of the present invention provide a light-emitting diode (LED) luminescence apparatus configured to receive an alternating current (AC) power.
Additional features of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention.
An exemplary embodiment of the present invention discloses a light-emitting diode (LED) luminescence apparatus configured to receive an alternating current (AC) power, which includes a plurality of LED units, and a plurality of constant current control units electrically connected to the plurality of LED units. The current control units are configured to control current flowing through each of the LED units so that the current has a specific magnitude.
Another exemplary embodiment of the present invention discloses a light-emitting diode (LED) luminescence apparatus configured to receive an alternating current (AC) power, which includes a plurality of LED units, and a plurality of constant current control units electrically connected to the plurality of LED units. The current control units are configured to control current flowing through each of the LED units so that the current has a specific magnitude. Furthermore, the plurality of LED units comprises a first LED unit configured to operate using a first driving voltage and a second LED unit configured to operate using a second driving voltage, and the first driving voltage is smaller than the second driving voltage.
Still another exemplary embodiment of the present invention discloses a light-emitting diode (LED) luminescence apparatus configured to receive an alternating current (AC) power, which includes a plurality of LED units, a plurality of constant current control units electrically connected to the plurality of LED units, and a light output compensation unit electrically connected to the plurality of constant current control units. The current control units are configured to control current flowing through each of the LED units so that the current has a specific magnitude. Furthermore, the light output compensation unit is configured to provide current to the LED units so that the LED luminescence apparatus emits light during an entire interval of AC power.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention, and together with the description serve to explain the principles of the invention.
The invention is described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the exemplary embodiments set forth herein. Rather, these exemplary embodiments are provided so that this disclosure is thorough, and will fully convey the scope of the invention to those skilled in the art. In the drawings, the size and relative sizes of layers and regions may be exaggerated for clarity. Like reference numerals in the drawings denote like elements.
It will be understood that when an element or layer is referred to as being “on” or “connected to” another element or layer, it can be directly on or directly connected to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on” or “directly connected to” another element or layer, there are no intervening elements or layers present.
Referring to
The AC power source 11 may be a commercial AC power source, and may provide AC voltage in a sinusoidal wave form.
The rectification circuit unit 12 may generate unidirectional ripple voltage by rectifying AC voltage provided by the AC power source 11. The rectification circuit unit 12 may be a bridge circuit that is implemented using a plurality of diodes.
The plurality of LED units 13-1 to 13-N may be connected in series to each other in forward direction. That is, one terminal of the rectification circuit unit 12 is connected to an anode, a positive terminal, of the LED unit 13-1, and a cathode, a negative terminal, of the LED unit 13-1 is connected to an anode of the LED unit 13-2. A cathode of the LED unit 13-2 is connected to an anode of the LED unit 13-3, and so on. Each of the LED units 13-1 to 13-N shown in
Each of the switches 14-1 to 14-(N−1) may be connected, at one end thereof, to a node where two of the plurality of LED units 13-1 to 13-N are connected to each other. That is, a first switch 14-1 may be connected to a node where a first LED unit 13-1 and a second LED unit 13-2 are connected to each other, and a second switch 14-2 may be connected between the second LED unit 13-2 and a third LED unit 13-3. An (N−1)th switch 14-(N−1) may be connected between an (N−1) th LED unit 13-(N−1) and an Nth LED unit 13-N.
These switches 14-1 to 14-(N−1) may operate in response to switch control signals S1 to SN output from the current comparison unit 16, which will be described later. Furthermore, the switches 14-1 to 14-N may operate in response to control signals from the constant current control circuit units 15-1 to 15-N.
The constant current control circuit units 15-1 to 15-N may control current flowing through the plurality of LED units 13-1 to 13-N so that it has a specific magnitude. The constant current control circuit units 15-1 to 15-(N−1) may be connected to the remaining ends of the switches 14-1 to 14-N.
The current comparison unit 16 may receive currents i2 to iN flowing through the switches 14-2 to 14-N in response to opening of the switches 14-2 to 14-N, which is respectively controlled by the constant current control circuit units 15-1 to 15-N. In greater detail, the current comparison unit 16 generates switching control signals S1 to SN to close (turn on) the switches 14-1 to 14-N or open (turn off) so that the constant current control circuit units 15-1 to 15-N sequentially operate. That is, each of the switching control signals S1 to SN switches a corresponding switch 14-1 to 14-N to an open state (turned-off state) when downstream stage currents i2 to iN are received and if any one thereof reaches a preset value. For example, the first switching control signal S1 switches the first switch 14-1 to an open state when the downstream stage currents i2 to iN are received and if any one thereof reaches the preset value, the second switching control signal S2 switches the second switch 14-2 to an open state (turned-off state) when the downstream stage currents i3 to iN are received and if any one thereof reaches the preset value, and the (N−1)th switch control signal S(N−1) switches the (N−1)th switch 15-(N−1) to an open state (turned-off state) when the downstream current iN is received and if the corresponding current reaches the preset value.
The operation of the LED luminescence apparatus using AC power according to the present exemplary embodiment shown in
First, when AC voltage is applied to the rectification circuit unit 12 by the AC power source 11, the rectification circuit unit 12 rectifies the AC voltage, and then outputs unidirectional ripple voltage. As shown in
Thereafter, as ripple voltage increases, the LED units 13-1 to 13-N can sequentially emit light. Such light emitting operation of the LED units will now be described with reference to
Furthermore,
When the magnitude of the ripple voltage provided to the LED units 13-1 to 13-4 increases and the ripple voltage reaches the driving voltage (forward voltage Vf1) of the first LED unit 13-1, current flows through the first LED unit 13-1 and light is emitted (at time t0 of
Here, the first switch 14-1 to the fourth switch 14-4 are initially set to a close state (turned-on state). Such input voltage Vf1 is the voltage which enables the first LED unit 13-1 to be turned on, and the current corresponding to the input voltage Vf1 flows through a path to the first constant current circuit control unit 15-1 via the first LED 13-1. In this case, the first switch 14-1 uniformly controls current passing through the first constant current control circuit unit 15-1 in response to a control signal output from the first constant current control circuit unit 15-1. The first constant current control circuit unit 15-1 performs constant current control so that reference current preset to drive the first LED unit 13-1 can flow through the first LED unit 13-1. The operation in which the first LED unit 13-1 initiates light emission corresponds to a time interval t0-t1 in
Thereafter, when the magnitude of the ripple voltage further increases and voltage applied to the second LED unit 13-2 reaches the driving voltage of the second LED unit 13-2 (when the magnitude of the ripple voltage becomes Vf2), current flows through the second LED unit 13-2 and the second LED unit 13-2 emits light (at time t1 of
Using this operation, control may be performed such that constant current flows through the first LED unit 13-1 and the second LED unit 13-2. Furthermore, as shown in
Similarly to the above-described procedure, when the ripple voltage further increases and voltage applied to the third LED unit 13-3 becomes the driving voltage of the third LED unit 13-3 (when the magnitude of the ripple voltage becomes Vf3), current flows through the third LED unit 13-3 and then the third LED unit 13-3 emits light (at time t2 of
Using this operation, control may be performed such that constant current flows through the first LED unit 13-1, the second LED unit 13-2, and the third LED unit 13-3. Furthermore, as shown in
Similarly to the above-described procedure, when the ripple voltage further increases, and voltage applied to the fourth LED unit 13-4 becomes the driving voltage of the fourth LED unit 13-4 (when the magnitude of the ripple voltage becomes Vf4), current flows through the fourth LED unit 13-4 and then the fourth LED unit 13-4 emits light (at time t3 of
Using this operation, control may be performed such that constant current flows through the first LED unit 13-1, the second LED unit 13-2, the third LED unit 13-3, and the fourth LED unit 13-4. Furthermore, as shown in
When ripple voltage passes over a peak and gradually decreases, the LED units are sequentially turned off in the sequence from the fourth LED unit 13-4 to the first LED unit 13-1. When the fourth LED unit 13-4 is turned off (at time t4), the current comparison unit 16 senses that the current i4 of the fourth constant current control circuit unit 15-4 is not the preset value, and inverts the fourth switching control signal S4, thus closing (turning on) the third switch 14-3. In this case, the first and second switching control signals S1 and S2 are maintained in their previous states, so that the first and second switches 14-1 and 14-2 are maintained in an open (turned-off) state. At the same time, the third switch 14-3 initiates constant current control in response to a control signal output from the third constant current control circuit unit 15-3 so that the current flowing through the third constant current control unit 15-3 is maintained at the reference current preset to drive the first to third LED units 13-1 to 13-3.
