CN101562395A - Voltage modulation circuit with light load efficiency improving function - Google Patents

Abstract

The invention relates to a voltage modulation circuit with a light-load efficiency improving function. The limiting voltage modulation circuit senses the current of the output end of the buck power conversion circuit, judges whether the load is in a light load state or a medium load state according to the current, and adjusts the output voltage of the active switch driving end in the switch driver, namely when the output current of the buck power conversion circuit is small and close to zero, the current load is in the light load state, so that the limiting voltage modulation circuit can adjust and reduce the driving voltage of the active switch to achieve the function of reducing the driving loss; on the contrary, if the output current of the buck power conversion circuit is increased, which indicates that the load is in a medium or heavy load state, the limit voltage modulation circuit can adjust and increase the driving voltage of the active switch to reduce the conduction loss.

Description

Voltage modulation circuit with light load efficiency improvement function

technical field

The invention relates to a voltage modulation circuit, in particular to a voltage modulation circuit with a light-load efficiency improvement function, which has the function of improving power conversion efficiency under light-load conditions.

Background technique

In the voltage modulation circuit used by the central processing unit, a stable working voltage must be provided to the central processing unit. Therefore, for the voltage modulation circuit, the central processing unit is its load. However, since the central processing unit will be in a busy or idle state based on user operations, the load will be in a heavy or light power consumption state at different times. Therefore, for the voltage modulation circuit, it is necessary to provide a stable working voltage according to the current load state.

Usually, the existing single-voltage output voltage modulation circuit is applied to the power supply circuit of the low-voltage load, and can be roughly divided into two categories: one is a non-isolated power supply circuit, and the other is an isolated power supply circuit. Wherein, the non-isolated power supply circuit includes, for example, a step-down power supply circuit or a buck-boost power supply circuit, while the isolated power supply circuit is, for example, a flyback power conversion circuit.

FIG. 5 shows a voltage modulation circuit implemented by a step-down power conversion circuit, which includes a PWM controller 50, a switch driver 60, multiple active switches Q1, Q2, inductor L and capacitor C. Wherein, the pulse width modulation controller obtains the voltage feedback signal of the voltage output terminal to determine the change of the load voltage Vout, so as to alternately control the conduction period of the active switches Q1 and Q2 through the switch driver 60 . FIG. 6 is a circuit block diagram of the switch driver 60 , which includes a logic circuit unit 61 , two power amplifiers 62 , 63 and a phase adjustment circuit 64 . Wherein, the input terminal of logic circuit unit 61 is a pulse width modulation signal terminal (PWM), is connected to the output terminal of pulse width modulation controller 50; This logic circuit unit 61 comprises two output terminals, through logic element and phase adjustment circuit 64 is connected to the power amplifiers 62 and 63, so as to adjust the pulse width of the driving signal output by the power amplifiers 62 and 63 according to the pulse width modulation signal output by the pulse width modulation controller 50, so as to determine the conduction period of each active switch. The high potential upper limit terminals UVCC and LVCC of the two power amplifiers 62 and 63 are respectively connected to two external voltages. In general circuit design, the two high potential upper limit terminals UVCC and LVCC are connected to the highest potential terminal VCC of the external DC power supply.

Although the above-mentioned existing step-down voltage modulation circuit can provide a stable working voltage for the load according to the state of light load or heavy load power voltage rise and fall, it has the function of voltage stabilization. However, no matter in the light load or heavy load state, due to the characteristics of the active switch, the overall power conversion effect is not good, and waste heat is easily generated, thereby increasing the temperature rise near the CPU and reducing the stability of the CPU operation.

