Wide voltage input pulse width modulation electromagnetic lock driving circuit method

Abstract

The invention relates to a wide-voltage-input pulse width modulation electromagnetic lock driving circuit method. The wide-voltage-input pulse width modulation electromagnetic lock driving circuit is characterized by comprising a voltage conversion circuit (1), an MOSFET driving circuit (2), a voltage sampling circuit (3), a current sampling circuit (4), a sampling holding circuit (5) and an alarm circuit (6). The CPU collects the value of the input voltage VIN through the voltage sampling circuit (3), a PWM signal with the duty ratio being Duty1 is output within 0-t1, at the moment, the input voltage is V1, the voltage difference between the two ends of the electromagnetic lock coil is V1, and it is ensured that the electromagnetic lock is lifted; a PWM signal with the duty ratio being Duty2 is output within t1-t2, at the moment, the input voltage is V1, the voltage difference between the two ends of the electromagnetic lock coil is V2, and the lock lifting state of the electromagnetic lock is maintained; the electromagnetic lock has the advantages of being high in applicability, low in calorific value and adjustable in power, can adapt to wide voltage input, can reduce energy consumption of the electromagnetic lock, reduces the calorific value of the coil, prolongs the service life, and meanwhile achieves fault early warning of the electromagnetic lock.

Description

Technical Field

[0001] The present invention relates to the technical field of electromagnetic locks, and in particular to a pulse width modulation electromagnetic lock driving circuit method with wide voltage input. Background Art

[0002] Electromagnetic locks are widely used in platform doors. Electromagnetic locks use the electromagnetic principle, which uses electromagnetic coils to generate electromagnetic force, causing the armature or iron core to move, driving the lock hook to move synchronously, locking or opening the sliding door in the platform door, and realizing the synchronous opening and closing of the subway train doors and sliding doors; at the same time, it prevents the sliding door from opening unexpectedly, ensuring the personal safety of platform passengers.

[0003] When the electromagnetic lock is powered on and starts working, the air gap is at the maximum distance, so a larger voltage is required to ensure the normal operation of the lock hook. When the lock hook is in the holding stage after the action is completed, the air gap is at the minimum distance at this time, so only a smaller voltage is required to maintain the state of the lock hook being lifted. Based on the above characteristics, in the actual application of platform door electromagnetic locks, some electromagnetic locks adopt a dual power supply mode, that is, a higher voltage is first applied to lift the electromagnetic lock, and after the action is completed and in the holding stage, a lower voltage is used to maintain the lifting state. In the process of switching the power supply voltage from a higher voltage to a lower voltage, a large reverse electromotive force will be generated at both ends of the electromagnetic lock coil, affecting the reliability of the electromagnetic lock; at the same time, when the power supply voltage is high, the power of the electromagnetic lock coil is very large, the heat is serious, and it is also easy to cause failures, reducing the service life of the electromagnetic lock.

[0004] The platform doors used on different lines have different power supply modes, and the electromagnetic locks between the lines cannot be interchanged. Summary of the invention

[0005] The purpose of the present invention is to provide an electromagnetic lock driving circuit based on pulse width modulation which has strong applicability, low heat generation, adjustable power, can adapt to wide voltage input, can reduce the energy consumption of the electromagnetic lock, reduce the heat generation of the coil, extend the service life, and at the same time realizes early warning of electromagnetic lock faults.

[0006] To achieve the above-mentioned purpose, the technical solution adopted by the present invention is to relate to a pulse width modulation electromagnetic lock driving circuit method with wide voltage input, which is characterized by: comprising a voltage conversion circuit, a MOS driving circuit, a voltage sampling circuit, a current sampling circuit, a sampling and holding circuit, an alarm circuit, and a burning circuit; The voltage conversion circuit includes an input voltage VIN, capacitors C1~C9, resistors R1~R4, an inductor L1 and a power chip U1. The input voltage VIN is used to provide direct current to the electromagnetic lock coil; capacitors C4~C7 are connected to the input voltage VIN for filtering; capacitors C1~C3, resistors R1~R4 and the inductor are connected to the power chip U1 to generate a direct current voltage D5V; capacitors C8 and C9 are connected to the direct current voltage D5V for filtering; the voltage conversion circuit generates a 5V output voltage which is respectively provided to the MOS drive circuit, the voltage sampling circuit, the current sampling circuit, the sample and hold circuit, the alarm circuit and the burning circuit.

