JP2005267357A - Power supply control circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power supply control circuit by which stable, efficient power supply is available by avoiding the peak-charging of nonlinear-load charge storage elements and dimming as well as overvoltage, and current surge protection are available when the power supply control circuit is applied to a low-voltage lighting circuit load. <P>SOLUTION: An AC voltage is applied to a first terminal BLK and a second terminal WHT. The power supply control circuit 100 includes a first power control circuit 108 and a second power control circuit 112 for controlling a first switching element 102 and a second switching element 104 providing currents to a load 106, respectively. The power supply control circuit 100 determines intervals of current intermission for the switching elements defining the voltage elevation level of the circuits. The switching elements 102, 104 are controlled to be non conductive during a period with the peak voltage of the input AC voltage as a center. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an electronic circuit, and more particularly, to a power supply control circuit that controls electric power acting on a load.

  In the well-known technique, there are various types of circuits that can limit the energy of the circuit. For example, when a dimming circuit is applied to a lamp, the luminance of the light source can be adjusted. US Pat. Nos. 5,686,799, 5,986,617, 5955841, which are representative examples of power supply control, dimming or feedback circuits, can be cited as references.

  However, known power supply control / dimming circuits typically degrade large amounts of performance in the case of non-linear loads, and some known circuits have load feedback and generate a large amount of electromagnetic interference (EMC). Reduces circuit performance and limits the use of feedback.

  As shown in FIG. 1, a dimming circuit 10 of a representative example includes a diode AC switching D (DIAC) connected to a gate terminal of a triac (TRIAC) TR, a resistor R connected to a potentiometer P, a resistor R, and a triac TR. And a black cable terminal BLK connected to the load LD and a white cable terminal WH connected to the load LD. The load LD is connected to the potentiometer P and the triac TR.

  As shown in FIG. 2, when the voltage across the potentiometer reaches a predetermined level VT, the diode AC switching D is started and the triac TR can switch the circuit to a conducting state. The input signal IS has a conducting area CR and a non-conducting area NCR according to the starting time of the diode AC switching D.

  These circuit designs may be effective for linear loads, but may cause circuit instability for non-linear loads. The capacitor and other energy storage devices are charged up to a certain voltage level and correspond to the peak Vp of the input signal. In other words, the non-linear load determines the voltage level of charging. In addition, current surges do not occur at an optimal time, thus degrading circuit performance.

  Accordingly, it is an object of the present invention to solve the above-mentioned drawbacks.

  A main object of the present invention is to provide a power supply control circuit capable of charging a nonlinear load in a stable and efficient state while avoiding peak charging of a charge storage element. When the present invention is applied to a lighting circuit, it can adapt to the demand of providing a low voltage level and can provide dimming or overvoltage and current surge protection by energizing the load.

  On the other hand, a power supply control circuit device according to the present invention includes first and second switching elements and a first power supply control circuit. The first and second switching elements are connected across the first and second rails to supply current to the load, the first power supply control circuit is connected to the first switching element, and the first power supply control circuit is AC When located in a portion during a half cycle of the signal, the first switching element is biased to be in a non-conductive state, the load is energized, and the peak voltage of the half cycle of the AC signal during the partial cycle is Occurs when the voltage between the first and second rails is greater than a predetermined critical voltage. In the embodiment, the center point of the first switching element in the non-conductive section coincides with the peak of the AC signal. With this structure, the energy storage element is charged to a level that matches a predetermined critical voltage rather than the peak voltage of a known circuit. This is because the predetermined voltage corresponds to the peak voltage.

  The power supply control circuit device according to the present invention further includes a current sensing circuit that is connected to the first switching element and provides current surge protection.

Hereinafter, the structure and features of the present invention will be described based on examples and drawings.
As shown in FIG. 3, in the power supply control circuit device 100 according to the embodiment of the present invention, the first and second switching elements 102 and 104 are connected by a half bridge to supply a current to the load 106, and the first power supply control circuit 108. Is connected between the first rail 110 and the first switching element 102, and the second power supply control circuit 112 is connected between the second switching element 104 and the second rail 114, and is connected to the first and second inductors L1. -1, L1-2 and capacitor C1 can provide EMC filtering for the input signals at the first and second terminals BLK, WHT. In an embodiment, the first input terminal BLK matches a known black cable, and the second input terminal WHT matches a known white cable, and can provide a standard 120V AC signal.

