WO2023098199A1

WO2023098199A1 - High-power-density auxiliary power supply based on self-excited buck converter

Info

Publication number: WO2023098199A1
Application number: PCT/CN2022/117122
Authority: WO
Inventors: 钱钦松; 董天昊; 谷诚; 郑德军; 孙伟锋; 时龙兴
Original assignee: 东南大学
Priority date: 2021-11-30
Filing date: 2022-09-05
Publication date: 2023-06-08
Also published as: CN114157147B; CN114157147A

Abstract

Disclosed in the present invention is a high-power-density auxiliary power supply circuit of a self-excited buck converter. The auxiliary power supply comprises a buck main loop (1), a reset drive circuit (2), a current limiting protection circuit (3), and a voltage stabilizing circuit (4), wherein an input end of the buck main loop (1) is connected to the current limiting protection circuit (3); an output end of the buck main loop (1) is connected to the voltage stabilizing circuit (4); an output end of the voltage stabilizing circuit (4), i.e., an output voltage (Vout), is connected to a load (Load); an input end of the current limiting protection circuit (3) is connected to an input voltage (Vin2); one end of the reset drive circuit (2) is connected to the current limiting protection circuit (3), and the other end is connected to the output voltage (Vout). The present invention solves the problems that an existing self-excited buck converter is low in power density, not wide enough in received input voltage, not high enough in working frequency, high in output ripple, and high in noise, and meanwhile, also achieves the functions of overvoltage protection, overcurrent protection, and adaptive soft start.

Description

High Power Density Auxiliary Power Supply Based on Self-excited Buck Converter

technical field

The invention relates to a self-excited DC-DC step-down converter auxiliary power supply with high power density, which is applicable to the application occasions of high voltage input and low voltage output.

Background technique

In some low-power power supply applications, self-excited converters have the advantages of simple circuit structure, high efficiency, and low cost compared with linear voltage regulators and other-excited converters.

The main switching tube and each control tube of a traditional self-excited buck converter are usually implemented with bipolar transistors. Chinese patent ZL99108088.2 discloses a self-excited DC-DC converter in the form of a bipolar transistor, as shown in FIG. 1 . Including the step-down converter circuit composed of PNP transistor Q1, inductor L1, diode D1 and capacitor C2, Vo is the DC output voltage, Vi is the DC input voltage, the negative terminal of Vi is directly connected to the negative terminal of Vo, and R7 is the output load , the capacitor C2 is connected in parallel across the load R7. The coupled inductor L2 is connected to the emitter and the base of the transistor Q1 through the capacitor C1 and the resistor R3 respectively, and is connected to the emitter and the collector of the transistor Q2. The base of the transistor Q1 is connected to the negative terminals of the DC input and the DC output through the resistor R4. The transistor Q2 is connected to the emitter of the transistor Q1 and the collector of the transistor Q3 through the resistors R1 and R2 respectively. The resistor R5 and the resistor R6 are connected in parallel to both ends of the load R7 through a series branch, and the connection point between R5 and R6 is connected to the base of the transistor Q3. The emitter of the transistor Q3 is connected to the negative terminals of the DC input and the DC output. The working principle of the bipolar transistor self-excited DC-DC converter is as follows: when the input voltage is powered on, Q1 is saturated and turned on, diode D1 and transistor Q2 are cut off, and Q1, L1, C2, R7, R5, R6 form loop, so that the inductor L1 and the capacitor C2 are charged. During the charging process, the current through L1 gradually increases, and the output voltage increases at the same time, and the emitter-collector voltage of transistor Q1 increases accordingly, so that the operating point of transistor Q1 gradually exits the saturation region, and the voltage at both ends of L1 decreases. The voltage across the coupling inductor L2 also decreases accordingly, which increases the shunt flow of the base current of the transistor Q1, causing the base current and collector current of Q1 to decrease rapidly. This phenomenon will make the emitter-collector of Q1 The electrode voltage increases further, whereby the circuit enters a deep positive feedback state. The result of this state is that the collector current through the transistor Q1 decreases rapidly. When the current is smaller than the current of the inductor L1, the diode D1 conducts to freewheel the L1, and then Q1 is cut off. At this time, L1, C2, R7, R5, R6, and D1 form a loop and enter the state of energy release. After the discharge of the inductor L1 is completed, the diode D1 is cut off, and the Q1 is saturated and turned on again, and enters the next self-excited cycle. After several working cycles, the output voltage Vo reaches the set voltage value, and the voltage feedback circuits R5, R6, Q3, R1, R2 start to work. When the output voltage value is higher than the set voltage value, the transistor Q3 enters the conduction state, causing Q2 to conduct and shunt a part of the base current of Q1, so that the transistor Q1 is turned off in advance, so that the conduction time of Q1 is reduced and the off time is reduced. When the output voltage value is lower than the set voltage value, the transistor Q3 is in the cut-off state, and the transistor Q2 is also cut off, and the turn-on time and turn-off time of Q1 return to the original state, thereby realizing the state of regulated output. The circuit has disadvantages: firstly, the circuit must participate in the self-excitation work through the coupled inductor L2. Due to the complicated production of the coupled inductor, it is not conducive to the miniaturization of electronic products and is prone to electromagnetic interference and additional parasitic effects. High power density. In addition, this product uses a bipolar transistor as a switch tube, which is not conducive to the integration and simplification of the circuit, and due to the working characteristics of the bipolar transistor, it is easy to be limited in the condition of high frequency and high voltage.

