阅读说明：本技术 一种双驱动电源缓启动电路 (Dual-drive power supply slow starting circuit ) 是由 闵田 聂辉 于 2021-08-24 设计创作，主要内容包括：本申请涉及一种双驱动电源缓启动电路,包括功率开关管、第一级驱动电路和第二级驱动电路,功率开关管源极与输入电源相连,漏极与输出电源相连；第一级驱动电路的输入端和输入电源相连,输出端连接在所述功率开关管的源极和栅极之间；第二级驱动电路的输入端和输出电源相连,输出端连接在所述功率开关管的漏极和栅极之间,其用于在所述功率开关管驱动导通后开始工作,实现驱动自锁,保证输出电源正常输出；同时,当输入电源跌落至欠压工作点时,第一级驱动电路和第二级驱动电路同时控制所述功率开关管断开。本申请提供的双驱动电源缓启动电路,可以实现自激驱动供电,并实现欠压保护功能,驱动可靠性更好；也可以防止输入电源出现震荡时误触发输出,安全性能更好。(The application relates to a double-drive power supply slow starting circuit which comprises a power switch tube, a first-stage drive circuit and a second-stage drive circuit, wherein a source electrode of the power switch tube is connected with an input power supply, and a drain electrode of the power switch tube is connected with an output power supply; the input end of the first-stage driving circuit is connected with an input power supply, and the output end of the first-stage driving circuit is connected between the source electrode and the grid electrode of the power switch tube; the input end of the second-stage driving circuit is connected with the output power supply, the output end of the second-stage driving circuit is connected between the drain electrode and the grid electrode of the power switching tube, and the second-stage driving circuit is used for starting to work after the power switching tube is driven to be switched on, so that driving self-locking is realized, and normal output of the output power supply is ensured; meanwhile, when the input power supply falls to an undervoltage working point, the first-stage driving circuit and the second-stage driving circuit simultaneously control the power switch tube to be switched off. The double-drive power supply slow starting circuit can realize self-excitation drive power supply and realize an under-voltage protection function, and has better drive reliability; and the output can be prevented from being triggered by mistake when the input power supply vibrates, and the safety performance is better.)

1. A dual drive power supply slow start circuit, comprising:

a power switch tube T3, the source electrode of which is connected with the input power supply and the drain electrode of which is connected with the output power supply;

the input end of the first-stage driving circuit is connected with the input power supply, the output end of the first-stage driving circuit is connected between the source electrode and the grid electrode of the power switch tube T3, and the first-stage driving circuit is used for controlling the power switch tube T3 to be switched on or switched off and controlling the power switch tube T3 to be switched off when the input power supply oscillates so as to prevent the power switch tube T3 from being switched on by mistake;

the input end of the second-stage driving circuit is connected with the output power supply, the output end of the second-stage driving circuit is connected between the drain electrode and the grid electrode of the power switch tube T3, and the second-stage driving circuit is used for starting to work after the power switch tube T3 is driven to be conducted, so that driving self-locking is realized, and normal output of the output power supply is ensured; at the same time, the user can select the desired position,

when the input power supply falls to an undervoltage working point, the first-stage driving circuit and the second-stage driving circuit simultaneously control the power switch tube T3 to be switched off, and undervoltage protection is realized.

2. A dual drive power supply slow start circuit according to claim 1, wherein said first stage drive circuit comprises:

the first driving charge bleeder circuit comprises a resistor R1, a resistor R2 and a capacitor C1, wherein the resistor R1 and the capacitor C1 are connected in parallel and then are connected in series with the resistor R2, one end, far away from the resistor R2, of the resistor R1 is connected with an input power supply, and one end, far away from the resistor R1, of the resistor R2 is grounded;

a first voltage dividing circuit including a resistor R3 and a resistor R4, the resistor R3 and the resistor R4 being connected in series between an input power source and ground;

a diode D1 having an anode connected to the connection point of the resistor R3 and the resistor R4 and a cathode connected to the connection point of the resistor R1 and the resistor R2;

the first driving circuit comprises a first transistor T1, a resistor R5, a capacitor C2 and a voltage regulator tube ZD1, wherein the drain electrode of the first transistor T1 is connected with the source electrode and the grid electrode of the power switch tube T3, the source electrode of the first transistor T1 sequentially passes through the resistor R5 and the capacitor C2 and then is grounded, the grid electrode of the first transistor T1 is grounded, the anode of the voltage regulator tube ZD1 is connected between the resistor R5 and the capacitor C2, and the cathode of the voltage regulator tube 1 is connected between the resistor R3 and the resistor R4.