[0007] The CPU in the MOSFET driving circuit is used to generate PWM pulses, and the duty cycle is determined according to the parameters of the electromagnetic lock coil and the input voltage VIN. The MOSFET driving circuit includes CPU U2, capacitor C10, resistors R5~R7, PNP transistor Q1, MOSFETQ2, and Schottky diode D1. Capacitor C10 is connected to the DC voltage D5V; the base of the PNP transistor Q1 is electrically connected to the resistor R6, the emitter is connected to the DC voltage D5V, and the collector is connected to the resistor R7; the source of MOSFET Q2 is grounded, the gate is connected to R7 and grounded through the resistor R5, and the drain is connected to the OUT2 end of the electromagnetic lock coil; the positive pole of the Schottky diode D1 is connected to the OUT2 end of the electromagnetic lock coil, and the negative pole is connected to the OUT1 end of the electromagnetic lock coil.

[0008] The voltage sampling circuit includes resistors R8~R10 and capacitors C13~C14, one end of resistor R8 is connected to the OUT1 end of the electromagnetic lock coil, and the other end is connected to resistor R9; the other end of resistor R9 is connected to resistor R10; the other end of resistor R10 is grounded; one end of capacitors C13 and C14 is connected to the OUT1 end of the electromagnetic lock coil, and the other end is grounded.

[0009] The current sampling circuit includes a Schottky diode D4, a capacitor C12, and a current detection chip U3. The positive electrode of the Schottky diode D4 is connected to the input voltage VIN, and the negative electrode is connected to the input of the current detection chip U3; the capacitor C12 is connected to the DC voltage D5V.

[0010] The sampling and holding circuit includes resistors R11~R14, capacitors C15~C18, Schottky diodes D2~D3, and an operational amplifier U4. One end of the resistor R13 is connected to the voltage sampling circuit, and the other end is connected to Pin5 of the operational amplifier U4; one end of the capacitor C17 is connected to Pin5 of the operational amplifier U4, and the other end is grounded; one end of the resistor R12 is connected to the current sampling circuit, and the other end is connected to Pin3 of the operational amplifier U4; one end of the capacitor C18 is connected to Pin3 of the operational amplifier U4, and the other end is grounded; one end of the resistor R11 is connected to Pin5 and Pin6 of the operational amplifier U4, and the other end is connected to the ADC_VOLTAGE pin of the CPU U2; one end of the resistor R14 is connected to Pin1 and Pin2 of the operational amplifier U4, and the other end is connected to the ADC_CURRENT pin of the CPU U2; one end of the capacitor C11 is connected to the ADC_CURRENT pin of the CPU U2, and the other end is grounded; one end of the capacitor C16 is connected to the CPU The cathode of Schottky diode D2 is connected to the DC voltage D5V, and the anode is connected to the ADC_CURRENT pin of CPU U2; the cathode of Schottky diode D3 is connected to the DC voltage D5V, and the anode is connected to the ADC_VOLTAGE pin of CPU U2.

[0011] The alarm circuit comprises a resistor R15 and LED1. One end of the resistor R15 is connected to the LED pin of the CPU U2, and the other end is connected to the cathode of LED1. The anode of LED1 is connected to the DC voltage D5V.

[0012] The burning circuit comprises a needle holder CNT1, Pin1 of the needle holder CNT1 is connected to TXD of CPU U2, Pin2 is connected to RXD of CPUU2, Pin3 is connected to DC voltage D5V, and Pin4 is connected to GND.

[0013] The working principle of the circuit is: when the input terminal VIN of the electromagnetic lock is V1, a DC 5V voltage is obtained through the power chip U2 to power the CPU; the CPU collects the value of the input voltage VIN through the voltage sampling circuit, and outputs a PWM signal with a duty cycle of Duty1 within 0~t1. At this time, the input voltage is V1, and the voltage difference across the electromagnetic lock coil is △V1, ensuring that the electromagnetic lock is lifted; a PWM signal with a duty cycle of Duty2 is output within t1~t2. At this time, the input voltage is V1, and the voltage difference across the electromagnetic lock coil is △V2, maintaining the electromagnetic lock in the lifted state; at t3, the input terminal VIN of the electromagnetic lock becomes V2, and the CPU outputs a PWM signal with a duty cycle of Duty3, so that the voltage difference across the electromagnetic lock coil remains △V2, maintaining the electromagnetic lock in the lifted state. By adjusting the duty cycle of the CPU output PWM pulse, the voltage difference at both ends of the electromagnetic lock coil can be changed, which reduces the power in the holding stage while ensuring the electromagnetic lock is lifted, realizing the power adjustable function and reducing the heat generated by the coil. The CPU compares the current sampling value with the set domain value. When a fault is detected, the alarm circuit works and the LED lights up.

