Emergency driving circuit of electromagnetic valve

Abstract

The application discloses an emergency driving circuit of an electromagnetic valve, which comprises a DC voltage reduction circuit, an energy storage circuit, a voltage stabilization circuit and a voltage regulation circuit. The DC voltage reduction circuit reduces the voltage of an external power supply to the voltage required by the energy storage circuit. The voltage stabilization circuit comprises a voltage stabilization chip and an enabling circuit. The output end of the energy storage circuit is connected with the input pin of the voltage stabilization chip. The input end of the enabling circuit is connected with the DC voltage reduction circuit. The output end of the enabling circuit is connected with the enabling pin of the voltage stabilization chip. When the external power supply is normal, the DC voltage reduction circuit normally outputs voltage. The photo-coupler of the enabling circuit is turned on. The voltage of the enabling pin of the voltage stabilization chip is pulled down. The voltage stabilization chip is in a dormant state. When the external power supply is out of service, the photo-coupler of the enabling circuit is cut off. The voltage level of the enabling pin of the voltage stabilization chip is changed to high. The voltage stabilization chip starts to work and outputs stable voltage. The voltage regulation circuit can change the output voltage of the voltage stabilization circuit. The application improves the reliability and service life of the hydraulic system, and has simple structure and small size.

Description

Technical Field

[0001] This invention relates to the field of industrial control valves, and in particular to an emergency drive circuit for a solenoid valve. Background Technology

[0002] Industrial control valves are mainly used in large industrial enterprises. In industrial automated production, control valves are one of the most important supporting equipment for automated control of the production process, and are widely used in petroleum, chemical, metallurgy, steel, papermaking, air separation and other fields. As the power mechanism of control valves, electro-hydraulic actuators have advantages over traditional pneumatic and electric actuators, such as small size, large thrust, and high intelligence, and also have a fault position function.

[0003] The fault-position function of industrial control valves is achieved by adding an accumulator to the hydraulic system. During normal operation, the control system pumps oil into the accumulator, storing pressure energy. If an external power failure causes the industrial control valve to malfunction, the solenoid valve opens, releasing the pressure energy from the accumulator and pushing the valve to a preset position, thus achieving the fault-position function. The fault-position function requires the solenoid valve to be closed under normal conditions and open in the event of an external power failure. In traditional control valve hydraulic circuits, because the power supply cannot provide the energy required for the solenoid valve to operate, normally open solenoid valves are chosen. In these valves, the electromagnet is energized during normal operation, keeping the valve closed; after a power failure, the electromagnet is de-energized, and the internal spring pushes the valve open. Because these valves require continuous energization during normal operation, they suffer from low power utilization, excessive heat generation, and short valve life, severely impacting the stability and overall lifespan of industrial control valves. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide an emergency drive circuit for a solenoid valve. Using this circuit, a normally closed solenoid valve can be selected. During normal operation, the emergency drive circuit is in sleep mode, the electromagnet is de-energized, and the internal spring of the solenoid valve keeps it closed. When the external power supply fails, the emergency drive circuit starts working, the solenoid valve is energized and opens, releasing the pressure energy in the accumulator and pushing the industrial control valve to a preset position, achieving the fault position function. This invention avoids the overheating and lifespan problems caused by the solenoid valve being constantly energized, saves energy, and extends the overall service life.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] An emergency drive circuit for an electromagnetic valve includes a DC step-down circuit, an energy storage circuit, a voltage regulator circuit, and a voltage adjustment circuit. The DC step-down circuit steps down the external power supply to the voltage required by the energy storage circuit. The energy storage circuit includes a supercapacitor for energy storage. The voltage regulator circuit includes a voltage regulator chip and an enable circuit. The output terminal of the energy storage circuit is connected to the input pin of the voltage regulator chip. The input terminal of the enable circuit is connected to the DC step-down circuit, and the output terminal of the enable circuit is connected to the enable pin of the voltage regulator chip. When the external power supply is normal, the DC step-down circuit outputs a normal voltage, the optocoupler of the enable circuit is turned on, the voltage of the enable pin of the voltage regulator chip is pulled low, and the voltage regulator chip is in a sleep state. When the external power supply fails, the optocoupler of the enable circuit is turned off, the level of the enable pin of the voltage regulator chip goes high, the voltage regulator chip starts working and outputs a stable voltage. The voltage adjustment circuit can change the output voltage of the voltage regulator circuit, outputting a higher voltage at the moment of start-up and then reducing the output voltage.

