Active clamping control circuit for improving efficiency of full-bridge power circuit

Abstract

The invention belongs to the technical field of switching power supplies, and discloses an active clamping control circuit for improving the efficiency of a full-bridge power circuit, which comprises a full-bridge power conversion circuit, a full-bridge rectification circuit and an active clamping circuit of the full-bridge rectification circuit, an input current is connected with the input end of the full-bridge power conversion circuit, and the dotted terminal and the synonym terminal of a secondary winding of a power converter of the full-bridge power conversion circuit are respectively connected with the first input end and the second input end of the full-bridge rectification circuit; the first output end of the full-bridge rectification circuit is connected with the first input end of an active clamping circuit of the full-bridge rectification circuit, and the output end of the active clamping circuit is connected with the third input end of the full-bridge rectification circuit; the second output end of the full-bridge rectification circuit is connected with the second input end of the active clamping circuit; and the second output end of the full-bridge rectification circuit is used as the output end of the active clamping control circuit for improving the efficiency of the full-bridge power circuit. According to the invention, energy loss can be reduced and efficiency can be effectively improved.

Description

Technical Field

[0001] The invention belongs to the technical field of switching power supplies, and in particular relates to an active clamping control circuit for improving the efficiency of a full-bridge power circuit. Background Art

[0002] At present, DC-DC power modules are widely used in defense, aerospace, weapons and other fields. With the upgrading of weapons and equipment, the rapid development of aerospace and power systems, higher requirements are put forward for the performance, weight, volume, efficiency and reliability of switching power supplies and power operation power supplies. The full-bridge converter is suitable for medium and large power applications, especially switching power supplies and power operation power supplies for communications. Therefore, it is of great significance to study and improve its efficiency. In the full-bridge rectifier circuit, the two groups of switch tubes on the secondary side are alternately turned on in each half cycle. When one group of switch tubes is turned off and the other group is not turned on, the rectifier diode undergoes a commutation process in this special working state, and some spike pulses are generated at the drain of the switch tube. Effective active clamping of the spike pulse can effectively improve the efficiency of the full-bridge circuit. Summary of the invention

[0003] The present invention studies an active clamping control circuit for improving the efficiency of a full-bridge power circuit. By clamping the peak pulses generated by the switch tube of the secondary full-bridge rectifier circuit during the switch tube commutation process, the withstand voltage requirement of the switch tube is reduced, thereby effectively improving the working efficiency of the switching power supply.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] An active clamping control circuit for improving the efficiency of a full-bridge power circuit comprises a full-bridge power conversion circuit, a full-bridge rectifier circuit and an active clamping circuit of the full-bridge rectifier circuit; wherein the input current is connected to the input end of the full-bridge power conversion circuit, the same-name end and the opposite-name end of the secondary winding of the power converter of the full-bridge power conversion circuit are respectively connected to the first input end and the second input end of the full-bridge rectifier circuit; the first output end of the full-bridge rectifier circuit is connected to the first input end of the active clamping circuit of the full-bridge rectifier circuit, the output end of the active clamping circuit of the full-bridge rectifier circuit is connected to the third input end of the full-bridge rectifier circuit; the second output end of the full-bridge rectifier circuit is connected to the second input end of the active clamping circuit of the full-bridge rectifier circuit; the second output end of the full-bridge rectifier circuit serves as the output end of the active clamping control circuit for improving the efficiency of the full-bridge power circuit.

[0006] Compared with the prior art, the present invention has the following beneficial effects:

[0007] (1) The present invention uses a full-bridge power converter and utilizes the parasitic diode of the switch tube to recover the leakage inductance energy of the primary winding of the transformer and clamp the peak voltage, thereby reducing the switching loss and achieving high efficiency.

[0008] (2) The present invention uses a full-bridge rectifier circuit, and two groups of switch tubes are alternately turned on, thereby improving efficiency.

[0009] (3) The present invention actively clamps the full-bridge rectifier circuit to clamp the leakage inductance energy of the two groups of switch tubes during the commutation period, thereby reducing energy loss. At the same time, after clamping, the withstand voltage of the secondary side switch tube can be selected to be smaller, effectively improving efficiency.

