Automobile washing pump driving circuit and overcurrent protection method thereof

Abstract

The application discloses a kind of automobile washing pump driving circuit and its overcurrent protection method, including main power circuit, main power circuit includes current sampling unit, pump power supply node and main power switch unit, current sampling unit is connected to RC integral delay unit for delay filtering to sampling voltage, main power switch unit is connected to overcurrent detection self-locking unit, RC integral delay unit is filtered voltage input overcurrent detection self-locking unit, overcurrent detection self-locking unit forms self-locking after overcurrent, and controls main power switch unit to close, overcurrent detection self-locking unit is also connected to the control and reset unit for removing its self-locking.It realizes the resettable pure hardware overcurrent self-locking and fast protection function that needs special IC to have before by extremely low cost discrete component, solves the problem of start peak false trigger.

Description

Technical Field

[0001] This invention relates to the field of automotive wash pump drive technology, and in particular to an automotive wash pump drive circuit and its overcurrent protection method. Background Technology

[0002] The windshield washer pump is an important component of a car's safety system, used to spray washer fluid onto the windshield to clean it in conjunction with the wipers. Currently, the mainstream washer pump drive solutions include relay-driven solutions, dedicated driver IC solutions, and discrete component-driven solutions. Among these, the discrete component-driven solution uses a MOSFET as the main power switch, providing simple overcurrent protection. Its cost falls between that of relays and dedicated ICs, making it the most cost-effective solution currently available.

[0003] However, discrete component solutions lack reliable resettable hardware latching functionality, causing repeated switching during overcurrent, which can easily burn out MOSFETs and sampling resistors. Furthermore, some discrete component solutions with hardware latching require system power-off to release, making software reset impossible and extremely inconvenient to use. The starting current of a DC brushed motor is 6-12 times its rated current, lasting 1-5ms. Existing solutions either reduce the protection response speed to avoid false triggering or have a fast response but frequent false triggering during startup. To withstand short-circuit current, high-power sampling resistors (typically 10W or more) must be used, significantly increasing BOM costs. Traditional PWM soft-start solutions require MCU support for PWM output, making implementation complex and unable to solve the problem of false triggering of hardware overcurrent protection.

[0004] In summary, the functions of resettable hardware overcurrent self-locking and fast protection can only be achieved through dedicated driver ICs, which are expensive (2-5 yuan per chip); while low-cost discrete component solutions either lack self-locking function, causing repeated switching on and off during overcurrent to damage the device, or require system power-off to release the self-locking function, and generally suffer from the problem of false triggering protection during DC brushed motor starting spikes. Summary of the Invention

[0005] The purpose of this invention is to provide a car wash pump drive circuit and its overcurrent protection method. It uses extremely low-cost discrete components to achieve the resettable pure hardware overcurrent self-locking and fast protection functions that previously required dedicated ICs, thus solving the problem of false triggering during startup spikes.

[0006] The above-mentioned technical objective of the present invention is achieved through the following technical solution: A car wash pump drive circuit includes a main power circuit, which comprises a current sampling unit, a pump power supply node, and a main power switching unit. The current sampling unit is connected to an RC integral delay unit that performs delay filtering on the sampled voltage, and the main power switching unit is connected to an overcurrent detection self-locking unit. The RC integral delay unit inputs the filtered voltage into the overcurrent detection self-locking unit. The overcurrent detection self-locking unit locks itself after an overcurrent occurs and controls the main power switch unit to shut down. The overcurrent detection self-locking unit is also connected to the control and reset unit that releases its self-lock.

[0007] Furthermore, the main power switching unit includes a P-MOS transistor Q3, with the source of the P-MOS transistor Q3 connected to the pump power supply node, the drain connected to the power output port, and the gate connected to the overcurrent detection self-locking unit.

[0008] Furthermore, the current sampling unit includes a sampling resistor or several sampling resistors connected in parallel, with one end of the current sampling unit connected to the power input terminal and the other end connected to the pump power supply node.

[0009] Furthermore, the RC integral delay unit includes an integral resistor R4 and an integral capacitor C1. One end of the integral resistor R4 is connected to the low-voltage side node of the current sampling unit, and the other end is connected to the trigger input terminal of the overcurrent detection self-locking unit and the integral capacitor C1, respectively. The other end of the integral capacitor C1 is connected to the high-voltage side node of the current sampling unit.

