Patent Application
20100320926
1. Field of the Invention
The present invention relates to a light modulation device and method thereof; in particular, to a sine wave light modulation control method and a device that utilizes AC voltage.
2. Description of Related Art
Light modulation device for light fixtures generally use thyristor phase control, which utilizes the advantageous characteristics and features of a thyristor for adjusting the size of the conduction angle via phase control, so as to achieve the object of controlling the light output of light fixtures. Due to the fact that thyristors are permanent, non-consumable components, and their breakdown rate is low, this type of thyristor phase control for light modulation is still widely used today.
Refer to
However, the aforementioned phase modulation control device for adjusting light performs positive phase modulation through SCR, for the simple fact that this type of light modulation control method is easy and effective. However, phase control generates a large amount of inrush current, leading to noise at the lamp, and therefore is likely to reduce the product life-span of the lamp. Additionally, this type of light modulation also generates high frequency interference, which may negatively affect power systems, and this type of light modulation method decreases the power factor of the load, so the alternating current (AC) voltage that has been inputted as power source cannot be effectively utilized, leading to wastage of power resource.
Therefore currently there are also light modulation methods that perform negative phase modulation via an insulated gate bipolar transistor (IGBT), so as to decrease effect of shortened product life-span of the lamp by limiting the inrush current. However, this type of control method still utilizes phase control, so that the problem issues of frequency interference, limited power efficiency, and low power factor remain.
The present invention provides a sine wave light modulation control method and device, so as to resolve the issues of the light modulation method of the prior art, such as a low power factor and limited power efficiency. Thereby, an object of the present invention is to directly provide a sine wave to a lamp, and to control the light intensity of the lamp by controlling the magnitude of the sine wave voltage, so as to noticeably raise the power factor.
In order to resolve the aforementioned technical issue, according to an embodiment of the present invention, a sine wave light modulation control method is provided, for controlling the light output of a lamp, the method includes: providing an AC voltage; rectifying the AC voltage into a first direct current (DC) pulse; modulating the first DC pulse into a modulated wave via pulse width modulation (PWM); filtering the modulated wave into a second DC pulse; switching the second DC pulse into a modulated AC voltage via a switching unit for use by the lamp; wherein the switching of the switching unit is by alternatingly switching the second DC pulse to a first conduction path and a second conduction path so as to output the modulated AC voltage, and the directions of the first conduction path and the second conduction path for the second DC pulse transmitted to the lamp are opposite to each other.
In order to resolve the aforementioned technical issue, according to an embodiment of the present invention, a sine wave light modulation control device is provided, for controlling the light output of a lamp, the device includes: a rectifier unit, a modulator unit, a filter unit, a switching unit, and a control unit. Therein the rectifier unit is used for rectifying an AC voltage to output a first DC pulse; the modulator unit is coupled to the rectifier unit and is used for modulating the first DC pulse into a modulated wave via pulse width modulation; the filter unit is coupled to the modulator unit and is used for filtering the modulated wave into a second DC pulse; the switching unit is coupled to the filter unit, and the switching unit provides a first conduction path and a second conduction path for alternatingly switching between the two paths so as to output a modulated AC voltage for use by the lamp; the control unit is coupled to the switching unit, the control unit is used for controlling the switching unit to alternatingly provide the second DC pulse to the first conduction path and the second conduction path so as to output the modulated AC voltage, and the directions of the first conduction path and the second conduction path for the second DC pulse transmitted to the lamp are opposite to each other.
Therefore in the above embodiment, the present invention switches the second DC pulse into the modulated AC voltage, so that the modulated AC voltage is a sine wave, thereby the lamp operates with sine wave, so as to achieve the technical effect of elevating power factor.
The aforementioned illustrations and following detailed descriptions are exemplary for the purpose of further explaining the scope of the present invention. Other objectives and advantages related to the present invention will be illustrated in the subsequent descriptions and appended drawings.
