Slow start circuit with negative feedback constant current control

Abstract

The invention provides a slow start circuit with negative feedback constant current control. The slow start circuit comprises a power supply start circuit, a Hall sampling circuit, a negative feedback regulation circuit and a surge suppression circuit, according to the circuit, by accurately controlling the starting slope and dynamic current limiting, the phenomena of surge current and overshoot are effectively restrained, and meanwhile the stability and reliability of a system are remarkably improved. The circuit is simple, a complex PWM control circuit is not needed, starting current is sampled in real time through the Hall sensor, rapid response is achieved through the negative feedback comparator, it is ensured that the constant current characteristic is accurate, the starting process is stable, and current impact is avoided. The method can meet the requirements of constant-current starting under different load conditions, and has good adaptability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power supply, in particular to a slow start circuit with negative feedback constant current control. BACKGROUND

[0002] In many electronic devices, especially in high-power power supply systems, due to the existence of large filter capacitors at the load end, during power-on, the capacitors are equivalent to a short circuit, which will generate a large inrush current. This inrush current is far beyond the normal working current of the device, which may cause fuse blowout, switch device damage, power grid voltage drop, and even cause the entire system to fail.

[0003] To solve this problem, a common anti-inrush circuit is widely used in the prior art. Its typical structure is to parallel a power MOS tube and a power resistor in the main power loop. During the initial stage of power-on, the MOS tube is in the off state, and the input voltage charges the load capacitor through the series power resistor. When the capacitor voltage is charged to close to the input voltage, the control circuit drives the MOS tube to conduct, shorting the power resistor.

[0004] Although the above prior art solution reduces circuit loss after power-on is completed, it has control difficulties and secondary impact. In addition, this starting process is usually not smooth, which may cause fluctuations in the output voltage and affect the stable operation of the system. SUMMARY

[0005] To solve the above problems, the present application proposes a slow start circuit with negative feedback constant current control. By adopting a closed-loop control strategy, the charging current is monitored in real time, and the MOS tube is controlled through a negative feedback mechanism, thereby realizing constant charging current. This design not only effectively suppresses the inrush current, but also ensures a smooth starting process and avoids the generation of secondary impact current. In addition, the closed-loop control strategy can also improve the adaptability of the system, so that it can maintain constant charging current under different load conditions, thereby significantly improving the reliability and stability of the system.

[0006] The present application is realized by the following scheme:

[0007] A slow start circuit with negative feedback constant current control, comprising a power supply starting circuit, a Hall sampling circuit, a negative feedback regulation circuit and an inrush suppression circuit;

[0008] The power supply starting circuit comprises a fuse F1, a resistor R1 and a voltage stabilizing tube V1. The fuse F1 provides overcurrent protection for the power input positive terminal, one end of which is connected to the power input positive terminal VIN+, the other end of which is connected to one end of the resistor R1 and the positive terminal of the capacitor C5. The other end of the resistor R1 is connected to the cathode of the voltage stabilizing tube V1, and the anode of the voltage stabilizing tube V1 is connected to the input negative terminal.

[0009] The Hall sampling circuit comprises a Hall sensor N2, a resistor R15, capacitors C2 and C3; wherein the positive terminal of the Hall sensor N2 is connected with the source of a MOS tube V5; the negative terminal of the Hall sensor N2 is connected with an input negative terminal; one end of the resistor R15 and the capacitor C2 is connected with the output terminal of the Hall sensor N2, and the other end of the resistor R15 and the capacitor C2 is connected with a power supply negative terminal; one end of the capacitor C3 is connected with the power supply terminal Vcc of the Hall sensor N2, and the other end of the capacitor C3 is connected with the input negative terminal;

[0010] The negative feedback adjusting circuit comprises an operational amplifier N1, resistors R2-R9, a capacitor C1, a triode V2 and a diode V3; wherein one end of the resistor R2 is connected with the emitter e of the triode V2, and the other end of the resistor R2 is connected with an input negative terminal; one end of the resistor R3 and the capacitor C1 is connected with the base b of the triode V2 and one end of the resistor R5, and the other end of the resistor R3 and the capacitor C1 is connected with the input negative terminal; one end of the resistor R4 is connected with the collector c of the triode; one end of the resistor R4 is connected with the cathode of the diode V3; the anode of the diode V3 is connected with one end of the resistor R9, and the other end of the resistor R9 is connected with the cathode of the voltage stabilizing tube V1; the other end of the resistor R5 is connected with the output of the operational amplifier N1 and one end of the resistor R6, and the other end of the resistor R6 is connected with one end of the resistor R7 and the negative terminal of the operational amplifier N1, and the other end of the resistor R7 is connected with the input negative terminal; one end of the resistor R8 is connected with the positive terminal of the operational amplifier N1, and the other end of the resistor R8 is connected with the output terminal of the Hall sensor N2;

[0011] The surge suppressing circuit comprises a MOS tube V5, resistors R10 and R11, a capacitor C4 and a voltage stabilizing tube V4; wherein the gate of the MOS tube V5 is connected with one end of the resistors R10 and R11, the drain of the MOS tube V5 is connected with the negative terminal of the capacitor C5; the source of the MOS tube V5 is connected with the anode of the voltage stabilizing tube V4 and one end of the capacitor C4, the other end of the resistor R10 and the cathode of the voltage stabilizing tube V4 are connected with one end of the resistor R9; the other end of the resistor R11 and the other end of the capacitor C4 are connected.

