Electromagnetic valve low-side driving diagnosis protection circuit

Abstract

The invention relates to an electromagnetic valve low-side driving diagnosis protection circuit which comprises a feedback acquisition circuit and an output driving protection circuit, the input end of the feedback acquisition circuit, the input end of the output driving protection circuit and one end of a load are all connected with a control output port of an electromagnetic valve, and the other end of the load is connected with a VBAT. The output end of the feedback acquisition circuit is connected to a sampling port of the processor, the output driving protection circuit comprises an AND gate and an MOS (Metal Oxide Semiconductor) tube, two input ends of the AND gate are respectively connected with a start protection port and a PWM (Pulse Width Modulation) signal output port of the processor, the output end of the AND gate is connected with a grid electrode of the MOS tube, a source electrode of the MOS tube is connected with a control output port of the electromagnetic valve, and a drain electrode of the MOS tube is grounded. According to the invention, the driving capability is amplified through the logic gate, and according to the collected voltage, when the load has a short-circuit VBAT fault, the voltage for starting the protection port can be lowered, so that the MOS tube is closed, and the circuit is prevented from being burnt by overlarge current.

Description

Technical Field

[0001] The present invention relates to the technical field of solenoid valve control, and particularly to a low-side drive diagnostic protection circuit for a solenoid valve. Background Art

[0002] In the existing low-side drive circuit for solenoid valves, it is generally an integrated chip solution, namely an intelligent low-side drive chip, and the automotive-grade solutions are basically monopolized by foreign large manufacturers' brands, such as INFINEON, ST, ON, etc. The costs of these chips are high and the current-carrying capacity is weak, and the general load capacity is below 5A. At the same time, limited by the chip packaging process, the surge resistance of the drive output port is weak, and additional surge protection devices, such as TVS and ESD devices, are required to assist in meeting the on-site electrical environment requirements, which have certain requirements for the application scenario and are relatively limited in application. And once the selection is completed and the design is finalized, since it is a chip solution, there is generally no PIN TO PIN replacement solution, and the compatibility is not strong. It is very difficult to upgrade and replace without changing the PCB, and the compatibility and adaptability are not as high as those of the discrete device solution. At the same time, the existing low-side drive circuit for solenoid valves does not have a corresponding protection circuit, and when a fault such as a short circuit occurs in the load, the circuit is easily burned out. Summary of the Invention

[0003] The present invention provides a low-side drive diagnostic protection circuit for a solenoid valve to solve the technical problems such as the circuit being easily burned out when a fault such as a short circuit occurs in the load as mentioned in the background art.

[0004] The technical solution of the present invention is as follows: A low-side drive diagnostic protection circuit for a solenoid valve includes a feedback acquisition circuit and an output drive protection circuit. The input end of the feedback acquisition circuit, the input end of the output drive protection circuit, and one end of the load are all connected to the control output port of the solenoid valve. The other end of the load is connected to the power supply VBAT. The output end of the feedback acquisition circuit is connected to the sampling port of the processor. The feedback acquisition circuit is used to collect the voltage of the control output port of the solenoid valve. The output drive protection circuit includes an AND gate U1 and a MOS transistor Q1. The two input ends of the AND gate U1 are respectively connected to the enable protection port and the PWM signal output port of the processor. The output end of the AND gate U1 is connected to the gate of the MOS transistor Q1. The source of the MOS transistor Q1 is connected to the control output port of the solenoid valve, and the drain of the MOS transistor Q1 is grounded.

[0005] Further, the feedback acquisition circuit includes: a first resistor R1, a first capacitor C1, a second resistor R2, a third resistor R3, a fourth resistor R4, a first diode D1, and a first voltage regulator Z1. One end of the first resistor R1 is connected to the sampling port of the processor, and the other end of the first resistor R1 is connected to one end of the first capacitor C1, one end of the second resistor R2, one end of the third resistor R3, the negative electrode of the first voltage regulator Z1, and one end of the fourth resistor R4. The other end of the first capacitor C1, the other end of the second resistor R2, and the positive electrode of the first voltage regulator Z1 are all grounded. The other end of the third resistor R3 is connected to the negative electrode of the first diode D1, the positive electrode of the first diode D1 is connected to the working voltage VCC, and the other end of the fourth resistor R4 is connected to the control output port of the solenoid valve.

[0006] Further, one end of the load is connected to the positive electrode of the second diode D2, and the other end of the load is connected to the negative electrode of the second diode D2.

[0007] Further, the first diode D1 and the second diode D2 are Schottky diodes.

[0008] Further, the processor uses an MCU.

[0009] Further, the MOS transistor Q1 is an NMOS transistor.

