Slow-drop gate voltage protection circuit and switching power supply

Abstract

The invention relates to a slow-drop gate voltage protection circuit and a switching power supply. The slow-drop gate voltage protection circuit comprises a driving module, a fault detection module, a clamping module, a switching module, an anti-false-triggering module and a slow-drop gate voltage module, in a normal working state, the driving module generates a driving signal according to the control signal so as to drive the switch module to be normally switched on and switched off; in an abnormal state, the voltage of the fault detection module is increased, the clamping module is switched on, and the anti-false-triggering module controls the voltage of the switch module to be slowly reduced from high voltage to switch-on voltage; and in an overcurrent / short circuit fault state, the clamping module is switched on to start the slow drop gate voltage module, and the slow drop gate voltage module controls the switch-on voltage of the switch module to drop slowly after being started. The problem that power loss of fault current is sharply increased within delay time between a fault signal and the starting protection circuit can be solved, the current change rate of a device cannot be increased, and a switching power supply, a power switching tube and a chip can be prevented from being burnt due to overlarge current.

Description

Technical Field

[0001] The present invention relates to the technical field of switching power supplies, and more particularly to a slow-drop gate voltage protection circuit and a switching power supply. Background Art

[0002] AC / DC (alternating current / direct current) and DC / DC (direct current / direct current) switching power supplies have the advantages of high efficiency and wide voltage range, and have been widely used in portable electronic devices and green lighting.

[0003] In the existing switching power supply, the switching power supply obtains the switch control signal through the PWM modulation signal (i.e., pulse width modulation signal), so as to control the power switch tube through the switch control signal. However, due to the complex application environment of the switching power supply, the load may suddenly change or even short-circuit, so the current is often too large, thus burning the power tube and chip of the switching power supply.

[0004] In order to solve the above problems, the commonly used protection measure is soft shutdown. Among them, soft shutdown means directly shutting down the power tube in case of overcurrent and short circuit. However, the anti-interference ability of soft switch is poor. Once an abnormal signal is detected, the action protection is immediately triggered, so it is very easy to cause false action. In order to enhance the anti-interference ability of the protection circuit, a certain delay time can be added between the fault signal and the start of the protection circuit. However, the fault current will increase sharply during this period, resulting in power loss, and will also cause the di / dt (current change rate) of the device to increase. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a slow-drop gate voltage protection circuit and a switching power supply in view of the problems existing in the prior art.

[0006] The technical solution adopted by the present invention to solve the technical problem is: constructing a slow-drop gate voltage protection circuit, including: a driving module, a fault detection module, a clamping module, a switch module, an anti-false triggering module and a slow-drop gate voltage module;

[0007] The input end of the driving module is connected to the main control unit, the output end of the driving module is connected to the switch module, the input end of the fault detection module is connected to the driving module, the output end of the fault detection module is connected to the switch module, the clamping modules are respectively connected to the anti-false triggering modules, and the slow gate voltage reduction module is respectively connected to the main control unit, the clamping module and the switch module;

[0008] In a normal working state, the driving module generates a driving signal according to the control signal output by the main control unit to drive the switch module to turn on and off normally;

[0009] In an abnormal state, the voltage of the fault detection module increases and turns on the clamping module, and the anti-false triggering module controls the voltage of the switch module to slowly decrease from a high voltage to a turn-on voltage;

[0010] In an overcurrent / short circuit fault state, the clamping module is turned on to start the slow gate voltage drop module. After the slow gate voltage drop module is started, the on-state voltage of the switch module is controlled to drop slowly.

[0011] In the slow-drop gate voltage protection circuit of the present invention, the driving module is a push-pull circuit; and the control signal is a PWM signal.

[0012] The slow-drop gate voltage protection circuit of the present invention further includes: a peak absorption module; the input end of the peak absorption module is connected to the power factor correction module, and the output end of the peak absorption module is connected to the transformer winding.

[0013] In the slow-drop gate voltage protection circuit of the present invention, the driving module comprises: a first switch tube, a second switch tube and an eighth resistor;

[0014] The first end of the first switch tube is connected to the main control unit through the eighth resistor, the second end of the first switch tube is connected to a high level, the third end of the first switch tube is connected to the second end of the second switch tube and connected to the switch module, the first end of the second switch tube is connected to the first end of the first switch tube, and the third end of the second switch tube is grounded.

[0015] In the slow-drop gate voltage protection circuit of the present invention, the switch module comprises: a fifth resistor and a power switch tube;

[0016] The first end of the fifth resistor is connected to the output end of the driving module, the second end of the fifth resistor is connected to the gate of the power switch tube, the drain of the power switch tube is connected to the fault detection module and the spike absorption module, the source of the power switch tube is grounded, and the gate of the power switch tube is also connected to the slow-drop gate voltage module.

