An overcurrent protection latch circuit for a power transistor

Abstract

The utility model belongs to vehicle drive circuit protection technical field especially for a kind of overcurrent protection latch circuit for power tube, including power tube drive circuit, overcurrent protection and latch circuit, fault detection circuit;Power tube drive circuit is constituted by resistance R2, drive circuit, power tube Q1, freewheeling diode D1, load inductance L1, and drive circuit is constituted by discrete component or drive chip;Overcurrent protection and latch circuit are constituted by resistance R1, resistance R3, resistance R4, resistance R5, capacitor C1, PNP triode Q2, NPN triode Q3;Fault detection circuit is constituted by resistance R6, resistance R7, diode D2, the utility model has short-circuit protection latch function, maintains protection state after short-circuit, and sends fault state to MCU to operate restart or report fault, reduce MOS damage probability, in addition still have the characteristics that circuit is simple, cost is low, circuit parameter is adjusted flexibly.

Description

Technical Field

[0001] This utility model belongs to the field of vehicle drive circuit protection technology, specifically relating to an overcurrent protection latching circuit for power transistors. Background Technology

[0002] Vehicles use components such as relays, horns, and electromagnetic brakes. These components typically require a drive circuit to drive their coils to generate a magnetic field to operate. However, because the coils may overheat during operation, leading to insulation failure and short circuits, damage can occur. If the drive circuit lacks protection, this can exacerbate the damage. Therefore, overcurrent protection circuits are added to coil drive circuits to reduce the probability of damage.

[0003] Existing power transistor overcurrent protection circuits (such as...) Figure 1 As shown, its input signal passes through resistor R3 to the drive circuit, which converts it into a drive signal for the power transistor Q1, causing Q1 to turn on. When Q1 is on, current flows through the load coil L1. If a short-circuit overcurrent occurs, the voltage across the sampling resistor R5 increases. R4 feeds this voltage back to the voltage comparator U1 (input negative). If the voltage exceeds the protection value set by the voltage divider between R1 and R2 at the "input positive" terminal, the output of U1 will pull the signal input to the drive circuit low to turn it off, thus achieving the overcurrent protection function.

[0004] However, due to the structure of the protection circuit, the overcurrent fault disappears immediately after the drive is turned off. If the input signal remains high, the protection circuit enters the next cycle. Therefore, the power transistor continues to operate in a pulsed high-current state, and the interval between each pulse is short. The power transistor may be damaged due to abnormal operation or continuous overheating over a long period of time. Therefore, the existing circuit does not have a protection latching function to keep the power transistor in a closed state after an overcurrent occurs. Utility Model Content

[0005] To address the aforementioned problems in the existing technology, this utility model provides an overcurrent protection latch circuit for power transistors, which has a short-circuit protection latch function. After a short circuit, it maintains the protection state and sends the fault status to the MCU for operation restart or fault reporting, reducing the probability of MOS damage. In addition, it has the characteristics of simple circuit, low cost, and flexible circuit parameter adjustment.

[0006] To achieve the above objectives, this utility model provides the following technical solution: an overcurrent protection latching circuit for a power transistor, comprising a power transistor driving circuit, an overcurrent protection and latching circuit, and a fault detection circuit;

[0007] The power transistor drive circuit consists of resistor R2, drive circuit, power transistor Q1, freewheeling diode D1, and load inductor L1. The drive circuit is composed of discrete components or a drive chip. The input signal is connected to one end of resistor R2, and the other end of resistor R2 is connected to the input of the drive circuit. The output of the drive circuit is connected to the gate of power transistor Q1. The anode of freewheeling diode D1 is connected to the drain of power transistor Q1, and the cathode of freewheeling diode D1 is connected to the B+ power supply. The load coil L1 is connected in parallel with freewheeling diode D1.

[0008] The overcurrent protection and latching circuit consists of resistors R1, R3, R4, and R5, capacitor C1, PNP transistor Q2, and NPN transistor Q3. One end of resistor R1 is connected to the input signal, and the other end of resistor R1 is connected to the emitter of PNP transistor Q2. One end of resistor R3 is connected to the input signal, and the other end of resistor R3 is grounded. The base of PNP transistor Q2 is connected to the input terminal of the driver circuit. The collector of PNP transistor Q2 is connected to the base of NPN transistor Q3. The collector of NPN transistor Q3 is connected to the base of PNP transistor Q2. The emitter of NPN transistor Q3 is grounded. One end of resistor R5 is connected to the source of power transistor Q1, and the other end of resistor R5 is grounded. One end of resistor R4 is connected to the source of power transistor Q1, and the other end of resistor R4 is connected to the base of NPN transistor Q3. One end of capacitor C1 is connected to the base of NPN transistor Q3, and the other end of capacitor C1 is grounded.

