This application claims priority to China Application Serial Number 201810421355.6, filed May 4, 2018, which is herein incorporated by reference in its entirety.
The present disclosure relates to a light emitting element driving device. More particularly, a high efficiency conversion device for processing a part of load energy to drive a light emitting element.
Light-emitting diode (LED) is a kind of a light emitting device driven by the current. The brightness of the LED is adjusted by controlling the current flowing through the LED. In the prior art, when the LED is connected to a DC voltage source for operation, the operating current of the LED is adjusted by a resistor, which is connected in series with the LED. The advantage of this circuit is simple and the disadvantage is low efficiency. In another prior art, the operating current of the LED is adjusted through a power converter. Compared with the above circuit with the series resistance, the circuit with the power converter has higher efficiency. However, in this circuit, the load of the LED is completely through the power converter. If this circuit is applied to the off-line LED driver, when a power factor correction circuit is added to this circuit to form a two-stage architecture, the overall operating efficiency still cannot be improved.
When designing a LED driving device, factors to be considered include the complexity of the circuit structure, the conversion efficiency and the stability of the current. Therefore, how to balance the above factors is very important.
One aspect of the present disclosure is a light emitting element driving device. The light emitting element driving device comprises an energy storage element, a power source and a converter circuit. The power source is electrically connected to a positive terminal of the energy storage element through a light emitting element in order to provide a current to the light emitting element and to charge the energy storage element. The converter circuit is electrically connected to the power source and the energy storage element, wherein the converter circuit comprises an inductance. When the converter circuit is in a first operational status, the energy storage element charges the inductance. When the converter circuit is in a second operational status, the inductance is discharged to the power source.
Another aspect of the present disclosure is a driving method of a light emitting element. The driving method comprises the following steps: providing a current to a light emitting element through a power source and charging an energy storage element, wherein the power source is electrically connected to a first terminal of the light emitting element, and a positive terminal of the energy storage element is directly connected to a second terminal of the light emitting element. Turning on a first switch element in order that the energy storage element charges a inductance when the power source provides the current to the light emitting element continuously. Turning off the first switch element in order that the inductance discharge to the power source.
Another aspect of the present disclosure is a light emitting element driving device. The light emitting element driving device comprises an energy storage element, a power source, a inductance, a first switch element and a second switch element. The power source is electrically connected to a positive terminal of the energy storage element through a light emitting element in order to provide a current to the light emitting element and to charge the energy storage element. The inductance is electrically connected to the energy storage element. The first switch element is electrically connected to the energy storage element and the inductance, wherein the energy storage element is configured to charge the inductance when the first switch element is turned on. The second switch element is electrically connected to the inductance and the power source, wherein the inductance discharges to the power source through the second switch element when the first switch element is turned off.
It is to be understood that both the foregoing general description and the following detailed description are by examples, and are intended to provide further explanation of the disclosure as claimed.
The present disclosure can be more fully understood by reading the following detailed description of the embodiment, with reference made to the accompanying drawings as follows:
For the embodiment below is described in detail with the accompanying drawings, embodiments are not provided to limit the scope of the present disclosure. Moreover, the operation of the described structure is not for limiting the order of implementation. Any device with equivalent functions that is produced from a structure formed by a recombination of elements is all covered by the scope of the present disclosure. Drawings are for the purpose of illustration only, and not plotted in accordance with the original size.
It will be understood that when an element is referred to as being “connected to” or “coupled to”, it can be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element to another element is referred to as being “directly connected” or “directly coupled,” there are no intervening elements present. As used herein, the term “and/or” includes an associated listed items or any and all combinations of more.
With regard to a driving device for LED, the conventional means connect a resistor in series with the LED to serve as a power converter in order that a constant current flow through the LED. The advantage of this means is simple and the disadvantage of this means is low efficiency, and it needs to adjust the resistance according to the LED specification. In order to improve efficiency, many improved power converters have been designed. Common types of power converters include buck converters, boost converters, and buck-boost converters, but the efficiency of these methods is still not ideal.
Please refer to
The converter circuit 130 is electrically connected to the power source 110 and the energy storage element C1. The converter circuit 130 at least includes an inductance L1. When the converter circuit 130 is in a first operational status, the energy storage element C1 charges the inductance L1. When the converter circuit 130 is in a second operational status, the inductance L1 is discharged (or fed back) to the power source 110 to achieve the function of energy-recycling.
This present disclosure controls the charging and discharging of the inductance L1 repeatedly, so that the energy of the energy storage element C1 passes through the inductance L1 and is fed back to the power source 110. Accordingly, the voltage across the energy storage element C1 is controlled, thereby stabilizing the voltage across the light emitting element 120 and the first current I1.
The circuit architecture of the present disclosure is to connect the output of the power source 110 in parallel to the series branch of the light emitting element 120 and the energy storage element C1. In this circuit architecture, the driving device 100 has the phenomenon of “V110=V120+VC1”. That is, the cross voltage across the power source 110 (V110) is equal to the sum of the cross-voltages of the light emitting element 120 and the energy storage element C1. In the present disclosure, since the converter circuit 130 process part of the load energy and can be energy-recycling, the driving apparatus 100 has a better conversion efficiency than the conventional power converter. In particular, when the power source 110 is the output of another stage converter circuit for providing power to the light emitting element 120, the overall conversion efficiency improved by the present disclosure will be more apparent.