[0007] The DC buck circuit includes a DC buck control chip, a voltage divider resistor a, an inductor a, and a capacitor. The input pin of the DC buck control chip is connected to an external power supply, and the output pin of the DC buck control chip is connected to one end of the inductor a. The voltage divider resistor a includes R1 and R2. The feedback pin of the DC buck control chip is connected to one end of R1 and R2 respectively. The other end of R1 is connected to the output terminal V2 of the DC buck circuit, and the other end of R2 is connected to the negative terminal of the capacitor. The positive terminal of the capacitor and the other end of the inductor a are both connected to the output terminal V2 of the DC buck circuit.

[0008] The DC step-down circuit includes diode a, the anode of diode a is connected to the cathode of capacitor, and the cathode of diode a is connected to the output pin of DC step-down control chip.

[0009] The energy storage circuit includes a capacitor equalization chip and a bleed resistor. The supercapacitor and the equalization chip are connected in parallel. The VDD pin of the equalization chip is connected to the positive terminal of the supercapacitor, the SEL pin of the equalization chip is connected to the negative terminal of the supercapacitor, and the bleed resistor is connected to the bleed port of the equalization chip.

[0010] The energy storage circuit includes a diode b. The positive terminal of the diode b is connected to the output terminal V2 of the DC step-down circuit through a resistor R, and the negative terminal of the diode b is connected to the VDD pin of the voltage equalization chip.

[0011] The output of the enable circuit is connected to the input pin of the voltage regulator chip via a 10k resistor.

[0012] The enabling circuit includes an inductor b and a diode c. The two ends of the inductor b are connected to the input pin and the SW pin of the voltage regulator chip, respectively. The positive terminal of the diode c is connected to the SW pin of the voltage regulator chip, and the negative terminal of the diode c is the output terminal.

[0013] The voltage regulation circuit includes a voltage divider circuit, a transistor, and a voltage comparator. The output terminal V2 of the DC step-down circuit is grounded through R6 and R7 connected in series. A filter capacitor a is connected in parallel with R7. One end of R6 and R7 is connected to the non-inverting input terminal of the voltage comparator. The inverting input terminal of the voltage comparator is connected to a 2.5V voltage. The output terminal of the voltage comparator is connected to the voltage divider circuit through a transistor. The voltage divider circuit includes R3, R4, and R5 connected in series. The two ends of R3 are connected to the emitter and collector of the transistor, respectively. One end of R4 and R5 is connected to the FB pin of the voltage regulator chip.

[0014] When the voltage across the filter capacitor a is higher than 2.5V, the voltage comparator outputs a high level, the transistor is cut off, and the voltage divider circuit uses R3, R4, and R5 to divide the voltage. The output voltage of the voltage regulator circuit is... When the voltage across filter capacitor a drops below 2.5V, the voltage comparator outputs a low level, the transistor conducts, R3 is bypassed, and the output voltage of the voltage regulator circuit becomes...

[0015] The output terminal of the voltage regulator circuit is grounded through filter circuit b.

[0016] The beneficial effects of this invention are:

[0017] After the emergency drive circuit starts working, the output voltage across the supercapacitor continuously decreases as it discharges. The voltage is then stabilized by a voltage regulator circuit to the level required by the solenoid valve, ensuring its normal operation. The voltage regulation circuit dynamically adjusts the voltage output to the solenoid valve, maximizing the operating time of the emergency drive circuit and meeting the needs of hydraulic system fault handling.

[0018] The system uses an energy storage circuit to store energy during normal operation and discharges to drive the solenoid valve during emergency operation. The emergency drive circuit of the solenoid valve can provide power output to the electromagnet for a period of time in the event of external power failure, ensuring that the hydraulic system can complete the fault handling function. This avoids the solenoid valve being in a energized state for a long time, solving the problems of low power efficiency, severe heat generation and short life of solenoid valve caused by long-term energization of the solenoid valve. It greatly improves the reliability and service life of the hydraulic system, and has a simple structure and small size. Attached Figure Description

[0019] Figure 1 This is a system schematic diagram of the present invention;

[0020] Figure 2 This is a schematic diagram of the DC step-down circuit of the present invention;

[0021] Figure 3 This is a schematic diagram of the energy storage circuit of the present invention;

[0022] Figure 4This is a schematic diagram of the voltage regulator circuit of the present invention;

[0023] Figure 5 This is a schematic diagram of the voltage regulation circuit of the present invention.