[0012] Preferably, the voltage of the power supply input positive terminal is 270V.

[0013] Compared with the prior art, the present application has the following advantages:

[0014] The application is provided in the power supply control system of only high-voltage DC bus, and the voltage stabilizing tube V1 connected with the resistor R1 is used for power supply of the negative feedback operational amplifier and the Hall, without additional auxiliary power supply; the controllable integrator composed of the series connection of the resistor and the capacitor is used for accurately controlling the rising slope of the MOSFET gate voltage, so as to realize the smooth transition of the load current from 0 to the preset current limiting value. The negative feedback loop is composed of the operational amplifier N1 and the Hall sensor, is used for detecting the load current and dynamically adjusting the constant current output, so as to stabilize the load current at the preset current limiting value. The current limiting value can be flexibly set by adjusting the ratio of the resistors R6 and R7, so as to meet the needs of different load scenes.

[0015] The circuit effectively suppresses the inrush current and overshoot phenomenon by accurately controlling the starting slope and dynamic current limiting, and significantly improves the stability and reliability of the system. The circuit is simple, without complex PWM control circuit, by using the Hall sensor to sample the starting current in real time, and combining the negative feedback comparator to quickly respond, so as to ensure the accurate constant current characteristics, smooth starting process and avoid current impact. The circuit can meet the constant current starting needs under different load conditions, and has good adaptability. BRIEF DESCRIPTION OF DRAWINGS

[0016] Fig. 1 It is a system block diagram of the soft-start circuit principle;

[0017] Fig. 2 It is a principle diagram of the soft-start circuit with negative feedback constant current control;

[0018] Fig. 3 It is the simulation waveforms of the output voltage and starting current of the soft-start circuit. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical scheme and advantages of the application more clear and understandable, the application will be further described in detail below with reference to the drawings.

[0020] In combination Figs. 1-3 Taking the input DC 270V high-voltage power supply bus system as an example, in combination Fig. 2 The working mode of the soft-start circuit designed according to the application is described in detail.

[0021] The soft-start circuit of the application is shown in Figs. 1-2 The whole circuit includes the power supply starting circuit, the Hall sampling circuit, the negative feedback adjusting circuit and the inrush suppression circuit, etc.

[0022] Fig. 2In the power supply starting circuit, the fuse F1, the resistor R1 and the voltage stabilizing tube V1 are included. The fuse F1 is connected with the positive terminal of the power supply input 270Vin+ and the negative terminal of the power supply input 270Vin-. The resistor R1 is connected with the negative terminal of the power supply input 270Vin- and the cathode of the voltage stabilizing tube V1. The anode of the voltage stabilizing tube V1 is connected with the negative terminal of the input.

[0023] Fig. 2 In the Hall sampling circuit, the Hall sensor N2, the resistor R15, the capacitors C2 and C3 are included. The positive terminal of the Hall sensor N2 is connected with the source (S) of the MOS tube V5. The negative terminal of the Hall sensor N2 is connected with the negative terminal of the input. The resistor R15 and the capacitor C2 are connected with the output terminal of the Hall sensor N2. The resistor R15 and the capacitor C2 are connected with the negative terminal of the power supply. The capacitor C3 is connected with the power supply terminal Vcc of the Hall sensor N2. The capacitor C3 is connected with the negative terminal of the input.

[0024] Fig. 2 In the negative feedback adjusting circuit, the operational amplifier N1, the resistors R2-R9, the capacitor C1, the transistor V2 and the diode V3 are included. The resistor R2 is connected with the emitter e of the transistor V2. The resistor R2 is connected with the negative terminal of the input. The resistor R3 and the capacitor C1 are connected with the base b of the transistor V2 and the resistor R5. The resistor R3 and the capacitor C1 are connected with the negative terminal of the input. The resistor R4 is connected with the collector c of the transistor V2. The resistor R4 is connected with the cathode of the diode V3. The anode of the diode V3 is connected with the resistor R9. The resistor R9 is connected with the cathode of the voltage stabilizing tube V1. The resistor R5 is connected with the output of the operational amplifier N1 and the resistor R6. The resistor R6 is connected with the resistor R7 and the negative terminal of the operational amplifier N1. The resistor R7 is connected with the negative terminal of the input. The resistor R8 is connected with the positive terminal of the operational amplifier N1 and the output terminal of the Hall sensor N2.