3. A dual drive power supply slow start circuit according to claim 1, wherein said second stage drive circuit comprises:

a second voltage division circuit including a resistor R9 and a resistor R10, the resistor R9 and the resistor R10 being connected in series between the output power source and ground;

the second driving circuit comprises a second transistor T2, a resistor R8, a capacitor C5 and a voltage regulator tube ZD2, wherein the drain electrode of the second transistor T2 is connected with the source electrode and the grid electrode of the power switch tube T3, the source electrode of the second transistor T2 sequentially passes through the resistor R8 and the capacitor C5 and then is grounded, the grid electrode of the second transistor T2 is grounded, the anode of the voltage regulator tube ZD2 is connected between the resistor R8 and the capacitor C5, and the cathode of the voltage regulator tube 2 is connected between the resistor R9 and the resistor R10.

4. The slow starting circuit for the dual drive power supply according to claim 3, wherein the second voltage division circuit further comprises a diode D2, the diode D2 is connected in series between a resistor R9 and a resistor R10, the anode of the diode D2 is connected with a resistor R9, and the cathode of the diode D2 is connected with the connection position of a voltage regulator ZD2 and the resistor R10.

5. The slow start circuit for dual drive power supplies according to claim 1, further comprising a current limiting circuit, wherein said current limiting circuit includes a resistor R6 and a resistor R7, said resistor R6 and said resistor R7 are connected in series with the source and gate of said power switch transistor T3, and the output terminal of said first stage driving circuit and the output terminal of said second stage driving circuit are connected between said resistor R6 and said resistor R7.

6. The slow start circuit for dual drive power supplies according to claim 5, further comprising a capacitor C4 having one end connected between said resistor R6 and said resistor R7 and the other end connected to ground.

7. A dual drive power supply soft start circuit as set forth in claim 1, further comprising a transient suppression diode TD1 having its anode connected to ground and its cathode connected to the input power supply.

8. The slow start circuit for dual drive power supplies according to claim 1, further comprising a diode D3 and a capacitor C6 connected in parallel, wherein the anode of the diode D3 is connected to ground and the cathode is connected to the output power supply.

9. The slow start circuit for dual drive power supply according to claim 1, further comprising a fuse FU1, said fuse FU1 being connected between the source of said power switch transistor T3 and the input power supply.

10. The dual drive power supply slow start circuit as claimed in claim 1, wherein said power switch transistor T3 is a PMOS transistor, and said first transistor T1 and said second transistor T2 are both NMOS transistors.

Technical Field

The application relates to the technical field of power supply application, in particular to a slow starting circuit with dual-drive power supplies.

Background

With the continuous development of communication technology, communication equipment has higher and higher requirements on power supplies, so that the power protection technology is more widely applied to the power supplies, and a power supply slow start circuit is generally used for power protection of the power supplies.

The existing power supply slow starting circuit adopts a single-drive control mode, and an auxiliary drive power supply and a drive chip are required to be additionally arranged to realize a slow starting function. However, in the conventional single-drive control mode, the PMOS power switch is easily damaged when the power-on input power supply oscillates, and the circuit fails when the drive circuit fails.

Therefore, how to solve the problems of easy false triggering and power failure in the related technology is the research and development core of the people.

Disclosure of Invention

The embodiment of the application provides a double-drive power supply slow starting circuit, which aims to solve the problems of easy false triggering and power failure in the related art and improve the reliability of the power supply slow starting circuit.

In a first aspect, a dual-drive power supply slow start circuit is provided, including:

a power switch tube T3, the source electrode of which is connected with the input power supply and the drain electrode of which is connected with the output power supply;

the input end of the first-stage driving circuit is connected with the input power supply, the output end of the first-stage driving circuit is connected between the source electrode and the grid electrode of the power switch tube T3, and the first-stage driving circuit is used for controlling the power switch tube T3 to be switched on or switched off and controlling the power switch tube T3 to be switched off when the input power supply oscillates so as to prevent the power switch tube T3 from being switched on by mistake;

the input end of the second-stage driving circuit is connected with the output power supply, the output end of the second-stage driving circuit is connected between the drain electrode and the grid electrode of the power switch tube T3, and the second-stage driving circuit is used for starting to work after the power switch tube T3 is driven to be conducted, so that driving self-locking is realized, and normal output of the output power supply is ensured; at the same time, the user can select the desired position,

when the input power supply falls to an undervoltage working point, the first-stage driving circuit and the second-stage driving circuit simultaneously control the power switch tube T3 to be switched off, and undervoltage protection is realized.