[0014] The present invention has the following characteristics and advantages due to the adoption of the above technical methods: 1. Strong applicability The present invention is applicable to wide voltage input and can maintain the stability of the electromagnetic lock coil voltage when the input voltage fluctuates; 2. Low heat generation and long service life The present invention effectively reduces the heat generated by the electromagnetic lock coil, reduces the power in the holding stage, and prolongs the service life of the electromagnetic lock; 3. Adjustable power Using PWM technology, the voltage difference across the electromagnetic lock coil can be changed by adjusting the duty cycle of the CPU output pulse, thereby adjusting the power according to the parameters of the electromagnetic lock coil and the input voltage; 4. Realize early warning of electromagnetic lock failure By sampling the electromagnetic lock current and comparing it with the set domain value, early warning of common door lock faults can be achieved, including the door lock not falling into place, not fully attracted, and stuck. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is the circuit principle diagram of the present invention; Figure 2 It is the voltage difference waveform across the electromagnetic lock coil when the input voltage VIN changes.

[0016] In the figure, 1. voltage conversion circuit; 2. MOS driving circuit; 3. voltage sampling circuit; 4. current sampling circuit; 5. sample and hold circuit; 6. alarm circuit; 7. burning circuit. DETAILED DESCRIPTION

[0017] In order to further explain the technical means and effects adopted by the invention to achieve the predetermined purpose, the specific implementation methods, structural features and effects of the invention are described in detail below in conjunction with the accompanying drawings and embodiments.

[0018] like Figure 1 As shown, the present invention relates to a pulse width modulation electromagnetic lock driving circuit method with wide voltage input, which is characterized by comprising a voltage conversion circuit (1), a MOSFET driving circuit (2), a voltage sampling circuit (3), a current sampling circuit (4), a sampling and holding circuit (5), an alarm circuit (6), and an alarm circuit (7). The voltage conversion circuit (1) comprises an input voltage VIN, capacitors C1-C9, resistors R1-R4, an inductor L1, and a power chip U1. The input voltage VIN is used to provide direct current to the electromagnetic lock wire; capacitors C4-C7 are connected to the input voltage VIN for filtering; capacitors C1-C3, resistors R1-R4, and inductors are connected to the power chip U1 for generating a direct current voltage D5V, which provides a 5V voltage for the MOSFET driving circuit (2), the voltage sampling circuit (3), the current sampling circuit (4), the sampling and holding circuit (5), and the alarm circuit (6); capacitors C8 and C9 are connected to the direct current voltage D5V for filtering.

[0019] The CPU in the MOSFET driving circuit (2) is used to generate PWM pulses, and the duty cycle is determined according to the parameters of the electromagnetic lock coil and the input voltage VIN. The MOSFET driving circuit 2 includes a CPU U2, a capacitor C10, resistors R5-R7, a PNP transistor Q1, a MOSFET Q2, and a Schottky diode D1; the capacitor C10 is connected to the DC voltage D5V; the base of the PNP transistor Q1 is electrically connected to the resistor R6, the emitter is connected to the DC voltage D5V, and the collector is connected to the resistor R7; the source of the MOSFET Q2 is grounded, the gate is connected to R7 and grounded through the resistor R5, and the drain is connected to the OUT2 end of the electromagnetic lock coil; the positive electrode of the Schottky diode D1 is connected to the OUT2 end of the electromagnetic lock coil, and the negative electrode is connected to the OUT1 end of the electromagnetic lock coil.

[0020] The voltage sampling circuit (3) comprises resistors R8-R10 and capacitors C13-C14, wherein one end of the resistor R8 is connected to the OUT1 end of the electromagnetic lock coil, and the other end is connected to the resistor R9; the other end of the resistor R9 is connected to the resistor R10; the other end of the resistor R10 is grounded; the capacitors C13 and C14 are connected in parallel, and one end is connected to the OUT1 end of the electromagnetic lock coil, and the other end is grounded; the electrical connection point between the resistors R9 and R10 is electrically connected to the fifth pin of the input end of the sampling and holding circuit (5) through the resistor R13, so that the sampling voltage is transmitted to the sampling and holding circuit (5).

