A self-driven synchronous rectification circuit capable of amplitude limiting and current limiting

Abstract

A self-driven synchronous rectification circuit capable of limiting amplitude and current includes a voltage doubling power supply unit, a driving voltage amplitude limiting unit, a driving pull-up unit, and a driving pull-down unit. The voltage doubling power supply unit is used to collect the voltage on the auxiliary source winding for voltage doubling power supply. The driving voltage amplitude limiting unit is used to limit the amplitude of the driving voltage of the secondary synchronous rectifier tube. The driving pull-up unit is used to pull the driving signal of the secondary synchronous rectifier tube to a high level to turn on the secondary synchronous rectifier tube. The driving pull-down unit is used to pull the driving signal of the secondary synchronous rectifier tube to a low level to turn off the secondary synchronous rectifier tube. The overall circuit principle structure of the present invention is simple, with low power consumption and high reliability. The driving voltage amplitude limiting circuit is powered by voltage doubling through the auxiliary winding of the transformer, and two switching tubes are alternately turned on to generate a driving signal to control the conduction and turn-off of the secondary synchronous rectifier switching tube.

Description

Technical Field

[0001] The present invention relates to the technical field of power supplies, and particularly relates to a self-driven synchronous rectification circuit capable of limiting amplitude and current. Background Art

[0002] As a DC / DC converter for the secondary power supply of a system, the switching power supply is widely used in military and civilian electronic systems such as aerospace, aviation, ships, weapons, electronics, railways, communications, medical electronics, and industrial automation equipment. In the design of a switching power supply, the design of the secondary synchronous rectification circuit has a crucial impact on the efficiency and reliability of the power supply module. Usually, one end of the secondary winding of the transformer is connected to the gate of the synchronous rectification tube to complete the self-driving of the synchronous rectification tube. However, as the input voltage of the power supply system becomes wider and wider, this traditional secondary-side synchronous rectification circuit can no longer meet the design requirements of the power supply module. Summary of the Invention

[0003] A self-driven synchronous rectification circuit capable of limiting amplitude and current proposed by the present invention can achieve amplitude and current limiting of the secondary synchronous rectification drive signal and improve the reliability of the product.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] A self-driven synchronous rectification circuit capable of limiting amplitude and current includes:

[0006] It includes a voltage doubling power supply unit, a drive voltage limiting unit, a drive pull-up unit, and a drive pull-down unit;

[0007] The input end of the voltage doubling power supply unit is connected to the auxiliary source winding, and the output end is connected to the input end of the drive voltage limiting unit, and is used to generate a supply voltage and send it to the drive voltage limiting unit;

[0008] The input end of the drive voltage limiting unit is connected to the output end of the voltage doubling power supply unit, and the output end of the drive voltage limiting unit is connected to the input end of the drive pull-up unit and serves as the switching tube conduction voltage of the drive pull-up unit;

[0009] The input end of the drive pull-up unit is connected to the output end of the drive voltage limiting unit, and the output end of the drive pull-up unit is the pull-up drive signal of the secondary rectification tube. After the primary switching tube is turned off, the drive pull-up unit controls the conduction of the secondary rectification tube. Among them, the switching tube in the drive pull-up unit controls the drive signal through a current limiting resistor, playing a role in driving current limiting;

[0010] The input end of the drive pull-down unit is the secondary transformer drive signal, and the output end of the drive pull-down unit is the pull-down drive signal of the secondary rectification tube. After the primary switching tube is turned on, the drive pull-down unit controls the turn-off of the secondary rectification tube.

[0011] Furthermore, the voltage multiplier power supply unit includes capacitors C1 and C2, and rectifying diodes D2 and D3. One end of capacitor C1 in the voltage multiplier power supply unit is connected to the auxiliary source transformer winding, and the other end of capacitor C1 is connected to the positive terminal of rectifying diode D2 and the negative terminal of rectifying diode D3. The negative terminal of rectifying diode D2 is connected to one end of capacitor C2, and the other end of capacitor C2 is connected to the positive terminal of rectifying diode D3 and the output ground.