[0010] Furthermore, the overcurrent detection unit includes a PNP type first transistor Q1.1 and an NPN type second transistor Q1.2; The emitter of the first transistor Q1.1 is connected to the high-voltage side of the output terminal of the RC integration delay unit, and its base is connected to the collector of the second transistor Q1.2 and the low-voltage side of the output terminal of the RC integration delay unit, respectively. The collector is connected to the current-limiting resistor R9 and the base of the second transistor Q1.2, respectively. The other end of the current-limiting resistor R9 and the emitter of the second transistor Q1.2 are connected to the main power switching unit.

[0011] Furthermore, the control and reset unit includes an NPN type third transistor Q2, the collector of the third transistor Q2 is connected to the seventh voltage divider resistor R7, the other end of the seventh voltage divider resistor R7 is connected to the gate of the P-MOS transistor Q3 and the sixth voltage divider resistor R6, and the other end of the sixth voltage divider resistor R6 is connected to the high-voltage side node of the current sampling unit. The base of the third transistor Q2 is connected to the fifth resistor R5 and the eighth resistor R8. The other end of the fifth resistor R5 is connected to the external WASH_PUMP port, and the other end of the eighth resistor R8 is grounded to the emitter of the third transistor Q2.

[0012] Furthermore, a clamping Zener diode D1 is connected between the high-voltage side node of the current sampling unit and the gate of the P-MOS transistor Q3 to limit the gate-source voltage of the P-MOS transistor Q3.

[0013] Furthermore, upon receiving a start command, inertial startup is performed, including: Output a high level to the WASH_PUMP pin; detect the level of the WASH_PUMP pin; if the level is still high, protection is not triggered, soft start succeeds, and the system enters a normal working state; If the level changes to low, protection is triggered, output a low level to the WASH_PUMP pin, release the self-locking and allow the motor to rotate by inertia; and restart according to the above process.

[0014] Furthermore, the device further comprises a fault output unit for outputting a fault signal, and the fault output unit is connected to the drain of a P-MOS transistor Q3.

[0015] Furthermore, the fault output unit comprises a magnetic bead F1, one end of the magnetic bead F1 is connected to a power output port, the other end is connected to a current-limiting resistor R11, and the other end of the current-limiting resistor R11 is respectively connected to a FAULT port, a pull-down resistor R12 and a filter capacitor C2, and the other ends of the pull-down resistor R12 and the filter capacitor C2 are grounded.

[0016] In another aspect, the present application also discloses an overcurrent protection method, comprising: after a main power switch unit is conducted, a main power loop operates, and supplies power to a washing pump through a pump power supply node, during operation, a current sampling unit samples the main power loop, an RC integration delay unit performs delay filtering on a sampled voltage and inputs the filtered voltage to an overcurrent detection self-locking unit, the overcurrent detection self-locking unit forms self-locking after detecting overcurrent and controls the main power switch unit to turn off, until the self-locking of the overcurrent detection self-locking unit is released through a control and reset unit.

[0017] Furthermore, the sampling current of the current sampling unit is I, the maximum safe continuous current is obtained according to the rated power of the current sampling unit, and the overcurrent self-locking current is obtained according to the sampling current I when the overcurrent detection self-locking unit forms self-locking, if the maximum safe continuous current is less than the overcurrent self-locking current, after the maximum safe continuous current < I < the overcurrent self-locking current and the condition accumulates for a preset time, the main power switch unit is turned off through the control and reset unit.

[0018] In summary, the present invention has the following beneficial effects: A pure hardware overcurrent self-locking circuit composed of only two common triodes is used to realize rapid short-circuit protection of <50μs; a mechanism that can release hardware self-locking through the same control pin without additional pins, and no system power-off is required; the problem of false triggering caused by start-up peak can be solved without PWM during inertia soft start; a software and hardware hierarchical overload protection scheme covers the power blind area of the sampling resistor, and reduces the power requirement of the sampling resistor from 10W to 3W; It drastically reduces costs: the overall BOM cost is 1 / 5 to 1 / 10 of that of a dedicated driver IC solution; through hardware and software hierarchical protection, the sampling resistor power is reduced from 10W to 3W, further reducing costs by 30%; protection response is extremely fast: the pure hardware short-circuit protection response time is <50μs, much faster than MCU software protection, effectively preventing short circuit damage to power devices; reliability is greatly improved: pure hardware self-locking prevents repeated switching during overcurrent; dual anti-false triggering mechanisms ensure 100% startup success rate; pure hardware protection is unaffected by MCU crashes. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the overall structure of a car wash pump drive circuit according to the present invention. Detailed Implementation

[0020] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings. These embodiments do not constitute a limitation of the present invention. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this application.