A subsequent current control operation is performed in the reverse order of the constant current control performed during the above-described interval t0 to t3, and thus a detailed description thereof will be omitted here.
Although the present exemplary embodiment has been described such that LED driving current is increased or decreased in stepped form by multi-stage constant current control, the present invention is not limited thereto, but the waveform of the LED driving current can be changed by variously setting reference current for constant current control.
Since the configuration of the LED luminescence apparatus of the exemplary embodiment shown in
In the present exemplary embodiment, each of the LED units is configured such that a plurality of LEDs is connected in parallel to each other, for example, a first LED unit 13-1-1 to 13-1-M is configured such that M LEDs are connected in parallel to each other. Here, the number of LEDs connected in parallel may be increased for the purpose of an increase in the luminous flux of an LED lighting lamp or an increase in the capability of the lamp.
As described above, exemplary embodiments of the present invention are configured to sequentially drive the series-connected LEDs at constant current using AC voltage, so that current that increases or decreases in stepped form can be provided, as shown in
Constant driving current can be provided in the event of a variation in AC voltage (distortion, or an increase or decrease in the magnitude of voltage) by controlling current so that it has a constant value at each stage, thereby improving the light output efficiency of AC-driven LEDs.
A method of generating the driving current of an LED in a stepped shape using multi-stage current driving is shown in
As shown in
As shown in
There is a relationship between the driving voltage (forward voltage: Vf) of LED units employed in the luminescence apparatus and the OFF interval, thus the driving voltage may be manipulated in order to minimize the OFF interval.
Hereinafter, techniques for minimizing the OFF interval according to exemplary embodiments of the present invention will be described with respect to
As shown in
Therefore, the percentage of LEDs in the OFF interval may be reduced by employing LEDs having different driving voltages Vf rather than employing LED units having the same driving voltage.
As shown in
When the number of LED units is four, that is, N=4, the driving voltages Vf1 to Vf4 of the LED units 13-1 to 13-4 (LED1 to LED4) are implemented as different voltages, in particular, in such a way that the driving voltage Vf1 of the first LED unit 13-1 (LED1) closest to a rectification circuit unit 12 is set to the smallest value, as shown in
Meanwhile, although the present exemplary embodiment has been described such that different stepped driving currents are used to drive the LED units at respective steps, the present invention is not limited thereto and can be implemented in various forms. For example, the LED units can be driven using the same current so that variations in the quantity of light depending on the voltages of LED units having a plurality of driving voltages Vf can be minimized. In this case, the driving current applied to the LED units can be formed in the shape of a single square wave.
That is, referring to
Since the construction of the LED luminescence apparatus of
In the present exemplary embodiment, each LED unit is implemented using a plurality of LEDs connected in parallel to each other. For example, a first LED unit 13-1-1 to 13-1-M can be implemented using M parallel-connected LEDs. In this case, the number of parallel-connected LEDs can be increased for the purpose of increasing the luminous flux of an LED luminescence lamp or increasing the capacity of the lamp.
As described above, the exemplary embodiments of the present invention are configured such that the driving voltages Vf of LED units may have a plurality of different values, thus reducing an OFF interval compared to the arrangement of LED units having the same driving voltage according to the conventional embodiment. By way of this configuration, the exemplary embodiments of the present invention not only may reduce a flicker phenomenon and increase the quantity of light, but also may improve the power factor and reduce the influence of harmonics.
A method of generating LED driving current in a stepped form using multi-stage current driving is described below with respect to
As shown in
However, as AC voltage increases or decreases, an LED driving voltage Vf may instantaneously vary. As shown in
Referring to
The AC power source 11 may be a commercial AC power source, and may provide AC voltage in a sinusoidal wave form.
The rectification circuit unit 12 may generate unidirectional ripple voltage by rectifying AC voltage provided by the AC power source 11. The rectification circuit unit 12 may be a bridge circuit that is implemented using a plurality of diodes.
The plurality of LED units 13-1 to 13-4 may be connected in series to each other. Each of the LED units 13-1 to 13-4 shown in
For convenience of description, the plurality of LED units 13-1 to 13-4 that are connected in series to each other is labeled a first LED unit, a second LED unit, a third LED unit, and a fourth LED unit in the sequence of the connection thereof.
Each of the switches 14-1 to 14-4 may be connected, at one end thereof, to a node where two of the plurality of LED units 13-1 to 13-4 are connected to each other. That is, a first switch 14-1 may be connected to a node where a first LED unit 13-1 and a second LED unit 13-2 are connected to each other, a second switch 14-2 may be connected to a node where the second LED unit 13-2 and a third LED unit 13-3 are connected to each other, and a third switch 14-3 may be connected to a node where a third LED unit 13-3 and a fourth LED unit 13-4 are connected to each other.
These switches 14-1 to 14-4 may operate in response to switch control signals S1 to S4 output from the current comparison unit 16, which will be described later. Furthermore, the switches 14-1 to 14-4 may operate in response to control signals from the constant current control circuit units 15-1 to 15-4.
The constant current control circuit units 15-1 to 15-4 may control current flowing through the plurality of LED units 13-1 to 13-4 so that it has a specific magnitude. The constant current control circuit units 15-1 to 15-4 may be connected to the remaining ends of the switches 14-1 to 14-4.
The constant current control circuit units 15-1 to 15-4 generate the switch control signals of switch units 10-1 to 10-4 (see
The current comparison unit 16 may receive currents i2 to i4 flowing through the switches 14-2 to 14-4 in response to the constant current control circuit units 15-1 to 15-4, and generate the switching control signals S1 to S4 of the switches 14-1 to 14-4. In greater detail, the current comparison unit 16 generates switching control signals S1 to S4 depending on the closing (turning on) or opening (turning off) of the switches 14-1 to 14-4 so that the constant current control circuit units 15-1 to 15-4 sequentially operate. That is, each of the switching control signals S1 to S4 switches a corresponding switch 14-1 to 14-4 to an open state (turned-off state) when downstream stage currents i2 to i4 are received and if any one thereof reaches a preset value. For example, the first switching control signal S1 switches the first switch 14-1 to an open state when the downstream stage currents i2 to i4 are received and if any one thereof reaches the preset value, the second switching control signal S2 switches the second switch 14-2 to an open state (turned-off state) when the downstream stage currents i3 to i4 are received and if any one thereof reaches the preset value, and the third switch control signal S3 switches the third switch 15-3 to an open state (turned-off state) when the downstream current i4 is received and if the corresponding current reaches the preset value.
The average current control circuit units 18-1 to 18-4 generate a Pulse-Width Modulation (PWM) signal so as to control the average value of current flowing through the switches 14-1 to 14-4. The average current control circuit units 18-1 to 18-4 may detect the current of the constant current control circuit units 15-1 to 15-4 and control the average value of driving current flowing through the LED units 13-1 to 13-4, regardless of AC power. For example, when the AC voltage is a voltage higher than a higher reference voltage level, the driving time of the corresponding switches 14-1 to 14-4 is decreased by reducing the duty of the PWM signal, so as to decrease the driving interval of the LED units 13-1 to 13-4. In contrast, when the AC voltage is lower voltage than a lower reference voltage level, the driving time of the corresponding switch 14-1 to 14-4 is increased by increasing the duty of the PWM signal, so as to increase the driving interval of the LED units 13-1 to 13-4.
Meanwhile, since the average current control circuit units 18-1 to 18-4 drive the switches 14-1 to 14-4 using a PWM signal, the LED driving current at each stage is generated in the form of pulse waves.
The signal generation unit 19 generates a ramp signal, and applies it to the average current control circuit units 18-1 to 18-4 to generate the PWM signal. Here, the frequency of the generated signal is determined depending on the average driving current of the LED units 13-1 to 13-4, and may be, for example, in the range of 1 KHz to 100 KHz.