[0010] In summary, the input voltage passes through the full-bridge power conversion circuit 1, passes through the power transformer, and is transferred to the voltage on the secondary side. The energy is transferred to the output voltage through the rectification method of alternating switches in each half cycle of the full-bridge rectifier circuit 2. In the full-bridge rectifier circuit 2, the leakage inductance energy generated by the alternating switches in each half cycle of the full-bridge rectifier circuit 2 during the commutation period is clamped by active clamping, thereby reducing energy loss. At the same time, after clamping, the withstand voltage of the secondary side switch tube can be selected to be smaller, thereby effectively improving efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 A structural diagram of an active clamping control circuit for improving the efficiency of a full-bridge power circuit according to the present invention;

[0012] Figure 2 It is a circuit diagram of a full-bridge conversion circuit and a full-bridge rectifier circuit;

[0013] Figure 3 Schematic diagram of an active clamping circuit for a full-bridge rectifier circuit.

[0014] The present invention is further explained below in conjunction with the accompanying drawings and specific embodiments. DETAILED DESCRIPTION

[0015] like Figure 1 As shown, the active clamping control circuit for improving the efficiency of a full-bridge power circuit provided by the present invention comprises a full-bridge power conversion circuit 1, a full-bridge rectifier circuit 2 and an active clamping circuit 3 of the full-bridge rectifier circuit.

[0016] Among them, the input current is connected to the input end of the full-bridge power conversion circuit 1, and the like-name end and the opposite-name end of the secondary winding of the power converter of the full-bridge power conversion circuit 1 are respectively connected to the first input end and the second input end of the full-bridge rectifier circuit 2; the first output end of the full-bridge rectifier circuit 2 is connected to the first input end of the active clamping circuit 3 of the full-bridge rectifier circuit, and the output end of the active clamping circuit 3 of the full-bridge rectifier circuit is connected to the third input end of the full-bridge rectifier circuit 2; the second output end of the full-bridge rectifier circuit 2 is connected to the second input end of the active clamping circuit 3 of the full-bridge rectifier circuit; the second output end of the full-bridge rectifier circuit 2 serves as the output end of the active clamping control circuit for improving the efficiency of the full-bridge power circuit.

[0017] In the above circuit design of the present invention:

[0018] As a preferred embodiment of the present invention, the full-bridge power conversion circuit 1 includes an input positive terminal Vin1+, an input ground PGND, a switch tube Q1, a switch tube Q2, a switch tube Q3, a switch tube Q4, a switch tube drive HO1, a switch tube drive HO2, a switch tube drive LO1, a switch tube drive LO2, a pull-down resistor R6, a pull-down resistor R5, a pull-down resistor R10, a pull-down resistor R11, a DC blocking capacitor C3, a DC blocking capacitor C4, a DC blocking capacitor C5, a DC blocking resistor R7, a current transformer CT1 and a power transformer T1, a diode D4, a diode D5, and sampling signals CT1, CT2, and CT. Among them:

[0019] The positive input terminal Vin1+ is connected to the drain of the switch tube Q1 and the drain of the switch tube Q2;

[0020] The switch tube driver HO1 is connected to the gate of the switch tube Q1 and one end of the pull-down resistor R6, the switch tube driver HO2 is connected to the gate of the switch tube Q2 and one end of the pull-down resistor R5, the switch tube driver L01 is connected to the gate of the switch tube Q3 and one end of the pull-down resistor R10, and the switch tube driver L02 is connected to the gate of the switch tube Q4 and one end of the pull-down resistor R11;

[0021] Capacitor C3, capacitor C4, capacitor C5, and resistor R7 are connected in parallel to form a DC isolation circuit; the left end of the DC isolation circuit and the other end of the pull-down resistor R6 are connected to the source of the switch tube Q1 and the drain of the switch tube Q3; the right end of the DC isolation circuit is connected to one end (pin 5) of the current transformer CT1; the other end (pin 6) of the current transformer CT1 is connected to the same-name end of the primary winding of the power transformer T1, and the opposite-name end of the primary winding of the power transformer T1 is connected to the other end of the pull-down resistor R5, the source of the switch tube Q2, and the drain of the switch tube Q4; Pin 1 and pin 2 of the current transformer CT1 are connected to diode D5 and diode D4 respectively.

[0022] The same-name end of the secondary winding of the power transformer T1 is connected to the first input end of the full-bridge rectifier circuit 2 , and the opposite-name end of the secondary winding of the power converter T1 is connected to the second input end of the full-bridge rectifier circuit 2 .