In some embodiments, the first stage drive circuit comprises:

the first driving charge bleeder circuit comprises a resistor R1, a resistor R2 and a capacitor C1, wherein the resistor R1 and the capacitor C1 are connected in parallel and then are connected in series with the resistor R2, one end, far away from the resistor R2, of the resistor R1 is connected with an input power supply, and one end, far away from the resistor R1, of the resistor R2 is grounded;

a first voltage dividing circuit including a resistor R3 and a resistor R4, the resistor R3 and the resistor R4 being connected in series between an input power source and ground;

a diode D1 having an anode connected to the connection point of the resistor R3 and the resistor R4 and a cathode connected to the connection point of the resistor R1 and the resistor R2;

the first driving circuit comprises a first transistor T1, a resistor R5, a capacitor C2 and a voltage regulator tube ZD1, wherein the drain electrode of the first transistor T1 is connected with the source electrode and the grid electrode of the power switch tube T3, the source electrode of the first transistor T1 sequentially passes through the resistor R5 and the capacitor C2 and then is grounded, the grid electrode of the first transistor T1 is grounded, the anode of the voltage regulator tube ZD1 is connected between the resistor R5 and the capacitor C2, and the cathode of the voltage regulator tube 1 is connected between the resistor R3 and the resistor R4.

In some embodiments, the second stage drive circuit comprises:

a second voltage division circuit including a resistor R9 and a resistor R10, the resistor R9 and the resistor R10 being connected in series between the output power source and ground;

the second driving circuit comprises a second transistor T2, a resistor R8, a capacitor C5 and a voltage regulator tube ZD2, wherein the drain electrode of the second transistor T2 is connected with the source electrode and the grid electrode of the power switch tube T3, the source electrode of the second transistor T2 sequentially passes through the resistor R8 and the capacitor C5 and then is grounded, the grid electrode of the second transistor T2 is grounded, the anode of the voltage regulator tube ZD2 is connected between the resistor R8 and the capacitor C5, and the cathode of the voltage regulator tube 2 is connected between the resistor R9 and the resistor R10.

In some embodiments, the second voltage division circuit further includes a diode D2, the diode D2 is connected in series between the resistor R9 and the resistor R10, the anode of the diode D2 is connected to the resistor R9, and the cathode of the diode D2 is connected to the junction of the voltage regulator ZD2 and the resistor R10.

In some embodiments, the dual-drive power supply slow start circuit further includes a current limiting circuit, the current limiting circuit includes a resistor R6 and a resistor R7, the resistor R6 and the resistor R7 are connected in series to the source and the gate of the power switch transistor T3, and the output terminal of the first-stage driving circuit and the output terminal of the second-stage driving circuit are both connected between the resistor R6 and the resistor R7.

In some embodiments, the dual-drive power supply soft start circuit further includes a capacitor C4, one end of which is connected between the resistor R6 and the resistor R7, and the other end of which is grounded.

In some embodiments, the dual drive power supply soft start circuit further includes a transient suppression diode TD1 having an anode connected to ground and a cathode connected to the input power supply.

In some embodiments, the dual-drive power supply slow start circuit further comprises a diode D3 and a capacitor C6 connected in parallel, wherein the anode of the diode D3 is grounded, and the cathode is connected to the output power supply.

In some embodiments, the dual-drive power supply soft start circuit further comprises a fuse FU1, and the fuse FU1 is connected between the source of the power switch tube T3 and the input power supply.

In some embodiments, the power switch transistor T3 is a PMOS transistor, and the first transistor T1 and the second transistor T2 are both NMOS transistors.

The beneficial effect that technical scheme that this application provided brought includes: self-excitation driving power supply can be realized, an undervoltage protection function is realized, and the reliability is better; and the false triggering conduction can be prevented, and the safety performance is better.