[0021] A car wash pump drive circuit adopts an architecture of high-end P-MOS drive + dual transistor pure hardware overcurrent self-locking + RC integral delay + hardware and software graded overload protection + inertial soft start, which facilitates the implementation of starting methods such as inertial soft start; like Figure 1 As shown, the system includes a main power circuit, which comprises, in series, a power input terminal VBAT (upper end of the current sampling unit), a current sampling unit, a pump power supply node V_PUMP (lower end of the current sampling unit), a main power switch unit, a power output port Washer_out, and a fault output unit. The current sampling unit is connected to an RC integral delay unit that performs delay filtering on the sampled voltage. The main power switch unit is connected to an overcurrent detection self-locking unit. The RC integral delay unit inputs the filtered voltage to the overcurrent detection self-locking unit. The overcurrent detection self-locking unit forms a self-lock after an overcurrent and controls the main power switch unit to shut down. The overcurrent detection self-locking unit is also connected to a control and reset unit that releases its self-lock.

[0022] The main power switching unit includes a P-MOS transistor Q3 (P-channel MOS transistor) and a gate current-limiting resistor R10. The source of the P-MOS transistor Q3 is connected to the pump power supply node V_PUMP, the drain is connected to the power output port Washer_out, and the gate is connected to the overcurrent detection self-locking unit (the emitter of the second transistor Q1.2) via the gate current-limiting resistor R10. Its on / off state is controlled by the overcurrent detection self-locking unit. The current sampling unit includes a sampling resistor or several sampling resistors connected in parallel (in this embodiment, the current sampling unit includes a first sampling resistor R1 and a second sampling resistor R2 connected in parallel, which are connected in series in the power supply circuit between the power input terminal VBAT and the pump power supply node V_PUMP). One end of the current sampling unit is connected to the power input terminal, and the other end is connected to the pump power supply node, which is used to convert the working current of the main power circuit into a voltage sampling signal with a corresponding amplitude.

[0023] The RC integral delay unit includes an integrating resistor R4 and an integrating capacitor C1. One end of the integrating resistor R4 is connected to the low-voltage side node of the current sampling unit (i.e., the pump power supply node V_PUMP), and the other end is connected to the trigger input terminal of the overcurrent detection self-locking unit and the integrating capacitor C1. The other end of the integrating capacitor C1 is connected to the high-voltage side node of the current sampling unit (i.e., the power input terminal VBAT). The integrating capacitor C1 and the voltage divider resistor R4 together form an RC integral network to delay and filter the sampled voltage signal, suppressing false triggering of protection caused by load start-up spikes and interference pulses.

[0024] The overcurrent detection unit includes a PNP type first transistor Q1.1 and an NPN type second transistor Q1.2; The emitter of the first transistor Q1.1 is connected to the high-voltage side of the output terminal of the RC integration delay unit (which is also the power input terminal VBAT in this embodiment). The base is connected to the collector of the second transistor Q1.2, the low-voltage side of the output terminal of the RC integration delay unit, and the third resistor R3. The other end of the third resistor R3 is connected to the power input terminal VBAT. The collector of the first transistor Q1.1 is connected to the current-limiting resistor R9 and the base of the second transistor Q1.2. The other end of the current-limiting resistor R9 and the emitter of the second transistor Q1.2 are connected to the gate current-limiting resistor R10. The other end of the gate current-limiting resistor R10 is connected to the main power switching unit (the gate of the P-MOS transistor Q3). The driving current is limited by the current-limiting resistor R9 to improve circuit stability. When the sampling current increases, the voltage drop generated by V_PUMP relative to VBAT, after being processed by the RC integral delay unit, causes the base potential of the first transistor Q1.1 to decrease. When the voltage between the emitter and base of the first transistor Q1.1 meets the conduction condition, the first transistor Q1.1 turns on, which in turn drives the second transistor Q1.2 to turn on. After the second transistor Q1.2 turns on, it further pulls down the base potential of the first transistor Q1.1, deepening the conduction of the first transistor Q1.1. The two form a positive feedback and quickly enter the saturation state, thus forming a self-locking protection structure.