The operation of the LED luminescence apparatus using AC power according to an exemplary embodiment of the present invention shown in
The first average current control circuit unit 18-1 detects the current of the first constant current control circuit unit 15-1, generates a PWM signal based on an error with respect to the reference current, and drives the first switch 14-1. That is, if the actual current is greater than or less than the reference current, the duty of the PWM signal is varied. Accordingly, as shown in
The second average current control circuit unit 18-2 detects the current of the second constant current control circuit unit 15-2, generates a PWM signal based on an error with respect to the reference current, and drives the second switch 14-2. Accordingly, as shown in
The third average current control circuit unit 18-3 detects the current of the third constant current control circuit unit 15-3, generates a PWM signal based on an error with respect to the reference current, and drives the third switch 14-3. Accordingly, as shown in
The fourth average current control circuit unit 18-4 detects the current of the fourth constant current control circuit unit 15-4, generates a PWM signal based on an error with respect to the reference current, and drives the fourth switch 14-4. Accordingly, as shown in
When ripple voltage passes over a peak and gradually decreases, the LED units are sequentially turned off in the sequence from the fourth LED unit 13-4 to the first LED unit 13-1. When the fourth LED unit 13-4 is turned off (at time t4), the current comparison unit 16 senses that the current i4 of the fourth constant current control circuit unit 15-4 is not the preset value, and inverts the third switching control signal S3, thus closing (turning on) the third switch 14-3. In this case, the first and second switching control signals S1 and S2 are maintained in their previous states, so that the first and second switches 14-1 and 14-2 are maintained in an open (turned-off) state. At the same time, current is input to the third constant current control circuit unit 15-3, and constant current control is initiated such that the reference current preset to drive the first to third LED units 13-1 to 13-3 can be maintained.
The third average current control circuit unit 18-3 detects the current of the third constant current control circuit unit 15-3, generates a PWM signal based on an error with respect to the reference current, and drives the third switch 14-3. Accordingly, as shown in
A subsequent current control operation is performed in the reverse order of the constant current control performed during the above-described interval t0 to t3, and thus a detailed description thereof will be omitted here.
Referring to
In
The constant current control circuit units 15-1 to 15-4 are connected to the sources s1 to s4 and gates g1 to g4 of the switching devices Q1 to Q4. Furthermore, the constant current control circuit units 15-1 to 15-4 control the switching devices Q1 to Q4, which include power semiconductors, such as field effect transistors (FETs) or bipolar junction transistors (BJTs), at linear regions. That is, the constant current control circuit units 15-1 to 15-4 generate signals that control Vgs of the switching devices Q1 to Q4 so that the driving current of the LED unit 13-1 fulfills a set peak current value. In this case, the switching devices Q1 to Q4 operate at linear regions. Specifically, each of the constant current control circuit units 15-1 to 15-4 senses the current flowing from the respective switching device Q1 to Q4 via the respective resistors R1 to R4, and generates a control signal to control the respective switching device Q1 to Q4 based on the amount of the sensed current. For this, each of the constant current control circuit units 15-1 to 15-4 may include a switching element (not shown) which is selectively turned on according to the sensed current. Such switching element may be power semiconductors, such as field effect transistors (FETs) or bipolar junction transistors (BJTs). That is, if the switching element is a BJT, a base terminal of the BJT is connected to the source s1 of the respective switching device Q1 to Q4, a collector terminal of the BJT is connected to a gate terminal g1 of the respective switching device Q1 to Q4, and an emitter terminal of the BJT is connected to the respective resistors R1 to R4.
The average current control circuit units 18-1 to 18-4 may be configured to include detection resistors R1 to R4 for detecting the current of the constant current control circuits 15-1 to 15-4, current conversion units 20-1 to 20-4 for converting the detected current into DC current, first comparators 21-1 to 21-4 for performing comparison with reference currents Iref1 to Iref4 and outputting error values, and second comparators 22-1 to 22-4 for comparing the error values of the first comparators 21-1 to 21-4 with the signal Vramp of the signal generation unit 19 and generating PWM signals.
Here, the detection resistors R1 to R4 are connected in series to the constant current control circuit units 15-1 to 15-4, and the current conversion units 20-1 to 20-4 are connected between the detection resistors R1 to R4 and the constant current control circuit units 15-1 to 15-4, and the current flowing from the constant current control circuit units 15-1 to 15-4 is changed to a predetermined level by averaging the current. For example, each of the current conversion units 20-1 to 20-4 may be configured to include a filter.
The outputs of the current conversion units 20-1 to 20-4 are connected to the negative (−) terminals of the first comparators 21-1 to 21-4, and the reference currents Iref1 to Iref4 are connected to the positive (+) terminals of the first comparators 21-1 to 21-4. The outputs of the first comparators 21-1 to 21-4 are connected to the positive (+) terminals of the second comparators 22-1 to 22-4, and the output Vramp of the signal generator 19 is connected to the negative (−) terminals of the second comparators 22-1 to 22-4.
Furthermore, the average current control circuit units 18-1 to 18-4 generate signals that control Vgs of the switching devices Q1 to Q4 so that the driving current of the LED units 13-1 to 13-4 fulfills the set average current. In this case, the switching devices Q1 to Q4 operate at switching ON/OFF intervals.
The operation of the average current control circuit unit will now be described with reference to
Here, since the operation of the average current control circuit units 18-1 to 18-4 is the same at individual current intervals, only the operation at a first interval, that is, time interval t0 to t1, will be described.
First, when the AC voltage is a reference voltage and the detection resistor R1 detects the current of the constant current control circuit unit 15-1, the current conversion unit 18-1 converts the detected current into DC current and inputs the DC current to the first comparator 21-1. The first comparator 21-1 compares reference current Iref1 with the output signal of the current conversion unit 20-1, and outputs an error signal corresponding to the error. For example, the first comparator 21-1 may output an error signal if the output signal of the current conversion unit 20-1 is less than or greater than to the reference current Iref1.
Thereafter, the second comparator 22-1 compares signal Vramp, input by the signal generation unit 19, with the output of the first comparator 21-1, and generates a PWM reference signal for driving the switching device Q1. As shown in
The switching device Q1 performs ON and OFF switching in response to the PWM reference signal of the average current control circuit unit 18-1, so that the driving current of the LED unit 13-1 is generated in the form of pulses having a constant duty.
Furthermore, when the AC voltage is an excessive voltage, the detected current input to the negative (−) terminal of the first comparator 21-1 increases, and the output of the first comparator 21-1 is a signal at a level lower than that of the reference AC voltage. Accordingly, as shown in
Accordingly, the switching device Q1 performs ON and OFF switching in response to the PWM signal having a reduced duty, and therefore the duty of the driving current of the LED unit 13-1 is reduced, thereby rendering it possible to control average current by reducing the driving interval of the LED unit 13-1.
Meanwhile, when the AC voltage is a low voltage and the detected current input to the negative (−) terminal of the first comparator 21-1 is reduced, the output of the first comparator 21-1 is a signal at a level higher than that of reference AC voltage. Accordingly, as shown in
Accordingly, the switching device Q1 performs ON and OFF switching in response to the PWM signal having an increased duty, and therefore the duty of the driving current of the LED unit 13-1 is increased, thereby rendering it possible to control average current by increasing the driving interval of the LED unit 13-1.
As described above, the present invention is configured to control the LED driving current using the PWM signal of the average current so that the LED driving current can have an average value regardless of variations in AC input voltage, thereby keeping the intensity of light emitted from the LEDs constant.
Furthermore, the present invention is configured to control a constant current control device, such as a BJT or an FET, in a hybrid manner in which linear region control and PWM switching have been combined together, the optical efficiency for input power can be increased, thereby mitigating loss in a driving circuit.
As shown in
However, as semiconductor elements for power are used as switching elements driven by such a PWM signal, and these switching elements perform switching in a high-frequency band, a large amount of noise may occur on input power at the time point at which the switching elements are turned on or off. That is, since the variation in current increases over time, various types of noise defined as Electromagnetic Interference (EMI) may be caused. In order to cancel such noise, an EMI filter unit may be separately added, thus increasing cost of the circuit and making it difficult to realize a small size and light weight of a power circuit.