[0023] The other end of the pull-down resistor R10 , the source of the switch tube Q3 , the source of the switch tube Q4 , and the other end of the pull-down resistor R11 are commonly connected to the input ground PGND.

[0024] The working principle of the full-bridge power conversion circuit 1 is as follows:

[0025] During operation, Q1 and Q4 are turned on at the same time, Q2 and Q3 are turned on at the same time, and these two groups of switch tubes are turned on alternately in each half cycle. When Q1 and Q4 are turned on, the input voltage Vin1+ is applied to the drain of the switch tube Q1, the source of Q1 is connected to the left end of the DC isolation circuit composed of C3, C4, C5, and R7 in parallel, the right end of the DC isolation circuit is connected to the left end of the current transformer CT1, the right end of CT1 is connected to the drain of the switch tube Q4 through the power transformer CT1, and the switch tube Q4 returns to the input ground through the source, forming a set of current loops; when Q2 and Q3 are turned on, the input voltage Vin1+ is applied to the drain of the switch tube Q2, the source of Q2 is connected to the right end of the current transformer CT1 through the power transformer, the left end of the current transformer CT1 is connected to the right end of the DC isolation circuit, the left end of the DC isolation circuit is connected to the drain of the switch tube Q3, and the switch tube Q3 returns to the input ground through the source, forming a set of current loops. In summary, the input voltage is connected to the input end of the full-bridge power conversion circuit 1, and passes through the full-bridge circuit composed of two groups of switch tubes Q1 and Q4, Q2 and Q3 respectively. The parasitic body diode of the switch tube is used to recover the leakage inductance energy of the primary winding of the transformer, and the peak voltage is clamped. The switching loss is small, and then the energy is transferred to the secondary side through the power transformer. The same-name end and the opposite-name end of the secondary winding are respectively connected to the first input end and the second input end of the full-bridge rectifier circuit 2.

[0026] In this embodiment, taking 9-36V input and output 12V30A as an example, the full-bridge power conversion circuit 1 is selected as follows: the switch tube Q1, the switch tube Q2, the switch tube Q3, and the switch tube Q4 are selected from Hengtai 200V switch tube HGN028NE6A, and the pull-down resistors R6, R5, R10, and R11 use 10K resistors; the DC blocking capacitors C3, C4, and C5 use 50V18uF capacitors, the DC blocking resistor R7 uses a 1K resistor, the current transformer CT1 uses BKEE6.0, and the diodes D4 and D5 use 1N4148WT diodes.

[0027] As a preferred embodiment of the present invention, the full-bridge rectifier circuit 2 includes an output positive terminal VOUT+, an output ground SGND, a switch tube SQ1, a switch tube SQ2, a switch tube SQ3, a switch tube SQ4, a switch tube driver S1, a switch tube driver S2, a switch tube driver S3, a switch tube driver S4, a pull-down resistor R3, a pull-down resistor R4, a pull-down resistor R12, a pull-down resistor R13, a clamping resistor R1, a clamping capacitor C1, a clamping resistor R2, a clamping capacitor C2, a clamping resistor R8, a clamping capacitor C6, a clamping resistor R9, a clamping capacitor C7, a capacitor C13 and an inductor L1; wherein:

[0028] The switch tube driver S1 is connected to the gate of the switch tube SQ1 and one end of the pull-down resistor R3, the switch tube driver S2 is connected to the gate of the switch tube SQ2 and one end of the pull-down resistor R4, the switch tube driver S3 is connected to the gate of the switch tube SQ3 and one end of the pull-down resistor R12, and the switch tube driver S4 is connected to the gate of the switch tube SQ4 and one end of the pull-down resistor R13;

[0029] The lower end of the first clamping circuit composed of the clamping resistor R1 in series with the clamping capacitor C1 is connected to the other end of the pull-down resistor R13, the source of the switch tube SQ1, the drain of the switch tube SQ3, and the upper end of the third clamping circuit composed of the resistor R8 in series with the clamping capacitor C6, and the connection point is connected to the same end of the secondary winding of the power transformer T1 of the full-bridge power conversion circuit 1 as the first input end of the full-bridge rectifier circuit 2;

[0030] The lower end of the second clamping circuit composed of the clamping resistor R2 in series with the clamping capacitor C2 is commonly connected to the other end of the pull-down resistor R13, the source of the switch tube SQ2, the drain of the switch tube SQ4, and the upper end of the fourth clamping circuit composed of the clamping resistor R9 in series with the clamping capacitor C7, and the connection point is connected to the opposite end of the secondary winding of the power transformer T1 of the full-bridge power conversion circuit 1 as the second input end of the full-bridge rectifier circuit 2;