The reasons for the poor conversion effect caused by active switching can be mainly divided into: switching loss (Switching Loss), conduction loss (Conduction Loss) and driving loss (Driver Loss). Among them, the switching loss is caused by the active switch being turned on and off when its terminal voltage is non-zero voltage or its terminal current is non-zero current at the moment of on-off switching. The conduction loss is generated when the active switch is turned on, and the current flows through a conduction resistance existing inside the active switch. The driving loss is due to the moment when the active switch is driven on or off. Therefore, the overall power loss of the active switch can be expressed by the following formula:

${\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; LOSS</span>}}<span\; class="notranslate">\; \&cong;</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; SW</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; CON</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; DRIVER</span>}}$

The following further explains the ratio of various conversion losses to the overall power loss under the conditions of medium load, heavy load and light load:

When the load is medium and heavy, the current flowing through the active switch increases, so the overall loss accounted for by the conduction loss is higher than the other two. Therefore, in order to reduce the overall loss under medium and high load conditions, the on-resistance of the active switch can be adjusted to reduce the conduction loss to achieve the purpose of reducing the loss. The conduction loss formula is explained by taking the MOSFET active switch as an example:

${\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; ON</span>}}<span\; class="notranslate">\; \&ap;</span>{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; ds</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; ds</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; ON</span>}<span\; class="notranslate">\; )</span>}$

Among them, the above-mentioned P _ON is the conduction loss power, I _ds is the conduction current of the active switch, and _rds(ON) is the conduction resistance.

Figure 7 shows the conduction characteristic curve of the MOSFET active switch model IRF6631, where the driving voltage V _GS of the active switch is inversely proportional to the on-resistance r _ds(ON) ; therefore, in order to reduce the on-resistance, the Under medium and heavy load conditions, the on-resistance can be reduced by increasing the driving voltage.

When the load is in a light load state, since the current flowing through the active switch is reduced, the driving loss and switching loss are higher than the conduction loss in the overall loss, and the driving loss and switching loss can be expressed by the following formula:

${\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; G</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}}<span\; class="notranslate">\; \&Center\; Dot;</span>{<span\; class="notranslate">\; \&Integral;</span>}_{\mathrm{<span\; class="notranslate">\; 0</span>}}^{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}}{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; GS</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; g</span>}}<span\; class="notranslate">\; \&CenterDot;</span>\mathrm{<span\; class="notranslate">\; dt</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; GS</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{<span\; class="notranslate">\; \&Integral;</span>}_{\mathrm{<span\; class="notranslate">\; 0</span>}}^{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}}{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; g</span>}}<span\; class="notranslate">\; \&CenterDot;</span>\mathrm{<span\; class="notranslate">\; dt</span>}$

P _G ＝f _S ·V _GS Q _{g_tol}

In the formula, _PG is the driving loss power, f _S is the switching frequency of the active switch, V _GS is the driving voltage of the active switch, and Q _{g_tol} is the amount of charge required for the active switch to turn on; voltage to reduce drive losses.

Looking back at the existing voltage modulation circuits through the above description, it can be seen from the block diagrams of the switch drivers shown in Figures 5 and 6 that no matter in the light load, medium or heavy load state, the highest potential terminals UVCC and LVCC of the two power amplifiers Both are connected to a fixed external DC voltage VCC. Therefore, the amplitudes of the driving signals output by the two power amplifiers 62 and 63 are the same, and only the pulse width is modulated according to the output feedback voltage. Therefore, the driving voltages of the two active switches are the same. Therefore, the current voltage modulation circuit does not change the driving voltage of the active switch according to the medium-to-heavy load or light-load state of the load. Compared with the above loss loss formula of the active switch, it can be seen that it cannot improve these losses, but only has the function of voltage stabilization. .

Contents of the invention

In view of the above shortcomings, the main purpose of the present invention is to provide a voltage modulation circuit with a light-load efficiency improvement function, which can adjust the amplitude of the pulse width drive signal of the active switch according to the current load state, heavy load state or light load state size.

