Double-transistor flyback conversion circuit

Abstract

The utility model discloses a double-transistor flyback conversion circuit. The double-transistor flyback conversion circuit is composed of a Q1, a Q2, a TX1, a D1 and a C4. The active clamping circuit is composed of a Q3, a Q4, a C1, a C2 and a C3; the TX1 is a flyback transformer and is composed of at least two windings P1 and S1; the D1 is an output rectification device, and the C4 is an output filter capacitor; q1 is a first flyback circuit switching tube, Q2 is a second flyback circuit switching tube, and the Q1 and the Q2 are both subjected to the same duty of the PWM controller. The circuit is favorable for improving the conversion efficiency of the power supply module while reducing the requirement of the power supply module on the voltage resistance performance of the power switch tube, can realize zero-voltage switching of Q1, Q2, Q3 and Q4, effectively reduces the switching loss, improves the working frequency, improves the product power density, can effectively reduce the voltage borne by Q1, Q2, Q3 and Q4 when the designed output reflection voltage is smaller than the input voltage, and improves the product power density. And the range of selectable devices is wider.

Description

Technical Field

[0001] The utility model relates to the field of converters, in particular to a double-tube flyback conversion circuit. Background Art

[0002] The dual-tube flyback converter is a common DC-DC converter with the advantages of high conversion efficiency, simple structure, and low voltage resistance requirements for the power switch tube. Therefore, it has been widely used in high-voltage input scenarios. However, the switch tube in the current dual-tube flyback converter can only achieve hard switching, which causes a certain amount of energy loss when the switch tube is turned on. In addition, when the high-voltage input is above 1000V, the voltage resistance requirements of the power switch tube are high, and the range of optional devices is very narrow. Therefore, a dual-tube flyback conversion circuit is provided. Utility Model Content

[0003] The purpose of the utility model is to provide a double-tube flyback conversion circuit to solve the problems raised by the above-mentioned background technology in view of the defects of the prior art.

[0004] To achieve the above-mentioned purpose, the utility model provides the following technical solutions: a dual-tube flyback conversion circuit, including a dual-tube flyback circuit and an active clamping circuit, wherein the dual-tube flyback circuit is composed of Q1, Q2, TX1, D1 and C4; the active clamping circuit is composed of Q3, Q4, C1, C2 and C3.

[0005] As a preferred technical solution of the present utility model, the TX1 is a flyback transformer, which is composed of at least two windings P1 and S1.

[0006] As a preferred technical solution of the utility model, D1 is an output rectifier device, C4 is an output filter capacitor; Q1 is a first flyback circuit switch tube, Q2 is a second flyback circuit switch tube, and both Q1 and Q2 are controlled by a PWM controller with the same duty cycle.

[0007] As a preferred technical solution of the utility model, Q3 and Q4 are controlled by AUX-PWM, have the same duty cycle and are driven complementary to or asynchronously non-complementarily with Q1 and Q2 at the same frequency.

[0008] As a preferred technical solution of the utility model, R4 is a current sampling resistor; C2 is an absorption capacitor, C2 absorbs the energy of the transformer leakage inductance when Q1 and Q2 are turned off, and C2 reversely charges the transformer when Q3 and Q4 are turned on. After Q3 and Q4 are turned off, the negative current of the primary side of the transformer is used to discharge the junction capacitance of Q1 and Q2 and enable Q1 and Q2 to be turned on with zero voltage.

[0009] As a preferred technical solution of the utility model, the operating frequency and duty cycle of Q1 and Q2 are adjusted according to the load.

[0010] As a preferred technical solution of the utility model, the voltage borne by Q1, Q2, Q3 and Q4 is: (VIN+VOUT*NP / NS) / 2; wherein NP is the number of turns of the primary side of the transformer, NS is the number of turns of the secondary side of the transformer, and VOUT*NP / NS is the output reflected to the primary side voltage.

[0011] The beneficial effects of the utility model are as follows: the circuit is conducive to reducing the power supply module's requirements on the withstand voltage performance of the power switch tube, while improving the conversion efficiency of the power supply module, and can achieve zero voltage opening of Q1, Q2, Q3 and Q4, effectively reducing switching losses, increasing the operating frequency, and increasing the product power density. When the designed output reflected voltage is less than the input voltage, the voltage borne by Q1, Q2, Q3 and Q4 can be effectively reduced, and the range of optional devices is wider. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a cross-sectional view of the utility model. DETAILED DESCRIPTION

[0013] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the protection scope of the present invention.

[0014] Example: See Figure 1 The utility model provides a technical solution: a double-tube flyback conversion circuit, including a double-tube flyback circuit and an active clamping circuit, wherein the double-tube flyback circuit is composed of Q1, Q2, TX1, D1 and C4; the active clamping circuit is composed of Q3, Q4, C1, C2 and C3.