[0024] In the diagram: 1. DC step-down circuit; 2. Energy storage circuit; 3. Voltage regulator circuit; 4. Voltage regulation circuit; 5. DC step-down control chip; 6. Voltage divider resistor a; 7. Inductor a; 8. Capacitor; 9. Supercapacitor; 10. Capacitor voltage equalization chip; 11. Diode b; 12. Voltage regulator chip; 13. Enable circuit; 14. Inductor b; 15. Diode c; 16. Voltage divider circuit; 17. Transistor; 18. Voltage comparator; 19. Filter capacitor a; 20. Filter circuit b; 21. Diode a; 22. Leakage resistor. Detailed Implementation

[0025] The present invention will be further described below with reference to the accompanying drawings and specific embodiments:

[0026] like Figures 1-5 As shown, an emergency drive circuit for a solenoid valve includes a DC step-down circuit 1, an energy storage circuit 2, a voltage regulator circuit 3, and a voltage adjustment circuit 4. The DC step-down circuit 1 steps down the external power supply to the voltage required by the energy storage circuit 2.

[0027] Reference Figure 1 , Figure 2 The DC step-down circuit 1 includes a DC step-down control chip 5, a voltage divider resistor a6, an inductor a7, a capacitor 8, and a diode a21. The output voltage V2 of the DC step-down circuit 1 is determined by the ratio of R1 and R2, calculated using the following formula: In this embodiment, R1 is selected as 3.9kΩ, R2 as 1kΩ, and the output voltage is 6.0V.

[0028] The input pin of DC buck control chip 5 is connected to an external power supply. The output pin of DC buck control chip 5 is connected to one end of inductor a7. The voltage divider resistor a6 includes R1 and R2. The feedback pin of DC buck control chip 5 is connected to one end of R1 and R2 respectively. The other end of R1 is connected to the output terminal V2 of DC buck circuit 1. The other end of R2 is connected to the negative terminal of capacitor 8. The positive terminal of capacitor 8 and the other end of inductor a7 are both connected to the output terminal V2 of DC buck circuit 1.

[0029] The positive terminal of diode a21 is connected to the negative terminal of capacitor 8, and the negative terminal of diode a21 is connected to the output pin of DC step-down control chip 5.

[0030] The working principle of DC step-down circuit 1 is as follows: The output pin of control chip 5 outputs a high voltage, inductor a7 and capacitor 8 begin storing energy, and the output voltage V2 gradually increases. This output voltage V2 is then divided by resistors R1 and R2 in voltage divider resistor a6 and input to the feedback pin of control chip 5, where it is compared with a 1.23V voltage internally. As the output voltage V2 gradually increases, if the voltage after voltage division by resistor 6 is higher than 1.23V, the output pin of control chip 5 stops outputting, and inductor a7 and capacitor 8 begin releasing the stored energy, causing the output voltage V2 to gradually decrease. Diode a21 acts as a freewheeling diode for inductor a7; when inductor a7 is discharging, diode a21 provides a current path for the discharge of inductor a7. As the output voltage V2 gradually decreases, if the voltage after voltage division by resistor 6 is lower than 1.23V, the output pin of control chip 5 outputs a high voltage. This cycle repeats until the desired output voltage is obtained at the output terminal.

[0031] Reference Figure 1 , Figure 3 The energy storage circuit 2 includes a supercapacitor 9 for energy storage, a capacitor voltage equalization chip 10, a bleeder resistor 22, and a diode b11. The supercapacitor 9 has a large capacity but a low voltage; therefore, capacitors can be connected in series to increase the energy storage voltage and in parallel to increase the energy storage capacity. The capacitor energy storage calculation method is as follows: In this example, two sets of supercapacitors are connected in series to increase the output voltage to 6V, and two sets are connected in parallel to increase the energy storage capacity. In this embodiment, 30F / 3V capacitors are combined in series and parallel to obtain a capacity of 15F / 6V.

[0032] The supercapacitor 9 and the voltage equalization chip 10 are connected in parallel. The voltage equalization chip 10 distributes the voltage V2 output by the DC step-down circuit 1 to each capacitor, so that the voltage on each capacitor is equal, reducing the voltage difference between multiple capacitors, thereby reducing the leakage current and loss of the capacitors, and ensuring the reliability and stability of the energy storage circuit 2.