The main technical means used to achieve the above purpose is to make the voltage modulation circuit include: a step-down power conversion circuit and a limit voltage modulation circuit. Wherein the step-down power conversion circuit includes: a pulse width modulation controller, a switch driver, at least one active switch, an inductive energy storage element and a capacitor, the capacitor constitutes the output end of the step-down power conversion circuit, and For load connection. The limiting voltage modulating circuit is connected to the output terminal of the step-down power conversion circuit to obtain the magnitude of the output current, and then judge whether the load is in a light-load or medium- or heavy-load state according to the magnitude of the current, and adjust the switch driver to drive the main The output voltage of the switch. When the output current of the step-down power conversion circuit is small and close to zero, it means that the current load is in a light load state, so the limit voltage modulation circuit will reduce the driving voltage of the active switch to reduce the driving loss; otherwise, If the output current of the step-down power conversion circuit increases, indicating that the load is in a medium or heavy load state, the limit modulation circuit will adjust and increase the driving voltage of the active switch to reduce the conduction loss.

Description of drawings

Fig. 1 is the circuit diagram of the first preferred embodiment of the present invention;

Fig. 2 is the circuit diagram of the first preferred embodiment of the limit voltage modulation circuit of the present invention;

Fig. 3 is the circuit diagram of the second preferred embodiment of the present invention;

Fig. 4 is the circuit diagram of the third preferred embodiment of the present invention;

Fig. 5 is the circuit diagram of existing voltage modulation circuit;

Fig. 6 is the block diagram of existing drive and phase control circuit;

Fig. 7 is a conduction characteristic curve diagram of an existing MOSFET active switch of the type IER6631.

Component symbols in the figure:

10 Pulse Modulation Controller 20 Switch Driver

30, 30a, 30b limit voltage modulation circuit 31 operational amplifier

32 Electronic switch 33 Voltage divider circuit

34 The first voltage divider circuit 35 The second voltage divider circuit

35a Second voltage divider circuit 50 Voltage modulation circuit

51 Pulse Width Modulation Controller 52 Switching Driver

521 Logic circuit unit 522 Power amplifier

523 Power amplifier 524 Phase adjustment circuit

53 Active switch 54 Inductance

55 Capacitance

Detailed ways

FIG. 1 shows a first preferred embodiment of the voltage modulation circuit of the present invention, the voltage modulation circuit includes a step-down power conversion circuit and a limit voltage jump circuit 30 . Among them, the step-down power conversion circuit includes:

A pulse width modulation controller 10, at least including a feedback voltage input terminal V _FEB and a pulse width modulation output terminal PWM;

A switch driver 20, including a logic circuit unit and two power amplifiers, the logic circuit unit includes a pulse width modulation signal terminal PWM and two output terminals, wherein the pulse width modulation signal terminal PWM is connected to the output of the pulse width modulation controller 10 terminal PWM, the two output terminals are respectively connected to the input terminals of the corresponding power amplifiers, and the output terminals of the two power amplifiers are the two output terminals of the switch driver 20;

The two active switches Q1, Q2 are connected in series with each other, and the driving ends of the active switches Q1, Q2 are correspondingly connected to the output end of the switch driver 20;

An inductor L, one end of which is connected to the series node of the two active switches Q1, Q2, and the other end forms an output end through a capacitor C, which is used for load connection, and for coupling and connection of the feedback voltage end V _FEB of the pulse width modulation controller 10, to Provide the current load voltage of the pulse width modulation controller 10 .

The input terminal of the limit voltage modulation circuit 30 obtains the magnitude of the current Iout of the inductor L, and obtains the voltage VIout corresponding to the current. The variable limit voltage terminal Vo of the limit voltage modulation circuit 30 is connected to the high potential upper limit terminal LVCC of a power amplifier in the switch driver 20 . The limit voltage modulation circuit 30 adjusts the voltage of the external voltage input terminal PVCC of the switch driver 20 according to the current output by the step-down power conversion circuit, or adjusts the high potential upper limit terminals of the two power amplifiers of the switch driver 20 together. UVCC, LVCC.