[0015] TX1 is a flyback transformer, which is composed of at least two windings P1 and S1.

[0016] D1 is the output rectifier device, C4 is the output filter capacitor; Q1 is the first flyback circuit switch tube, Q2 is the second flyback circuit switch tube, Q1 and Q2 are both controlled by the PWM controller and have the same duty cycle.

[0017] Q3 and Q4 are controlled by AUX-PWM, with the same duty cycle and complementary or asynchronous non-complementary drive at the same frequency as Q1 and Q2.

[0018] R4 is a current sampling resistor; C2 is an absorption capacitor. C2 absorbs the energy of the transformer leakage inductance when Q1 and Q2 are turned off. C2 reversely charges the transformer when Q3 and Q4 are turned on. After Q3 and Q4 are turned off, the negative current of the primary side of the transformer is used to discharge the junction capacitance of Q1 and Q2 and turn on Q1 and Q2 with zero voltage.

[0019] The operating frequency and duty cycle of Q1 and Q2 are adjusted according to the load.

[0020] The maximum voltage that Q1 and Q2 of an ordinary dual-tube flyback withstand is: the input voltage VIN; the voltage that Q1, Q2, Q3 and Q4 of the utility model withstand is: (VIN+VOUT*NP / NS) / 2; where NP is the number of turns of the primary side of the transformer, NS is the number of turns of the secondary side of the transformer, and VOUT*NP / NS is the voltage reflected from the output to the primary side.

[0021] A control method for a dual-switch flyback converter circuit, the specific steps are as follows:

[0022] S1: PWM drives Q1 and Q2 to turn on, and the input power supply VBUS excites the P1 winding through Q1, Q2 and R4 to store and convert energy. Then PWM drives Q1 and Q2 to turn off. The energy stored in the P1 winding is coupled to the S1 winding through the magnetic core and transferred to C4 through D1 to power the load;

[0023] S2: Since the P1 winding and the S1 winding cannot be fully coupled, the energy stored in the leakage inductance of the P1 winding cannot be transferred to C4 when Q1 and Q2 are turned off, and can only be transferred to C1 through the body diodes of Q3 and Q4;

[0024] S3: When AUX-PWM controls Q3 and Q4 to turn on, the energy transferred to C1 will be transferred back to the P1 winding leakage inductance. AUX-PWM controls Q3 and Q4 to turn off, and the energy stored in the P1 winding leakage inductance is used to discharge the DS junction capacitance of Q1 and Q2, thereby achieving the effect of turning on Q1 and Q2 at zero DS voltage.

[0025] This circuit is beneficial to improve the conversion efficiency of the power module while reducing the power module's requirements for the withstand voltage performance of the power switch tube. It can achieve zero voltage turn-on of Q1, Q2, Q3 and Q4, effectively reduce switching losses, increase operating frequency, and improve product power density. When the designed output reflected voltage is less than the input voltage, the voltage borne by Q1, Q2, Q3 and Q4 can be effectively reduced, and the range of optional devices is wider.

[0026] The above embodiments only express several implementation methods of the utility model, and the descriptions are relatively specific and detailed, but they cannot be understood as limiting the scope of the utility model patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the utility model, which all belong to the protection scope of the utility model.

Claims

1. A dual-tube flyback conversion circuit, comprising a dual-tube flyback circuit and an active clamping circuit, characterized in that: The dual-tube flyback circuit is composed of Q1, Q2, TX1, D1 and C4; the active clamp circuit is composed of Q3, Q4, C1, C2 and C3; TX1 is a flyback transformer, which is composed of at least two windings P1 and S1; D1 is an output rectifier device, and C4 is an output filter capacitor; Q1 is a first flyback circuit switch tube, Q2 is a second flyback circuit switch tube, and Q1 and Q2 are both controlled by a PWM controller and have the same duty cycle; Q3 and Q4 are controlled by AUX-PWM, with the same duty cycle and complementary or asynchronous non-complementary drive with Q1 and Q2 at the same frequency; R4 is a current sampling resistor; C2 is an absorption capacitor, which absorbs the energy of the transformer leakage inductance when Q1 and Q2 are turned off, and reversely charges the transformer when Q3 and Q4 are turned on. After Q3 and Q4 are turned off, the negative current of the primary side of the transformer is used to discharge the junction capacitance of Q1 and Q2 and turn on Q1 and Q2 with zero voltage.

2. The double-transistor flyback converter circuit according to claim 1, characterized in that: The operating frequency and duty cycle of Q1 and Q2 are adjusted according to the load.

3. The double-transistor flyback converter circuit according to claim 1, characterized in that: The voltage borne by Q1, Q2, Q3 and Q4 is: (VIN+VOUT*NP / NS) / 2; wherein NP is the number of turns of the primary side of the transformer, NS is the number of turns of the secondary side of the transformer, and VOUT*NP / NS is the voltage reflected from the output to the primary side.

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