[0025] In some embodiments, a clamping Zener diode D1 (directly connected between the emitter of the first transistor Q1.1 and the emitter of the second transistor Q1.2) is connected between the high-voltage side node of the current sampling unit and the gate of the P-MOS transistor Q3 to limit the gate-source voltage of the P-MOS transistor Q3 and prevent the device from being damaged by overvoltage.

[0026] The control and reset unit includes an NPN type third transistor Q2. The collector of the third transistor Q2 is connected to the seventh voltage divider resistor R7. The other end of the seventh voltage divider resistor R7 is connected to the gate of the P-MOS transistor Q3 (directly connected to the emitter of the second transistor Q1.2) and the sixth voltage divider resistor R6. The other end of the sixth voltage divider resistor R6 is connected to the high-voltage side node (also the power input terminal VBAT) of the current sampling unit. The base of the third transistor Q2 is connected to the fifth resistor R5 (current limiting resistor) and the eighth resistor R8 (pull-down resistor). The other end of the fifth resistor R5 is connected to the external WASH_PUMP port (output reset port), and the other end of the eighth resistor R8 and the emitter of the third transistor Q2 are grounded. This makes the fifth resistor R5 and the eighth resistor R8 connected in series and connected to the external WASH_PUMP port, which is used to provide drive current and level control for the third transistor Q2. When a high-level signal is input to the WASH_PUMP port, the third transistor Q2 is turned on, thereby changing the potential distribution of the common node of the sixth voltage divider resistor R6 and the seventh voltage divider resistor R7 through the resistor network. This causes the gate-source voltage of the P-MOS transistor Q3 to change and meet the conduction condition, thereby driving the main power switch Q3 to turn on. The resistor network, together with the third transistor Q2, forms a modulation path for the gate potential of the main power switch Q3, thereby controlling the state of the main power switch. Under normal operating conditions, the third transistor Q2 is either off or on to cooperate with the control of the main power switch unit. When overcurrent protection is triggered and a self-locking state is formed, the overcurrent detection self-locking unit maintains the P-MOS transistor Q3 in the off state. When the external control unit applies a control signal through the WASH_PUMP port to turn on the third transistor Q2, the potential distribution of the relevant nodes of the overcurrent detection self-locking unit is changed through its connection with the sixth voltage divider resistor R6, the seventh voltage divider resistor R7, and the gate drive path of the main power switch Q3, thereby breaking the positive feedback condition inside the self-locking unit and releasing the self-locking state. After the self-locking is released, the gate-source voltage of the P-MOS transistor Q3 returns to the conduction condition, and the circuit re-enters the normal operating state. In some embodiments, the WASH_PUMP port presents different levels under different operating states to realize the multiplexing function of external control and status indication. When the external control unit applies a control signal to the WASH_PUMP port, the bias condition of the self-locking unit can be changed through Q2, thereby realizing the release and reset of the protection state.

[0027] The fault output unit is connected to the drain of P-MOS transistor Q3. The fault output unit specifically includes a ferrite bead F1. One end of the ferrite bead F1 is connected to the power output port, and the other end is connected to the current limiting resistor R11. The other end of the current limiting resistor R11 is connected to the FAULT port (fault output port), the pull-down resistor R12, and the filter capacitor C2. The other ends of the pull-down resistor R12 and the filter capacitor C2 are grounded to GND. This allows the power output port Washer_out to be connected to the FAULT port via the ferrite bead F1 and the current limiting resistor R11, and the FAULT port to be connected to the ground terminal GND via the pull-down resistor R12 and the filter capacitor C2. In some embodiments, a second Zener diode D2 is connected in reverse parallel between the FAULT port and the ground terminal GND to clamp the output level to a safe range that matches the I / O port of the back-end control unit, while also providing electrostatic discharge protection.