[0033] The VDD pin of the voltage equalization chip 10 is connected to the positive terminal of the supercapacitor 9, and the supercapacitor 9 provides power to the voltage equalization chip 10; the SEL pin of the voltage equalization chip 10 is connected to the negative terminal of the supercapacitor 9, and the SEL pin is the voltage selection pin of the voltage equalization chip 10. The BW6103 uses 2.95V as the voltage equalization voltage and is compatible with the supercapacitor 9 with a voltage of 3V.

[0034] The bleed resistor 22 is connected to the bleed port of the voltage equalization chip 10. When the voltage at the VDD pin of the voltage equalization chip 10 exceeds 2.95V, some energy is released through the bleed resistor 22 to maintain the voltage at the set 2.95V.

[0035] The anode of diode b11 is connected to the output terminal V2 of DC step-down circuit 1 via resistor R, and the cathode of diode b11 is connected to the VDD pin of voltage equalization chip 10. Diode b11 is connected in series at the input terminal of energy storage circuit 2. The unidirectional conduction characteristic of the diode prevents current backflow. When the external power supply fails, the output voltage of DC step-down circuit 1 is lower than the voltage of energy storage circuit 2. Diode b11 is used to prevent current from flowing back from energy storage circuit 2 to DC step-down circuit 1.

[0036] Supercapacitor 9 stores energy through a current-limiting resistor R. During the charging process, the voltage across the capacitor is... In the formula, R is the current-limiting resistor and C is the capacitance. From this, the charging time required for energy storage circuit 2 can be calculated as follows: When t = 5RC, that is, when the charging time reaches 5 times the time constant, U c =0.99V2, U C This refers to the voltage after all capacitors are connected in series and parallel, which can be considered as the basic completion of the charging process.

[0037] Reference Figure 1 , Figure 4 The voltage regulator circuit 3 includes a voltage regulator chip 12, an enable circuit 13, an inductor b14, and a diode c15. The output terminal of the energy storage circuit 2 is connected to the input pin (VIN pin) of the voltage regulator chip 12. The input terminal of the enable circuit 13 is connected to the DC step-down circuit 1 through a 1k current-limiting resistor. The output terminal of the enable circuit 13 is connected to the enable pin of the voltage regulator chip 12. The output terminal of the enable circuit 13 is connected to the input pin of the voltage regulator chip 12 through a 10k resistor.

[0038] The two ends of inductor B14 are connected to the input pin and SW pin of voltage regulator chip 12, respectively. The positive terminal of diode C15 is connected to the SW pin of voltage regulator chip 12, and the negative terminal of diode C15 is the output terminal.

[0039] Its working principle is as follows: When the external power supply is normal, the DC step-down circuit 1 outputs a normal voltage, the optocoupler of the enable circuit 13 is turned on, the voltage of the enable pin of the voltage regulator chip 12 is pulled low, and the voltage regulator chip 12 is in a sleep state; when the external power supply fails, the optocoupler of the enable circuit 13 is turned off, the level of the enable pin of the voltage regulator chip 12 becomes high, the voltage regulator chip 12 starts to work, and outputs a stable voltage to provide power to the solenoid valve. The output voltage of the voltage regulator chip 12 is determined by the voltage of the FB pin and can be selected according to the power supply requirements of the solenoid valve. During the operation of the emergency drive circuit, as the supercapacitor 9 continues to discharge, the output voltage of the energy storage circuit 2 will continuously decrease. The voltage regulator chip 12 is used to regulate the voltage, providing a stable power supply to the solenoid valve. The voltage regulator chip 12 uses the SW pin to control the high-speed switching of the inductor b14, utilizing the principle that the inductor generates high voltage at the moment of current cut-off to regulate the output voltage of the circuit. As the output voltage of energy storage circuit 2 decreases, the output voltage of voltage regulator circuit 3 will be higher than that of energy storage circuit 2. Therefore, diode C15 is used to prevent the output of voltage regulator circuit from flowing back to energy storage circuit 2.

[0040] Reference Figure 1 , Figure 5 The voltage regulation circuit 4 can change the output voltage of the voltage regulator circuit 3. According to the characteristics of the solenoid valve, a higher opening voltage is required when the solenoid valve opens, and a lower holding voltage is required after opening. Therefore, the voltage regulator circuit outputs a higher voltage at the moment of starting operation, and then reduces the output voltage. The energy storage circuit 2 stores limited energy, and a lower operating voltage can maintain the output time for a longer period of time.