[0031] The upper end of the first clamping circuit is connected to the drain of the switch tube SQ1, the upper end of the second clamping circuit, the drain of the switch tube SQ2, and the left end of the inductor L1. The connection point VLI is connected to the first input end of the active clamping circuit 3 of the full-bridge rectifier circuit as the first output end of the full-bridge rectifier circuit 2; the lower end of the third clamping circuit is connected to the source of the switch tube SQ3, the lower end of the fourth clamping circuit, and the source of the switch tube SQ4. The connection point is connected to the output ground SGND as the first output end of the full-bridge rectifier circuit 2;

[0032] The right end of the inductor L1 is connected to one end of the capacitor C13, and the connection point is connected to the second input end of the active clamping circuit 3 of the full-bridge rectifier circuit as the second output end of the full-bridge rectifier circuit 2, and the second output end of the full-bridge rectifier circuit 2 serves as the output of the active clamping control circuit for improving the efficiency of the full-bridge power circuit; one end of the capacitor C13 is connected to the output ground SGND.

[0033] The working principle of the full-bridge rectifier circuit 2 is as follows:

[0034] During operation, SQ1 and SQ4 are turned on at the same time, SQ2 and SQ3 are turned on at the same time, and the two sets of switch tubes are turned on alternately in each half cycle. When the forward half-wave is turned on, SQ1 and SQ4 are turned on, and the power transformer T1 is connected to the source of SQ1, through the switch tube SQ1, the drain of the switch tube SQ1 is connected to point VLI, point VLI is connected to the left end of the inductor L1, through the inductor L1, the right end of the inductor is connected to the output positive terminal VOUT+, the output positive terminal VOUT+ is connected to the output ground SGND through the filter capacitor C13, SGND is connected to the source of the switch tube SQ4, through the switch tube SQ4, the drain of SQ4 is connected to the power transformer T1, and returns to the power transformer T1, forming a set of switch loops; When the negative half-wave is turned on, SQ2 and SQ3 are turned on, and the power transformer T1 is connected to the source of SQ2, through the switch tube SQ2, the drain of the switch tube SQ2 is connected to point VLI, point VLI is connected to the left end of the inductor L1, through the inductor L1, the right end of the inductor L1 is connected to the output positive terminal VOUT+, the output positive terminal VOUT+ is connected to the output ground SGND through the filter capacitor C13, SGND is connected to the source of the switch tube SQ3, through the switch tube SQ3, the drain of SQ3 is connected to the power transformer T1, and returns to the power transformer T1, forming a set of switching loops. In addition, a clamping circuit in which a clamping resistor R1 and a clamping capacitor C1 are connected in series is connected between the drain and source of the SQ1 switch tube, a clamping circuit in which a clamping resistor R2 and a clamping capacitor C2 are connected in series is connected between the drain and source of the SQ2 switch tube, a clamping circuit in which a clamping resistor R8 and a clamping capacitor C6 are connected in series is connected between the drain and source of the SQ3 switch tube, and a clamping circuit in which a clamping resistor R9 and a clamping capacitor C7 are connected in series is connected between the drain and source of the SQ4 switch tube. The RC clamping circuit is a supplement to the active clamping control circuit and can effectively absorb and process high-frequency spikes. In summary, energy passes through the first input end of the full-bridge rectifier circuit 2 and then passes through the switch tubes SQ1 and SQ4 to the first output end and passes through the second input end of the full-bridge rectifier circuit 2 and then passes through the switch tubes SQ2 and SQ3 to the second output end. The two groups of switch tubes are alternately turned on to achieve energy rectification.

[0035] In this embodiment, taking 9-36V input and output 12V30A as an example, the full-bridge rectifier circuit 2 is selected as follows: the switch tube SQ1, the switch tube SQ2, the switch tube SQ3, and the switch tube SQ4 can use Hengtai HGN035N08AL switch tubes, the pull-down resistors R3, R4, R12, and R13 use 10K resistors, the clamping resistors R1, R2, R8, and R9 use 7.5R resistors, the clamping capacitors C1, C2, C6, and C7 use 220pf capacitors, the capacitor C13 selects 18uF50V capacitors, and the inductor L1 selects RM8.4A11 magnetic core.