In order to solve this problem, the LED luminescence apparatus of
Referring to
The AC power source 11 may by a commercial AC power source capable of supplying AC voltage in a sinusoidal wave form.
The rectification circuit unit 12 may generate unidirectional ripple voltage Vrec by rectifying the AC voltage supplied by the AC power source 11. The rectification circuit unit 12 may be a bridge circuit implemented using a plurality of diodes.
The LED channel units 100 to n×100 are connected in parallel to each other, and may be sequentially operated in response to PWM signals PWM1 to PWMn generated by the PWM signal generation unit 30, which will be described later. For example, the LED channel unit 1100, the LED channel unit 2200, . . . , the LED channel unit n n×100 may be sequentially operated. In this case, the LED channel units 100 to n×100 are constructed to have the same structure, and will be described in detail below with reference to
As shown in
The LED units 113-1 to 113-4 may be connected in series to each other. A single LED unit shown in
Each of the switches Q1 to Q4 may be connected, at one end thereof, to a node where two of the plurality of LED units 113-1 to 113-4 are connected to each other. That is, a first switch Q1 may be connected to a node where a first LED unit 113-1 and a second LED unit 113-2 are connected to each other, a second switch Q2 may be connected to a node where the second LED unit 113-2 and a third LED unit 113-3 are connected to each other, and a third switch Q3 may be connected to a node where the third LED unit 113-3 and a fourth LED unit 113-4 are connected to each other.
The switches Q1 to Q4 may operate in response to switch control signals S1 to SN output from a current control circuit unit 118, which will be described later. Further, the switches Q1 to Q4 may operate in response to control signals output from the constant current control circuit units 115-1 to 115-4.
The constant current control circuit units 115-1 to 115-4 may control current flowing through the plurality of LED units 113-1 to 113-4 so that it has a predetermined magnitude. The constant current control circuit units 115-1 to 115-4 may be connected to the remaining ends of the switches Q1 to Q4.
The constant current control circuit units 115-1 to 115-4 generate switch control signals for the switch units 10-1 to 10-4 implemented as switches Q1 to Q4, which will be described later, and generate control signals Vgs to control the maximum current.
Meanwhile, the switches Q1 to Q4 and the constant current control circuit units 115-1 to 115-4 constitute constant current control units 110-1 to 110-4. In more detail, the control signals from the constant current control circuit units 115-1 to 115-4 are applied to the gates g1 to g4 of the respective switches Q1 to Q4. The constant current control units 110-1 to 110-4 generate constant currents satisfying the driving voltages Vf1 to Vf4 of the respective LED units 113-1 to 113-4.
The constant current control circuit units 115-1 to 115-4 are connected to the sources s1 to s4 and the gates g1 to g4 of the respective switches Q1 to Q4. Further, the constant current control circuit units 115-1 to 115-4 perform control such that the switches Q1 to Q4 implemented using power semiconductor elements, such as Field Effect Transistors (FET) or Bipolar Junction Transistors (BJT), are operated in a linear region. That is, the constant current control circuit units 115-1 to 115-4 generate signals for controlling Vgs of the switches Q1 to Q4 so that the driving currents of the LED units 113-1 to 113-4 satisfy set peak currents.
The current control circuit unit 118 may receive currents flowing through the switches Q2 to Q4 via the constant current control circuit units 115-1 to 115-4 and may generate switching control signals S1 to S4 for the switches Q1 to Q4. In detail, the current control circuit unit 118 generates the switching control signals S1 to S4 so that the constant current control circuit units 115-1 to 115-4 are sequentially operated depending on the closed state (turned-on state) or the open state (turned-off state) of the switches Q1 to Q4. That is, the current control circuit unit 118 receive downstream currents from the constant current control circuit units 115-2 to 115-4 in a subsequent stage, and switches relevant switches S1 to S4 to an open state (turned-off state) when any one of the received currents reaches a predetermined value. For example, for the first switching control signal S1, the current control circuit unit 118 receives downstream currents from the constant current control circuit units 115-2 to 115-4 in a subsequent stage and control the first switching control signal S1 to switch the first switch Q1 to an open state when any of the currents reaches a predetermined value. For the second switching control signal S2, the current control circuit unit 118 receives downstream currents from the constant current control circuit units 115-3 and 115-4 in a subsequent stage and control the second switching control signal S2 to switch the second switch Q2 to an open state (turned-off state) when any one of the currents reaches the predetermined value. For the third switch control signal S3, the current control circuit unit 118 receives downstream current from the constant current control circuit unit 115-4 in a subsequent stage, and control the third switching control signal S3 to switch the third switch Q3 to an open state (turned-off state) when the current reaches the predetermined value.
Further, the current control circuit unit 118 generates PWM signals required to control a mean value of the currents flowing through the switches Q1 to Q4. The current control circuit unit 118 may detect the currents flowing through the constant current control circuit units 115-1 to 115-4 regardless of the AC power source, and then control a mean value of driving currents flowing through the LED units 113-1 to 113-4. For example, when the AC voltage is higher than a reference voltage level, the driving times of the switches Q1 to Q4 are reduced by reducing the duty cycle of a relevant PWM signal so that the intervals, during which the LED units 113-1 to 113-4 are turned on, are reduced. In contrast, when the AC voltage is lower than a reference voltage, the driving times of the switches Q1 to Q4 are increased by increasing the duty cycle of a relevant PWM signal so that the intervals, during which the LED units 113-1 to 113-4 are turned on, are increased.
Meanwhile, since the current control circuit unit 118 drives the switches Q1 to Q4 using the PWM signals, LED driving current in each stage is generated in the form of a pulse wave. That is, the current control circuit unit 118 generates signals for controlling Vgs of the switches Q1 to Q4 so that the driving current of each of the LED units 113-1 to 113-4 satisfies preset mean current. In this case, the switches Q1 to Q4 are operated in a switching (ON/OFF) region, so that the driving current of each of the LED units 113-1 to 113-4 is formed in the shape of a pulse having a certain duty cycle.
The PWM signal generation unit 30 may include a frequency detection unit 31 for detecting the frequency of the AC power source 11, a reference frequency oscillation circuit 32 for oscillating at a reference frequency different from the detected frequency, a frequency division circuit 33 for dividing the reference frequency, and a PWM output decision unit 34 for deciding on PWM output using frequency-divided signals.
The frequency detection unit 31 generates a square wave signal by detecting zero crossings (zero crossing detection) in the AC power source 11, and the reference frequency oscillation circuit 32 generates a reference signal having a PWM frequency synchronized with the generated square wave signal. In this case, the frequency of the oscillation signal can be set to various frequencies. The frequency division circuit 33 divides the reference PWM frequency signal by a multiple of an integer. The signal which has been frequency-divided in this way has a duty cycle of 50%, and is frequency-divided by an integer n (Fs/n) from a clock pulse, the ratio of ON/OFF times of which is 1. Here, the frequency-divided signal is the reference signal of the PWM output decision unit 34, and the PWM output decision unit 34 generates n PWM decision signals PWM1 to PWMn corresponding to the number of channels, which will be described in detail with reference to
As shown in
The operation of the LED luminescence apparatus using AC power according to the present exemplary embodiment shown in
The operation of the LED luminescence apparatus using AC power shown in FIG. 16 and
First, when AC voltage is input by the AC power source 11 to the rectification circuit unit 12, the rectification circuit unit 12 rectifies the AC voltage and outputs unidirectional ripple voltage Vrec. As shown in
As the ripple voltage Vrec input to the LED channel unit 1100 increases, the LED units 113-1 to 113-4 may sequentially emit light. The light emission operations of the LED units are described with reference to
Further,
When the magnitude of the ripple voltage Vrec supplied to the LED units 113-1 to 113-4 increases, and the ripple voltage Vrec reaches the driving voltage (forward voltage: Vf1) of the first LED unit 113-1, current flows through the first LED unit 113-1 and then light is emitted (at time t0 of
In this case, in response to the PWM decision signals PWM1 to PWMn generated by the PWM output decision unit 34, the individual LED channel units 100 to 400 can be sequentially operated. That is, as shown in
Here, since the PWM decision signals PWM1 to PWM4 overlap one another in some intervals, two or three of the LED channel units 100 to 400 are simultaneously driven in some intervals, in which case the first LED units 113-1 of the LED channel units 100 to 400 are simultaneously turned on and, consequently, the LED driving current is generated in the form of DC level-shifted current.