[0009] The fault detection circuit consists of resistors R6 and R7, and diode D2. One end of resistor R6 is connected to the drain of power transistor Q1, and the other end of resistor R6 is connected to the output signal. One end of resistor R7 is connected to the output signal, and the other end is grounded. The anode of diode D2 is connected to the output signal, and the cathode of diode D2 is connected to the 3V3 power supply.

[0010] As a preferred technical solution of the overcurrent protection latching circuit for power transistors according to this utility model, the circuit can maintain the overcurrent protection state to reduce the probability of power transistor damage.

[0011] As a preferred technical solution of the overcurrent protection latch circuit for power transistors according to this utility model, the circuit can report the fault status to the MCU for operation restart or fault reporting.

[0012] Compared with the prior art, the beneficial effects of this utility model are:

[0013] This utility model mainly consists of a power transistor drive circuit, an overcurrent protection and latching circuit, and a fault detection circuit. It has a short-circuit protection latching function, which maintains the protection state after a short circuit and sends the fault state to the MCU for operation restart or fault reporting, reducing the probability of MOS damage. In addition, it has the characteristics of simple circuit, low cost, and flexible circuit parameter adjustment. Attached Figure Description

[0014] The accompanying drawings are provided to further illustrate the present invention and form part of the specification. They are used together with the embodiments of the present invention to explain the present invention, but do not constitute a limitation thereof. In the drawings:

[0015] Figure 1 This is a schematic diagram of the overcurrent protection circuit for power transistors in the prior art;

[0016] Figure 2 This is a schematic diagram of the structure of this utility model.

[0017] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model. Example

[0018] Please see Figure 1-2 The present invention provides the following technical solution: an overcurrent protection latching circuit for a power transistor, comprising a power transistor driving circuit, an overcurrent protection and latching circuit, and a fault detection circuit;

[0019] Furthermore, the power transistor drive circuit consists of resistor R2, drive circuit, power transistor Q1, freewheeling diode D1, and load inductor L1. The drive circuit is composed of discrete components or drive chip. The input signal is connected to one end of resistor R2, and the other end of resistor R2 is connected to the input of the drive circuit. The output of the drive circuit is connected to the gate of power transistor Q1. The anode of freewheeling diode D1 is connected to the drain of power transistor Q1, and the cathode of freewheeling diode D1 is connected to the B+ power supply. The load coil L1 is connected in parallel with freewheeling diode D1.

[0020] Furthermore, the overcurrent protection and latching circuit consists of resistors R1, R3, R4, and R5, capacitor C1, PNP transistor Q2, and NPN transistor Q3. One end of resistor R1 is connected to the input signal, and the other end of resistor R1 is connected to the emitter of PNP transistor Q2. One end of resistor R3 is connected to the input signal, and the other end of resistor R3 is grounded. The base of PNP transistor Q2 is connected to the input terminal of the drive circuit. The collector of PNP transistor Q2 is connected to the base of NPN transistor Q3. The collector of NPN transistor Q3 is connected to the base of PNP transistor Q2. The emitter of NPN transistor Q3 is grounded. One end of resistor R5 is connected to the source of power transistor Q1, and the other end of resistor R5 is grounded. One end of resistor R4 is connected to the source of power transistor Q1, and the other end of resistor R4 is connected to the base of NPN transistor Q3. One end of capacitor C1 is connected to the base of NPN transistor Q3, and the other end of capacitor C1 is grounded.

[0021] Furthermore, the fault detection circuit consists of resistors R6 and R7, and diode D2. One end of resistor R6 is connected to the drain of power transistor Q1, and the other end of resistor R6 is connected to the output signal. One end of resistor R7 is connected to the output signal, and the other end is grounded. The anode of diode D2 is connected to the output signal, and the cathode of diode D2 is connected to the 3V3 power supply.