[0021] The current sampling circuit (4) comprises a Schottky diode D4, a capacitor C12, and a current detection chip U3; the positive electrode of the Schottky diode D4 is connected to the input voltage VIN, and the negative electrode is connected to the input of the current detection chip U3; the DC voltage D5V is electrically connected to the power supply end of the current detection chip U3, and the positive power supply end of the current detection chip U3 and the DC voltage D5V are electrically connected to the negative end of the current detection chip U3 and connected to the capacitor C12; the first and second pins of the current sampling end of the current detection chip U3 are electrically connected in parallel to the negative electrode of the Schottky diode D4, and the third and fourth pins are electrically connected in parallel to the load circuit of the MOSFET drive circuit (2), so as to obtain the load current of the MOSFET drive circuit (2).

[0022] The sampling and holding circuit (5) comprises resistors R11-R14, capacitors C15-C18, Schottky diodes D2-D3, and an operational amplifier U4, wherein one end of the resistor R13 is connected to the voltage sampling circuit (3), and the other end is connected to Pin5 of the operational amplifier U4 of the sampling and holding circuit (5); one end of the capacitor C17 is connected to Pin5 of the operational amplifier U4, and the other end is grounded; one end of the resistor R12 is connected to the current sampling circuit 4, and the other end is connected to Pin3 of the operational amplifier U4; one end of the capacitor C18 is connected to Pin3 of the operational amplifier U4, and the other end is grounded; one end of the resistor R11 is connected to Pin5 and Pin6 of the operational amplifier U4, and the other end is connected to the ADC_VOLTAGE pin of the CPU U2; one end of the resistor R14 is connected to Pin1 and Pin2 of the operational amplifier U4, and the other end is connected to the ADC_CURRENT pin of the CPU U2; one end of the capacitor C11 is connected to the CPU The cathode of Schottky diode D2 is connected to the DC voltage D5V, and the anode is connected to the ADC_CURRENT pin of CPU U2; the cathode of Schottky diode D3 is connected to the DC voltage D5V, and the anode is connected to the ADC_VOLTAGE pin of CPU U2.

[0023] The alarm circuit (6) comprises a resistor R15 and an LED1. One end of the resistor R15 is connected to the LED pin of the CPU U2, and the other end is connected to the cathode of the LED1. The anode of the LED1 is connected to the DC voltage D5V.

[0024] The burning circuit (7) comprises a needle holder CNT1, Pin 1 of the needle holder CNT1 is connected to TXD of CPU U2, Pin 2 is connected to RXD of CPU U2, Pin 3 is connected to DC voltage D5V, and Pin 4 is connected to GND.

[0025] like Figure 1, Figure 2 As shown, the voltage conversion circuit (1) obtains a DC 5V voltage through the power chip U2 to power the CPU; the CPU collects the value of the input voltage VIN through the voltage sampling circuit (3), and outputs a PWM signal with a duty cycle of Duty1 within 0~t1. At this time, the input voltage is V1, and the voltage difference across the electromagnetic lock coil is △V1, ensuring that the electromagnetic lock is lifted; the CPU outputs a PWM signal with a duty cycle of Duty2 within t1~t2. At this time, the input voltage is V1, and the voltage difference across the electromagnetic lock coil is △V2, maintaining the electromagnetic lock in the lifted state; at time t3, the input terminal VIN of the electromagnetic lock changes to V2, and the CPU outputs a PWM signal with a duty cycle of Duty3, so that the voltage difference across the electromagnetic lock coil remains △V2, maintaining the electromagnetic lock in the lifted state. By adjusting the duty cycle of the PWM pulse output by the CPU, the voltage difference at both ends of the electromagnetic lock coil can be changed, thereby reducing the power in the holding stage while ensuring that the electromagnetic lock is lifted, realizing the power adjustable function and reducing the heat generated by the coil. The CPU compares the sampled value of the current sampling circuit (4) with the set domain value. When a fault is detected, the alarm circuit (6) works and the LED lights up.