Next, when the magnitude of the ripple voltage Vrec further increases and voltage applied to the second LED unit 113-2 becomes the driving voltage of the second LED 113-2 (when the magnitude of the ripple voltage Vrec becomes Vf2), current flows through the second LED unit 113-2, and then light is emitted (at time t1 of
Using this operation, control may be performed such that constant current flows through the first LED unit 113-1 and the second LED unit 113-2. Further, as shown in
Similarly to the above description, when the ripple voltage Vrec further increases and voltage applied to the third LED unit 113-3 becomes the driving voltage of the third LED unit 113-3 (when the magnitude of the ripple voltage Vrec becomes Vf3), current flows through the third LED unit 113-3, and light is emitted (at time t2 of
Using this operation, control may be performed such that constant current flows through the first LED unit 113-1, the second LED unit 113-2, and the third LED unit 113-3. Further, as shown in
Similarly to the above description, when the ripple voltage Vrec further increases and voltage applied to the fourth LED unit 113-4 becomes the driving voltage of the fourth LED unit 113-4 (when the magnitude of the ripple voltage Vrec becomes Vf4), current flows through the fourth LED unit 113-4, and light is emitted (at time t3 of
Using this operation, control may be performed such that constant current flows through the first LED unit 113-1, the second LED unit 113-2, the third LED unit 113-3, and the fourth LED unit 113-4. Further, as shown in
When the ripple voltage Vrec passes over a peak and gradually decreases, the LED units are sequentially turned off in the sequence from the fourth LED unit 113-4 to the first LED unit 113-1. When the fourth LED unit 113-4 is turned off (at time t4), the current control circuit unit 118 detects that the current of the fourth constant current control circuit unit 115-4 is not the predetermined value, inverts the third switching control signal S3, and then closes (turns on) the third switch Q3. In this case, the first switching control signal S1 and the second switching control signal S2 are maintained in their previous states, so that the first switch Q1 and the second switch Q2 are maintained in an open (turned-off) state. At the same time, current flows into the third constant current control circuit unit 115-3, and constant current control is initiated so that preset current is maintained to drive the first to third LED units 113-1 to 113-3.
In this case, the current control circuit unit 118 detects the current of the third constant current control circuit unit 115-3, generates a PWM signal depending on an error between the detected current and the reference current, and then drives the third switch Q3. Therefore, as shown in
A subsequent current control operation is performed in the reverse order of the constant current control performed during the above-described interval t0 to t3, and thus a detailed description thereof is omitted.
Although the present exemplary embodiment has been described such that LED driving current is increased or decreased in a stepped shape via multi-stage constant current control, the present invention is not limited thereto and reference current for constant current control can be set to various forms so that the waveform of the LED driving current can also be changed.
Hereinafter, the peak current control and average current control of the LED driving current will be described in detail with reference to
In order to describe an operation in which the LED channel units 100 to 400 are sequentially operated in response to PWM decision signals PWM1 to PWMn, and then the LED driving currents are generated in the form which they overlap each other in some intervals,
As shown in
In this case, the PWM output decision unit 34 generates the PWM decision signals PWM1 to PWM4, as shown in
That is, as shown in
Next, the LED channel unit 2200 is driven in response to the second PWM decision signal PWM2. The current control circuit unit 218-1 of the LED channel unit 2200 outputs the switch control signal S1, so that the first LED unit 213-1 emits light via the constant current control unit 210-1. That is, LED driving current Ch2 is formed by the LED channel unit 2200 in response to the second PWM decision signal PWM2. Here, the LED driving current Ch2 of the LED channel unit 2200 is formed in the same pattern as the second PWM decision signal PWM2, for example, it does not flow in the first interval during the four intervals constituting a single cycle of the 2-frequency-divided signal Fs/2.
Thereafter, the LED channel unit 3300 is driven in response to the third PWM decision signal PWM3. The current control circuit unit 318-1 of the LED channel unit 3300 outputs the switch control signal S1, so that the first LED unit 313-1 emits light via the constant current control unit 310-1. That is, LED driving current Ch3 is formed by the LED channel unit 3300 in response to the third PWM decision signal PWM3. Here, the LED driving current Ch3 of the LED channel unit 3300 is formed in the same pattern as the third PWM decision signal PWM3, for example, it does not flow in the second and fourth intervals during the four intervals constituting a single cycle of the 2-frequency-divided signal Fs/2.
Finally, the LED channel unit 4400 is driven in response to the fourth PWM decision signal PWM4. The current control circuit unit 418-1 of the LED channel unit 4400 outputs the switch control signal S1, so that the fourth LED unit 413-1 emits light via the constant current control unit 410-1. That is, LED driving current Ch4 is formed by the LED channel unit 4400 in response to the fourth PWM decision signal PWM4. Here, the LED driving current Ch4 of the LED channel unit 4400 is formed in the same pattern as the fourth PWM decision signal PWM4, for example, it does not flow in the first and third intervals during the four intervals constituting a single cycle of the 2-frequency-divided signal Fs/2.
Consequently, since the LED channel units 100 to 400 are sequentially driven in response to the PWM decision signals PWM1 to PWM4, the total LED driving current ILED obtained by summing the driving currents of the first LED units 113-1 to 413-1 of the LED channel units 100 to 400 can be generated in the form of DC level-shifted pulse waves that overlap one another in some intervals. That is, in
Although
Since the LED luminescence apparatus according to the exemplary embodiment shown in
The fifth LED unit 113-5 is operated at a driving voltage Vf5 that is lower than the driving voltage Vf1 of the first LED unit 113-1, and the constant current control unit 110-5 and the current control circuit unit 118 are operated at the corresponding driving voltage. That is, the current control circuit unit 118, such as that shown in
Using this operation, the fifth LED unit 113-5 first emits light at voltage Vf5 where the input power is lower than the driving voltage of the first LED unit 113-1 in multi-stage stepped current operation, thereby reducing the LED OFF interval. That is, as shown in
However, according to the present exemplary embodiment, in this early interval, the fifth LED unit 113-5 having driving voltage Vf5 lower than the driving voltages Vf1 to Vf4 of the LED driving units 113-1 to 113-4 emits light, thereby reducing the LED OFF interval A to the LED OFF interval B achieved by the fifth LED unit 113-5, as shown in
As described above, the exemplary embodiments of the present invention may have constant current control units configured using a plurality of channels and the outputs of the constant current control units are continuously provided in response to PWM decision signals obtained by frequency division and interleaving, so that the cost of the power circuit of an LED luminescence apparatus can be reduced and the small size and light weight of the LED luminescence apparatus can be realized because an EMI filter is configured using only a resistor and a capacitor and therefore simplifying the structure of the LED luminescence apparatus.
Furthermore, the present invention is additionally provided with an LED whose driving voltage Vf is low, thereby reducing light output OFF intervals.
As shown in
The operation of the LED luminescence apparatus using AC power shown in
Consequently, since the LED channel units 100 to 400 are sequentially driven in response to the PWM decision signals PWM1 to PWM4, total LED driving current ILED obtained by summing up the driving currents of the first LED units 113-1 to 413-1 of the LED channel units 100 to 400 can be formed as continuous current.
As described above, exemplary embodiments of the present invention disclose that constant current control units are configured for a plurality of channels and the outputs of the constant current control units are continuously provided in response to PWM decision signals obtained by frequency division, so that the cost of the power circuit of an LED luminescence apparatus can be reduced and the small size and light weight of the LED luminescence apparatus can be realized because there is no need to separately provide an EMI filter composed of a coil and a capacitor.
As shown in
The rectification unit 12 may include a plurality of diodes D1 to D4 constituting a bridge circuit, and is configured to convert the AC voltage Vac into the ripple voltage VBD and output the ripple voltage VBD. The ripple voltage VBD may be supplied to the external LEDs via the external connection terminals of the LED driving circuit package.