[0041] The voltage regulation circuit 4 includes a voltage divider circuit 16, a transistor 17, a voltage comparator 18, and a filter capacitor a19. The output terminal V2 of the DC step-down circuit 1... Figure 1 The V2 at the output of DC step-down circuit 1 and the V2 at the voltage regulation circuit 4 are the same voltage and are directly connected (the connection line is not shown in the figure). They are grounded through R6 and R7 connected in series. R7 is connected in parallel with filter capacitor a19. The end of R6 and R7 connected to the non-inverting input (+) of voltage comparator 18, that is, the positive terminal of filter capacitor a19 is connected to the non-inverting input of voltage comparator 18. The inverting input (-) of voltage comparator 18 is connected to 2.5V. The output of voltage comparator 18 is connected to voltage divider circuit 16 through a 10k current-limiting resistor and transistor 17. Voltage divider circuit 16 includes R3, R4 and R5 connected in series. The two ends of R3 are connected to the emitter and collector of transistor 17, respectively. The end of R4 and R5 connected to the FB pin of voltage regulator chip 12.

[0042] The working principle of voltage regulation circuit 4 is as follows: When the external power supply is normal, DC step-down circuit 1 outputs a normal voltage, which affects the filter capacitor a19 (i.e., Figure 5C1) is charged. The voltage across filter capacitor a19 is compared with 2.5V by voltage comparator 18. When the voltage across filter capacitor a19 is higher than 2.5V, voltage comparator 18 outputs a high level, transistor 17 is cut off, and voltage divider circuit 16 uses R3, R4, and R5 to divide the voltage. The output voltage of voltage regulator circuit 3 is... Vo, or Vout in the diagram, represents the closed-loop circuit located at the FB pin of voltage regulator chip 12 and Vo. The FB pin provides feedback, and Vo is the output. The output voltage Vo is adjusted through feedback. When the external power supply fails, filter capacitor a19 discharges through resistor R7. As the discharge time progresses, the voltage across filter capacitor a19 drops below 2.5V. At this point, voltage comparator 18 outputs a low level, transistor 17 conducts, R3 is bypassed, and the output voltage of voltage regulator circuit 3 becomes... The voltage regulator circuit 3 reduces the output voltage, thereby extending the working time of the emergency drive circuit.

[0043] In voltage regulation circuit 4, the output voltage switching time can be adjusted via resistor R7. R6 and R7 form a voltage divider circuit, and the voltage is divided to obtain... This serves as the charging voltage for capacitor C1. Capacitor C1 and resistor R7 form a discharge circuit. When the external power supply fails, capacitor C1 begins to discharge through R7, and the voltage across C1 starts to decrease. The larger the resistance of R7, the slower the discharge rate, and the slower the voltage across C1 decreases. When the voltage across C1 drops to 2.5V, voltage comparator 18 outputs a low voltage, transistor 17 conducts, and resistor R3 is bypassed, completing the voltage regulation process. The voltage across capacitor C1 during discharge is... When U c1 Voltage regulation is completed when the voltage equals 2.5V. The voltage regulation time can be calculated as follows:

[0044] The output voltage of voltage regulator circuit 3 can be determined by R3, R4, and R5, and the calculation formula is as follows: In this example, R3 is selected as 8.2kΩ, R4 as 47kΩ, and R5 as 1kΩ. When the emergency drive circuit starts working, the voltage regulator circuit 3 outputs a voltage of 12.4V. After the set delay time, the output voltage is reduced to 10.6V, which satisfies the requirements of the solenoid valve, reduces the power consumption of the solenoid valve, and achieves a longer duration.

[0045] The output terminal of the voltage regulator circuit 3 is grounded through the filter circuit b20.

[0046] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An emergency drive circuit for a solenoid valve, characterized in that: The system includes a DC step-down circuit (1), an energy storage circuit (2), a voltage regulator circuit (3), and a voltage adjustment circuit (4). The DC step-down circuit (1) steps down the external power supply to the voltage required by the energy storage circuit (2). The energy storage circuit (2) includes a supercapacitor (9) for energy storage. The voltage regulator circuit (3) includes a voltage regulator chip (12) and an enable circuit (13). The output of the energy storage circuit (2) is connected to the input pin of the voltage regulator chip (12). The input of the enable circuit (13) is connected to the DC step-down circuit (1), and the output of the enable circuit (13) is connected to the voltage regulator chip (12). 2) When the external power supply is normal, the DC step-down circuit (1) outputs a normal voltage, the optocoupler of the enable circuit (13) is turned on, the voltage of the enable pin of the voltage regulator chip (12) is pulled low, and the voltage regulator chip (12) is in a sleep state. When the external power supply fails, the optocoupler of the enable circuit (13) is turned off, the level of the enable pin of the voltage regulator chip (12) becomes high, the voltage regulator chip (12) starts to work and outputs a stable voltage. The voltage regulation circuit (4) can change the output voltage of the voltage regulator circuit (3), outputting a higher voltage at the moment of starting to work, and then reducing the output voltage.