The limit voltage modulation circuit 30 and the switch driver 20 can be integrated into a single integrated circuit. In addition, the limit voltage modulation circuit 30 and the switch driver 20 can be integrated into a single integrated circuit with the pulse width modulation controller 10 , or the two active switches Q1 , Q2 and the switch driver 20 can be integrated into a single integrated circuit.

FIG. 2 shows a preferred embodiment of the above limit voltage modulation circuit 30. The limit voltage modulation circuit 30 includes:

An operational amplifier 31, which includes two input terminals and an output terminal, wherein the non-inverting input terminal is respectively connected to a fixed reference voltage Vref and a voltage signal corresponding to the output current Iout of the step-down power conversion circuit through two resistors Ra and Rb VIout, that is, a current transformer (current transformer) can be coupled to the output terminal of the step-down power conversion circuit to obtain the voltage VIout corresponding to the output current; in this embodiment, the fixed reference voltage Vref can be a Zener diode ( ZD) or a regulator (ShuntRegulator);

An electronic switch 32, the control end of which is connected to the output end of the operational amplifier 31, which is controlled by the operational amplifier 31 to turn on and off, and one end of the electronic switch 32 is connected to the high potential end of the external DC power supply (+5V to +12V) , while the other end is the variable limit voltage terminal Vo; in this embodiment, the electronic switch 32 adopts an NPN type BJT transistor, and the control end is the base, and the other two ends are respectively the collector and the emitter, and the external DC The high potential end of the power supply is connected to the collector, and the emitter is a variable limit voltage end; in addition, the electronic switch can also be a MOSFET; and

A voltage divider circuit 33 is composed of two resistors R1 and R2 connected in series, one end of which is connected to the other end of the electronic switch 32 , the other end is grounded, and the series node is connected to the inverting input end of the operational amplifier 31 .

It can be seen from the above circuit structure that the operational amplifier 31 constitutes a forward amplifying circuit, and the variable limiting voltage terminal Vo of the forward amplifying circuit has the formula $V_o=[(V_{\mathrm{ref}}\&times;\frac{R_b}{R_a+R_b})+V_{\mathrm{Iout}}\&times;\frac{R_a}{R_a+R_b})]\&times;(1+\frac{R_1}{R_2})$ It can be known that the load terminal current Iout is linearly proportional to the variable limit voltage Vo terminal voltage.

For example, when the resistance value of each resistor is adjusted and V _ref =2.5V, the formula of the variable limit voltage terminal Vo of the forward amplifier circuit becomes $V_o=\frac{5}{3}\&times;(5+V_{\mathrm{Iout}}),$ When the load terminal is in a light-load state (that is, the current at the input terminal of the voltage modulation circuit is close to 0), set Iout=0, and put V _Iout ＝0 into the above formula, then the variable limit voltage terminal Vo outputs 8.3V. If the load terminal current rise, the corresponding voltage VIout increases to 1.5v, then the limit voltage terminal Vo can be changed to output 10.8V, when the current continues to rise, that is, when the load enters a heavy load, it can be seen that the current increases until the corresponding voltage reaches 3V, and it can be changed at this time The limited voltage terminal Vo will output 13.3V.

It can be seen that the limit voltage modulation circuit 30 of the present invention can indeed provide a limit voltage modulated with the output terminal current of the step-down power supply call circuit to the high potential upper limit terminal LVCC of the power amplifier of the switch driver 20; in addition, because the output terminal The magnitude of the current can reflect that the load is in a light-load or medium-heavy load state, so when the load (Load) is in a light-load state, the limit voltage modulation circuit 30 will synchronously adjust and reduce the upper limit of the high potential of the power amplifier output to the switch driver 30 The voltage of the terminal LVCC/PVCC reduces the amplitude of the pulse width drive signal output by the power amplifier connected to the external voltage input terminal PVCC; therefore, in the light load state, the voltage of the drive signal output by the drive voltage terminal LGATE will be reduced. That is, the driving voltage corresponding to the active switch decreases, thereby reducing the driving loss of the active switch. Conversely, when the load is in a medium or heavy load state, the limit voltage modulation circuit 30 will increase the driving voltage to reduce channel loss.