[0017] In the slow-drop gate voltage protection circuit of the present invention, the fault detection module comprises: a third resistor and a fourth diode;

[0018] The first end of the third resistor is connected to the output end of the driving module, the second end of the third resistor is connected to the anode of the fourth diode and connected to terminal a, the cathode of the fourth diode is connected to the drain of the power switch tube, and the terminal a is connected to the clamping module.

[0019] In the slow-drop gate voltage protection circuit of the present invention, the clamping module comprises: a first voltage regulator tube;

[0020] The cathode of the first voltage regulator tube is connected to the end point a, and the anode of the first voltage regulator tube is connected to the anti-false triggering module.

[0021] In the slow-drop gate voltage protection circuit of the present invention, the anti-false triggering module comprises: a second capacitor;

[0022] The input end of the second capacitor is connected to the anode of the first voltage regulator and the slow-drop gate voltage module, and the second end of the second capacitor is grounded.

[0023] In the slow-drop gate voltage protection circuit of the present invention, the slow-drop gate voltage module includes: a first resistor, a second resistor, a fourth resistor, a first capacitor, a third switch tube, a fourth switch tube, a second voltage regulator tube and a third voltage regulator tube;

[0024] The second end of the fourth switch tube is connected to the gate of the power switch tube, the first end of the fourth switch tube is connected to the anode of the second voltage regulator tube, and the third end of the fourth switch tube is grounded through the fourth resistor; the first end of the third switch tube is connected to the anode of the first voltage regulator tube, the second end of the third switch tube is grounded, the third end of the third switch tube is connected to the second end of the first resistor through the transmitting part of the photocoupler, the first end of the first resistor is connected to the high level through the second resistor, the first capacitor is connected to the second resistor in parallel, the cathode of the third voltage regulator tube is connected to the high level, and the anode of the third voltage regulator tube is connected to the cathode of the second voltage regulator tube.

[0025] The present invention also provides a switching power supply, comprising: the above-mentioned slow-drop gate voltage protection circuit.

[0026] The implementation of the slow gate voltage drop protection circuit and the switching power supply of the present invention has the following beneficial effects: including: a driving module, a fault detection module, a clamping module, a switch module, an anti-false triggering module and a slow gate voltage drop module; in normal working state, the driving module generates a driving signal according to the control signal to drive the switch module to normally turn on and off; in abnormal state, the voltage of the fault detection module increases and turns on the clamping module, and the anti-false triggering module controls the voltage of the switch module to slowly drop from a high voltage to a turn-on voltage; in overcurrent / short circuit fault state, the clamping module is turned on to start the slow gate voltage drop module, and after the slow gate voltage drop module is started, the turn-on voltage of the switch module is controlled to slowly drop. The present invention can solve the problem that the fault current sharply increases the power loss during the delay time between the fault signal and the start-up of the protection circuit, and will not cause the current change rate of the device to increase, and can also prevent the current from being too large to burn the switching power supply and the power switch tube and chip. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0028] Figure 1 It is a principle block diagram of the slow-drop gate voltage protection circuit provided by the present invention;

[0029] Figure 2 The invention discloses a circuit diagram of a slow-drop gate voltage protection circuit. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] refer to Figure 1 , Figure 1 This is a principle block diagram of the slow-drop gate voltage protection circuit provided by the present invention.

[0032] like Figure 1 As shown, the slow-drop gate voltage protection circuit includes: a driving module 12 , a fault detection module 13 , a clamping module 14 , a switch module 15 , an anti-false triggering module 16 and a slow-drop gate voltage module 17 .

[0033] The input end of the driving module 12 is connected to the main control unit, the output end of the driving module 12 is connected to the switch module 15, the input end of the fault detection module 13 is connected to the driving module 12, the output end of the fault detection module 13 is connected to the switch module 15, the clamping module 14 is respectively connected to the anti-false triggering module 16, and the slow-drop gate voltage module 17 is respectively connected to the main control unit, the clamping module 14 and the switch module 15.