The embodiment of the application provides a double-drive power supply slow starting circuit, because a first-stage drive circuit and a second-stage drive circuit drive a power switch tube T3 together, the first-stage drive circuit is connected with an input power supply VIN, and the second-stage drive circuit is connected with an output power supply VO, after the output power supply VO outputs normally, on one hand, the drive self-locking can be realized, even if the input power supply generates micro-oscillation to cause the first transistor T1 to be cut off, the power switch tube T3 can still be controlled to be switched on through the second transistor T2, so that the slow starting circuit cannot be powered down due to the micro-oscillation of the input power supply, and the normal power supply of the power supply is ensured; on the other hand, only when the input power VIN falls to the undervoltage operating point of the regulator tube, the first transistor T1 and the second transistor T2 are both turned off, and then the power switch tube T3 is controlled to be turned off, so as to realize the undervoltage protection function, therefore, the driving reliability of the dual-drive power supply slow start circuit is better, an auxiliary power supply and a driving chip are not required to be added, the circuit structure is simpler, the cost is lower, the false triggering output when the input power supply vibrates can be prevented, and the safety is better.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

FIG. 1 is a schematic diagram of a slow start circuit for a dual-driver power supply according to an embodiment of the present disclosure;

FIG. 2 is a schematic diagram of another dual-drive power supply slow start circuit according to an embodiment of the present disclosure.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some embodiments of the present application, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

Referring to fig. 1, the present embodiment provides a dual-drive power supply slow start circuit, which includes a power switch transistor T3, a first stage driving circuit, and a second stage driving circuit.

The source electrode of the power switch tube T3 is connected with an input power supply, and the drain electrode thereof is connected with an output power supply;

the input end of the first-stage driving circuit is connected with an input power supply, the output end of the first-stage driving circuit is connected between the source electrode and the grid electrode of the power switch tube T3, the first-stage driving circuit is used for controlling the power switch tube T3 to be switched on or switched off, and the power switch tube T3 is controlled to be switched off when the input power supply oscillates, so that the power switch tube T3 is prevented from being switched on by mistake;

the input end of the second-stage driving circuit is connected with the output power supply, the output end of the second-stage driving circuit is connected between the drain electrode and the grid electrode of the power switch tube T3, and the second-stage driving circuit is used for starting to work after the power switch tube T3 is driven to be conducted, so that driving self-locking is realized, and normal output of the output power supply is ensured; at the same time, the user can select the desired position,

when the input power supply falls to an undervoltage working point, the first-stage driving circuit and the second-stage driving circuit simultaneously control the power switch tube T3 to be switched off, and undervoltage protection is realized.

In the embodiment of the application, an input power supply is VIN, an output power supply is VO, a power switch tube T3 is driven by a first-stage driving circuit and a second-stage driving circuit together, the first-stage driving circuit is connected with the input power VIN, the second-stage driving circuit is connected with the output power VO, after the output power VO is normally output, on one hand, driving self-locking can be realized, even if the input power supply generates micro-oscillation to cause the first transistor T1 to be cut off, the power switch tube T3 can be controlled to be switched on by the second transistor T2, so that the slow start circuit cannot be powered down due to the micro-oscillation of the input power supply, and the normal power supply of the power supply is ensured; on the other hand, only when the input power VIN drops to the under-voltage operating point of the regulator tube, the first transistor T1 and the second transistor T2 are both turned off, so as to control the power switch tube T3 to be turned off, thereby implementing the under-voltage protection function. Compared with the prior art, the double-drive power supply slow start circuit provided by the embodiment of the application controls the power switch tube T3 to be switched on or switched off together through the two drive circuits, can realize self-excitation drive power supply after the power supply is stably output, and controls the power switch tube T3 to be switched off when the input power supply falls to an undervoltage working point, so that an undervoltage protection function is realized, and the drive reliability is better; and when the input power supply is electrified and vibrates, the power switch tube T3 is prevented from being triggered and conducted by mistake, and the safety performance is better.

Further, in the embodiment of the present application, the first stage driving circuit includes a first driving charge draining circuit, a first voltage dividing circuit, a diode D1, and a first driving circuit.

The first driving charge bleeder circuit comprises a resistor R1, a resistor R2 and a capacitor C1, wherein the resistor R1 and the capacitor C1 are connected in parallel and then connected in series with the resistor R2, one end, far away from the resistor R2, of the resistor R1 is connected with an input power supply, and one end, far away from the resistor R1, of the resistor R2 is grounded.

The first voltage division circuit comprises a resistor R3 and a resistor R4, wherein the resistor R3 and the resistor R4 are connected between an input power supply and the ground in series.

The diode D1 has an anode connected to the connection point of the resistor R3 and the resistor R4, and a cathode connected to the connection point of the resistor R1 and the resistor R2.