[0025] Fig. 2 In the surge suppression circuit, the MOS tube V5, the resistors R10-R11, the capacitor C4 and the voltage stabilizing tube V4 are included. The gate (G) of the MOS tube V5 is connected with the resistors R10 and R11. The drain (D) of the MOS tube V5 is connected with the negative terminal of the capacitor C5. The source (S) of the MOS tube V5 is connected with the anode of the voltage stabilizing tube V4 and the capacitor C4. The resistor R10 is connected with the cathode of the voltage stabilizing tube V4. The resistor R11 is connected with the capacitor C4.

[0026] The working process of the slow start circuit is as follows: under the condition of high voltage bus DC 270V power supply, after the power supply system is powered on, the operational amplifier N1 and the Hall N2 are powered through R1. At the moment of starting voltage, the MOS tube driving voltage is 0, the MOS tube is completely cut off, the resistance between the drain D and the source S is extremely large, and the load ground circuit is disconnected. With the charging of C4, the driving voltage of the MOS tube slowly rises and starts to conduct, and its equivalent resistance slowly decreases from infinity. The load capacitor C5 starts to charge through the gradually decreasing resistance. Because the initial resistance is very large, the inrush current is effectively suppressed. The Hall N2 starts to detect the current in the main circuit and converts the current signal into a voltage signal and sends it to the positive terminal of the operational amplifier. With the increase of the main circuit current, the output voltage of the operational amplifier N1 gradually rises until the control triode V2 is turned on, adjusting the driving voltage of the MOS tube. The size of the slow start inrush current can be adjusted by the voltage division ratio of the resistors R6 and R7.

[0027] The specific embodiments described herein are merely illustrative of the spirit of the present application. Those skilled in the art of the present application can make various modifications, supplements or use similar ways to replace the described specific embodiments, but will not deviate from the spirit of the present application or exceed the scope defined by the appended claims.

Claims

1. A soft-start circuit with negative feedback constant current control, characterized in that, This includes a power supply startup circuit, a Hall sampling circuit, a negative feedback regulation circuit, and a surge suppression circuit; The power supply startup circuit includes a fuse F1, a resistor R1, and a Zener diode V1. The fuse F1 provides overcurrent protection for the positive power input terminal. One end of the fuse F1 is connected to the positive power input terminal VIN+, and the other end is connected to one end of the resistor R1 and the positive terminal of the capacitor C5. The other end of the resistor R1 is connected to the cathode of the Zener diode V1, and the anode of the Zener diode V1 is connected to the negative input terminal. The Hall sampling circuit includes a Hall sensor N2, a resistor R15, and capacitors C2 and C3. The positive terminal of the Hall sensor N2 is connected to the source of the MOSFET V5; the negative terminal of the Hall sensor N2 is connected to the negative input terminal; one end of the resistor R15 and capacitor C2 is connected to the output terminal of the Hall sensor N2, and the other end of the resistor R15 and capacitor C2 is connected to the negative power supply terminal; one end of capacitor C3 is connected to the power supply terminal Vcc of the Hall sensor N2, and the other end of capacitor C3 is connected to the negative input terminal. The negative feedback regulation circuit includes operational amplifier N1, resistors R2-R9, capacitor C1, transistor V2, and diode V3. One end of resistor R2 is connected to the emitter (e) of transistor V2, and the other end is connected to the negative input terminal. One end of resistor R3 and capacitor C1 is connected to the base (b) of transistor V2 and one end of resistor R5, and the other end of resistor R3 and capacitor C1 is connected to the negative input terminal. One end of resistor R4 is connected to the collector (c) of transistor V2 and one end of diode V3. The anode of diode V3 is connected to one end of resistor R9, and the other end of resistor R9 is connected to the cathode of Zener diode V1. The other end of resistor R5 is connected to the output of operational amplifier N1 and one end of resistor R6. The other end of resistor R6 is connected to one end of resistor R7 and the negative terminal of operational amplifier N1, and the other end of resistor R7 is connected to the negative input terminal. One end of resistor R8 is connected to the positive terminal of operational amplifier N1, and the other end of resistor R8 is connected to the output terminal of Hall sensor N2. The surge suppression circuit includes a MOSFET V5, resistors R10 and R11, a capacitor C4, and a Zener diode V4. The gate of the MOSFET V5 is connected to one end of resistors R10 and R11, and the drain of the MOSFET V5 is connected to the negative terminal of capacitor C5. The source of the MOSFET V5 is connected to the anode of the Zener diode V4 and one end of capacitor C4. The other end of resistor R10 and the cathode of the Zener diode V4 are connected to one end of resistor R9. The other end of resistor R11 is connected to the other end of capacitor C4.

2. The soft-start circuit with negative feedback constant current control according to claim 1, characterized in that, The positive terminal voltage of the power supply input is 270V.

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