[0036] As a preferred embodiment of the present invention, the active clamping circuit 3 of the full-bridge rectifier circuit includes an active clamping power supply circuit, an active clamping drive circuit and an active clamping absorption circuit. Wherein:

[0037] The active clamping power supply circuit includes a resistor R24, a resistor R25, a capacitor C12 and a transistor SQ5; wherein one end of the resistor R24 ​​is connected to the collector of the transistor SQ5, and the connection point is connected to the second output end (VOUT+) of the full-bridge rectifier circuit 2 as the second input end of the active clamping circuit 3 of the full-bridge rectifier circuit; the other end of the resistor R24 ​​is commonly connected to the base of the transistor SQ5, one end of the resistor R25, and one end of the capacitor C12; the other end of the resistor R25 is connected to the other end of the capacitor C12, and the connection point is connected to the first input end of the active clamping drive circuit as the first output end of the active clamping power supply circuit; the emitter of the transistor SQ5 is connected to the second input end (VDD1) of the active clamping drive circuit as the second output end of the active clamping power supply circuit, and is used to power the active clamping drive circuit.

[0038] The active clamp driving circuit includes a resistor R14, a resistor R15, a resistor R19, a resistor R20, a resistor R21, a resistor R23, a coupling capacitor C8, a capacitor C10, a capacitor C11, a diode D1, a diode D3, a cathode of a voltage regulator Z1 and a driving chip IC1; wherein, a power supply VDD pin (pin 1) of the driving chip IC1, an IN+ non-inverting input pin (pin 6), one end of a bypass capacitor C11, one end of a pull-down resistor R23, IN- (pin 5) of the driving chip IC1, and one end of a parallel circuit are connected together, and the connection point is connected to the second output end of the active clamp power supply circuit as a second input end of the active clamp driving circuit, wherein the parallel circuit is composed of a resistor R14 and a resistor R15 connected in series, a resistor R19 and a resistor R20 connected in series, a resistor R21 and a diode D1 connected in series. After the series connection, the three paths are connected in parallel; the other end of the parallel circuit is connected to one end of the coupling capacitor C8; the output pin OUTH (pin 2) of the driver chip IC1 is connected to OUTL (pin 3) and one end of the capacitor C10, and the GND end of the driver chip IC1 and the anode of the voltage regulator tube Z1, the cathode of the diode D3, the other end of the resistor R23, and the other end of C11 are connected to the output ground SGND; the anode of the diode D3 is connected to the other end of the capacitor C10, and the connection point is connected to the second input end of the active clamping absorption circuit as the output end of the active clamping drive circuit; the other end of the coupling capacitor C8 is connected to the first input end of the active clamping absorption circuit as the first output end of the active clamping drive circuit, and the connection point is connected to the first output end of the full-bridge rectifier circuit 2 as the first input end of the active clamping circuit 3 of the full-bridge rectifier circuit.

[0039] The active clamping absorption circuit includes a resistor R16, a resistor R17, a resistor R18, a resistor R22, a switch tube Q5, a capacitor C9 and a diode D2. Among them, the gate of the switch tube Q5 and one end of the pull-down resistor R22 are connected together, and the connection point is connected to the output end of the active clamping drive circuit as the second input end of the active clamping absorption circuit, and one end of R16, R17 and R18 is connected in parallel to the drain of the switch tube Q5, and the other end is connected to one end of the capacitor C9 and the anode of the diode D2. The other end of the capacitor C9 is connected to the first output end of the active clamping drive circuit as the first input end of the active clamping absorption circuit, and the connection point is connected to the first output end of the full-bridge rectifier circuit 2 as the first input end of the active clamping circuit 3 of the full-bridge rectifier circuit; the other end of the pull-down resistor R22 is grounded together with the source of the switch tube Q5 and the cathode of the diode D2.