Accompanying drawing 3 shows the second preferred embodiment of the step-down power conversion circuit of the present invention, its structure is roughly the same as that of the first preferred embodiment, except that it only includes a single active switch, and the other active switch Q2 consists of a diode D instead. The anode of the diode is grounded, and the cathode is connected to the source of the active switch Q1, forming a freewheeling diode.

Accompanying drawing 4 shows the third preferred embodiment of the step-down power conversion circuit of the present invention, which is a flyback power conversion circuit, mainly comprising:

A pulse width modulation controller 10, at least including a feedback voltage input terminal V _FEB and a pulse width modulation output terminal PWM;

A switch driver 20, which includes a logic circuit unit and at least one power amplifier, the logic circuit unit includes a pulse width modulation signal terminal PWM and at least one output terminal, wherein the pulse width modulation signal terminal PWM is connected to the pulse width modulation controller The output terminal PWM of 10, and the high potential upper limit terminal PVCC/LVCC of each power amplifier is connected to the variable limit voltage terminal Vo of the limit voltage modulation circuit 30, and the output terminal of each power amplifier is the output terminal of the switch driver 20;

Transformer T1, its primary side is connected to a DC power supply (+12V), and its secondary side is connected to a capacitor C, which is used as the output terminal Vout of the step-down power conversion circuit for load connection and for the feedback of the pulse width modulation controller 10 The voltage terminal V _FEB is coupled and connected, so as to provide the pulse width modulation controller 10 with the voltage currently used by the load;

An active switch Q1 is connected in series with the primary side of the transformer T1 and the DC power circuit, and its drive terminal G is connected to an output terminal LGATE of the switch driver 20 to be turned on and off by the switch driver 20 controller to determine the conduction period.

It can be seen from the above-mentioned embodiments that the limit voltage modulation circuit of the present invention can indeed provide a limit voltage modulated with the load terminal voltage to the external input terminal of the switch driver, and can synchronously adjust and improve Or adjust and reduce the voltage output to the external voltage input terminal of the switch driver, so that the amplitude of the pulse width driving signal output by the power amplifier connected to the external voltage input terminal can be reduced or increased, thereby effectively reducing the driving loss at light loads, and at medium and heavy loads. It can also reduce the conduction loss when loaded.

Claims (7)