  In general, the power supply control circuits 108 and 112 determine the conduction and non-conduction intervals of the switching elements 102 and 104. Thereby, even in the case of a non-linear load, the energy storage device (for example, a large-capacity capacitor) is charged to a predetermined level. That is, the capacitor is released from being charged at the peak time of voltage (ie, peak charging). Compared to known circuits, the present invention significantly reduces surge current.

  FIG. 4 shows the structure of the circuit actually implemented in FIG. 3, in which similar reference elements are indicated by similar reference numerals. As shown in the figure, the first and second power supply control circuits 108 and 112 are activated when the AC signal of the load 106 has a negative half cycle. Accordingly, it is considered that the power supply control circuit can interpret the operation of another power supply control circuit by its operation. The first and second power supply control circuits are also shown in the drawing, and one of the power supply control circuits controls the switching element.

  The first and second switching elements 102 and 104 are composed of MOSFET devices and include gate terminals Q11G and Q01G, source terminals Q11S and Q01S, and drain terminals Q11D and Q01D, respectively. The first switching element 102 has a source terminal Q11S connected to the first rail 110, a drain terminal Q11D connected to the load 106 by connection to the first load terminal 106b, and a gate terminal Q11G connected to the first power supply control circuit 108. Is done. The second switching element 104 has a drain terminal Q01D connected to the second load terminal 106a, a source terminal Q01S connected to the second rail 114, and a gate terminal Q01G connected to the second power supply control circuit 112.

  These switching devices consist of BJT transistors and FET transistors. Those who are familiar with this technology can meet the demands of individual applications in place of a variety of switching devices with equivalent effects. Although the present invention takes a half-bridge structure as an example, other structures such as a full-bridge structure can be applied to the present invention.

  As shown in the lower right part of FIG. 4, the second power supply control circuit 112 includes a first switching control element Q02 made of a bipolar transistor, a base terminal B, a connector terminal C, and an emitter terminal E. The connector terminal C is connected to the gate terminal Q01G of the second switching element 104, and the emitter terminal E is connected to the second rail 114. The first potentiometer P01 has a first terminal connected to the second rail 114 and a second terminal connected to the base terminal B, and is connected to the first rail 110 via a resistor PR1 and a diode DR1.

  The first capacitor C01, the first resistor R01, and the first diode D01 are connected in series and connected across the first and second rails 110 and 114. The second and third resistors R02 and R03 are connected in series and connected between the gate terminal Q01G and a certain point, and a certain point thereof is located between the first capacitor C01 and the first resistor R01. The capacitor CD is connected between the second rail 114 and a certain point, and the certain point is located between the second and third resistors R02 and R03.

  In operation, the second switching element 104 is biased to act on a certain level on the gate terminal G01G and become conductive, similar to operating this circuit and applying current to the load 106, A certain level is stored in the first capacitor C01 in advance, and is charged through the first diode D01 and the first resistor R01. The energy of the first capacitor C01 maintains the conduction state of the second switching element 104. The first power supply control circuit 108 provides an AC signal to the load 106 by biasing the first switching element 102 so as to be in a conductive state. The switching elements 102 and 104 are controlled so as to be biased to a half cycle, respectively, and reverse conductivity of the two switching elements is achieved via the well-known first and second freewheeling diodes FW1 and FW2. Each freewheeling diode is connected across a transistor.

  When the voltage of the first potentiometer P01 is greater than a predetermined critical voltage, a certain level is applied to the base terminal B of the first switching control Q02, and the first switching control element is switched to a conductive state. When the first switching control element Q02 is switched to the conductive state, the gate terminal Q01G of the second switching element 104 is connected to the second rail 114, thereby turning off the second switching element. The first potentiometer P01 reads and adjusts the voltage between the first and second rails 110 and 114, the resistor RR1 and the diode DR1, determines a predetermined critical voltage Vth between the two rails 110 and 114, and It is possible to efficiently activate one switching control element Q02 (conduction state) and turn off the second switching element 104 (non-conduction state).

  In the embodiment, the first and second power supply control circuits 108 and 112 correspond to the potentiometers in a relative operation method, so that the first and second switching elements 102 and 104 are almost the same in the AC load waveform. Turn off at the moment.