[0040] The working principle of the active clamping circuit 3 of the full-bridge rectifier circuit is as follows:

[0041] The VLI node signal is used as the input signal of the first input terminal of the active clamp circuit driving circuit to control the MOS tube Q5 of the active clamp absorption circuit to discharge the energy absorbed in the clamp capacitor C9 into the load; when one group of switch tubes is turned off and the other group is not turned on, VLI is high level, input to the inverting input pin IN- of the driver chip IC1 at a high level, and the output pins OUTH and OUTL output a low level, which is inverted by the capacitor C10 and the diode D3 and then input to the MOS tube Q5 drive pin at a high level. Through the MOS tube Q5 (P tube), the P tube is turned off, and the clamping capacitor C9 is charged; when one group of switch tubes is turned on and the other group is turned off, VLI is low level, and the input to the inverting input pin IN- of the driver chip IC1 is low level, and the output pins OUTH and OUTL output high level. After being inverted by C10 and D3, it is input to the MOS tube Q5 drive pin low level, passes through the MOS tube Q5 (P tube), the P tube is turned on, and the clamping capacitor C9 is discharged through the parallel resistors R16, R17, R18 and the MOS tube Q5. In summary, the first output end of the full-bridge rectifier circuit 2 is connected to the first input end of the active clamping circuit 3 of the full-bridge rectifier circuit, as the input end of the power supply circuit of the active clamping circuit 3 of the full-bridge rectifier circuit, the second output end of the full-bridge rectifier circuit 2 is connected to the second input end of the active clamping circuit 3 of the full-bridge rectifier circuit, the leakage inductance energy of the switch tubes SQ1 and SQ2 is connected to the second input end of the active clamping circuit 3 of the full-bridge rectifier circuit as the second output end of the full-bridge rectifier circuit 2, and the node signal is clamped. After the second input end of the active clamping circuit 3 of the full-bridge rectifier circuit is controlled by the active clamping of this part of the circuit, it is connected from the output end of the active clamping circuit 3 of the full-bridge rectifier circuit to the third input end of the full-bridge rectifier circuit 2. At this time, the leakage inductance energy of the switch tubes SQ1 and SQ2 is effectively clamped and controlled. The purpose of improving the efficiency of the full-bridge power circuit is achieved.

[0042] In this embodiment, taking 9-36V input and output 12V30A as an example, the active clamping circuit 3 of the full-bridge rectifier circuit is selected as follows: resistor R24 ​​is a 5K resistor, resistor R25 is a 510R resistor, capacitor C12 is a 220pF capacitor, transistor SQ5 can be FMMT619, resistor R14, resistor R15, resistor R19, resistor R20, resistor R21, resistor R23 are 1K resistors, coupling capacitor C8 is 100pF, capacitor C10 is 1nF, capacitor C11 is 220nF, diode D1 and diode D3 are 1N4148WT, Zener diode Z1 is BZX584C5V1, driver chip IC1 is RMJ27511; resistors R16, R17 and R18 are 10R resistors, resistor R22 is 500R resistor, switch tube Q5 is JRZ20P1K5H, capacitor C9 is 220nF, and diode D2 is DSS34.

Claims

1. An active clamping control circuit for improving the efficiency of a full-bridge power circuit, characterized in that: The invention comprises a full-bridge power conversion circuit (1), a full-bridge rectifier circuit (2) and an active clamping circuit (3) of the full-bridge rectifier circuit; wherein the input current is connected to the input end of the full-bridge power conversion circuit (1); the same-name end and the opposite-name end of the secondary winding of the power converter of the full-bridge power conversion circuit (1) are respectively connected to the first input end and the second input end of the full-bridge rectifier circuit (2); the first output end of the full-bridge rectifier circuit (2) is connected to the first input end of the active clamping circuit (3) of the full-bridge rectifier circuit; the output end of the active clamping circuit (3) of the full-bridge rectifier circuit is connected to the third input end of the full-bridge rectifier circuit (2); the second output end of the full-bridge rectifier circuit (2) is connected to the second input end of the active clamping circuit (3) of the full-bridge rectifier circuit; and the second output end of the full-bridge rectifier circuit (2) serves as the output end of the active clamping control circuit for improving the efficiency of the full-bridge power circuit.