[0010] Advantages of the present invention: The present invention amplifies the driving ability through a logic gate, and according to the voltage collected by the feedback acquisition circuit, when a short circuit to VBAT occurs in the load, the voltage of the enabled protection port Protection Enable can be pulled down, thereby turning off the MOS transistor to prevent the circuit from being burned by excessive current.

[0011] The present invention connects the second diode D2 in parallel at both ends of the load. The second diode D2 provides a path for the load current to flow, playing a freewheeling role and suppressing the surge voltage at the output port.

[0012] The present invention adopts a discrete solution. For different application scenarios, devices with different voltages are selected, which well meet the voltage and current requirements of different solenoid valves. Without changing the PCB, the customer's needs can be met. At the same time, since the discrete solution uses materials with large mass production and wide application in the market, the overall cost has obvious advantages compared with the integrated chip solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a circuit diagram of a solenoid valve low-side drive diagnostic protection circuit of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0014] To enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. The described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0015] In the technical solution of the present invention, Figure 1 is a schematic structural diagram provided according to the specific structure of a solenoid valve low-side drive diagnostic protection circuit of the present invention. As Figure 1 shown, the present invention includes: a feedback acquisition circuit and an output drive protection circuit. The input end of the feedback acquisition circuit, the input end of the output drive protection circuit, and one end of the load are all connected to the control output port of the solenoid valve. The other end of the load is connected to the power supply VBAT. The output end of the feedback acquisition circuit is connected to the sampling port of the processor. The feedback acquisition circuit is used to collect the voltage of the control output port of the solenoid valve; The output drive protection circuit includes: an AND gate U1 and a MOS transistor Q1. The two input ends of the AND gate U1 are respectively connected to the enable protection port and the PWM signal output port of the processor. The output end of the AND gate U1 is connected to the gate of the MOS transistor Q1. The source of the MOS transistor Q1 is connected to the control output port of the solenoid valve. The drain of the MOS transistor Q1 is grounded.

[0016] In an embodiment of the present invention, the feedback acquisition circuit includes: a first resistor R1, a first capacitor C1, a second resistor R2, a third resistor R3, a fourth resistor R4, a first diode D1, and a first voltage regulator Z1. One end of the first resistor R1 is connected to the sampling port of the processor. The other end of the first resistor R1 is connected to one end of the first capacitor C1, one end of the second resistor R2, one end of the third resistor R3, the negative electrode of the first voltage regulator Z1, and one end of the fourth resistor R4. The other end of the first capacitor C1, the other end of the second resistor R2, and the positive electrode of the first voltage regulator Z1 are all grounded. The other end of the third resistor R3 is connected to the negative electrode of the first diode D1. The positive electrode of the first diode D1 is connected to the operating voltage VCC. The other end of the fourth resistor R4 is connected to the control output port of the solenoid valve.

[0017] In an embodiment of the present invention, one end of the load is connected to the positive electrode of a second diode D2, and the other end of the load is connected to the negative electrode of the second diode D2.

[0018] In an embodiment of the present invention, the first voltage regulator diode Z1 has a typical regulated voltage value of 5.1V with an accuracy of ±2%. The MOS transistor Q1 is an NMOS. The first diode D1 and the second diode D2 are Schottky diodes. The VCC is a 5V power supply with an accuracy of ±2%. The processor uses an MCU.

[0019] The technical working principle of the present invention is as follows: It should be noted that in the figure, the Protection Enable pin is the protection enable port, the MCU PWM_OUT pin is the PWM signal output port, and the MCU_ADC_INPUT pin is the sampling port of the processor. Vout is the voltage of the control output port of the solenoid valve. 1. When the solenoid valve load is normally connected, the Protection Enable pin outputs a high level at this time, and the Vgs voltage of the MOS transistor Q1 follows the output of the MCU PWM_OUT.

[0020] When the MCU PWM_OUT pin outputs "ON": The input voltage of the MCU_ADC_INPUT pin: Vadc≈(Vcc - Vd) / (1 + R3(R2 + R4) / (R2*R4)), where Vd is the forward voltage drop of D1.

[0021] When the MCU PWM_OUT pin outputs "OFF": The input voltage of the MCU_ADC_INPUT pin: Vadc is close to Vz1. (VBAT > VCC) 2. When the load is open-circuited during the operation of the solenoid valve, the Protection Enable pin outputs a high level at this time, and the Vgs voltage of the MOSFET follows the output of the MCU PWM_OUT.

[0022] When the MCU PWM_OUT pin outputs "ON": The input voltage of the MCU_ADC_INPUT pin: Vadc≈(Vcc - Vd) / (1 + R3(R2 + R4) / (R2*R4)), where Vd is the forward voltage drop of D1.

[0023] When the MCU PWM_OUT pin outputs "OFF": The input voltage of the MCU_ADC_INPUT pin: Vadc≈R2*(Vcc - Vd) / (R3 + R2) 3. When the load is short-circuited to VBAT during the operation of the solenoid valve, the Protection Enable pin outputs a high level at this time, and the Vgs voltage of the MOSFET follows the output of the MCU PWM_OUT.

