Over-current protection delay recovery circuit for power tube

Abstract

The utility model belongs to the technical field of circuits, and particularly relates to an overcurrent protection delay recovery circuit for a power tube, which comprises a power tube driving circuit, an overcurrent protection circuit and a protection delay recovery circuit. Through cooperative application of the power tube driving circuit, the over-current protection circuit and the protection delay recovery circuit, the circuit has a short-circuit protection delay recovery function, the protection state is maintained for a period of time after short circuit, and when a short-circuit fault continuously exists, the working pressure of the power tube is reduced, so that the damage probability of the power tube is reduced; meanwhile, circuit parameters are flexibly adjusted, protection delay time can be changed by replacing voltage-regulator tubes D2 with different voltage-regulator values or adjusting resistance-capacitance parameters R6 and C1, and a current-limiting value can be jointly set by changing the voltage division ratio of R1 and R2 and changing the resistance value of a sampling resistor R5 so as to adapt to actual requirements.

Description

TECHNICAL FIELD

[0001] The utility model belongs to circuit technical field, concretely relates to a kind of overcurrent protection delay recovery circuit for power tube. BACKGROUND

[0002] Components such as relay, horn, electromagnetic brake and the like are used in vehicle, and such components usually need driving circuit to drive the coil to generate magnetic field and work;But due to the coil may appear high temperature when working, leading to insulation failure and short circuit damage, if driving circuit is not protected, it will lead to aggravate damage, so the coil driving circuit will increase overcurrent protection circuit to reduce the probability of damage.

[0003] The prior art power tube overcurrent protection circuit as shown in Figure 1 Input signal is sent into driving circuit through resistance R3 to send PWM signal into driving circuit, and is converted into driving signal of power tube by driving circuit and is input into Q1 gate, so that power tube Q1 works in switch state;When Q1 is turned on, current flows through load coil L1, at this time, if short-circuit overcurrent occurs, the voltage at both ends of sampling resistance R5 rises, and R4 feeds back this voltage to voltage comparator U1 "input negative", if it is higher than the protection value set by R1 and R2 voltage division of "input positive" end, U1 output will pull down the PWM signal input into driving circuit to close, to realize the function of overcurrent protection;Due to the structure of protection circuit, overcurrent state disappears immediately after driving is closed, if driving signal is effective again when short-circuit fault exists, protection circuit enters next cycle, so power tube works in pulse high current state, and the interval time of each pulse is short, and power tube will be damaged due to long-time working state abnormality or continuous heating.

[0004] Therefore, the prior art circuit does not have the function of protection delay recovery to make power tube cool down and recover after exiting overcurrent state. CONTENT OF UTILITY MODEL

[0005] To solve the above problems existing in the prior art, the utility model provides an overcurrent protection delay recovery circuit for power tube, which has short-circuit protection delay recovery function, maintains protection state for a period of time after short-circuit, reduces the working pressure of power tube when short-circuit fault exists, and reduces the damage probability of power tube.

[0006] To achieve the above object, the utility model provides the following technical scheme: a kind of overcurrent protection delay recovery circuit for power tube, including power tube drive circuit, overcurrent protection circuit and protection delay recovery circuit;Power tube drive circuit includes resistance R3, drive circuit, power tube Q1, freewheeling diode D1 and load coil L1, drive circuit input signal connection resistance R3 one end, resistance R3 other end connects drive circuit input, drive circuit output is connected to the gate of power tube Q1, freewheeling diode D1 anode connects power tube Q1 drain, freewheeling diode D1 cathode connects B+ power supply, load coil L1 is connected in parallel on diode D1;Overcurrent protection circuit includes voltage comparator U1, resistance R1, resistance R2, resistance R4 and resistance R5, resistance R1 and resistance R2 are connected in series to constitute voltage divider, voltage divider output is connected to the "input positive" of voltage comparator U1, resistance R5 one end connects power tube Q1 source, resistance R5 other end connects ground, resistance R4 one end connects power tube Q1 source, resistance R4 other end connects the "input negative" of voltage comparator U1;Protection delay recovery circuit includes stabilivolt D2, NPN triode Q2, NPN triode Q3, resistance R6, resistance R7 and capacitor C1, stabilivolt D2 cathode connects voltage comparator U1 output end, stabilivolt D2 anode connects NPN triode Q2 base, resistance R6 one end connects stabilivolt D2 cathode, resistance R6 other end connects 5V, capacitor C1 one end connects stabilivolt D2 cathode, capacitor C1 other end connects ground, NPN triode Q2 emitter connects ground, NPN triode Q2 collector connects NPN triode Q3 base, resistance R7 one end connects NPN triode Q3 base, resistance R7 other end connects 5V, NPN triode Q3 emitter connects ground, NPN triode Q3 collector connects drive circuit input end.

[0007] As a kind of overcurrent protection delay recovery circuit for power tube of the utility model, drive circuit includes discrete component or drive chip.