In some embodiments, the power source 110 includes an AC voltage source 111, an adjustment circuit 112, and an input capacitor C2. The adjustment circuit 112 is electrically connected to the AC voltage source 111 for receiving an AC voltage generated by the AC voltage source 111 and outputting an adjustment voltage. In some embodiments, the adjustment circuit 112 is a Power Factor Correction (PFC), a High Voltage Direct Current (HVDC) or a bridge rectifier. In some embodiments, the power source 110 may be a battery. The input capacitor C2 is electrically connected to the output of the adjustment circuit 112 for receiving the adjustment voltage. The input capacitor C2 provides energy to the light emitting element 120 and the energy storage element C1 to provide a first current I1 to the light emitting element 120. In some embodiments, the input capacitor C2 is connected in parallel with the series branch of the light emitting element 120 and the energy storage element C1, and is used to receive the energy of energy-recycling from the inductance L1.
In some embodiments, the converter circuit 130 of the light emitting element driving device 100 further includes a first switch element W1 and a second switch element W2. The first switch element W1 is electrically connected to the inductance L1 and the energy storage element C1. The second switch element W2 is electrically connected to the inductance L1 and the power source 110. When the first switch element W1 is turned on, the energy storage element C1 is configured to charge the inductance L1. The “charge” described here means that the second current I2 flowing through the inductance L1 is gradually increased to store energy. When the second switch element W2 is turned on or the first switch element W1 is turned off, the inductance L1 is configured to discharge to the power source 110. Compared with the conventional power converter, the circuit architecture of the present disclosure provides a current path to the power source 110 through the light emitting element 120 and the energy storage element C1, so that the conversion efficiency can be improved.
In order for those skilled in the art to understand the technology of the present disclosure, the operation of the light emitting element driving device will be described here. Please refer to
First, as shown in
As the voltage stored by the energy storage element C1 increases, the first current I1 provided with the light emitting element 120 will gradually decrease, and the converter circuit 130 will be in the first operational status (As shown in
Referring to
In some embodiments, the first switch element W1 is controlled to switch between turn on and turn off according to a reference signal, so that the inductance L1 is repeatedly charged and discharged (Refer to
In order to achieve the aforementioned purpose, the converter circuit 130 can use a corresponding control method. In some embodiments, when the converter circuit 130 is further controlled in a Boundary Conduction Mode (BCM) between the CCM and the DCM, the electrical characteristics of the driving device 100 will conform to the identity: “I1=(I2-peak)/2”. That is, the first current I1 on the light emitting element 120 is equal to half of the peak current (e.g., the second current I2 flowing through the inductance L1) in the converter circuit 130.
For example, if the power source 110 provides an input voltage of 48 volts, the inductance of the inductance L1 is 40 uH, the expected operating state of the light emitting element 120 is 36 volts and 1050 milliamperes, the first switch element W1 operates at 100 kHz, and the period 78%. At this time, the voltage across the energy storage element C1 should be 12 volts and the peak current in the converter circuit 130 is 2100 milliamps.
Since the converter circuit 130 has the characteristics of the aforementioned identity when operated in the BCM, the driving device 100 can detect the current value of the converter circuit 130 and control the converter circuit 130 to be in the first operational status or the second operational status. In some embodiments, the converter circuit 130 of the light emitting element driving device 100 further includes a control circuit 131. The control circuit 131 is configured to output the control signal to the first switch element W1 according to the reference signal to control the first switch element W1 to turn on or off. The control circuit 131 is further configured to change the time point of turning on or turning off of the first switch element W1 according to the detection current flowing through at least one of the first switch element W1, the second switch element W2, and the inductance L1.
For example, when the detection current reaches a default value (e.g., 2100 mA), the control circuit 131 turns off the first switch element W1 so that the converter circuit 130 is in the second operational status. In some embodiments, when the control circuit 131 controls the first switch element W1 to be turned on, the first switch element W1, the energy storage element C1, and the inductance L1 form a charging path P1. On the other hand, when the control circuit 131 controls the first switch element W1 to be turned off, the second switch element W2 which are turned on, the inductance L1, and the power source 110 will form the discharge path P2.
Please refer to
Compared to the embodiment shown in
In some embodiments, as shown in
As described above, if the converter circuit 130 is operated in the BCM, the first current I1 on the light emitting element 120 is equal to half of the peak current in the converter circuit 130 (e.g., the peak value of the second current I2 flowing through the inductance L1). Therefore, in some embodiments, the converter circuit 130 detects a current (e.g., second current I2, third current I3, or fourth current I4) flowing through at least one of the first switch element W1, the second switch element W2, and the inductance L1, and then, controls the first switch element W1 to turn on or off according to the detection current. For example, if the light emitting element 120 emits an ideal light intensity and the required first current I1 is 1050 mA, the light emitting element driving device 100 can set twice the first current I1 as a default value (e.g., 2100 mA). When the converter circuit 130 detects that the detection current reaches a default value, the control circuit 131 controls the first switch element W1 to turn off so that the converter circuit 130 is in the second operation state. In other embodiments, the light emitting element 120 may electrically connected in series with a current detecting element (e.g., a resistor), so that the converter circuit 130 may detect the first current I1 on the light emitting element 120, and control the first switch element W1 to turn off when the first current I1 reaches a default value.
The present disclosure can stably maintain the first current I1 flowing through the light emitting element 120. In other embodiments, when the light intensity of the light emitting element 120 needs to be adjusted, the first current I1 on the light emitting element 120 may be changed correspondingly by changing the value of the default value. Referring to
It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present disclosure without departing from the scope or spirit of the present disclosure. In view of the foregoing, it is intended that the present disclosure cover modifications and variations of this present disclosure provided they fall within the scope of the following claims.
Number | Date | Country | Kind |
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201810421355.6 | May 2018 | CN | national |