[0034] Specifically, when the switching power supply is in a normal working state, the driving module 12 generates a driving signal according to the control signal output by the main control unit to drive the switch module 15 to turn on and off normally. When the switching power supply is in an abnormal state, the voltage of the fault detection module 13 increases and turns on the clamping module 14, and the anti-false triggering module 16 controls the voltage of the switch module 15 to slowly drop from the high voltage to the on-voltage. When the switching power supply is in an overcurrent / short circuit fault state, the clamping module 14 is turned on to start the slow gate voltage drop module 17, and the on-voltage of the switch module 15 is controlled to slowly drop after the slow gate voltage drop module 17 is started. In the embodiment of the present invention, by setting the anti-false triggering module 16, when an abnormal situation occurs in the switching power supply, the protection circuit can be prevented from malfunctioning and false triggering can be prevented. By setting the slow gate voltage drop module 17, when an overcurrent or short circuit fault occurs in the switching power supply, the on-voltage of the switch module 15 can be slowly reduced through the action of the slow gate voltage drop module 17, thereby effectively solving the problems existing in the soft shutdown method.

[0035] Optionally, in an embodiment of the present invention, the driving module 12 is a push-pull circuit; and the control signal is a PWM signal.

[0036] Furthermore, if Figure 1 As shown, the slow-drop gate voltage protection circuit also includes: a peak absorption module 11; the input end of the peak absorption module 11 is connected to the power factor correction module, and the output end of the peak absorption module 11 is connected to the transformer winding. By setting the peak absorption module 11, the peak voltage / current can be absorbed to improve the stability and reliability of the signal.

[0037] refer to Figure 2 , Figure 2 A circuit diagram of a preferred embodiment of the slow-drop gate voltage protection circuit provided by the present invention.

[0038] Specifically, Figure 2 As shown, VBUS is the voltage output by the power factor correction module, +15V is the high level provided by the power supply circuit in the switching power supply, and PWM is the PWM signal output by the main control unit. The main control unit is the main controller in the switching power supply (such as LED drive power supply). Figure 2 The PWM control system in is the main control unit, and -15V is equivalent to the ground wire.

[0039] like Figure 2 As shown, the driving module 12 includes: a first switch tube Q1, a second switch tube Q2 and an eighth resistor R8; the first end of the first switch tube Q1 is connected to the main control unit through the eighth resistor R8, the second end of the first switch tube Q1 is connected to the high level (+15V), the third end of the first switch tube Q1 is connected to the second end of the second switch tube Q2 and connected to the switch module 15, the first end of the second switch tube Q2 is connected to the first end of the first switch tube Q1, and the third end of the second switch tube Q2 is grounded.

[0040] Optionally, in an embodiment of the present invention, the first switch tube Q1 and the second switch tube Q2 form a push-pull circuit, wherein the first switch tube Q1 and the second switch tube Q2 can be triodes or MOS tubes.

[0041] like Figure 2 As shown, the switch module 15 includes: a fifth resistor R5 and a power switch tube Q5; the first end of the fifth resistor R5 is connected to the output end of the driving module 12, the second end of the fifth resistor R5 is connected to the gate of the power switch tube Q5, the drain of the power switch tube Q5 is connected to the fault detection module 13 and the spike absorption module 11, the source of the power switch tube Q5 is grounded, and the gate of the power switch tube Q5 is also connected to the slow gate voltage reduction module 17. Optionally, the power switch tube Q5 can be a MOS tube.

[0042] like Figure 2As shown, the fault detection module 13 includes: a third resistor R3 and a fourth diode D4; the first end of the third resistor R3 is connected to the output end of the driving module 12, the second end of the third resistor R3 is connected to the anode of the fourth diode D4 and connected to the end point a, the cathode of the fourth diode D4 is connected to the drain of the power switch tube Q5, and the end point a is connected to the clamping module 14.

[0043] Optionally, in this embodiment, if Figure 2 As shown, the clamping module 14 includes: a first voltage regulator tube DZ1 ; a cathode of the first voltage regulator tube DZ1 connected to an end point a, and an anode of the first voltage regulator tube DZ1 connected to an anti-false triggering module 16 .

[0044] Optionally, in this embodiment, if Figure 2 As shown, the false trigger prevention module 16 includes: a second capacitor C2; the input end of the second capacitor C2 is connected to the anode of the first voltage regulator tube DZ1 and the slow gate voltage drop module 17, and the second end of the second capacitor C2 is grounded.

[0045] Optionally, in this embodiment, if Figure 2 As shown, the slow gate voltage drop module 17 includes: a first resistor R1, a second resistor R2, a fourth resistor R4, a first capacitor C1, a third switch tube Q3, a fourth switch tube Q4, a second voltage regulator tube ZD2 and a third voltage regulator tube ZD3.