[0008] As a kind of overcurrent protection delay recovery circuit for power tube of the utility model, resistance R1 and resistance R2 voltage division ratio can change, cooperate to change sampling resistance R5 resistance value to set the current limiting value of circuit together.

[0009] As a kind of overcurrent protection delay recovery circuit for power tube of the utility model, by replacing stabilivolt D2 voltage stabilizing value or resistance-capacitance parameter R6 and C1, protection delay time can be changed.

[0010] Compared with the prior art, the utility model discloses the beneficial effect is: the utility model discloses when using, through the cooperation and application of power tube drive circuit, overcurrent protection circuit and protection delay recovery circuit, make the circuit have short -circuit protection delay recovery function, and the protection state is maintained for a period of time after short -circuit, when short -circuit fault continues to exist, reduce the working pressure of power tube and reduce its damage probability;

[0011] Meanwhile the utility model circuit parameter adjusts nimble, such as replacing the voltage stabilizing pipe D2 of different voltage stabilizing value or adjusting resistance and capacitance parameter R6 and C1, can change protection delay time, and the current -limiting value can be set through the change R1 with R2 voltage division ratio and the change sampling resistance R5 resistance value together, to adapt actual demand. BRIEF DESCRIPTION OF DRAWINGS

[0012] The accompanying drawings are included to provide a further understanding of the present application and are incorporated in and constitute a part of this specification, illustrate embodiments of the present application and are used to explain the present application, and do not constitute a limitation on the present application. In the drawings:

[0013] Figure 1 It is the schematic diagram of prior art power tube overcurrent protection circuit;

[0014] Figure 2 It is the schematic diagram of the utility model circuit. DETAILED DESCRIPTION

[0015] 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. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of the present application. EMBODIMENT

[0016] The utility model provides the following technical scheme: a kind of overcurrent protection delay recovery circuit for power tube as shown in Figure 2 It includes power tube drive circuit, overcurrent protection circuit and protection delay recovery circuit.

[0017] Wherein power tube drive circuit includes resistance R3, drive circuit, power tube Q1, freewheeling diode D1 and load coil L1.

[0018] Drive circuit includes discrete component or drive chip, one end of input signal connection resistance R3, resistance R3 other end connects drive circuit input, drive circuit output is connected to the gate of power tube Q1, freewheeling diode D1 anode connects power tube Q1 drain, freewheeling diode D1 (diode D1) cathode connects B+ power supply, load coil L1 is connected in parallel on diode D1.

[0019] The overcurrent protection circuit includes voltage comparator U1, resistor R1, resistor R2, resistor R4, and resistor R5.

[0020] Resistor R1 and resistor R2 are connected in series to form a voltage divider, and the output of the voltage divider is connected to the "positive input" of voltage comparator U1 to provide a reference voltage. One end of sampling resistor R5 (i.e., resistor R5) is connected to the source of power transistor Q1, and the other end of resistor R5 is connected to ground. One end of feedback resistor R4 (i.e., resistor R4) is connected to the source of power transistor Q1, and the other end of resistor R4 is connected to the "negative input" of voltage comparator U1.

[0021] The protection delay recovery circuit includes zener diode D2, NPN transistor Q2, NPN transistor Q3, resistor R6, resistor R7, and capacitor C1.

[0022] The cathode of zener diode D2 is connected to the output of voltage comparator U1, and the anode of zener diode D2 is connected to the base of NPN transistor Q2. One end of resistor R6 is connected to the cathode of zener diode D2, and the other end of resistor R6 is connected to 5V. One end of capacitor C1 is connected to the cathode of zener diode D2, and the other end of capacitor C1 is connected to ground. The emitter of NPN transistor Q2 is connected to ground, the collector of NPN transistor Q2 is connected to the base of NPN transistor Q3, one end of resistor R7 is connected to the base of NPN transistor Q3, and the other end of resistor R7 is connected to 5V (i.e., the end of resistor R7 opposite to NPN transistor Q3 is connected to 5V). The emitter of NPN transistor Q3 is connected to ground, and the collector of NPN transistor Q3 is connected to the input of the drive circuit.

[0023] 5V is the system power supply, and the input signal is generally sent by MCU. When the circuit is working, MCU sends a PWM signal, which is converted into a power transistor drive signal by the drive circuit and input to the gate of Q1 (power transistor Q1). After the power transistor is turned on, current flows from B+ through the coil load. If the load is short-circuited at this time, the voltage across R5 (sampling resistor R5) rises. This voltage enters the "negative input" of voltage comparator U1 through feedback resistor R4 and is compared with the "positive input" voltage. If it is higher than the protection reference value set by resistors R1 and R2, the output of voltage comparator U1 will be pulled low to discharge the stored charge of capacitor C1, NPN transistor Q2 will be turned off, NPN transistor Q3 will be turned on, and NPN transistor Q3 will pull the PWM signal input to the drive circuit low to turn off, and the corresponding power transistor Q1 will be turned off.