[0028] In this embodiment, it is applicable to a 12V vehicle power system (compatible with 8-32V) and drives a DC brushed washing pump with a rated current of 2A and a maximum starting current of 12A. Examples of core component parameters are as follows (other parameter components can also be used): P-MOS transistor Q3: WSF45P06, P-channel MOS transistor, Vds=-60V, Id=-45A, Rds(on)≤9mΩ; The first transistor Q1.1: MMBT3906, a PNP transistor, Vceo=40V, Ic=0.2A; The second transistor Q1.2: MMBT3904, NPN transistor, Vceo=40V, Ic=0.2A; The third transistor Q2: MMBT3904, NPN transistor, Vceo=45V, Ic=0.1A; The first sampling resistor R1 and the second sampling resistor R2 are both 0.2Ω / 3W with an accuracy of ±5%. Their total resistance after being connected in parallel is 0.1Ω. Integrating resistor R4: 4.7kΩ / 0.1W, accuracy ±5%; Integrating capacitor C1: 1μF / 10V, X7R ceramic capacitor; Current-limiting resistor R9: 1kΩ / 0.1W, accuracy ±5%; Eighth resistor R8: 10kΩ / 0.1W, accuracy ±5%; Fifth resistor R5: 1kΩ / 0.1W, accuracy ±5%; Clamping Zener diode D1: 12V / 0.5W Zener diode; Second Zener diode D2: 3.3V / 0.2W Zener diode; Ferrite bead F1: 1kΩ@100MHz ferrite bead; Filter capacitor C2: 100nF / 25V, X7R ceramic capacitor.

[0029] This embodiment also discloses an overcurrent protection method, including, 1. Standby state: The MCU sets the WASH_PUMP pin to high impedance, and the gate of P-MOS transistor Q3 is pulled up to 12V, reliably cutting off; II. Soft start process: The MCU executes multiple short-term power-on-power-off cycles to gradually build up back electromotive force using the mechanical inertia of the motor, thereby gradually reducing the starting current. In this embodiment, the soft-start parameters are set to 10ms upon power-on, 5ms upon power-off, and 5 retries. The principle behind this setting is as follows: 1. RC integration time constant: τ_RC = R4×C1 = 4.7kΩ×1μF = 4.7ms. When the current is the maximum starting current of 12A, the sampling voltage drop is 1.2V. The time for the voltage across the integrating capacitor C1 to rise to 0.7V is: \(t_{trigger} = τ_RC × ln(\frac{1.2V}{1.2V-0.7V}) ≈ 4.1ms\). Therefore, the power-on time must be greater than 4.1ms to allow the motor to obtain sufficient angular momentum, while being less than 10ms to avoid the integrating capacitor C1 being fully charged and triggering the protection. 2. Motor mechanical time constant: The mechanical time constant τ_m of a DC brushed washing pump is usually 10-50ms; 10ms after power-on, the motor speed can reach 30%-40% of the rated speed, and the back electromotive force is established to 3.6V-4.8V. At this time, the starting current is reduced from 12A to: \(I = \frac{12V-4V}{1Ω} = 8A\), which is very close to the hardware protection threshold of 7A. 3. Reset time constant of the self-locking circuit: τ_reset = R4×C1= 4.7ms. Therefore, the power-off time must be greater than 4.7ms to allow C4 to discharge completely and ensure that the protection will not be triggered immediately when the power is restored. At the same time, the power-off time cannot be too long, otherwise the motor speed will drop by more than 30%, the back electromotive force will disappear, and the starting current will rise again. 4. Derivation of maximum number of retry cycles: After each power-on, the back electromotive force increases by about 2V and the starting current decreases by about 2A; after 5 cycles, the back electromotive force is built up to above 10V and the starting current is reduced to below 2A, entering the normal working state.

[0030] Specifically, it includes the following steps: Upon receiving the start command, an inertial start is first performed, including: S1, initial retry count is 0. S2 outputs a 3.3V high level to the WASH_PUMP pin for 10ms. S3, Detect the WASH_PUMP pin level: If the level is still high, it means that the protection has not been triggered, the soft start was successful, and the system has entered normal working state. If the level goes low, it means that the protection has been triggered. Execute S4 to perform the self-locking release operation. S4 outputs a 0V low level to the WASH_PUMP pin for 5ms, releasing the self-lock and allowing the motor to rotate by inertia; The retry count is incremented by 1. If the retry count is less than 5, the process returns to step S2. If 5 retries fail, the system is considered a genuine fault, and the startup is stopped and reported.

[0031] III. Normal operating status: After successful soft start, the MCU continuously outputs a high level of 3.3V, the P-MOS transistor Q3 is saturated and conducting (gate voltage approximately 4.09V, Vgs=-7.91V), and the washing pump operates normally; Under normal operating conditions, after the main power switch unit is turned on, the main power circuit works and supplies power to the washing pump through the pump power supply node. When the rated current is 2A, the sampling voltage drop is 0.2V, and the first transistor Q1.1 remains off. At this time, the WASH_PUMP pin is 3.3V and the FAULT pin is 3.3V.