[0012] Furthermore, the driving voltage limiting unit includes resistors R2 and R3, capacitor C3, and zener diode D4. One end of resistor R2 in the driving voltage limiting unit is connected to capacitor C2 of the voltage multiplier power supply circuit and the negative terminal of rectifying diode D2. The other end of resistor R2 is connected to one end of resistor R3 and the negative terminal of zener diode D4. The other end of resistor R3 is connected to one end of capacitor C3, and the other end of capacitor C3 is connected to the positive terminal of zener diode D4 and then to the output ground.

[0013] Furthermore, the driving pull-up unit includes diode D1, NMOS transistor Q1, and resistor R1. The positive terminal of diode D1 in the driving pull-up unit is connected to the auxiliary source transformer winding, and the negative terminal of diode D1 is connected to the drain of NMOS transistor Q1. The primary of NOMS transistor Q1 is connected to R3 and one end of C3 in the driving voltage limiting unit. The source of NMOS transistor Q1 is connected to one end of resistor R1, and the other end of resistor R1 is connected to the driving signal of the secondary synchronous rectification circuit.

[0014] Furthermore, the driving pull-down unit includes resistor R4 and NMOS transistor Q2. One end of resistor R4 in the driving pull-down unit is connected to the secondary transformer driving winding and the primary of NMOS transistor Q2. The other end of resistor R4 and the source of NMOS transistor Q2 are connected to the output ground, and the drain of NMOS transistor Q2 is connected to the driving signal of the secondary synchronous rectification circuit.

[0015] As can be seen from the above technical solutions, for the self-driven synchronous rectification circuit with amplitude and current limiting of the present invention, the voltage on the auxiliary source winding is rectified by voltage doubling and supplied to the driving voltage limiting unit. Only by rectifying the voltage of the center tap pulse of the transformer by voltage doubling can the voltage be provided for the subsequent driving voltage limiting unit, saving the design of the external power supply circuit. The driving voltage limiting unit enables the switching tube in the driving pull-up unit to conduct and keeps the driving voltage at a stable value. Through the action of the current limiting resistor, the primary conduction current of the switching tube in the driving pull-up unit will not exceed the limit value, ensuring the reliability of the subsequent rectification circuit. When the primary switching tube is turned off, the switching tube in the driving pull-up unit will pull up the driving signal, thus ensuring the conduction of the subsequent rectifying tube. When the primary switching tube is turned on, the switching tube in the driving pull-down unit will pull down the driving signal, thus ensuring the turn-off of the subsequent rectifying tube. The whole circuit principle structure is simple, with low power consumption, high reliability, small occupied space and high applicability of the circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is the circuit block diagram of the present invention;

[0017] Figure 2 is the circuit schematic diagram of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0018] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some but not all of the embodiments of the present invention.

[0019] As Figure 1 shown, the self-driven synchronous rectification circuit with amplitude and current limiting described in this embodiment includes a voltage doubling power supply unit, a driving voltage limiting unit, a driving pull-up unit and a driving pull-down unit.

[0020] Among them, the voltage doubling power supply unit is used to collect the voltage on the auxiliary source winding for voltage doubling power supply;

[0021] The driving voltage limiting unit is used to limit the driving voltage of the secondary synchronous rectifying tube;

[0022] The driving pull-up unit is used to pull up the driving signal of the secondary synchronous rectifying tube to a high level and perform current limiting control to make the secondary synchronous rectifying tube conduct;

[0023] The driving pull-down unit is used to pull down the driving signal of the secondary synchronous rectifying tube to a low level to turn off the secondary synchronous rectifying tube.

[0024] Specifically, the input end of the voltage multiplier power supply unit 1 is connected to the auxiliary source winding, and the output end is connected to the input end of the drive voltage limiting unit 2, which is used to generate the supply voltage and send it to the drive voltage limiting unit 2.

[0025] The input end of the drive voltage limiting unit 2 is connected to the output end of the voltage multiplier power supply unit 1, and the output end of the drive voltage limiting unit 2 is connected to the input end of the drive pull-up unit 3 and serves as the switching tube conduction voltage of the drive pull-up unit 3.