[0024] After the over-current fault disappears, the voltage comparator U1 output exits the low level state, and the 5V power supply charges the capacitor C1 through the resistor R6 again until the voltage is higher than the sum of the voltage stabilizing value of the voltage stabilizing tube D2 and the off voltage of the NPN transistor Q2, the NPN transistor Q2 is turned on again, and the PWM signal can re-enter the driving circuit after the NPN transistor Q3 is turned off. During this time, the power tube Q1 is in a closed state, and the power tube has enough time to cool down. Even if the load is still in a short-circuit state at this time, the power tube will not be turned on, so there is no damage caused by the fact that the power tube works in a high-frequency pulse large current state and heats up when the load is short-circuited in the prior art driving circuit (such as shown in Figure 1 The voltage division ratio of the resistor R1 and the resistor R2 can be changed, and the sampling resistor R5 value is changed to set the current limiting value of the circuit (the current limiting value can be set by changing the voltage division ratio of R1 and R2 and changing the sampling resistor R5 value to adapt to the actual needs); by changing the voltage stabilizing value of the voltage stabilizing tube D2 or the resistance and capacitance parameters R6 and C1, the protection delay time can be changed, and the circuit parameters can be adjusted flexibly.

[0025] The over-current protection delay recovery circuit for the power tube is not limited to the description and embodiments. Therefore, equivalent changes or modifications made to the structure, features and principles described in the patent application range of the utility model should be included in the patent application range of the utility model, such as: the power tube driving can use discrete components or driving chips, and all voltage comparators (including totem output type and open drain type) can complete the circuit of the utility model.

[0026] Finally, it should be pointed out that: the above-mentioned is only the preferred embodiment of the utility model, and is not used to limit the utility model, although the utility model has been described in detail with reference to the foregoing embodiments, and for those skilled in the art, the technical solutions recorded in the foregoing embodiments can be modified, or some technical features can be replaced. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the utility model should be included in the protection range of the utility model.

Claims

1. An overcurrent protection delay recovery circuit for a power transistor, characterized by comprising: The power tube driving circuit, the over-current protection circuit and the protection delay recovery circuit are included. The power tube driving circuit includes a resistor R3, a driving circuit, a power tube Q1, a freewheeling diode D1 and a load coil L1. One end of the resistor R3 is connected to the input signal of the driving circuit, and the other end of the resistor R3 is connected to the input of the driving circuit. The output of the driving circuit is connected to the gate of the power tube Q1. The anode of the freewheeling diode D1 is connected to the drain of the power tube Q1, and the cathode of the freewheeling diode D1 is connected to the B+ power supply. The load coil L1 is connected in parallel to the diode D1. The over-current protection circuit includes a voltage comparator U1, resistors R1, R2, R4 and R5. The resistors R1 and R2 are connected in series to form a voltage divider. The output of the voltage divider is connected to the "positive input" of the voltage comparator U1. One end of the resistor R5 is connected to the source of the power tube Q1, and the other end of the resistor R5 is connected to the ground. One end of the resistor R4 is connected to the source of the power tube Q1, and the other end of the resistor R4 is connected to the "negative input" of the voltage comparator U1. The protection delay recovery circuit includes a voltage stabilizing tube D2, NPN transistors Q2 and Q3, a resistor R6, a resistor R7 and a capacitor C1. The cathode of the voltage stabilizing tube D2 is connected to the output of the voltage comparator U1, and the anode of the voltage stabilizing tube D2 is connected to the base of the NPN transistor Q2. One end of the resistor R6 is connected to the cathode of the voltage stabilizing tube D2, and the other end of the resistor R6 is connected to 5V. One end of the capacitor C1 is connected to the cathode of the voltage stabilizing tube D2, and the other end of the capacitor C1 is connected to the ground. The emitter of the NPN transistor Q2 is connected to the ground, and the collector of the NPN transistor Q2 is connected to the base of the NPN transistor Q3. One end of the resistor R7 is connected to the base of the NPN transistor Q3, and the other end of the resistor R7 is connected to 5V. The emitter of the NPN transistor Q3 is connected to the ground, and the collector of the NPN transistor Q3 is connected to the input of the driving circuit.

2. The overcurrent protection delay recovery circuit for a power transistor according to claim 1, wherein: The driving circuit includes discrete components or a driving chip.

3. The overcurrent protection delay recovery circuit for a power transistor according to claim 1, wherein: The voltage dividing ratio of the resistors R1 and R2 can be changed, and the sampling resistor R5 is changed to set the current limiting value of the circuit.

4. The overcurrent protection delay recovery circuit for a power transistor according to claim 1, wherein: The protection delay time can be changed by changing the voltage stabilizing value of the voltage stabilizing tube D2 or the resistance and capacitance parameters R6 and C1.

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