1. A voltage modulation circuit with light-load efficiency improvement function, characterized in that, comprising: A step-down power conversion circuit, comprising a pulse width modulation controller, a switch driver, at least one active switch, an inductive energy storage element and a capacitor, wherein the capacitor constitutes an output terminal of the step-down power conversion circuit, for load connection; and A limit voltage modulation circuit, the output end of which is connected to the switch driver of the step-down power conversion circuit, and the input end of which is connected to the output end of the step-down power conversion circuit to obtain the output current. The limit voltage modulation The circuit judges that the load is in a light-load or medium-heavy load state according to the magnitude of the current, so as to adjust the magnitude of the driving voltage for driving the active switch in the switch driver. 2. The voltage modulation circuit with light-load efficiency improvement function as claimed in claim 1, wherein the limit voltage modulation circuit comprises: An operational amplifier, including two input terminals and an output terminal, wherein the non-inverting input terminal is respectively connected to a fixed reference voltage and a voltage input terminal through two resistors, and the voltage input terminal receives the output current corresponding to the limit voltage modulation circuit voltage signal; An electronic switch, the control end of which is connected to the output end of the operational amplifier, which is turned on and off by the operational amplifier controller, and one end of the electronic switch is connected to an external DC power supply, while the other end is a variable limiting voltage end; and A voltage divider circuit is composed of two resistors connected in series, one end of which is connected to the other end of the electronic switch, and the other end is grounded, and its series node is connected to the inverting input end of the operational amplifier. 3. The voltage modulation circuit with light load efficiency improvement function as claimed in claim 2, wherein the fixed reference voltage of the operational amplifier is a Zener diode or a voltage regulator. 4. The voltage modulation circuit with light-load efficiency improvement function as claimed in claim 3, wherein the electronic switch is an NPN BJT transistor or a MOSFET. 5. The voltage modulation circuit with light-load efficiency improvement function according to any one of claims 2 to 4, wherein the step-down power conversion circuit includes two active switches, wherein: The pulse width modulation controller at least includes an output feedback voltage input terminal and a pulse width modulation output terminal; The switch driver includes a logic circuit unit and two power amplifiers, wherein the logic circuit unit includes a pulse width modulation signal terminal and two output terminals, wherein the pulse width modulation signal terminal is connected to the output terminal of the pulse width modulation controller , and the two output ends are respectively connected to the input ends of the corresponding power amplifiers; and the high potential upper limit end of at least one power amplifier is connected to the variable limit voltage end of the limit voltage modulation circuit; The two active switches are connected in series with each other, and the driving end of each active switch is connected to the output end of the corresponding power amplifier of the switch driver; The inductive energy storage element is an inductor, one end of which is connected to the series node of the two active switches, and the other end forms an output end through a capacitor, which is connected to the load and coupled to the feedback voltage end of the pulse width jump controller, To provide the current load voltage of the pulse width modulation controller. 6. The voltage modulation circuit with light-load efficiency improvement function according to any one of claims 2 to 4, wherein the step-down power conversion circuit is an active switch, wherein: The pulse width modulation controller at least includes an output feedback voltage input terminal and a pulse width modulation output terminal; The switch driver includes a logic circuit unit and at least one power amplifier, the logic circuit unit includes a pulse width modulation signal terminal and at least one set of output terminals, wherein the pulse width modulation signal terminal is connected to the output of the pulse width modulation controller terminals, and each output terminal is respectively connected to the input terminal of the corresponding power amplifier; and, wherein the high potential upper limit terminal of each power amplifier is connected to the variable limit voltage terminal of the limit voltage modulation circuit; The active switch is grounded in series with a diode, wherein the cathode of the diode is connected to the active switch, and the anode is connected to ground, and the driving terminal of the active switch is connected to a power amplifier output terminal in the switch driver; The inductive energy storage element is an inductor, one end of which is connected to the series node of the active switch and the diode, and the other end forms an output end through the capacitor, which is connected to the load and coupled to the feedback voltage end of the pulse width modulation controller. Provide the current load voltage of the pulse width modulation controller. 7. The voltage modulation circuit with light-load efficiency improvement function according to any one of claims 2 to 4, wherein the step-down power conversion circuit is a flyback power conversion circuit, which includes an active switch ,in: The pulse width modulation controller at least includes an output feedback voltage input terminal and a pulse width modulation output terminal; The switch driver includes a logic circuit unit and at least one power amplifier, the logic circuit unit includes a pulse width modulation signal terminal and at least one set of output terminals, wherein the pulse width modulation signal terminal is connected to the output terminal of the pulse width modulation controller, Each output terminal is respectively connected to the input terminal of the corresponding power amplifier; and, the high potential upper limit terminal of each power amplifier is connected to the variable limit voltage terminal of the limit voltage modulation circuit; The inductive energy storage element is a transformer, its primary side is connected to the DC power supply, and its secondary side is connected to the capacitor, which is used as the output terminal of the step-down power conversion circuit for load connection and feedback voltage for the pulse width modulation controller terminal coupling connection to provide the current load power voltage of the pulse width modulation controller; The active switch is connected in series with the primary side of the transformer and the DC power supply circuit, and the driving end of the active switch is connected to one of the output ends of the power amplifier of the switch driver, so that the switch driver controls its on-off and determines the turn-on cycle.

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