The low voltage control unit 1200 may include a circuit power supply unit 1210 for generating low voltage power that can be supplied, as supply voltage, to various types of internal circuits using the ripple voltage VBD generated by the rectification unit 12, a voltage detection unit 1220 for detecting the magnitude of the ripple voltage VBD, a reference frequency generation unit 1230 for operating using the low voltage power generated by the circuit power supply unit 1210 and generating a reference frequency, and a reference pulse generation unit 1240 for operating using the low voltage power generated by the circuit power supply unit 1210 and generating a reference pulse required to control the operation of the LED driving switch unit 1300 according to the reference frequency generated by the reference frequency generation unit 1230 and the magnitude of the voltage detected by the voltage detection unit 1220.
In order to implement the above-described circuits, the low voltage control unit 1200 has resistive elements required to divide the ripple voltage VBD which is a high voltage.
The LED driving switch unit 1300 may include a plurality of switch units 1310 to 1340 and a plurality of current control units 1350 to 1380. The plurality of switch units 1310 to 1340 may be connected to the respective cathodes of a plurality of external series-connected LEDs LED1 to LED4 that form a single channel.
The plurality of current control units 1350 to 1380 control currents which are supplied to the LEDs via the switch units so as to be constant currents.
For example, when the voltage detection unit 1220 detects the ripple voltage VBD and the ripple voltage reaches a preset threshold, the reference pulse generation unit 1240 generates a reference pulse to turn on the first switch unit 1310 so that the first switch unit 1310 enters a conductive state, and to turn off the remaining second to fourth switch units 1320 to 1340 so that the switches 1320 to 1340 enter an open state. Using this operation, current is applied to the first LED LED1 and then the first LED LED1 emits light. In this case, the first current control unit 1350 controls current flowing through the first LED LED1 and the first switch unit 1310 as to be constant current.
Next, when the voltage detection unit 1220 detects the ripple voltage VBD and the ripple voltage reaches another preset threshold, the reference pulse generation unit 1240 generates a second reference pulse to turn on the second switch unit 1320 so that the second switch unit 1320 enters a conductive state, and to turn off the remaining first, third and fourth switch units 1310, 1330 and 1340 so that the switches 1310, 1330 and 1340 enter an open state. Using this operation, current is applied to the first and second LEDs LED1 and LED2 and then the first and second LEDs LED1 and LED2 emit light. In this case, the second current control unit 136 controls current flowing through the first and second LEDs LED1 and LED2 and the second switch unit 1320 as to be constant current.
Next, when the voltage detection unit 1220 detects the ripple voltage VBD and the ripple voltage reaches a further preset threshold, the reference pulse generation unit 1240 generates a third reference pulse to turn on the third switch unit 1330 so that the third switch unit 1330 enters a conductive state, and to turn off the remaining first, second and fourth switch units 1310, 1320 and 1340 so that the switches 1310, 1320 and 1340 enter an open state. Using this operation, current is applied to the first to third LEDs LED1 to LED3 and then the first to third LEDs LED1 to LED3 emit light. In this case, the third current control unit 1370 controls current flowing through the first to third LEDs LED1 to LED3 and the third switch unit 1330 as to be constant current.
Next, when the voltage detection unit 1220 detects the ripple voltage VBD and the ripple voltage reaches yet another preset threshold, the reference pulse generation unit 1240 generates a fourth reference pulse to turn on the fourth switch unit 1340 so that the fourth switch unit 1340 enters a conductive state, and to turn off the remaining first to third switch units 1310 to 1330 so that the switches 1310 to 1330 enter an open state. Using this operation, current is applied to the first to fourth LEDs LED1 to LED4 and then the first to fourth LEDs LED1 to LED4 emit light. In this case, the fourth current control unit 1380 controls current flowing through the first to fourth LEDs LED1 to LED4 and the fourth switch unit 1340 as to be constant current.
The ripple voltage detected by the voltage detection unit 1220 periodically repeats while increasing and decreasing, so that the above-described LED control performed by the LED driving switch unit 1300 may allow stepped current, in which rising and falling ripple voltage is periodically repeated, to flow through the LED channel CH1.
Referring to
That is, the LED driving circuit package 1000 according to the present exemplary embodiment includes the PCB 2100, the silicon substrate 2000 bonded to the top surface of the PCB 2100, and the rectification unit 12 and passive elements 2900 mounted on the top surface of the PCB 2100.
The low voltage control circuit unit 1200 and LED driving switch units 1300a and 1300b described in
The rectification unit 12 may be implemented using four PN junction diodes. Generally, as the PN junction diodes, diodes that are able to suppress reverse voltage having magnitude that is about 1.5 to 2 times that of input AC voltage may be used. Therefore, in order to implement both the rectification unit and the low voltage circuit unit together on the silicon substrate, an additional process for isolating high voltage from low voltage during the manufacturing of the semiconductor device may be required. Thus, the diodes used to constitute the rectification unit 12 may be implemented in such a way that the diodes are independently mounted on the PCB 2100 using individual elements or the like.
Meanwhile, some of the diodes included in the rectification unit 12 can be implemented as overvoltage and surge voltage suppressor diodes such as Zener diodes or Transient Voltage Suppression (TVS) diodes, rather than PN junction diodes. The present exemplary embodiment has rectification unit 12 diodes that are not implemented in the silicon substrate 2000 and are mounted on the PCB 2100, thus enabling elements to be easily changed in a packaging process.
Further, the passive resistive elements 2900 may be mounted on the PCB 2100 in the form of separate individual elements without being integrated into the silicon substrate 2000.
Since the circuit of the present exemplary embodiment is supplied with and operated by various types of AC power ranging from 80 Vrms to 265 Vrms, it must acquire power (voltage and current) from AC voltage unlike typical circuits that are supplied with and driven by separate external power. Therefore, the circuit power supply unit 1210 of the low voltage control circuit unit 1200 requires passive resistive elements having high power consumption. With just a semiconductor manufacturing process using a silicon substrate, it may be difficult to implement passive elements having high power consumption, and thus necessary passive elements 2900 having high power consumption can be mounted on the PCB 2100 so as to divide the AC rectified voltage in the present exemplary embodiment.
In the exemplary embodiment shown in
In consideration of insulation from the PCB 2100, the silicon substrate 2000 may be bonded to the top of the upper heat dissipation pad 31 using a non-conducting adhesive 2700.
Meanwhile, although not shown in the drawings, in a modification of the embodiment shown in
The rectification unit 12 and the silicon substrate 2000 are arranged adjacent to the center portion of the top surface of the PCB 2100, and electrode pads L, N, A to F, A′ to F′, and 2400 may be formed on the top surface of the PCB 2100 along the edges of the PCB 2100. The electrode pads L, N, A to F, A′ to F′, and 2400 may form electrical connections to the rectification unit 12 and the silicon substrate 2000 through wires 2300. The electrode pads L, N, A to F, A′ to F′, and 2400 may be electrically connected to an external connection electrode 2600 formed on the bottom surface of the PCB 2100 through a conductive via 2500.
When forming electrical connections through the wires 2300, the electrical connections may be formed so that wires through which high voltage flows and wires through which low voltage flows are spatially isolated so as to remove electrical interference therebetween. For this operation, it is preferable that the electrode pads L and N to which AC power is externally applied, and the electrode pads A and A′ to which the ripple voltage VBA formed by the rectification unit 12 is applied, be arranged adjacent to the rectification unit 12, thus the length of the wires for electrical connections to be made as short as possible.
The above-described PCB 2100, silicon substrate 2000, rectification unit 12, passive elements 2900, and bonding wires 2300 may form an integrated mold part 3000 using various kinds of molding materials including a resin material or the like, and thus are integrally molded together.
The embodiment shown in
In the present exemplary embodiment, high voltage diodes constituting the rectification unit 12 may be mounted on the silicon substrate 2000 using a conducting or non-conducting adhesive (made of, for example, an epoxy material) 4100. In the silicon substrate 2000, a region required to mount the high voltage diodes may be provided in an area spaced apart from the area in which the low voltage control circuit unit 1200 and the LED driving switch units 1300a and 1300b are integrated.
Furthermore, connection pads 4200 for forming electrical connections between the electrode pads 4400 and the rectification unit 12 may be formed on the silicon substrate 2000. Wires 4300 may be bonded to the connection pads 4200 so as to individually form electrical connections to the rectification unit 12 and to the external electrodes 4400.