  FIG. 4A displays the circuit of FIG. 4 and adds specific numerical values for the elements thereto, which are not intended to limit the present invention to specific numerical values, but are given only as examples. Those skilled in the art can arbitrarily change this value according to specific demands.

  As shown in FIG. 5A and FIG. 4, PNC1 and PNC2 are the time points when the first and second switching elements 102 and 104 are turned off (non-conduction), and the first and second switching elements are activated in PC1 and PC2. (Non-conductive areas) NCR1 and NCR2 for displaying the non-conductive state of the switching elements 102 and 104 every half cycle. According to the figure, when the voltage of the potentiometer P01 reaches the critical voltage Vth and coincides with the peak charging voltage Vc, the switching elements 102 and 104 activated (conducted) in a half cycle are turned off between the PNC1 and the corresponding point PC1, When the signal between the first and second rails falls below the critical voltage Vth, the switching element 102 or 104 returns to the conductive state. The critical voltage Vth of the potentiometer P01 coincides with the voltage Vc between the two rails 110 and 114, and can be lowered below the peak voltage Vp of the AC load signal.

  FIG. 5B shows that the current surges CS1-4 correspond to the change points PNC1, PNC2, PC1, and PC2 in FIG. 5A. As shown in the figure, the known circuit has two current surges, whereas the circuit of the present invention has four current surges CS1-4 per period, and the frequency of the current surge is twice that of the input signal. is there. For example, if the current surge frequency is about 120 Hz instead of 60 Hz, light flickering and noise can be reduced. Further, since the magnitudes of the four current surges CS1-4 are much smaller than the peak of the AC signal of the known circuit, it is possible to greatly reduce the burden on each element of the circuit.

  The energy storage element, for example, a large-capacity capacitor is charged to the voltage level of the AC signal changing points PC1, PNC1, PC2, and PNC2. Accordingly, the charging of the capacitor to the voltage level Vc is determined by adjusting the potentiometer P01 of the power supply control circuit 112. Each element and operation method of the second power supply control circuit 112 may be applied to the first power supply control circuit 108 and the first switching element 102. Further, the sizes of the non-conduction areas NCR1 and NCR2 can be adjusted according to the demand of a specific application, for example, dimming. For example, it is possible to directly control the DC voltage of the power supply circuit by matching the luminance of the light source and the voltage level Vc (see FIG. 5A) for charging the storage element.

  In the embodiment shown in FIG. 5C, the critical voltage Vth of the potentiometer P01 limits the charging voltage Vc to a certain level, which is almost at the predetermined peak voltage Vp of the AC signal. When a surge occurs, the AC signal voltage is limited to Vc, and a non-conductive area is formed in a time zone in which the voltage between the first and second rails 110 and 114 is higher than a predetermined peak voltage Vp. Therefore, it is possible to provide overvoltage protection by limiting the voltage level.

  FIG. 6 shows that the power supply control circuit device 100 ′ has an effect of current surge protection, and adds a partial function to the circuit shown in FIG. . In the embodiment, the first power supply control circuit 112 ′ has a sensing resistor RF 01 connected between the source terminal Q 01 S of the second switching element and the second rail 114. The diode DF01 is connected to the source terminal Q01S and the base terminal B of the first switching control element Q02. Since the capacitor CF01 is connected to the base terminal B and the second rail 114, a current limiting mechanism is formed between the sensing resistor RF01, the capacitor CF01, the diode DF01, and the first switching control element Q02.

  When the second switching element 104 is energized and the generated voltage is higher than a predetermined voltage and the first switching control element Q02 is biased to be in a conductive state via the base terminal B, the second switching element 104 Turns off. Therefore, the current passing through the second switching element 104 is limited to a predetermined level. Thereby, it is considered that the impedance of the capacitor CF01 can maintain the first switching control element Q02 in a conductive state at a predetermined time interval, and matches the required AC signal cycle.

  FIG. 7 shows a power supply control circuit 200 according to another embodiment of the present invention. The circuit 200 includes a first control circuit 202 and a second control circuit 204 located on both sides of the load 206. The load 206 may be a non-linear load. The four resistors RC1-4 and the potentiometer P1 are connected in series and connected across the first and second rails 208 and 210.