[0026] The input end of the drive pull-up unit 3 is connected to the output end of the drive voltage limiting unit 2, and the output end of the drive pull-up unit 3 is the pull-up drive signal of the secondary rectifying diode. After the primary switching tube is turned off, the drive pull-up unit 3 controls the conduction of the secondary rectifying diode. Among them, the switching tube in the drive pull-up unit 3 controls the drive signal through the current limiting resistor, which can play a role in driving current limiting.

[0027] The input end of the drive pull-down unit 4 is the secondary transformer drive signal, and the output end of the drive pull-down unit 4 is the pull-down drive signal of the secondary rectifying diode. After the primary switching tube is turned on, the drive pull-down unit 4 controls the turn-off of the secondary rectifying diode.

[0028] As Figure 2 shown, the voltage multiplier power supply unit 1 of this embodiment is composed of capacitors C1, C2, rectifying diodes D2, D3. One end of the capacitor C1 is connected to the auxiliary source transformer winding, and the other end is connected to the positive electrode of the rectifying diode D2 and the negative electrode of the rectifying diode D3. The negative electrode of the rectifying diode D2 is connected to one end of the capacitor C2, and the other end of the capacitor C2 is connected to the positive electrode of the rectifying diode D3 and the output ground.

[0029] The drive voltage limiting unit 2 is composed of resistors R2, R3, capacitor C3, and zener diode D4. One end of the resistor R2 is connected to the capacitor C2 of the voltage multiplier power supply circuit and the negative end of the rectifying diode D2, and the other end of the resistor R2 is connected to one end of the resistor R3 and the negative end of the zener diode D4. The other end of the resistor R3 is connected to one end of the capacitor C3, and the other end of the capacitor C3 is connected to the positive end of the zener diode D4 and then to the output ground.

[0030] The drive pull-up unit 3 is composed of diode D1, NMOS transistor Q1, and resistor R1. The positive end of the diode D1 is connected to the auxiliary source transformer winding, the negative end of the diode D1 is connected to the drain of the NMOS transistor Q1, the primary of the NOMS transistor Q1 is connected to one end of R3 and C3 in the drive voltage limiting unit, the source of the NMOS transistor Q1 is connected to one end of the resistor R1, and the other end of the resistor R1 is the drive signal of the secondary synchronous rectification circuit.

[0031] The driving pull-down unit 4 is composed of a resistor R4 and an NMOS transistor Q2. One end of the resistor R4 is connected to the driving winding of the secondary transformer and the primary of the NMOS transistor Q2. The other end of the resistor R4 and the source of the NMOS transistor Q2 are connected to the output ground. The drain of the NMOS transistor Q2 is the driving signal of the secondary synchronous rectification circuit.

[0032] Working principle: In the voltage-doubling power supply unit 1, the voltage pulse on the auxiliary source winding passes through C1, D2, and D3, and is filtered by C2 to form a voltage-doubling rectification circuit, becoming the DC voltage supplied to the driving voltage limiting unit 2. The driving voltage limiting unit 2 forms a stable voltage driving signal through R2 and the zener diode D4, which is filtered by R3 and C3 and then enters the primary of the switching transistor Q1 in the driving pull-up unit 3. In the driving pull-up unit 3, the drain of the switching transistor Q1 is reversely connected to the diode D1 to prevent current backflow. At the same time, the source is connected to the current-limiting resistor R1 to form a driving signal that can limit the amplitude and current. When the primary switching transistor is turned off, the diode D1 is turned on, and the driving signal is pulled high through the switching transistor Q1 to turn on the secondary rectifying diode. In the driving pull-down unit 4, when the primary switching transistor is turned on, the switching transistor Q2 is turned on to pull down the driving signal to turn off the secondary rectifying diode.

[0033] As can be seen from the above, a self-driven synchronous rectification circuit with amplitude and current limiting described in the present invention is applicable to various isolated switching power supplies. Through this circuit, the driving signal of the secondary rectifying diode can be generated to ensure the stable operation of the secondary synchronous rectification circuit. Moreover, the circuit requires fewer components, has low power consumption, is safe and reliable, is beneficial to reducing the size of the power supply module, improving the reliability of the converter, and providing guarantee for system safety.