[0046] The second end of the fourth switch tube Q4 is connected to the gate of the power switch tube Q5, the first end of the fourth switch tube Q4 is connected to the anode of the second voltage regulator tube ZD2, and the third end of the fourth switch tube Q4 is grounded through the fourth resistor R4; the first end of the third switch tube Q3 is connected to the anode of the first voltage regulator tube DZ1, the second end of the third switch tube Q3 is grounded, the third end of the third switch tube Q3 is connected to the second end of the first resistor R1 through the transmitting part of the photoelectric coupler, the first end of the first resistor R1 is connected to the high level through the second resistor R2, the first capacitor C1 is connected in parallel with the second resistor R2, the cathode of the third voltage regulator tube ZD3 is connected to the high level, and the anode of the third voltage regulator tube ZD3 is connected to the cathode of the second voltage regulator tube ZD2. Optionally, in the embodiment of the present invention, the third switch tube Q3 and the fourth switch tube Q4 can be triodes or MOS tubes.

[0047] Specifically, Figure 2 As shown, when the switching power supply is in a normal working state, since the voltage at point C is pulled down by the power switch tube Q5, the voltage at point a is clamped below its breakdown voltage by the first voltage regulator tube DZ1, and therefore, the third switch tube Q3 remains in a cut-off state. At this time, the slow-drop gate voltage module 17 does not work, and the push-pull circuit composed of the first switch tube Q1 and the second switch tube Q2 drives the power switch tube Q5 to be normally turned on and off through the fifth resistor R5 according to the driving signal generated by the PWM signal.

[0048] When an abnormal situation occurs in the switching power supply (such as the voltage at point a is pulled up instantly and is higher than the clamping voltage of the first voltage regulator DZ1), the first voltage regulator DZ1 is broken down. At this time, due to the effect of the second capacitor C2, it can provide a very short delay for hard switching occasions (the delay time is determined by the characteristics of the second capacitor C2), so that when the power switch tube Q5 is turned on, its Vce has a certain time to drop from the high voltage to its turn-on voltage, thereby avoiding malfunction of the protection circuit.

[0049] When the switching power supply has an overcurrent or short circuit fault, the Vce of the power switch tube Q5 rises, and the voltage at point a rises accordingly. When the voltage at point a rises to a certain value, the first voltage regulator tube DZ1 is broken down. At this time, the third switch tube Q3 is turned on, causing the voltage at point b to drop. The first capacitor C1 is charged through the first resistor R1, and the voltage across the first capacitor C1 starts to rise from zero. Correspondingly, the voltage at point d also starts to drop. When the voltage across the first capacitor C1 rises to about 1.4V, the voltage at point d rises from 15V to 25V. It drops to 13.6V (15-1.4=13.6V), reaching the turn-on voltage of the fourth switch tube Q4, so that the fourth switch tube Q4 is turned on. When the fourth switch tube Q4 is turned on, the gate voltage Vge of the power switch tube Q5 decreases as the voltage across the first capacitor C1C1 increases. When the voltage across the first capacitor C1 rises to the turn-on voltage of the third voltage regulator tube ZD3, the third voltage regulator tube ZD3 is turned on. At this time, the Vg of the power switch tube Q5 is clamped and fixed at a certain value, and the process of slowly reducing the gate voltage ends. At the same time, the photoelectric coupler is turned on and sends an overcurrent signal to the main control unit, and the main control unit starts the overcurrent protection. Among them, by adjusting the capacitance value of the first capacitor C1, the charging speed of the first capacitor C1 can be controlled, and then the decreasing speed of the power switch tube Q5 Vge can be controlled.

[0050] like Figure 2 As shown, during the process of slowly reducing the gate voltage, if the fault signal (such as an overcurrent or short circuit fault signal) disappears, the voltage at point a decreases, the third switch tube Q3 resumes the cut-off state, the first capacitor C1 discharges through the second resistor R2, the voltage at point d increases, the fourth switch tube Q4 also resumes the cut-off state, the Vge of the power switch tube Q5 increases, and the circuit resumes the normal working state.

[0051] The present invention further provides a switching power supply, which includes the slow-drop gate voltage protection circuit disclosed in the embodiment of the present invention. Optionally, the switching power supply can be an LED driving power supply.

[0052] The present invention solves the problem that the fault current will sharply increase the power loss during the delay time between the fault signal and the start-up protection circuit, and at the same time cause a large current change rate of the device, thereby effectively reducing the power loss. Moreover, the present invention uses low-cost discrete components to build overcurrent protection, and does not require complex software algorithms and hardware structures to avoid excessive overcurrent and burning the power switch and chip of the switching power supply, which significantly improves the reliability of the switching power supply, and can also obtain a stable voltage output.

[0053] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0054] Professionals may further appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in the above description according to function. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professionals and technicians may use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0055] The steps of the method or algorithm described in conjunction with the embodiments disclosed herein may be implemented directly using hardware, a software module executed by a processor, or a combination of the two. The software module may be placed in a random access memory (RAM), a memory, a read-only memory (ROM), an electrically programmable ROM, an electrically erasable programmable ROM, a register, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.