  The first control circuit 202 includes a BJT transistor, and includes first and second switching elements Q11 and Q21 connected to the Darlington structure, thereby supplying a current to the load 206. The third switching element Q3 is also composed of a BJT transistor, an emitter terminal E connected to the first rail 208, a base terminal connected to a fixed point between the first and second resistors RC1 and RC2, and a second of the Darlington pair. It has a connector terminal connected to the base terminal of switching element Q21. The diode D11 is connected between the first rail 208 and the load 206, and drives the circuit when the AC signals of the black terminal BLK and the white terminal WHT are located in the negative half cycle.

  In operation, if the voltage between the first and second rails 208, 210 is greater than a predetermined critical voltage, the third switching element Q31 is biased to become conductive. At the same time as the third switching element Q31 is turned on, the second and first switching elements Q21 and Q11 of the Darlington pair are turned off. The AC signal acting on the load is similar to FIG. 5A, the voltage of which is limited to a predetermined level Vc. The limiting voltage of the circuit is determined by the resistance from potentiometer P1. Thereby, the limiting voltage is controlled in a state lower than the predetermined peak voltage Vp, and it is considered that it can be applied to dimming applications or can provide overvoltage protection when larger than the predetermined peak voltage Vp. It is done.

  As shown in FIG. 8, the circuit according to the present invention has an effect of surge current protection as compared with that shown in FIG. The first control circuit 202 has a sensing resistor RF connected between the first rail 208 and the first resistor RC1, and senses a conductive state when the load current is larger than a predetermined amount set by the potentiometer P1. The voltage of the resistor RF biases the third switching control element Q31 and turns off Darlington pair Q21 and Q11.

  As shown in FIG. 9, another power supply control circuit 300 according to the present invention refers to one rail. From the figure, it is considered that the circuit has the same structure and operation as those shown in FIG. 7, and the circuit 300 has the first input terminal BLK and the second input terminal WHT and is connected to the load.

  The circuit 300 has a potentiometer P1, a counting resistor RSC, and a load terminal (having a second input terminal WHT), which are connected in series. The potentiometer P1 provides a voltage when the load voltage increases beyond a predetermined amount set by the potentiometer, and is biased so that the switching control elements Q31 and Q32 become conductive. When the switching control elements Q31, Q32 are conducted, the Darlington pair Q12, Q22 and Q21, Q11 are turned off, providing a predetermined non-conducting area.

  As shown in FIG. 10, in another embodiment of the present invention, the counting resistor RSC has a value of about 1M and maintains the current within a safety standard level, for example, UL (Underwriters Laboratories). The numerical values of the circuit elements of the present invention are shown in the figure. Accordingly, in this embodiment or other embodiments of the present invention, the numerical values of these elements are given as examples for the purpose of explanation, and those skilled in the art can easily change them. . Further, the structure of the present invention is very useful, and for example, one end (that is, the white cable WHT) of this embodiment is difficult to move.

  As shown in FIG. 10, the power supply control circuit 400 is substantially the same as FIG. 9, and the circuit uses the ground as a reference. Thereby, it is considered that the relatively small voltage between the white cable terminal WHT and the ground GND is related to the voltage and the current passing through the counting resistor RSC. For example, a numerical value of 120 V / 1 MΩ = 120 uA reaches the UL safety standard.

  As shown in FIG. 11, 400 'according to the embodiment is substantially the same as that shown in FIG. 10, and further has an effect of current limiting, and includes first and second sensing resistors RF1 and RF2. When the current passing through the load is larger than a predetermined critical voltage set by the potentiometer P1, the first and second switching control elements Q31 and Q32 are biased so that the voltages of the two sensing resistors RF1 and RF2 become conductive. That turns off the circuit.

  As shown in FIG. 12, in the power supply control circuit 500 according to another embodiment of the present invention, the input waveforms of the first and second input terminals BLK and WHT are rectified by full bridge rectifiers D1, D2, D3, and D4. . The circuit 500 includes first and second switching elements Q1 and Q2 (Darlington structure formed of BJT transistors in the present embodiment), thereby supplying a current to the load LD. The connector terminals C1, C2 of the two switching elements Q1, Q2 are connected to the first rail RL1, and normally maintain the switching elements in a saturated state. The emitter terminal E of the first switching element Q1 is connected to the second rail RL2 via the sensing resistor RF. The triac TR is connected across the first and second rails RL1, RL2, and its gate terminal G is connected to the diode DPM1. The sensing capacitor CF is connected between the gate terminal G of the triac TR and the second rail RL2. Resistor RC is connected in parallel with sensing capacitor CF.