[0034] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A self-driven synchronous rectification circuit capable of amplitude limiting and current limiting, characterized in that: It includes a voltage multiplier power supply unit (1), a driving voltage limiting unit (2), a driving pull-up unit (3), and a driving pull-down unit (4). The input end of the voltage multiplier power supply unit (1) is connected to the auxiliary source winding, and the output end is connected to the input end of the driving voltage limiting unit (2), which is used to generate a power supply voltage and send it to the driving voltage limiting unit. The input end of the driving voltage limiting unit (2) is connected to the output end of the voltage multiplier power supply unit (1), and the output end of the driving voltage limiting unit (2) is connected to the input end of the driving pull-up unit (3), and is used as the switching tube conduction voltage of the driving pull-up unit. The input end of the driving pull-up unit (3) is connected to the output end of the driving voltage limiting unit (2), and the output end of the driving pull-up unit (3) is the pull-up driving signal of the secondary rectifying diode. After the primary switching tube is turned off, the driving pull-up unit (3) controls the conduction of the secondary rectifying diode. Among them, the switching tube in the driving pull-up unit (3) controls the driving signal through a current limiting resistor, playing a role in driving current limiting. The input end of the driving pull-down unit (4) is the secondary transformer driving signal, and the output end of the driving pull-down unit (4) is the pull-down driving signal of the secondary rectifying diode. After the primary switching tube is turned on, the driving pull-down unit (4) controls the turn-off of the secondary rectifying diode. The voltage multiplier power supply unit (1) includes capacitors C1 and C2, and rectifying diodes D2 and D3. One end of the capacitor C1 in the voltage multiplier power supply unit is connected to the auxiliary source transformer winding, the other end of the capacitor C1 is connected to the positive end of the rectifying diode D2 and the negative end of the rectifying diode D3, the negative end of the rectifying diode D2 is connected to one end of the capacitor C2, and the other end of the capacitor C2 is connected to the positive end of the rectifying diode D3 and connected to the output ground. The driving voltage limiting unit (2) includes a resistor R2, and one end of the resistor R2 is connected to the capacitor C2 of the voltage multiplier power supply circuit and the negative end of the rectifying diode D2.

2. The self-driven synchronous rectification circuit capable of amplitude limiting and current limiting according to claim 1, characterized in that: The driving voltage limiting unit (2) includes a resistor R3, a capacitor C3, and a zener diode D4. The other end of the resistor R2 in the driving voltage limiting unit (2) is connected to one end of the resistor R3 and the negative end of the zener diode D4, the other end of the resistor R3 is connected to one end of the capacitor C3, and the other end of the capacitor C3 is connected to the positive end of the zener diode D4 and connected to the output ground.

3. The self-driven synchronous rectification circuit capable of amplitude limiting and current limiting according to claim 1, characterized in that: The driving pull-up unit (3) includes a diode D1, an NMOS transistor Q1, and a resistor R1. The positive end of the diode D1 in the driving pull-up unit (3) is connected to the auxiliary source transformer winding, the negative end of the diode D1 is connected to the drain of the NMOS transistor Q1, the primary of the NOMS transistor Q1 is connected to one end of the R3 and C3 in the driving voltage limiting unit, the source of the NMOS transistor Q1 is connected to one end of the resistor R1, and the other end of the resistor R1 is connected to the driving signal of the secondary synchronous rectification circuit.

4. The self-driven synchronous rectification circuit capable of amplitude limiting and current limiting according to claim 1, characterized in that: The driving pull-down unit (4) includes a resistor R4 and an NMOS transistor Q2. One end of the resistor R4 in the driving pull-down unit (4) is connected to the secondary transformer driving winding and the primary of the NMOS transistor Q2. The other end of the resistor R4 and the source of the NMOS transistor Q2 are connected to the output ground, and the drain of the NMOS transistor Q2 is connected to the driving signal of the secondary synchronous rectification circuit.

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