2. The active clamping control circuit for improving the efficiency of a full-bridge power circuit as claimed in claim 1, characterized in that: The full-bridge power conversion circuit (1) comprises an input positive terminal Vin1+, an input ground PGND, a switch tube Q1, a switch tube Q2, a switch tube Q3, a switch tube Q4, a switch tube driver HO1, a switch tube driver HO2, a switch tube driver LO1, a switch tube driver LO2, a pull-down resistor R6, a pull-down resistor R5, a pull-down resistor R10, a pull-down resistor R11, a DC blocking capacitor C3, a DC blocking capacitor C4, a DC blocking capacitor C5, a DC blocking resistor R7, a current transformer CT1 and a power transformer T1, a diode D4, a diode D5, and sampling signals CT1, CT2, CT; wherein: The positive input terminal Vin1+ is connected to the drain of the switch tube Q1 and the drain of the switch tube Q2; The switch tube driver HO1 is connected to the gate of the switch tube Q1 and one end of the pull-down resistor R6, the switch tube driver HO2 is connected to the gate of the switch tube Q2 and one end of the pull-down resistor R5, the switch tube driver L01 is connected to the gate of the switch tube Q3 and one end of the pull-down resistor R10, and the switch tube driver L02 is connected to the gate of the switch tube Q4 and one end of the pull-down resistor R11; Capacitor C3, capacitor C4, capacitor C5, and resistor R7 are connected in parallel to form a DC isolation circuit; the left end of the DC isolation circuit and the other end of the pull-down resistor R6 are connected to the source of the switch tube Q1 and the drain of the switch tube Q3; the right end of the DC isolation circuit is connected to one end (pin 5) of the current transformer CT1; the other end (pin 6) of the current transformer CT1 is connected to the same-name end of the primary winding of the power transformer T1, and the opposite-name end of the primary winding of the power transformer T1 is connected to the other end of the pull-down resistor R5, the source of the switch tube Q2, and the drain of the switch tube Q4; the 1st and 2nd pins of the current transformer CT1 are connected to the diode D5 and the diode D4 respectively; The same-name end of the secondary winding of the power transformer T1 is connected to the first input end of the full-bridge rectifier circuit (2), and the opposite-name end of the secondary winding of the power converter T1 is connected to the second input end of the full-bridge rectifier circuit (2); The other end of the pull-down resistor R10 , the source of the switch tube Q3 , the source of the switch tube Q4 , and the other end of the pull-down resistor R11 are commonly connected to the input ground PGND.

3. The active clamping control circuit for improving the efficiency of a full-bridge power circuit according to claim 1 as claimed in claim 2, characterized in that: The full-bridge rectifier circuit (2) comprises an output positive terminal VOUT+, an output ground SGND, a switch tube SQ1, a switch tube SQ2, a switch tube SQ3, a switch tube SQ4, a switch tube driver S1, a switch tube driver S2, a switch tube driver S3, a switch tube driver S4, a pull-down resistor R3, a pull-down resistor R4, a pull-down resistor R12, a pull-down resistor R13, a clamping resistor R1, a clamping capacitor C1, a clamping resistor R2, a clamping capacitor C2, a clamping resistor R8, a clamping capacitor C6, a clamping resistor R9, a clamping capacitor C7, a capacitor C13 and an inductor L1; wherein: The switch tube driver S1 is connected to the gate of the switch tube SQ1 and one end of the pull-down resistor R3, the switch tube driver S2 is connected to the gate of the switch tube SQ2 and one end of the pull-down resistor R4, the switch tube driver S3 is connected to the gate of the switch tube SQ3 and one end of the pull-down resistor R12, and the switch tube driver S4 is connected to the gate of the switch tube SQ4 and one end of the pull-down resistor R13; The lower end of the first clamping circuit formed by the clamping resistor R1 in series with the clamping capacitor C1 is connected to the other end of the pull-down resistor R13, the source of the switch tube SQ1, the drain of the switch tube SQ3, and the upper end of the third clamping circuit formed by the resistor R8 in series with the clamping capacitor C6, and the connection point is connected to the same end of the secondary winding of the power transformer T1 of the full-bridge power conversion circuit (1) as the first input end of the full-bridge rectifier circuit (2); The lower end of the second clamping circuit composed of the clamping resistor R2 in series with the clamping capacitor C2 is connected to the other end of the pull-down resistor R13, the source of the switch tube SQ2, the drain of the switch tube SQ4, and the upper end of the fourth clamping circuit composed of the clamping resistor R9 in series with the clamping capacitor C7, and the connection point is connected to the opposite end of the secondary winding of the power transformer T1 of the full-bridge power conversion circuit (1) as the second input end of the full-bridge rectifier circuit (2); The upper end of the first clamping circuit is connected to the drain of the switch tube SQ1, the upper end of the second clamping circuit, the drain of the switch tube SQ2, and the left end of the inductor L1, and the connection point VLI is connected to the first input end of the active clamping circuit (3) of the full-bridge rectifier circuit as the first output end of the full-bridge rectifier circuit (2); the lower end of the third clamping circuit is connected to the source of the switch tube SQ3, the lower end of the fourth clamping circuit, and the source of the switch tube SQ4, and the connection point is connected to the output ground SGND as the first output end of the full-bridge rectifier circuit (2); The right end of the inductor L1 is connected to one end of the capacitor C13, and the connection point is connected to the second input end of the active clamping circuit (3) of the full-bridge rectifier circuit as the second output end of the full-bridge rectifier circuit (2), and the second output end of the full-bridge rectifier circuit (2) serves as the output of the active clamping control circuit for improving the efficiency of the full-bridge power circuit; one end of the capacitor C13 is connected to the output ground SGND.