[0032] IV. Overcurrent protection status: including software overload protection and pure hardware self-locking; A) Software overload protection includes the following: The sampling current of the current sampling unit is I. Based on the rated power of the current sampling unit, the maximum safe continuous current is obtained: The rated power of the sampling resistor is 3W. Considering a 50% power derating, the maximum safe continuous current is: \(I_{safe} = \sqrt{\frac{3W×0.5}{0.1Ω}} ≈ 3.87A ≈ 4A\). The overcurrent self-locking current is obtained from the sampling current I when the overcurrent detection self-locking unit forms self-locking, which is the hardware self-locking protection threshold of 7A; Therefore, the maximum safe continuous current is smaller than the overcurrent self-locking current, and a power blind area of 4A-7A exists. When the maximum safe continuous current < I < overcurrent self-locking current and this condition accumulates for a preset time, the main power switch unit is turned off by the control and reset unit; in this embodiment, the differential voltage across the sampling resistor is collected by the ADC of the MCU, and the real-time current I is calculated. When the current I exceeds 4A and the duration exceeds 100 ms, the software actively turns off the circuit to cover the power blind area; Specifically, when 4A < I < 7A, the sampling voltage drop is 0.4V-0.7V, and hardware self-locking is not triggered. In this embodiment, overcurrent protection is triggered by software, current is calculated through voltage collected by the ADC, and after the accumulated overcurrent time exceeds 100 ms, WASH_PUMP is actively pulled down to 0V to actively turn off the P-MOS tube Q3.

[0033] B) Pure hardware self-locking comprises: when I > overcurrent self-locking current 7A, pure hardware self-locking is triggered, and the power supply is cut off within < 50μs, During operation, the current sampling unit samples the main power loop, and the RC integral delay unit performs delay filtering on the sampled voltage and inputs the filtered voltage to the overcurrent detection self-locking unit, the overcurrent detection self-locking unit forms self-locking after detecting overcurrent and controls the main power switch unit to turn off, until the self-locking of the overcurrent detection self-locking unit is released through the control and reset unit; Specifically, when the sampling current increases (when the current exceeds 7A and the duration exceeds the RC time constant of 4.7 ms, the voltage drop across the sampling resistor exceeds 0.7V), V_PUMP generates a voltage drop relative to VBAT, which after the action of the RC integral delay unit reduces the base potential of the first triode Q1.1. When the voltage between the emitter and the base of the first triode Q1.1 meets the conduction condition, the first triode Q1.1 conducts, which in turn drives the second triode Q1.2 to conduct; after the second triode Q1.2 conducts, it further pulls down the base potential of the first triode Q1.1, deepening the conduction degree of the first triode Q1.1. The two triodes form positive feedback and quickly enter a saturation state, thereby forming a self-locking protection structure.

[0034] V. Self-locking release state: the MCU pulls the WASH_PUMP pin down to 0V and keeps it for 5 ms, so that the third triode Q2 is cut off, and then the second triode Q1.2 and the first triode Q1.1 are cut off, breaking the positive feedback loop and releasing the self-locking. Then the MCU outputs a high level again to start the water pump, for example, re-executes the soft-start process; Specifically, after a high-level signal is input to the WASH_PUMP port, the third transistor Q2 is turned on, thereby changing the potential distribution of the common node of the sixth voltage divider resistor R6 and the seventh voltage divider resistor R7 through the resistor network. This causes the gate-source voltage of the P-MOS transistor Q3 to change and meet the conduction condition, thereby driving the main power switch Q3 to turn on.

[0035] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art can make various modifications or equivalent substitutions to the present invention within the scope of its essence and protection. Such modifications or equivalent substitutions should also be considered to fall within the protection scope of the present invention.

Claims

1. A car wash pump drive circuit, characterized in that: The system includes a main power circuit, which comprises a current sampling unit, a pump power supply node, and a main power switching unit. The current sampling unit is connected to an RC integral delay unit that performs delay filtering on the sampled voltage. The main power switching unit is connected to an overcurrent detection self-locking unit. The RC integral delay unit inputs the filtered voltage into the overcurrent detection self-locking unit. The overcurrent detection self-locking unit locks itself after an overcurrent occurs and controls the main power switch unit to shut down. The overcurrent detection self-locking unit is also connected to the control and reset unit that releases its self-lock.