The silicon substrate 2000 may be bonded to the top of a heat dissipation pad 4800 to provide heat dissipation. The silicon substrate 2000 and the heat dissipation pad 4800 may be mutually bonded to each other using a non-conducting adhesive 4700 so as to form an electric insulator.
The above-described heat dissipation pad 4800, silicon substrate 2000, rectification unit 12 and bonding wires 2300 may form an integrated mold part 3000 using various kinds of molding materials such as a resin material or the like, and thus are integrally molded together. On the bottom surface of the mold part 3000, electrode pads L, N, A to F, A′ to F′, and 4400 may be formed at locations spaced apart from the heat dissipation pad 4800.
These electrode pads L, N, A to F, A′ to F′, and 44 may form electrical connections to the silicon substrate 2000 via wire bonding while being used as external connection electrodes for inputting/outputting electrical signals to/from the outside of the package.
Similarly to the exemplary embodiment shown in
As shown in
As shown in
Another exemplary embodiment of the present invention may be implemented such that all diodes used in the rectification unit 12 are mounted on the diode mounting pad 5100 in the form of individual elements using the conducting adhesive 4100.
In
As shown in
In
Therefore, as shown in
Further, in the exemplary embodiment of
As shown in
In particular, the LEDs of the channels CH1 and CH2 are arranged in a line for each channel and the LED driving circuit package 1000 is disposed between the LEDs of the respective channels, so that an arrangement of LEDs providing efficient lighting may be possible.
Meanwhile, a heat dissipation means for efficiently discharging heat radiated from the LED driving circuit package 1000 and the LEDs LED1 to LED8 may be provided on the substrate 8100 of the luminescence module 8000.
As shown in
Each of the LED units 13-1 to 13-4 according to the exemplary embodiment described in
As shown in
The LED package of
Although not shown in the drawing, a heat dissipation pad for effectively dissipating and discharging heat generated by the LED chip may be formed on the die attach area 6200. Further, on a surface opposite the one surface of the board to which the LED chip 5000 is attached and on which the electrode pad units P1 to P5 are formed, a plurality of terminal units corresponding to the electrode pad units P1 to P5 in a one-to-one correspondence may be formed so as to form electrical connections to the electrode pad units P1 to P5. These terminal units may be connected to a rectification circuit unit and may be configured to input/output driving current and set up connections to switches.
As shown in
The LED package shown in
For example, the p-type electrode 7310p of the first LED chip 7310 may be wire-bonded to the first electrode pad unit P1, the n-type electrode 7310n of the first LED chip 7310 and the p-type electrode 7320p of the second LED chip 7320 may be wire-bonded in common to the second electrode pad unit P2, the n-type electrode 7320n of the second LED chip 7320 and the p-type electrode 7330p of the third LED chip 7330 may be wire-bonded in common to the third electrode pad unit P3, the n-type electrode 7330n of the third LED chip 7330 and the p-type electrode 7340p of the fourth LED chip 7340 may be wire-bonded in common to the fourth electrode pad unit P4, and the n-type electrode 7340n of the fourth LED chip 7340 may be wire-bonded to the fifth electrode pad unit P5.
Using this connection structure, the four LED chips form a connection structure in which they are connected in series to each other. Further, the first electrode pad unit P1 and the fifth electrode pad unit P5 are connected to a rectification circuit unit, and the second to fourth electrode pad units P2 to P4 are respectively connected to a plurality of switches, thus enabling the LED units to be sequentially driven, as described above.
As shown in
Meanwhile, as shown in
Similarly to the above-described LED package of
The LED package of
In the connection structure of the LED chips, as shown in
Meanwhile, in the LED package of
As shown in
Meanwhile, similarly to the embodiment of
Further, as shown in
The exemplary embodiments described above with respect to
As described above, the series-connected LEDs are sequentially driven at constant current using AC voltage, so that current that increases or decreases in a stepped form can be provided as illustrated in
Furthermore, current at each stage is controlled to have constant magnitude, so that constant driving current can be provided even in the event of variation in AC voltage (distortion, or increase or decrease in the magnitude of voltage). Thus, the light output efficiency of AC-driven LEDs can be improved.
Referring to
Accordingly, an exemplary embodiment of the present invention provides an LED luminescence apparatus using AC power, in which the plurality of LED units can emit light during entire intervals without generating the above-described non-light-emitting areas.
Referring to
The configuration of the LED luminescence apparatus using AC power according to the present exemplary embodiment is substantially the same as the configuration of the LED luminescence apparatus using AC power according to the exemplary embodiment described above with respect to
Accordingly, for simplification of description, detailed descriptions of the AC power source 11, the rectification circuit unit 12, the plurality of LED units 13-1 to 13-N, the plurality of switches 14-1 to 14-N, and the plurality of constant current control circuit units 15-1 to 15-N of the LED luminescence apparatus using AC power according to the present exemplary embodiment will be omitted here.
However, the current comparison unit 16 according to the present exemplary embodiment further outputs the control signal SC, compared to the exemplary embodiment described above with respect to
The current comparison unit 16 may receive currents it to iN flowing through the plurality of switches 14-1 to 14-N from the constant current control circuit units 15-1 to 15-N, and generate a switching control signal SC to control turn-on/turn-off of the switch 22 of the light output comparison unit 20.
That is, the current comparison unit 16 receives the currents it to iN such that when any one of the currents reaches a preset value, the current comparison unit 16 outputs a control signal to switch the switch 22 to be in the open (turn-off) or close (turn-on) state.
For example, the current comparison unit 16 receives the currents it to iN from the constant current control circuit units 15-1 to 15-N such that when the current it reaches a minimum point, the current comparison unit 16 outputs the control signal SC to switch the switch 22 to be in the open (turn-off) state, and when the current iN reaches a maximum point, the current comparison unit 16 outputs the control signal SC to switch the switch 22 to be in the close (turn-on) state.
Referring to
One end of the current restriction unit 21 is connected to an output end of the rectification circuit unit 12. The other end of the current restriction unit 21 is connected to an anode of the first diode D1. The current restriction unit 21 is a circuit, which controls the magnitude of current provided to the capacitor C through the first diode D1 and current filled in the capacitor C, and may be configured by at least one resistance device.
A cathode of the first diode D1 is connected to one end of the capacitor C. The other end of the capacitor C is connected to the switch 22.
The switch 22 of the present disclosure may be configured by using a field effect transistor (FET) device, in which a reverse-direction diode is provided. The other end of the capacitor C may be connected to a drain terminal of the switch 22. A ground electrode may be connected to a source terminal of the switch 22. The switch control unit 23 may be connected to a gate terminal of the switch 22.
The switch control unit 23 receives the control signal SC input from the current comparison unit 16, and outputs a control signal, which controls the open (turn-off)/close (turn-on) state of the switch 22 depending on the control signal SC, to the gate terminal of the switch 22.
The anode of the second diode D2 is connected to a node of the first diode D1 and the capacitor C. The cathode of the second diode D2 is connected to a node of the first LED unit 13-1 and the current restriction unit 21.
In the present exemplary embodiment, the first diode D1 and the second diode D2 may be used for LEDs. If LEDs are implemented by the first diode D1 and the second diode D2, the light emission efficiency of the LED luminescence apparatus may increase.
The operation of the light output compensation unit 20 and the light emitting operation of the plurality of LED units 13-1 to 13-N, which are related to each other as described above, will be described with reference to
When the magnitude of the ripple voltage provided to the plurality of LED units 13-1 to 13-4 increases and becomes the driving voltage (forward voltage) Vf1 of the first LED unit 13-1, current flows through the first LED unit 13-1 so that the first LED unit 13-1 emits light (time t0 of
Subsequently, when the magnitude of the ripple voltage further increases, and the voltage applied to the plurality of LED units 13-1 to 13-N becomes the driving voltage of the first and second LED units 13-1 and 13-2 (when the magnitude of the ripple voltage becomes Vf2), current flows through the second LED unit 13-2 so that the second LED unit 13-2 emits light (time t1 of
Using this operation, control may be performed such that constant current flows through the first LED unit 13-1 and the second LED unit 13-2. As illustrated in
Similarly to the above-described procedure, when the ripple voltage further increases, and voltage applied to the plurality of LED units 13-1 to 13-N becomes the driving voltage of the first to third LED units 13-1 to 13-3 (when the magnitude of the ripple voltage becomes Vf3), current flows through the third LED unit 13-3 so that the third LED unit 13-3 emits light (time t2 of
Using this operation, control may be performed such that constant current flows through the first to third LED units 13-1 to 13-3. As illustrated in
Similarly to the above-described procedure, when the ripple voltage further increases, and voltage applied to the plurality of LED units 13-1 to 13-N becomes the driving voltage of the first to fourth LED units 13-1 to 13-4 (when the magnitude of the ripple voltage becomes Vf4), current flows through the fourth LED unit 13-4 so that the fourth LED unit 13-4 emits light (time t3 of
Using this operation, control may be performed such that constant current flows through the first to fourth LED units 13-1 to 13-4. As illustrated in
Furthermore, in the present exemplary embodiment, when the current i4 of the fourth constant current control circuit unit 15-4 reaches a first preset value, the current comparison unit 16 generates the control signal SC to close (turn on) the switch 22 of the light output compensation unit 20.