The present invention provides a sine wave light modulation control method and device with high power factor, for modulating the light intensity of a lamp, and a technical feature of the present invention is to directly provide sine wave for use by the lamp, so as to achieve the effect of light modulation by changing the voltage of the sine wave.
Please refer to
First an AC voltage is provided from a power source (S301), and the power source maybe an utility outlet;
Next the AC voltage is rectified into a first DC pulse as output signal (S303);
Then modulate the first DC pulse into a modulated wave (S305), wherein the modulation of this step is done by high frequency pulse width modulation (PWM) to the first DC pulse, so as to determine the voltage of the first DC pulse according to the duty cycle of the pulse width;
The modulated wave is filtered into a second DC pulse for output (S307), because the modulated wave is generated by applying high frequency pulse width modulation to the first DC pulse, so that the modulated wave includes some high frequency signals. Therefore, the filtering in this step filters out the high frequency signal within the modulated wave via low-pass filtering;
Next the second DC pulse is converted into a modulated AC voltage via DC/AC conversion (S309), and the modulated AC voltage is a sine wave;
Lastly, the modulated AC voltage is provided directly for use by the lamp (S311), so that the lamp may light up according to the modulated AC voltage, thereby the light intensity of the lamp may change according to the voltage of the modulated AC voltage.
The aforementioned DC/AC conversion of step S309 is done by a switching unit that switches the output path of the second DC pulse, specifically the second DC pulse will be alternatingly switched to be outputted through the first conduction path and the second conduction path for every half cycle of the second DC pulse, and thereby converted by switching the second DC pulse into the modulated AC voltage, furthermore the directions of the first conduction path and the second conduction path for the second DC pulse transmitted to the lamp are opposite to each other.
For further explanation of the various wave forms resulting from the steps in
Please refer to
Next please refer to
Next please refer to
The modulator unit 42 is coupled to the output terminal of the rectifier unit 40, so as to receive the first DC pulse, and the first DC pulse is modulated via high frequency pulse width modulation into a modulated wave for controlling voltage. The modulator 42 of the present embodiment is composed of a power switch IGBT1 and a pulse width modulation driving circuit 421, wherein the pulse width modulation driving circuit controls the conduction or cut-off of the power switch IGBT1 via high frequency, thereby the first DC pulse may be modulated so as to generate the modulated wave that may vary in voltage.
The filter unit 44 is coupled to the output of the modulator unit 42, for receiving the modulated wave, and the filter unit 44 filters the high frequency signal of the modulated wave so as to output a second DC pulse. The filtering unit 44 of the present embodiment is a low pass filter circuit.
The switching unit 46 is coupled to the output of the filter unit 44, for converting by switching the second DC pulse into the modulated AC voltage to the lamp for use. The switching unit 46 of the present embodiment provides a plurality of switches, so as to form different conduction paths for the second DC pulse to travel to the lamp. The switching unit 46 shown in
The control unit 48 is coupled between the switching unit 46 and the modulator unit 42; the control unit 48 is primarily for controlling the operation of the switching unit 46 and the modulator 42. The control unit 48 outputs a control signal PWM1 to the pulse width modulation driving circuit 421 according to an input voltage Vset, whereby the input voltage Vset is used for adjusting the voltage of the sine wave that is provided to the lamp. The adjustment of the input voltage Vset may be initiated by pressing a key or button. For example, when the input voltage Vset may be adjusted between 0-100V AC, then if the input voltage is 50V AC, then the control signal PWM1 outputted by the control unit 48 is a pulse with 50% duty cycle.