Contents of the invention

Technical problem: The purpose of the present invention is to provide a self-excited buck converter auxiliary power supply with high power density. The invention solves the problems of not high enough power density, not wide enough voltage input, not high enough working frequency and complex circuit structure in the existing self-excited step-down converter.

Technical solution: A high power density self-excited step-down converter auxiliary power supply of the present invention includes: a step-down main circuit, a reset drive circuit, a current limiting protection circuit, and a voltage stabilizing circuit; wherein, the input end of the step-down main circuit Connect to the current limiting protection circuit, the output terminal of the step-down main circuit is connected to the voltage stabilizing circuit, the output terminal of the voltage stabilizing circuit is connected to the load, the input terminal of the current limiting protection circuit is connected to the input voltage; one terminal of the reset driving circuit is connected to the current limiting protection circuit circuit, and the other end is connected to the output voltage.

in,

The step-down main loop includes an eighth capacitor, a ninth capacitor, a sixth diode, a second inductor, and a fifth PMOS transistor; wherein, the step-down main loop is connected to the current-limiting protection circuit through the source of the fifth PMOS transistor, and the step-down The drain of the voltage main circuit is connected to the eighth capacitor and the sixth diode, and connected to the positive terminal of the output voltage through the second inductor.

The reset drive circuit includes an eleventh capacitor, a thirteenth capacitor, a tenth resistor, an eleventh resistor, an eighth NMOS transistor, a fifth diode, a seventh diode, and a control signal interface; the reset drive circuit Connect to the sixth PMOS transistor through the fifth diode, and connect to the positive output voltage terminal through the thirteenth capacitor; the gate of the eighth NMOS transistor is connected to the control terminal through the eleventh capacitor, and the drain of the eighth NMOS transistor is connected to the first The thirteenth capacitor, the tenth resistor, and the source are grounded.

The current limiting protection circuit includes a ninth resistor, a twelfth resistor, an eighth resistor and a sixth PMOS transistor; the gate of the sixth PMOS transistor is connected to the eighth resistor and the drain of the seventh NMOS transistor, and the drain of the sixth PMOS transistor The pole is connected to the gate of the fifth PMOS transistor, the source of the sixth PMOS transistor is connected to the twelfth resistor, the other end of the twelfth resistor is connected to the drain of the fifth PMOS transistor in the step-down main circuit, and the other end of the eighth resistor The current sampling resistor is connected to the twelfth resistor.

The voltage stabilizing circuit includes a seventh capacitor, a seventh PMOS transistor and a voltage stabilizing diode; the voltage stabilizing circuit is connected to the current limiting protection circuit through the drain of the seventh NMOS transistor, the gate of the seventh NMOS transistor is connected to the positive voltage output terminal, and the seventh NMOS transistor is connected to the positive voltage output terminal. The source of the NMOS transistor is connected to the seventh capacitor and the Zener diode.

The sixth capacitor is used as an input filter capacitor and connected in parallel to the positive terminal and the negative terminal of the input voltage.