When the control signal SC is input, the switch control unit 23 closes (turns-on) the switch 22. Then, current flows through the rectification circuit unit 12, the current restriction unit 21, the first diode D1, the capacitor C, and the switch 22, and the capacitor C is filled with the ripple voltage rectified in the rectification circuit unit 12.
A signal output from the switch control unit 23 to the gate terminal of the switch 22 is a pulse width modulation (PWM) signal. The capacitor C is filled with voltage during the time when the switch 22 is turned on. Subsequently, when the ripple voltage passes over a peak and gradually decreases, and the current i4 of the fourth constant current circuit control unit 15-4 reaches a second preset value, a control signal SC to open (turn off) the switch 22 of the light output compensation unit 20 is generated.
When the control signal SC to open (turn off) the switch 22 is input, the switch control unit 23 opens (turns off) the switch 22. Then, the current path formed from the rectification circuit unit 12 to the capacitor C disappears so that the operation of filling the capacitor C with ripple voltage is stopped.
However, in order to avoid deteriorating the quality characteristics of the input power, in the present exemplary embodiment the capacitor C may be filled with current during the time when the most current flows through the plurality of LED units 13-1 to 13-N.
When the ripple voltage passes over a peak and gradually decreases, the LED units are sequentially turned off in the sequence from the fourth LED unit 13-4 to the first LED unit 13-1.
When the magnitude of the ripple voltage provided to the plurality of LED units 13-1 to 13-4 decreases and becomes the driving voltage Vf3 of the first to third LED units 13-1 to 13-3, the fourth LED unit 13-4 is turned off (time t4). In this case, the current comparison unit 16 senses that the current i4 of the fourth constant current control circuit unit 15-4 is not a preset value, and outputs the third switching control signal S3 to close (turn on) the third switch 14-3, so that the third switch 14-3 is turned on. The current comparison unit 16 outputs the first and second switching control signals S1 and S2 to maintain previous states, so that the first and second switches 14-1 and 14-2 maintain their open (turn-off) states. At the same time, the third switch 14-3 maintains its turn-on state, and the third constant current control unit 15-3 initiates constant current control in response to a control signal from the third constant current control circuit unit 15-3 such that the reference current preset to drive the first to third LED units 13-1 to 13-3 is maintained. The light emitting operations of the first to third LED units 13-1 to 13-3 correspond to the time intervals t4 and t5 in
When the magnitude of the ripple voltage further decreases and becomes the driving voltage Vf2 of the first and second LED units 13-1 and 13-2, the third LED unit 13-3 is turned off (time t5). In this case, the current comparison unit 16 senses that the current i3 of the third constant current control circuit unit 15-3 is not a preset value, and outputs the second switching control signal S2 to close (turn on) the second switch 14-2, so that the second switch 14-2 is turned on. The current comparison unit 16 outputs the first switching control signal S1 to maintain a previous state, so that the first switch 14-1 maintains its open (turn-off) state. At the same time, the second switch 14-2 maintains its turn-on state, and the second constant current control unit 15-2 initiates constant current control in response to a control signal from the second constant current control circuit unit 15-2 such that the reference current preset to drive the first and second LED units 13-1 and 13-2 is maintained. The light emitting operations of the first and second LED units 13-1 and 13-2 correspond to the time intervals t5 and t6 in
Similarly to the above-described procedure, when the magnitude of the ripple voltage further decreases and becomes the driving voltage Vf1 of the first LED unit 13-1, the second LED unit 13-2 is turned off (time t6). In this case, the current comparison unit 16 senses that the current i2 of the second constant current control circuit unit 15-2 is not a preset value, and outputs the first switching control signal S1 to close (turn on) the first switch 14-1, so that the first switch 14-1 is turned on. The current comparison unit 16 outputs the second to fourth switching control signals S2 to S4 to maintain previous states, so that the second to fourth switches 14-2 to 14-4 maintain their open (turn-off) states. At the same time, the first switch 14-1 maintains its turn-on state, and the first constant current control unit 15-1 initiates constant current control in response to a control signal from the first constant current control circuit unit 15-1 such that the reference current preset to drive the first LED unit 13-1 is maintained. The light emitting operation of the first LED unit 13-1 corresponds to the time intervals t6 and t7 in
When the ripple voltage further decreases, and voltage applied to the plurality of LED units 13-1 to 13-N becomes threshold voltage Vd of the second diode D2, current paths to the capacitor C, the second diode D2, and the first LED unit 13-1 are formed. Then, the first LED unit 13-1 emits light by current provided from the capacitor C. The light emitting operation of the first LED unit 13-1 corresponds to the time intervals t7 and t8 in
In the present exemplary embodiment, the threshold voltage Vd of the second diode D2 is set to below the first driving voltage Vf1, but may be modified. For example, if the threshold voltage Vd of the second diode D2 is set to the second driving voltage Vf2, the light emitting operations of the first and second LED units 13-1 and 13-2 may correspond to the time intervals t6 to t10 in
As described, in the present exemplary embodiment, current filled in the capacitor C of the light output compensation unit 20 is applied to the LED units at the LED non-light-emitting intervals according to the exemplary embodiment described above with respect to
A subsequent current control operation is performed by repeating the constant current control performed during the above-described intervals t0 to t8, and thus detailed descriptions thereof will be omitted here.
The present exemplary embodiment has been described such that LED driving current increases or decreases in a stepped form by multi-stage constant current control. However, the present disclosure is not limited thereto. The waveform of the LED driving current may be modified by variously setting reference currents for constant current control.
In the present exemplary embodiment, the series-connected LEDs may be sequentially driven at constant current using AC voltage, so that current that increases or decreases in a stepped form can be provided as illustrated in
Furthermore, current at each stage is controlled to have constant magnitude, so that constant driving current can be provided even in the event of variation in AC voltage (distortion, or increase or decrease in the magnitude of voltage). Thus, the light output efficiency of AC-driven LEDs can be improved.
Furthermore, the LED units may be driven at the areas in which LEDs do not emit light due to AC power, by using the current filled in the capacitor C, so that the LED luminescence apparatus can emit light during the entire interval of AC power without generating non-light-emitting intervals (LED off intervals).
It will be apparent to those skilled in the art that various modifications and variation can be made in the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.
This application claims the benefit of U.S. Provisional Patent Application Nos. 61/437,288, filed on Jan. 28, 2011; 61/437,296, filed on Jan. 28, 2011; 61/437,932, filed on Jan. 31, 2011; 61/438,304, filed on Feb. 1, 2011; 61/438,308, filed on Feb. 1, 2011; 61/442,732, filed on Feb. 14, 2011; 61/467,782, filed on Mar. 25, 2011; and 61/565,574, filed on Dec. 1, 2011, which are all hereby incorporated by reference for all purposes as if fully set forth herein.
| Number | Date | Country | |
|---|---|---|---|
| 61437288 | Jan 2011 | US | |
| 61437296 | Jan 2011 | US | |
| 61565574 | Dec 2011 | US | |
| 61437932 | Jan 2011 | US | |
| 61438304 | Feb 2011 | US | |
| 61438308 | Feb 2011 | US | |
| 61442732 | Feb 2011 | US | |
| 61467782 | Mar 2011 | US |