2. The electromagnetic valve emergency drive circuit as described in claim 1, characterized in that: The DC step-down circuit (1) includes a DC step-down control chip (5), a voltage divider resistor a (6), an inductor a (7), and a capacitor (8). The input pin of the DC step-down control chip (5) is connected to an external power supply, and the output pin of the DC step-down control chip (5) is connected to one end of the inductor a (7). The voltage divider resistor a (6) includes R1 and R2. The feedback pin of the DC step-down control chip (5) is connected to one end of R1 and R2 respectively. The other end of R1 is connected to the output terminal V2 of the DC step-down circuit (1). The other end of R2 is connected to the negative terminal of the capacitor (8). The positive terminal of the capacitor (8) and the other end of the inductor a (7) are both connected to the output terminal V2 of the DC step-down circuit (1).

3. The electromagnetic valve emergency drive circuit as described in claim 2, characterized in that: The DC step-down circuit (1) includes a diode a (21), the positive terminal of which is connected to the negative terminal of the capacitor (8), and the negative terminal of which is connected to the output pin of the DC step-down control chip (5).

4. The electromagnetic valve emergency drive circuit as described in claim 1, characterized in that: The energy storage circuit (2) includes a capacitor equalization chip (10) and a bleeder resistor (22). The supercapacitor (9) and the equalization chip (10) are connected in parallel. The VDD pin of the equalization chip (10) is connected to the positive terminal of the supercapacitor (9), and the SEL pin of the equalization chip (10) is connected to the negative terminal of the supercapacitor (9). The bleeder resistor (22) is connected to the bleeder port of the equalization chip (10).

5. The electromagnetic valve emergency drive circuit as described in claim 4, characterized in that: The energy storage circuit (2) includes a diode b (11). The positive terminal of the diode b (11) is connected to the output terminal V2 of the DC step-down circuit (1) through a resistor R, and the negative terminal of the diode b (11) is connected to the VDD pin of the voltage equalization chip (10).

6. The electromagnetic valve emergency drive circuit as described in claim 1, characterized in that: The output of the enabling circuit (13) is connected to the input pin of the voltage regulator chip (12) through a 10k resistor.

7. The electromagnetic valve emergency drive circuit as described in claim 6, characterized in that: The enabling circuit (13) includes an inductor b (14) and a diode c (15). The two ends of the inductor b (14) are connected to the input pin and the SW pin of the voltage regulator chip (12) respectively. The positive terminal of the diode c (15) is connected to the SW pin of the voltage regulator chip (12), and the negative terminal of the diode c (15) is the output terminal.

8. The electromagnetic valve emergency drive circuit as described in claim 1, characterized in that: The voltage regulation circuit (4) includes a voltage divider circuit (16), a transistor (17), and a voltage comparator (18). The output terminal V2 of the DC step-down circuit (1) is grounded through R6 and R7 connected in series. R7 is connected in parallel with a filter capacitor a (19). One end of R6 and R7 is connected to the non-inverting input terminal of the voltage comparator (18). The inverting input terminal of the voltage comparator (18) is connected to a 2.5V voltage. The output terminal of the voltage comparator (18) is connected to the voltage divider circuit (16) through the transistor (17). The voltage divider circuit (16) includes R3, R4, and R5 connected in series. The two ends of R3 are connected to the emitter and collector of the transistor (17) respectively. One end of R4 and R5 is connected to the FB pin of the voltage regulator chip (12).

9. The electromagnetic valve emergency drive circuit as described in claim 8, characterized in that: When the voltage across the filter capacitor a (19) is higher than 2.5V, the voltage comparator (18) outputs a high level, and the transistor (17) is cut off. At this time, the voltage divider circuit (16) is divided by R3, R4, and R5, and the output voltage of the voltage regulator circuit (3) is... When the voltage across the filter capacitor a(19) drops below 2.5V, the voltage comparator (18) outputs a low level, the transistor (17) turns on, R3 is bypassed, and the output voltage of the voltage regulator circuit (3) becomes 10. The emergency drive circuit for a solenoid valve as described in claim 1, characterized in that: The output terminal of the voltage regulator circuit (3) is grounded through the filter circuit b (20).

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