The first driving circuit comprises a first transistor T1, a resistor R5, a capacitor C2 and a voltage regulator tube ZD1, wherein the drain electrode of the first transistor T1 is connected with the source electrode and the grid electrode of the power switch tube T3, the source electrode of the first transistor T1 sequentially passes through the resistor R5 and the capacitor C2 and then is grounded, the grid electrode of the first transistor T1 is grounded, the anode of the voltage regulator tube ZD1 is connected between the resistor R5 and the capacitor C2, and the cathode of the voltage regulator tube ZD1 is connected between the resistor R3 and the resistor R4.

Further, in the embodiment of the present application, the second stage driving circuit includes a second voltage dividing circuit and a second driving circuit.

The second voltage division circuit comprises a resistor R9 and a resistor R10, and the resistor R9 and the resistor R10 are connected between the output power supply and the ground in series.

The second driving circuit comprises a second transistor T2, a resistor R8, a capacitor C5 and a voltage regulator tube ZD2, wherein the drain electrode of the second transistor T2 is connected with the source electrode and the grid electrode of the power switch tube T3, the source electrode of the second transistor T2 sequentially passes through the resistor R8 and the capacitor C5 and then is grounded, the grid electrode of the second transistor T2 is grounded, the anode of the voltage regulator tube ZD2 is connected between the resistor R8 and the capacitor C5, and the cathode of the voltage regulator tube ZD2 is connected between the resistor R9 and the resistor R10.

Furthermore, in the embodiment of the present application, the second voltage dividing circuit further includes a diode D2, the diode D2 is connected in series between the resistor R9 and the resistor R10, the anode of the diode D2 is connected to the resistor R9, and the cathode of the diode D2 is connected to the junction of the voltage regulator ZD2 and the resistor R10.

Furthermore, in this embodiment, the dual-drive power supply slow start circuit further includes a current limiting circuit, the current limiting circuit includes a resistor R6 and a resistor R7, the resistor R6 and the resistor R7 are connected in series to the source and the gate of the power switching transistor T3, and the output terminal of the first-stage driving circuit and the output terminal of the second-stage driving circuit are both connected between the resistor R6 and the resistor R7.

Furthermore, in the embodiment of the present application, the dual-drive power supply soft start circuit further includes a capacitor C3, and the capacitor C3 is connected across the source and the gate of the power switch transistor T3.

As shown in fig. 2, in the embodiment of the present application, the dual-drive power supply slow start circuit further includes a capacitor C4, one end of the capacitor C4 is connected between the resistor R6 and the resistor R7, and the other end is grounded.

Furthermore, in the embodiment of the present application, the dual-drive power supply slow start circuit further includes a transient suppression diode TD1, an anode of which is grounded, and a cathode of which is connected to the input power supply.

The transient suppression diode TD1, also called TVS tube, of the embodiment of the application is a diode-type high-efficiency protection device, and utilizes the reverse breakdown working principle of a P-N junction to guide electrostatic high-voltage pulse into the ground, so that components in a double-drive power supply slow start circuit can be protected.

Furthermore, in the embodiment of the present application, the dual-drive power supply slow start circuit further includes a diode D3 and a capacitor C6 connected in parallel, wherein an anode of the diode D3 is grounded, and a cathode is connected to the output power supply.

Furthermore, in this embodiment, the dual-drive power supply slow start circuit further includes a fuse FU1, and the fuse FU1 is connected between the source of the power switch T3 and the input power supply, so as to protect the dual-drive power supply slow start circuit.

Preferably, in the embodiment of the present application, the power switch transistor T3 is a PMOS transistor, and both the first transistor T1 and the second transistor T2 are NMOS transistors.

The double-drive power supply slow starting circuit comprises a plurality of transistors, resistors, capacitors, voltage stabilizing tubes and the like, and adopts discrete devices to build the circuit, so that the drive control chip and the auxiliary power supply are reduced, the cost is reduced, the structure is simple, the parameter configuration flexibility is better, and the practicability is better.

Preferably, in the embodiment of the present application, the ratio of the resistor R1 to the resistor R2, and the ratio of the resistor R3 to the resistor R4 are approximately equal, the resistors R1 and R2 are in the K Ω class, and the resistors R3 and R4 are in the M Ω class.

In the embodiment of the present application, since the delayed turn-on time of the first transistor T1 is related to the resistor R3 and the capacitor C2, the delayed turn-on time of the first transistor T1 can be adjusted by setting the parameter configurations of the resistor R3 and the capacitor C2, and the delayed turn-on time of the second transistor T2 is related to the resistor R9 and the capacitor C5, and the delayed turn-on time of the second transistor T2 can be adjusted by setting the parameter configurations of the resistor R9 and the capacitor C5; and further, the conduction delay time of the power switch tube T3 can be adjusted, the circuit slow start output is realized, and the power switch tube T3 is not damaged due to overlarge transient conduction power.