2. The car wash pump drive circuit according to claim 1, characterized in that: The main power switching unit includes a P-MOS transistor Q3. The source of the P-MOS transistor Q3 is connected to the pump power supply node, the drain is connected to the power output port, and the gate is connected to the overcurrent detection self-locking unit.

3. A car wash pump drive circuit according to claim 1 or 2, characterized in that: The RC integral delay unit includes an integral resistor R4 and an integral capacitor C1. One end of the integral resistor R4 is connected to the low-voltage side node of the current sampling unit, and the other end is connected to the trigger input terminal of the overcurrent detection self-locking unit and the integral capacitor C1, respectively. The other end of the integral capacitor C1 is connected to the high-voltage side node of the current sampling unit.

4. A car wash pump drive circuit according to claim 1 or 2, characterized in that: The overcurrent detection unit includes a PNP type first transistor Q1.1 and an NPN type second transistor Q1.2; The emitter of the first transistor Q1.1 is connected to the high-voltage side of the output terminal of the RC integration delay unit, and its base is connected to the collector of the second transistor Q1.2 and the low-voltage side of the output terminal of the RC integration delay unit, respectively. The collector is connected to the current-limiting resistor R9 and the base of the second transistor Q1.2, respectively. The other end of the current-limiting resistor R9 and the emitter of the second transistor Q1.2 are connected to the main power switching unit.

5. The car wash pump drive circuit according to claim 2, characterized in that: The control and reset unit includes an NPN type third transistor Q2. The collector of the third transistor Q2 is connected to the seventh voltage divider resistor R7. The other end of the seventh voltage divider resistor R7 is connected to the gate of the P-MOS transistor Q3 and the sixth voltage divider resistor R6. The other end of the sixth voltage divider resistor R6 is connected to the high-voltage side node of the current sampling unit. The base of the third transistor Q2 is connected to the fifth resistor R5 and the eighth resistor R8. The other end of the fifth resistor R5 is connected to the external WASH_PUMP port, and the other end of the eighth resistor R8 is grounded to the emitter of the third transistor Q2.

6. The car wash pump drive circuit according to claim 5, characterized in that: Upon receiving the start command, inertial startup is initiated, including: Output a high level to the WASH_PUMP pin; check the level of the WASH_PUMP pin; if it is still high, the protection has not been triggered, the soft start is successful, and it enters the normal working state; If the signal goes low, the protection is triggered, and a low level is output to the WASH_PUMP pin to release the latch and allow the motor to rotate by inertia; then the motor restarts according to the above procedure.

7. The car wash pump drive circuit according to claim 2, characterized in that: It also includes a fault output unit that outputs a fault signal, which is connected to the drain of the P-MOS transistor Q3.

8. The car wash pump drive circuit according to claim 7, characterized in that: The fault output unit comprises a magnetic bead F1, one end of the magnetic bead F1 is connected to a power output port, and the other end is connected to a current-limiting resistor R11, the other end of the current-limiting resistor R11 is respectively connected to a FAULT port, a pull-down resistor R12 and a filter capacitor C2, and the other ends of the pull-down resistor R12 and the filter capacitor C2 are grounded.

9. An overcurrent protection method, based on a car wash pump drive circuit as described in claim 1, characterized in that: comprising, after the main power switch unit is conducted, the main power loop operates, and supplies power to the washing pump through the pump power supply node, during operation, the current sampling unit samples the main power loop, the RC integral delay unit performs delay filtering on the sampled voltage and inputs the filtered sampled voltage to the overcurrent detection self-locking unit, the overcurrent detection self-locking unit forms self-locking after detecting overcurrent and controls the main power switch unit to turn off, until the self-locking of the overcurrent detection self-locking unit is released through the control and reset unit.

10. The overcurrent protection method according to claim 9, characterized in that: the sampling current of the current sampling unit is I, the maximum safe continuous current is obtained according to the rated power of the current sampling unit, and the overcurrent self-locking current is obtained according to the sampling current I when the overcurrent detection self-locking unit forms self-locking, if the maximum safe continuous current is less than the overcurrent self-locking current, after the maximum safe continuous current < I < the overcurrent self-locking current and the current is accumulated for a preset time, the main power switch unit is turned off through the control and reset unit.

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