4. The active clamping control circuit for improving the efficiency of a full-bridge power circuit according to claim 1 as claimed in claim 3, characterized in that: The active clamping circuit (3) of the full-bridge rectifier circuit comprises an active clamping power supply circuit, an active clamping drive circuit and an active clamping absorption circuit; wherein: The active clamping power supply circuit comprises a resistor R24, a resistor R25, a capacitor C12 and a transistor SQ5; wherein one end of the resistor R24 ​​is connected to the collector of the transistor SQ5, and the connection point is connected to the second output end of the full-bridge rectifier circuit (2) as the second input end of the active clamping circuit (3) of the full-bridge rectifier circuit; the other end of the resistor R24 ​​is connected to the base of the transistor SQ5, one end of the resistor R25 and one end of the capacitor C12; the other end of the resistor R25 is connected to the other end of the capacitor C12, and the connection point is connected to the first input end of the active clamping drive circuit as the first output end of the active clamping power supply circuit; the emitter of the transistor SQ5 is connected to the second input end of the active clamping drive circuit as the second output end of the active clamping power supply circuit; The active clamp driving circuit includes a resistor R14, a resistor R15, a resistor R19, a resistor R20, a resistor R21, a resistor R23, a coupling capacitor C8, a capacitor C10, a capacitor C11, a diode D1, a diode D3, a cathode of a voltage regulator Z1 and a driving chip IC1; wherein, a power supply VDD pin of the driving chip IC1, an IN+ non-inverting input pin, one end of a bypass capacitor C11, one end of a pull-down resistor R23, IN- of the driving chip IC1, and one end of a parallel circuit are connected together, and the connection point is connected to the second output end of the active clamp power supply circuit as the second input end of the active clamp driving circuit, wherein the parallel circuit is connected in series with the resistor R14 and the resistor R15, the resistor R19 and the resistor R20, and the resistor R21 and the diode D1. The three paths are connected in parallel; the other end of the parallel circuit is connected to one end of the coupling capacitor C8; the output pin OUTH of the driver chip IC1 is connected to OUTL and one end of the capacitor C10; the GND end of the driver chip IC1 and the anode of the voltage regulator tube Z1, the cathode of the diode D3, the other end of the resistor R23, and the other end of C11 are connected to the output ground SGND; the anode of the diode D3 is connected to the other end of the capacitor C10, and the connection point is connected to the second input end of the active clamping absorption circuit as the output end of the active clamping drive circuit; the other end of the coupling capacitor C8 is connected to the first input end of the active clamping absorption circuit as the first output end of the active clamping drive circuit, and the connection point is connected to the first output end of the full-bridge rectifier circuit (2) as the first input end of the active clamping circuit (3) of the full-bridge rectifier circuit; The active clamping absorption circuit comprises a resistor R16, a resistor R17, a resistor R18, a resistor R22, a switch tube Q5, a capacitor C9 and a diode D2; wherein the gate of the switch tube Q5 and one end of the pull-down resistor R22 are connected together, and the connection point is connected to the output end of the active clamping drive circuit as the second input end of the active clamping absorption circuit; one end of R16, R17 and R18 connected in parallel is connected to the drain of the switch tube Q5, and the other end is connected to one end of the capacitor C9 and the anode of the diode D2; the other end of the capacitor C9 is connected to the first output end of the active clamping drive circuit as the first input end of the active clamping absorption circuit, and the connection point is connected to the first output end of the full-bridge rectifier circuit (2) as the first input end of the active clamping circuit (3) of the full-bridge rectifier circuit; the other end of the pull-down resistor R22, the source of the switch tube Q5 and the cathode of the diode D2 are grounded together.

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