  When the voltage of the sensing resistor RF increases to a predetermined level or higher, the first and second switching elements Q1, Q2 are biased by biasing the triac TR so that the potential of the gate terminal G of the triac TR becomes conductive. Is turned off until the next zero crossing. The energy stored in the sensing capacitor CF can maintain the conduction state of the triac TR and provide control of the load cycle. In other words, the circuit can be kept off in a predetermined AC cycle. The present invention may also be used as a self-resetting electronic fuse.

  Since the power supply control circuit of the present invention has various variability and applicability, it is not limited to circuit protection, voltage reference or voltage fuse.

It is a figure which shows the structure of a known wall-type light control circuit. It is a figure which shows the voltage waveform of the circuit of FIG. It is a figure which shows the structure of the power supply control circuit by this invention. FIG. 4 is a diagram illustrating an embodiment of the circuit of FIG. 3. This is the same as the circuit of FIG. It is a figure which shows the voltage waveform which generate | occur | produces in the circuit of FIG. It is a figure which shows the electric current waveform which generate | occur | produces in the circuit of FIG. It is a waveform which shows the state of the overvoltage protection of this invention. It is a figure which shows that an Example has the effect of a current limitation substantially the same as the circuit of FIG. 1 is an embodiment of a power supply control circuit according to the present invention. It is a figure which shows that an Example has the effect of a current limitation substantially the same as the circuit of FIG. It is another Example of the power supply control circuit by this invention. It is another Example of the power supply control circuit by this invention. It is another Example of the power supply control circuit by this invention. It is another Example of the power supply control circuit by this invention.

Claims (37)