[0056] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot limit the scope of protection of the present invention. All equivalent changes and modifications made to the scope of the claims of the present invention should fall within the scope of the claims of the present invention.

Claims

1. A slow-drop gate voltage protection circuit, characterized in that: include: Driving module, fault detection module, clamping module, switch module, anti-false triggering module and slow gate voltage reduction module; The input end of the driving module is connected to the main control unit, the output end of the driving module is connected to the switch module, the input end of the fault detection module is connected to the driving module, the output end of the fault detection module is connected to the switch module, the clamping modules are respectively connected to the anti-false triggering modules, and the slow gate voltage reduction module is respectively connected to the main control unit, the clamping module and the switch module; In a normal working state, the driving module generates a driving signal according to the control signal output by the main control unit to drive the switch module to turn on and off normally; In an abnormal state, the voltage of the fault detection module increases and turns on the clamping module, and the anti-false triggering module controls the voltage of the switch module to slowly decrease from a high voltage to a turn-on voltage; In an overcurrent / short circuit fault state, the clamping module is turned on to start the slow gate voltage drop module. After the slow gate voltage drop module is started, the on-state voltage of the switch module is controlled to drop slowly.

2. The slow-drop gate voltage protection circuit according to claim 1, characterized in that: The driving module is a push-pull circuit; and the control signal is a PWM signal.

3. The slow-drop gate voltage protection circuit according to claim 1, characterized in that: Also includes: Peak absorption module; The input end of the peak absorption module is connected to the power factor correction module, and the output end of the peak absorption module is connected to the transformer winding.

4. The slow-falling gate voltage protection circuit according to any one of claims 1 to 3, characterized in that: The driving module includes: a first switch tube, a second switch tube and an eighth resistor; The first end of the first switch tube is connected to the main control unit through the eighth resistor, the second end of the first switch tube is connected to a high level, the third end of the first switch tube is connected to the second end of the second switch tube and connected to the switch module, the first end of the second switch tube is connected to the first end of the first switch tube, and the third end of the second switch tube is grounded.

5. The slow-drop gate voltage protection circuit according to claim 3, characterized in that: The switch module includes: a fifth resistor and a power switch tube; The first end of the fifth resistor is connected to the output end of the driving module, the second end of the fifth resistor is connected to the gate of the power switch tube, the drain of the power switch tube is connected to the fault detection module and the spike absorption module, the source of the power switch tube is grounded, and the gate of the power switch tube is also connected to the slow-drop gate voltage module.

6. The slow-drop gate voltage protection circuit according to claim 5, characterized in that: The fault detection module includes: a third resistor and a fourth diode; The first end of the third resistor is connected to the output end of the driving module, the second end of the third resistor is connected to the anode of the fourth diode and connected to terminal a, the cathode of the fourth diode is connected to the drain of the power switch tube, and the terminal a is connected to the clamping module.

7. The slow-drop gate voltage protection circuit according to claim 6, characterized in that: The clamping module includes: a first voltage regulator tube; The cathode of the first voltage regulator tube is connected to the end point a, and the anode of the first voltage regulator tube is connected to the anti-false triggering module.

8. The slow-drop gate voltage protection circuit according to claim 7, characterized in that: The anti-false triggering module includes: a second capacitor; The input end of the second capacitor is connected to the anode of the first voltage regulator and the slow-drop gate voltage module, and the second end of the second capacitor is grounded.

9. The slow-drop gate voltage protection circuit according to claim 8, characterized in that: The slow gate voltage drop module includes: a first resistor, a second resistor, a fourth resistor, a first capacitor, a third switch tube, a fourth switch tube, a second voltage regulator tube and a third voltage regulator tube; The second end of the fourth switch tube is connected to the gate of the power switch tube, the first end of the fourth switch tube is connected to the anode of the second voltage regulator tube, and the third end of the fourth switch tube is grounded through the fourth resistor; the first end of the third switch tube is connected to the anode of the first voltage regulator tube, the second end of the third switch tube is grounded, the third end of the third switch tube is connected to the second end of the first resistor through the transmitting part of the photocoupler, the first end of the first resistor is connected to the high level through the second resistor, the first capacitor is connected to the second resistor in parallel, the cathode of the third voltage regulator tube is connected to the high level, and the anode of the third voltage regulator tube is connected to the cathode of the second voltage regulator tube.

10. A switching power supply, characterized in that: include: The slow-falling gate voltage protection circuit according to any one of claims 1 to 9.

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