In the embodiment of the application, an input power supply is denoted by VIN, an output power supply is denoted by VO, the voltage at the junction of a resistor R1 and a resistor R2 is denoted by V1, the voltage at the junction of a resistor R3 and a resistor R4 is denoted by V2, the voltage at the junction of a voltage regulator ZD1 and a resistor R5 is denoted by VT1, the drain voltage of a first transistor T1 is V3, the voltage at the junction of a resistor R9 and a resistor R10 is denoted by V4, and the voltage at the junction of a voltage regulator ZD2 and a resistor R8 is denoted by VT 2.

The working principle of the double-drive power supply slow starting circuit is as follows:

when VIN is just connected to a power supply, the VIN voltage starts to climb from 0V, when V2 is smaller than the under-voltage threshold of a voltage regulator tube ZD1, the voltage regulator tube ZD1 is cut off, VT1 is 0V, a first transistor T1 is cut off, VGS of T3 is 0, a power switch tube T3 is cut off, an output power VO is 0, and the output circuit is ensured to have no output;

when V2 is greater than the undervoltage threshold of the voltage regulator tube ZD1, and VIN oscillates and falls in the connected state, V1 is less than V2, the diode D1 is turned on, the voltage of the capacitor C2 and the charge of the gate of the first transistor T1 are quickly released through the voltage regulator tube ZD1, the diode D1, the capacitor C1 and the resistor R2, so that the voltage of VT1 is lower than the start threshold voltage of the first transistor T1, the first transistor T1 is turned off, the voltage VGS of the gate and the source of the power switch tube T3 is 0, the power switch tube T3 is turned off, the output power supply VO is 0, and the circuit is ensured to have no output when the input oscillates;

when V2 is greater than the undervoltage threshold of the zener diode ZD1 and the input is stable, V1 is equal to V2, the diode D1 is turned off, the capacitor C2 is charged, when VT1 is higher than the opening threshold of the first transistor T1, the first transistor T1 is turned on, the drain voltage V3 of the first transistor T1 is equal to 0V, the voltage VGS between the gate and the source of the power switch T3 is equal to-VIN, the power switch T3 is turned on, the output power VO is equal to VIN, and the circuit has steady-state output;

after the power switch tube T3 is switched on, an output power supply VO is VIN, through parameter configuration of a resistor R9, a resistor R10, a capacitor C5 and a voltage regulator tube ZD2, V4 is larger than the under-voltage threshold of the voltage regulator tube ZD2, the voltage regulator tube ZD2 is switched on, the capacitor C5 is charged, when VT2 is higher than the switching threshold of the second transistor T2, the second transistor T2 is switched on and is switched on in cooperation with the T1, and normal output of the output power supply VO is dually guaranteed;

after the VO is normally output, when VIN voltage oscillates, the first transistor T1 is turned off, but at this time, VT2 cannot discharge due to the action of diode D2, the second transistor T2 is still in a conducting state, only when VIN falls below the under-voltage threshold of the voltage regulator ZD1, the output power supply VO also falls below the under-voltage threshold of the voltage regulator ZD2, and because the second transistor T2 is connected with the output power supply VO, the second transistor T2 is turned off, so that the power switch tube T3 is turned off, and the output power supply VO does not output.

Therefore, the dual-drive power supply slow start circuit is adopted in the embodiment of the application, the two-stage drive circuit is started slowly in time division sequentially, finally, dual drives play a role simultaneously to achieve circuit output self-locking, the power supply can be ensured to work normally, when the input voltage has large oscillation and voltage drop during starting, the first-stage drive circuit can be locked to prevent the PMOS power tube from being conducted mistakenly and the PMOS power tube from being damaged due to overpower, and the protection function of the starting power PMOS tube is achieved. Compared with the existing single-drive control mode, the circuit driving reliability in the embodiment of the application is higher.

In the description of the present application, it should be noted that the terms "upper", "lower", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, which are only for convenience in describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and operate, and thus, should not be construed as limiting the present application. Unless expressly stated or limited otherwise, the terms "mounted," "connected," and "connected" are intended to be inclusive and mean, for example, that they may be fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art as appropriate.

It is noted that, in the present application, relational terms such as "first" and "second", and the like, are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.

The above description is merely exemplary of the present application and is presented to enable those skilled in the art to understand and practice the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.