Furthermore, in order to ensure the voltage of the sine wave utilized by the lamp accurately adheres to the input voltage Vset, the control unit 48 adopts feedback control mechanism. The control unit 48 receives a feedback voltage from the lamp, and compares this feedback voltage with the input voltage Vset. When the feedback voltage is greater than the input voltage Vset, then the control unit 48 lowers the duty cycle of the control signal PWM1; on the other hand if the feedback voltage is less than the input voltage Vset, then the control unit 48 increases the duty cycle of the control signal PWM1. As to how the control unit 48 receives this feedback voltage, this technique is will known to those skilled in the art, for example a transformer T1 may be connected at two ends of the lamp so as to receive the voltage at the two ends of the lamp.
Additionally, the control unit 48 also provides control of the switching unit 46. For example, the control units 48 may control the second DC pulse to alternatingly pass through the first conduction path or the second conduction path so as to reach the lamp, by controlling the conduction time of the plurality of switches SW1-SW4. To be more specific, the control unit 48 receives AC voltage from input Vin, and when the AC voltage is at the positive half cycle then the control unit 48 controls to conduct the switch SW1 and the switch SW4, and to cut-off the switch SW2 and the switch SW3; on the other hand, when the AC voltage is at the negative half cycle then the control unit 48 controls to conduct the switch SW2 and the switch SW3, and to cut-off the switch SW1 and the switch SW4.
Next please refer to
The modulator unit 52 is coupled to the output terminal of the rectifier unit 50, so as to receive the first DC pulse, and the first DC pulse is modulated via high frequency pulse width modulation into a modulated wave for controlling voltage. The modulator unit 52 is includes two power switches IGBT2 and IGBT3, and a pulse width modulation driving circuit 521. Therein the pulse width modulation driving circuit 521 controls the conduction and cut-off of the power switches IGBT2 and IGBT3 at high frequency. Thereby, the first DC pulse with separated positive and negative half cycle may be modulated so as to generate the modulated wave that may vary in voltage.
The filter unit 54 is coupled to the output of the modulator unit 52, for receiving the modulated wave with separated positive and negative half cycle, and the filter unit 54 filters the high frequency signal of the modulated wave via low-pass filtering into a second DC pulse with separated positive and negative half cycle. The filter unit 54 of the present embodiment includes 2 low-pass filter circuits so as to respectively filter the modulated wave with separated positive and negative half cycle.
The switching unit 56 is coupled to the output of the filter unit 54, for converting by switching the second DC pulse with separated positive and negative half cycle into the modulated AC voltage to the lamp for use. The switching unit 56 of the present embodiment provides different conduction paths for the second DC pulse to travel to the lamp via a plurality of switches. The switching unit 56 shown in
The control unit 58 is coupled between the switching unit 56 and the modulator unit 52; the control unit 58 is primarily for controlling the operation of the switching unit 56 and the modulator unit 52. The control unit 58 outputs two control signals PWM2, PWM3 to the pulse width modulation driving circuit 521 according to an input voltage Vset, the input voltage Vset is used for adjusting the voltage of the sine wave that is provided to the lamp for use.
Furthermore, in order to ensure the voltage of the sine wave utilized by the lamp accurately adheres to the input voltage Vset, the control unit 58 adopts feedback control mechanism, the feedback control mechanism is the same as aforementioned
The aforementioned power switch may be an insulated gate bipolar transistor (IGBT) or a metal-oxide-semiconductor field-effect transistor (MOSFET). The plurality of switches may be a silicon controlled rectifier (SCR). The control unit may be a micro-processor, a micro controller unit (MCU) or a system on chip (SOC), however the examples of the power switch, the plurality of switches, and the control unit given here are not meant to be limiting, any other electronic components that may accomplish equivalent functions are deem to be within the scope of the present invention.
As aforementioned, the sine wave light modulation control method of the present invention provides a sine wave directly for use by the lamp after being processed via the steps in
The descriptions illustrated supra set forth simply the preferred embodiments of the present invention; however, the characteristics of the present invention are by no means restricted thereto. All changes, alternations, or modifications conveniently considered by those skilled in the art are deemed to be encompassed within the scope of the present invention delineated by the following claims.