First and second switching elements connected across the first and second rails and supplying current to the load;
A first power supply control circuit connected to the first switching element, wherein when the first power supply control circuit is located in a part of a half cycle of the AC signal, the first switching element is biased to be in a non-conductive state. The first power supply control circuit is generated when the peak voltage of the half cycle of the AC signal during a partial cycle is greater than a predetermined critical voltage. When,
A power supply control circuit device comprising:   The power supply control circuit device according to claim 1, wherein the first switching element is centered on a peak voltage of a half cycle of the AC signal in a non-conducting state section.   The power supply control circuit device according to claim 1, wherein the first power supply control circuit includes a potentiometer that is connected across the first and second rails and sets a predetermined critical voltage.   4. The first switching element is biased so as to be in a non-conductive state when the voltage across the potentiometer is greater than a predetermined critical voltage by having a switching control element connected to the potentiometer. The power supply control circuit device described.   The power supply control circuit device according to claim 4, further comprising a capacitor that biases the first switching element so as to be in a conductive state.   2. The power supply control circuit device according to claim 1, wherein overvoltage protection is provided by increasing a predetermined critical voltage to a predetermined peak or more of a half cycle of an AC signal.   The power supply control circuit device according to claim 1, wherein the predetermined critical voltage is equal to or lower than a predetermined peak of a half cycle of the AC signal.   A switching control element connected to the first switching element, and a sensing resistor connected between the first rail and the first switching element, and the switching control when the current of the first switching element is larger than a predetermined critical current The power supply control circuit device according to claim 1, wherein the first switching element is biased so that the element is in a non-conductive state.   The power supply control circuit device according to claim 1, wherein the power supply control circuit device can be charged to a predetermined critical voltage by having a large-capacity capacitor. The power supply control circuit device according to claim 1, wherein the first switching element forms a part of a Darlington pair.   11. The power supply control circuit device according to claim 10, wherein in the Darlington pair, the load and the second switching element are connected across the first and second rails by connecting ends.   The power supply control circuit device according to claim 11, wherein the load is located between the first and second switching elements.   The power supply control circuit device according to claim 10, further comprising a first diode connected across the first switching element and a second diode connected across the second switching element.   The power supply control circuit device according to claim 1, wherein the power supply control circuit device has a reference voltage level in a single rail.   The power supply control circuit device according to claim 14, wherein the single rail corresponds to a known black cable terminal, and the second why cable terminal is not connected correspondingly.   15. The power supply control circuit device according to claim 14, wherein a ground fault current of the ground is minimized by having a high impedance resistor connected to a load.   The power supply control circuit device according to claim 1, wherein the power supply control circuit device has a reference voltage level at a ground end.   18. The power supply control circuit device according to claim 17, wherein the power supply control circuit device has a known white and black input terminal, and receives an AC input signal, and the white terminal is connected to a load.   19. The power supply control circuit device according to claim 18, wherein the power control circuit device is grounded by having a high impedance resistance, and a potential difference between the ground terminal and the white terminal matches a current of the high impedance resistance. First and second switching elements that are connected across the first and second rails and apply current to the load;
A first power supply control circuit for controlling the conduction state of the first switching element;
A second power supply control circuit for controlling the conduction state of the second switching element,
The first power supply control circuit has a control device connected between the first and second rails and connected to the switching control device, biases the switching control device so as to be in a conductive state via the control device, and A power supply control circuit capable of biasing the first switching element so as to be in a non-conductive state when the voltage of the first and second rails is higher than a predetermined critical voltage set by the control device. apparatus.   The first power supply control circuit has a sensing resistor connected to the first switching element, biases the switching control element so as to be in a conducting state, and the current of the sensing resistor rises above a predetermined critical current. The power supply control circuit device according to claim 20, wherein First and second input terminals for receiving an input AC signal;
First and second diodes connected in series, connected across the first and second rails, and the first input terminal connected to a fixed point therebetween,
A switching circuit having at least one switching element and connected across the first and second rails via a sensing resistor;
A switching limiting element having first, second and third terminals, wherein the first and second terminals are connected to the first and second rails, and the first terminal is connected to the first switching circuit; The terminal is connected to the sensing resistor, biases the switching limiting element so that the sensing resistor becomes conductive, and also enters the switching circuit so that it becomes non-conductive when the voltage across the sensing resistor is greater than a predetermined critical voltage. A switching limiting element to bias, and
A power supply control circuit device comprising:   The power supply control circuit device according to claim 22, wherein a non-conducting state of the switching limiting element is maintained by including a capacitor connected across the sensing resistor.   There are third and fourth diodes connected in series and connected across the first and second rails, the load is connected between the second terminal and a certain point, the certain point is the third, fourth The power supply control circuit device according to claim 22, wherein the power supply control circuit device is located between the diodes.   A circuit comprising: determining a critical voltage to limit an AC signal, and biasing a switching element that energizes a load to become non-conductive when the AC signal is higher than the critical voltage. Power control method.   26. The circuit power supply control method according to claim 25, further comprising a process of matching the center point of the switching element in the non-conducting time zone with the peak of the AC signal.   26. The circuit power control method of claim 25, comprising the process of charging the capacitor to a critical voltage level.   26. The method according to claim 25, further comprising a process of generating four current surges every period of the AC signal.   26. The circuit power supply control method according to claim 25, further comprising a process of biasing the switching element so as to be in a non-conductive state when the current of the switching element is larger than a predetermined critical current.   26. The method according to claim 25, further comprising a process of determining a critical voltage with a potentiometer.   26. The method according to claim 25, further comprising a process of providing overvoltage protection by setting the critical voltage to be equal to or higher than a predetermined peak voltage of the AC signal.   26. The method of claim 25, further comprising adjusting a critical voltage to provide a dimming function of the lamp. Providing the first and second switching elements and connecting the first and second rails so as to straddle the current;
Connecting the first control circuit to the first switching element and connecting the second control circuit to the second switching element;
A process of connecting the potentiometer across the first and second rails;
When the switching control element is connected to the potentiometer and the voltage between the first and second rails is greater than a predetermined critical voltage set by the potentiometer, the potentiometer biases the switching control element and becomes non-conductive. A process for biasing the first switching element to
A power supply control method for a circuit, comprising:   A sensing resistor is connected between the first switching element and the switching control element, and when the current of the sensing resistor is larger than a predetermined current, the sensing resistor biases the switching control element and is in a non-conductive state. The method of claim 32, comprising the step of biasing one switching element to provide current surge protection.   33. A method for controlling the power supply of a circuit according to claim 32, comprising the step of providing a current to the load and providing overvoltage protection by selecting a critical voltage and raising it above a predetermined peak voltage of the AC signal. .   33. The circuit power supply control method according to claim 32, further comprising a process of supplying a current to the load by matching the center point of the first switching element in the non-conducting time zone with the peak of the AC signal.   The method of claim 32, further comprising providing a lamp dimming function by adjusting the critical voltage.

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