[0022] The working principle of this invention is as follows: The 3V3 power supply is the system power supply. When the circuit is working, the MCU sends a high-level input signal to the circuit, which is converted into a power transistor drive signal input to the gate of Q1 by the drive circuit. After the power transistor is turned on, current flows from B+ through the coil load. If a short circuit occurs in the load at this time, the voltage across R5 rises. This voltage enters the base of transistor Q3 through feedback resistor R4. When it is 0.7V higher than the Q3 start-up voltage, Q3 turns on, pulling the base signal of Q2 low. At this time, the input signal is still high, and the input signal enters the gate of Q2 through R1. The emitter is turned on, so Q2 turns on and continuously sends the signal to the base of Q3. At this time, Q3 continues to conduct, pulling the signal input to the drive circuit low, and the power transistor Q1 turns off, realizing the function of overcurrent protection latch. The voltage divider between R6 and R7 sends the drain voltage output signal of Q1 to the MCU. When Q1 is normally conducting, the output signal is low. If overcurrent protection occurs, Q1 turns off, and the output detection signal is high. At this time, the MCU can determine that a fault has occurred. If it is necessary to reset the fault and try to turn Q1 back on, it is only necessary to turn off the input signal and then set it high to restore operation.

[0023] In this implementation scheme: This utility model mainly consists of a power transistor drive circuit, an overcurrent protection and latching circuit, and a fault detection circuit. It has a short-circuit protection latching function, which maintains the protection state after a short circuit and sends the fault state to the MCU for operation restart or fault reporting, reducing the probability of MOS damage. In addition, it has the characteristics of simple circuit, low cost, and flexible circuit parameter adjustment.

[0024] The key innovation of this implementation plan is the addition of a short-circuit protection latching function compared to existing technical solutions.

[0025] The MCU detects MOS fault status and can restart the circuit or report the fault.

[0026] The circuit parameters are flexible to adjust, and the current limiting value can be set by changing the resistance value of resistor R5.

[0027] Other alternatives to this implementation scheme: replace the overcurrent detection circuit with a voltage comparator.

[0028] In addition, all content not described in detail in this embodiment falls within the scope of existing technology and common knowledge.

[0029] Finally, it should be noted that the above are merely preferred embodiments of this utility model and are not intended to limit the utility model. Although the utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. An overcurrent protection latching circuit for a power transistor, characterized in that: This includes power transistor drive circuits, overcurrent protection and latching circuits, and fault detection circuits; The power transistor drive circuit consists of resistor R2, drive circuit, power transistor Q1, freewheeling diode D1, and load inductor L1. The drive circuit is composed of discrete components or a drive chip. The input signal is connected to one end of resistor R2, and the other end of resistor R2 is connected to the input of the drive circuit. The output of the drive circuit is connected to the gate of power transistor Q1. The anode of freewheeling diode D1 is connected to the drain of power transistor Q1, and the cathode of freewheeling diode D1 is connected to the B+ power supply. The load coil L1 is connected in parallel with freewheeling diode D1. The overcurrent protection and latching circuit consists of resistors R1, R3, R4, and R5, capacitor C1, PNP transistor Q2, and NPN transistor Q3. One end of resistor R1 is connected to the input signal, and the other end of resistor R1 is connected to the emitter of PNP transistor Q2. One end of resistor R3 is connected to the input signal, and the other end of resistor R3 is grounded. The base of PNP transistor Q2 is connected to the input terminal of the driver circuit. The collector of PNP transistor Q2 is connected to the base of NPN transistor Q3. The collector of NPN transistor Q3 is connected to the base of PNP transistor Q2. The emitter of NPN transistor Q3 is grounded. One end of resistor R5 is connected to the source of power transistor Q1, and the other end of resistor R5 is grounded. One end of resistor R4 is connected to the source of power transistor Q1, and the other end of resistor R4 is connected to the base of NPN transistor Q3. One end of capacitor C1 is connected to the base of NPN transistor Q3, and the other end of capacitor C1 is grounded. The fault detection circuit consists of resistors R6 and R7, and diode D2. One end of resistor R6 is connected to the drain of power transistor Q1, and the other end of resistor R6 is connected to the output signal. One end of resistor R7 is connected to the output signal, and the other end is grounded. The anode of diode D2 is connected to the output signal, and the cathode of diode D2 is connected to the 3V3 power supply.

2. The overcurrent protection latching circuit for a power transistor according to claim 1, characterized in that: This circuit can maintain the overcurrent protection state to reduce the probability of power transistor damage.

3. The overcurrent protection latching circuit for a power transistor according to claim 1, characterized in that: This circuit can report the fault status to the MCU for operation restart or fault reporting.

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