[0024] When the output of the MCU PWM_OUT pin is "ON": Input voltage of the MCU_ADC_INPUT pin: Vadc ≈ 0V When the output of the MCU PWM_OUT pin is "OFF": Input voltage of the MCU_ADC_INPUT pin: Vadc is close to Vz1. (VBAT > VCC) 4. When the load is shorted to ground during the operation of the solenoid valve, the Protection Enable pin outputs a high level at this time, and the Vgs voltage of the MOSFET follows the output of the MCU PWM_OUT.

[0025] When the output of the MCU PWM_OUT pin is "ON": Input voltage of the MCU_ADC_INPUT pin: Vadc ≈ (Vcc - Vd) / (1 + R3(R2 + R4) / (R2*R4)), where Vd is the voltage drop across D1.

[0026] When the output of the MCU PWM_OUT pin is "OFF": Input voltage of the MCU_ADC_INPUT pin: Vadc ≈ (Vcc - Vd) / (1 + R3(R2 + R4) / (R2*R4)), where Vd is the voltage drop across D1.

[0027] Through the above analysis, when the output of the MCU PWM_OUT pin is "ON", if a load short - to - VBAT fault occurs, Vadc ≈ 0V (the normal voltage is not equal to 0). At this time, the MCU reports an error and pulls down through Protection Enable to turn off the MOSFET.

[0028] If the output of the MCU PWM_OUT pin is "OFF", when an open - circuit or short - to - ground fault mode occurs, the Vadc voltage is not equal to the normal operating voltage and the deviation is large. At this time, an open - circuit or short - to - ground fault is reported, and the MCU reports an error for warning.

[0029] The output of the MCU PWM_OUT is amplified in driving ability through a logic gate, and according to the voltage collected by the feedback acquisition circuit, when a load short - to - VBAT fault occurs, the voltage of Protection Enable can be pulled down, thereby turning off the MOS tube to prevent the circuit from being burned by excessive current.

[0030] When the output of the MCU PWM_OUT pin changes from the "ON" state to the "OFF" state, since the solenoid valve current cannot change suddenly, the diode D2 provides a path for the load current to flow, acting as a freewheeling diode and suppressing the surge voltage at the output port.

[0031] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the examples, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A solenoid valve low-side drive diagnostic protection circuit, characterized in that: include: A feedback collection circuit and an output drive protection circuit, wherein the input end of the feedback collection circuit, the input end of the output drive protection circuit and one end of the load are all connected to the control output port of the solenoid valve, the other end of the load is connected to the power supply VBAT, the output end of the feedback collection circuit is connected to the sampling port of the processor, and the feedback collection circuit is used to collect the voltage of the control output port of the solenoid valve; The output drive protection circuit includes: an AND gate U1 and a MOS tube Q1, wherein the two input ends of the AND gate U1 are respectively connected to the protection enabling port and the PWM signal output port of the processor, the output end of the AND gate U1 is connected to the gate of the MOS tube Q1, the source of the MOS tube Q1 is connected to the control output port of the solenoid valve, and the drain of the MOS tube Q1 is grounded.

2. The electromagnetic valve low-side drive diagnostic protection circuit according to claim 1, characterized in that: The feedback acquisition circuit includes: a first resistor R1, a first capacitor C1, a second resistor R2, a third resistor R3, a fourth resistor R4, a first diode D1 and a first voltage regulator Z1, one end of the first resistor R1 is connected to the sampling port of the processor, the other end of the first resistor R1 is connected to one end of the first capacitor C1, one end of the second resistor R2, one end of the third resistor R3, the negative electrode of the first voltage regulator Z1, and one end of the fourth resistor R4, the other end of the first capacitor C1, the other end of the second resistor R2, and the positive electrode of the first voltage regulator Z1 are all grounded, the other end of the third resistor R3 is connected to the negative electrode of the first diode D1, the positive electrode of the first diode D1 is connected to the working voltage VCC, and the other end of the fourth resistor R4 is connected to the control output port of the solenoid valve.

3. The electromagnetic valve low-side drive diagnostic protection circuit according to claim 1, characterized in that: One end of the load is connected to the anode of the second diode D2 , and the other end of the load is connected to the cathode of the second diode D2 .

4. The electromagnetic valve low-side drive diagnostic protection circuit according to claim 3, characterized in that: The first diode D1 and the second diode D2 are Schottky diodes.

5. The electromagnetic valve low-side drive diagnostic protection circuit according to claim 1, characterized in that: The processor is MCU.

6. The electromagnetic valve low-side drive diagnosis protection circuit according to claim 1, characterized in that: The MOS tube Q1 is an NMOS tube.

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