Beneficial effect: compared with the prior art, the beneficial effect of the present invention is mainly manifested in:

(1) The present invention has the feature of accepting a wide range of inputs.

(2) The reset driving circuit of the present invention has a control signal interface of the main control chip. The control signal can determine the upper limit of the operating frequency of the buck converter while controlling the start of the main circuit of the buck converter. At the same time, the step-down converter in the present invention can work at a relatively high operating frequency, has the characteristics of low ripple and low noise, and generates relatively low electromagnetic interference.

(3) The main power tube and each control tube of the present invention are all metal-oxide-semiconductor field-effect transistors, which are easy to integrate. In addition, there is no need to use coupled inductors to participate in the self-excited work of the circuit, which can better simplify the complexity of the circuit and achieve higher power density. It is very suitable for application scenarios such as auxiliary power supply circuits in low-power switching power supplies.

(4) The present invention realizes the functions of overvoltage protection, overcurrent protection and adaptive soft start.

Description of drawings

Fig. 1 is a circuit diagram of an existing self-excited step-down converter;

Fig. 2 is a circuit diagram of the present invention;

Fig. 3 is the working waveform diagram of the present invention working under a certain load;

Fig. 4 is a working waveform diagram of the present invention working under different load modes;

In the figure, there are: step-down main circuit 1, reset driving circuit 2, current limiting protection circuit 3, voltage stabilizing circuit 4; input voltage V _in2 , output voltage V _out , eighth capacitor C8, ninth capacitor C9, sixth diode Tube D6, second inductor L2, fifth PMOS tube Q5, eleventh capacitor C11, thirteenth capacitor C13, tenth resistor R10, eleventh resistor R1, eighth NMOS tube Q8, fifth diode D5, The seventh diode D7, the control signal interface Control; the ninth resistor R9, the twelfth resistor R12, the eighth resistor R8, the sixth PMOS transistor Q6; the seventh capacitor C7, the seventh PMOS transistor Q7, the Zener diode D8, The sixth capacitor C6.

Detailed ways

The specific embodiments of the present invention will be further introduced below in conjunction with the accompanying drawings.

As shown in Figure 2, the present invention is a self-excited step-down converter. The circuit structure of the present invention includes: a step-down main circuit 1, a reset drive circuit 2, a current limiting protection circuit 3, and a voltage stabilizing circuit 4; The output terminal of the voltage stabilizing circuit 4 is connected to the voltage stabilizing circuit 4, the output terminal of the voltage stabilizing circuit 4 is the output voltage V _out connected to the load Load, the input terminal of the current limiting protection circuit 3 is connected to the input voltage V _in2 ; one terminal of the reset driving circuit 2 is connected to the current limiting protection circuit 3. The other terminal is connected to the output voltage V _out . The step-down main loop includes an eighth capacitor C8, a ninth capacitor C9, a sixth diode D6, a second inductor L2, and a fifth PMOS transistor Q5. The reset driving circuit includes an eleventh capacitor C11, a thirteenth capacitor C13, a tenth resistor R10, an eleventh resistor R11, an eighth NMOS transistor Q8, a fifth diode D5, a seventh diode D7 and a control signal interface. The current limiting protection circuit includes a ninth resistor R9, a twelfth resistor R12, an eighth resistor R8 and a sixth PMOS transistor Q6. The voltage stabilizing circuit includes a seventh capacitor C7, a seventh PMOS transistor Q7 and an eighth voltage stabilizing diode D8. The sixth capacitor C6 is used as an input filter capacitor and connected in parallel to the positive terminal of the input voltage and the negative terminal of the input voltage.

In the circuit diagram of the present invention, the input voltage V _in2 is the output voltage of the power supply circuit. The main power fifth PMOS transistor Q5, the second inductor L2 and the sixth diode D6 constitute the main circuit of the step-down converter. A current sampling twelfth resistor R12 and a fifth diode D5 are connected in series before the main circuit of the step-down converter, and the anode of the fifth diode D5 is connected to the positive terminal of the input voltage.

In the reset drive circuit, the gate of the eighth NMOS transistor Q8 is connected to the eleventh capacitor C11 and the eleventh resistor R11, the source is grounded, and the drain is connected to the thirteenth capacitor C13 and the tenth resistor R10. The other end of the eleventh capacitor C11 is connected to the main control chip signal to control the conduction state of the eighth NMOS transistor Q8, and the other end of the eleventh resistor R11 is grounded to form a filter circuit with the eleventh capacitor C11. The tenth resistor R10 and the fifth diode D5 are connected in series to the drain of the sixth PMOS transistor Q6 in the current limiting and control circuit, and the other end of the thirteenth capacitor C13 is connected to the positive end of the output voltage. The circuit is used to periodically pull down and turn on the fifth main power PMOS transistor Q5 in the main circuit of the step-down converter.

In the current limiting and control circuit, the gate of the sixth PMOS transistor Q6 is connected to the drain of the eighth resistor R8 and the drain of the seventh PMOS transistor Q7 in the voltage stabilizing circuit, and the drain is connected to the cathode of the fifth diode D5, and the drain of the eighth resistor R8 The other end is connected with the twelfth current sampling resistor R12. The circuit is used to pull up the main power fifth PMOS transistor Q5 to end the current working cycle when the voltage stabilization control and the current limiting control are triggered.

In the voltage stabilizing circuit, the gate of the seventh PMOS transistor Q7 is connected to the positive terminal of the output voltage, and the source is connected to the voltage stabilizing transistor, that is, the cathode of the eighth diode D8. This circuit is used to control the stability of the output voltage.

The switching tubes and control tubes used in the present invention are all metal oxide semiconductor field effect transistors, which are easy to integrate and have good application value in reducing the volume of the power supply and increasing the power density.

Below in conjunction with Fig. 3 illustrate the operating principle of this inventive circuit:

In the working waveform diagram shown in Figure 3, at time t0, the gate and source voltages of the fifth main power PMOS transistor Q5 are close to the input voltage, and the gate-source voltage of the fifth PMOS transistor Q5 does not reach the threshold voltage, thus the circuit Job not turned on. At this time, the main control chip gives a turn-on signal to reset and start the gate of the eighth PMOS transistor Q8, and the eighth PMOS transistor Q8 is turned on and pulls down the gate voltage of the fifth PMOS transistor Q5. At this time, the gate-source voltage of the fifth main power PMOS transistor Q5 reaches the threshold voltage and is turned on, and the current of the second inductor L2 rises.

The twelfth resistor R12 in the current limiting and control circuit samples the current of the second inductor L2, if the current output exceeds the set value, the divided voltage of the twelfth resistor R12 will exceed the current limiting control sixth PMOS transistor Q6 At time t1 in the figure, the sixth PMOS transistor Q6 will be turned on to pull up the gate voltage of the fifth PMOS transistor Q5 of the main power transistor to turn it off, close the working cycle and wait for the main control chip to give the next turn-on signal to enter the next duty cycle. Therefore, the purpose of reducing the turn-on time of the fifth PMOS transistor Q5 of the main power transistor and increasing the turn-off time can be achieved by detecting the current passing through the second inductor L2.

In each working cycle, the ninth capacitor C9 will gain or lose a certain amount of charge, so that the output voltage will have a certain change. If in a certain cycle, when the reference voltage value of the voltage stabilizing diode D8 increases to exceed the sum of the threshold voltage of the seventh PMOS transistor Q7 of the voltage stabilizing control, the voltage stabilizing regulation is turned on, and the seventh PMOS transistor Q7 of the voltage stabilizing control is turned on, Make the gate-source voltage of the sixth PMOS transistor Q6 reach the threshold voltage and be turned on, so as to turn off the main power transistor and the fifth PMOS transistor Q5 to turn off the current working cycle. At this time, wait for the main control chip to give the next turn-on signal to enter the next working cycle. Therefore, the purpose of reducing the turn-on time of the fifth PMOS transistor Q5 of the main power transistor and increasing the turn-off time can be achieved by detecting the output voltage value. When the output voltage falls back below the set value again, the seventh PMOS transistor Q7 is turned off so that the sixth PMOS transistor Q6 is turned off, and the turn-on time and turn-off time of the fifth PMOS transistor Q5 of the main power transistor return to normal, which is determined by This achieves the purpose of stabilizing the voltage.

As shown in Fig. 4, when the present invention works in the light load mode, it will automatically work at a lower operating frequency, thereby entering the DCM mode. In this mode, the current passing through the second inductor L2 will drop to 0 when the main power transistor is turned off, thereby reducing the switching loss. When the present invention works in the heavy load mode, it will automatically work at a higher operating frequency, thereby entering the CCM mode, thereby effectively reducing the output ripple.

The undisclosed technologies of the present invention belong to the common knowledge of those skilled in the art.

Claims

A self-excited step-down converter auxiliary power supply with high power density, characterized in that the auxiliary power supply includes: a step-down main circuit (1), a reset drive circuit (2), a current limiting protection circuit (3), a voltage stabilizing Circuit (4); wherein, the input terminal of the step-down main circuit (1) is connected to the current limiting protection circuit (3), the output terminal of the step-down main circuit (1) is connected to the voltage stabilizing circuit (4), and the voltage stabilizing circuit (4) The output terminal of the output voltage (V out ) is connected to the load (Load), the input terminal of the current limiting protection circuit (3) is connected to the input voltage (V in2 ); one terminal of the reset driving circuit (2) is connected to the current limiting protection circuit (3) , and the other end is connected to the output voltage (V out ).
The self-excited step-down converter auxiliary power supply with high power density according to claim 1, characterized in that, the step-down main circuit (1) includes an eighth capacitor (C8), a ninth capacitor (C9), and a ninth capacitor (C9). Six diodes (D6), a second inductor (L2), and a fifth PMOS transistor (Q5); wherein, the step-down main circuit (1) is connected to the current limiting protection circuit (3) through the source of the fifth PMOS transistor (Q5) , the drain of the step-down main circuit (1) is connected to the eighth capacitor (C8), the sixth diode (D6), and connected to the positive terminal of the output voltage (V out ) through the second inductor (L2).
The self-excited step-down converter auxiliary power supply with high power density according to claim 1, characterized in that, the reset driving circuit (2) comprises an eleventh capacitor (C11), a thirteenth capacitor (C13), The tenth resistor (R10), the eleventh resistor (R11), the eighth NMOS tube (Q8), the fifth diode (D5), the seventh diode (D7) and a control signal interface (Control); reset The driving circuit (2) is connected to the sixth PMOS transistor (Q6) through the fifth diode (D5), and connected to the positive terminal of the output voltage (V out ) through the thirteenth capacitor (C13); the eighth NMOS transistor (Q8) The gate of the NMOS tube is connected to the control terminal (Control) through the eleventh capacitor (C11), the drain of the eighth NMOS transistor (Q8) is connected to the thirteenth capacitor (C13), the tenth resistor (R10), and the source is grounded.
The self-excited step-down converter auxiliary power supply with high power density according to claim 1, characterized in that, the current limiting protection circuit (3) includes a ninth resistor (R9), a twelfth resistor (R12), The eighth resistor (R8) and the sixth PMOS transistor (Q6); the gate of the sixth PMOS transistor (Q6) is connected to the eighth resistor (R8) and the drain of the seventh NMOS transistor (Q7), and the sixth PMOS transistor (Q6) The drain of the transistor is connected to the gate of the fifth PMOS transistor (Q5), the source of the sixth PMOS transistor (Q6) is connected to the twelfth resistor (R12), and the other end of the twelfth resistor (R12) is connected to the step-down main circuit (1) The drain of the fifth PMOS transistor (Q5), the other end of the eighth resistor (R8) is connected to the current sampling resistor, that is, the twelfth resistor (R12).
The self-excited step-down converter auxiliary power supply with high power density according to claim 1, characterized in that, the voltage stabilizing circuit (4) includes a seventh capacitor (C7), a seventh PMOS transistor (Q7) and a stabilizing Diode (D8); the voltage regulator circuit (4) is connected to the current limiting protection circuit (3) through the drain of the seventh NMOS transistor (Q7), and the gate of the seventh NMOS transistor (Q7) is connected to the positive terminal of the voltage output (V out ) , the source of the seventh NMOS transistor (Q7) is connected to the seventh capacitor (C7) and the Zener diode (D8).
The high power density self-excited step-down converter auxiliary power supply according to claim 1, characterized in that the sixth capacitor (C6) is used as an input filter capacitor and connected in parallel to the positive terminal and negative terminal of the input voltage (V in2 ) .