[0026] The present invention uses pulse width modulation (PWM) technology to drive the electromagnetic lock via a MOSFET drive circuit (2). When the electromagnetic lock is in the lock lifting stage, the CPU controls the duty cycle of the output pulse to provide a higher voltage to the coil, so that the lock lifting action is completed; when the electromagnetic lock pin is lifted, the voltage difference at both ends of the electromagnetic lock coil is reduced by changing the duty cycle of the CPU output pulse, thereby effectively reducing the heat generated by the coil while maintaining the lifted state, thereby extending the life of the electromagnetic lock. At the same time, the CPU can adjust the duty cycle of the output pulse in real time according to the input voltage, so as to achieve the stability of the electromagnetic lock coil voltage under the condition of a wide input voltage.

[0027] The above contents are further detailed descriptions of the present invention in combination with specific preferred implementation modes, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions.

[0028] For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A pulse width modulation electromagnetic lock driving circuit method with wide voltage input, characterized in that: The invention comprises a voltage conversion circuit (1), a MOSFET driving circuit (2), a voltage sampling circuit (3), a current sampling circuit (4), a sampling and holding circuit (5), and an alarm circuit (6); the CPU collects the value of the input voltage VIN through the voltage sampling circuit (3), and outputs a PWM signal with a duty cycle of Duty1 within 0~t1, at which time the input voltage is V1, and the voltage difference across the electromagnetic lock coil is △V1, thereby ensuring that the electromagnetic lock is lifted; and outputs a PWM signal with a duty cycle of Duty2 within t1~t2, at which time the input voltage is V1, and the voltage difference across the electromagnetic lock coil is △V2, thereby maintaining the electromagnetic lock in a lifted state; At time t3, the input terminal VIN of the electromagnetic lock changes to V2. At this time, the CPU outputs a PWM signal with a duty cycle of Duty3, so that the voltage difference between the two ends of the electromagnetic lock coil remains △V2, maintaining the electromagnetic lock in the unlocking state. The CPU compares the sampling value of the current sampling circuit (4) with the set domain value. When a fault is detected, the alarm circuit (6) works and the LED lights up.

2. The method for driving a pulse width modulation electromagnetic lock circuit with a wide voltage input according to claim 1 is characterized in that: The voltage conversion circuit (1) comprises an input voltage VIN, capacitors C1-C9, resistors R1-R4, an inductor L1 and a power chip U1; The input voltage VIN is used to provide direct current to the electromagnetic lock coil; capacitors C4~C7 are connected to the input voltage VIN for filtering; capacitors C1~C3 resistors R1~R4 and inductors are connected to the power chip U1 to generate a direct current voltage D5V; the direct current 5V voltage is used to power the MOSFET drive circuit (2), the voltage sampling circuit (3), the current sampling circuit (4), the sample and hold circuit (5), and the alarm circuit (6); capacitors C8 and C9 are connected to the direct current voltage D5V for filtering.

3. The method for driving a pulse width modulation electromagnetic lock circuit with a wide voltage input according to claim 1 is characterized in that: The CPU in the MOSFET driving circuit (2) is used to generate PWM pulses, and the duty cycle is determined according to the parameters of the electromagnetic lock coil and the input voltage VIN; the MOSFET driving circuit includes a CPU U2, a capacitor C10, resistors R5-R7, a PNP transistor Q1, a MOSFETQ2, and a Schottky diode D1, wherein the capacitor C10 is connected to the DC voltage D5V; the base of the PNP transistor Q1 is electrically connected to the resistor R6, the emitter is connected to the DC voltage D5V, and the collector is connected to the resistor R7; the source of the MOSFET Q2 is grounded, the gate is connected to R7 and grounded through the resistor R5, and the drain is connected to the OUT2 end of the electromagnetic lock coil; the positive electrode of the Schottky diode D1 is connected to the OUT2 end of the electromagnetic lock coil, and the negative electrode is connected to the OUT1 end of the electromagnetic lock coil.

4. The method for driving a pulse width modulation electromagnetic lock circuit with a wide voltage input according to claim 1, characterized in that: The voltage sampling circuit (3) comprises resistors R8-R10 and capacitors C13-C14, wherein one end of the resistor R8 is connected to the OUT1 end of the electromagnetic lock coil, and the other end is connected to the resistor R9; the other end of the resistor R9 is connected to the resistor R10; the other end of the resistor R10 is grounded; the capacitors C13 and C14 are connected in parallel, and one end is connected to the OUT1 end of the electromagnetic lock coil, and the other end is grounded; the electrical connection point between the resistors R9 and R10 is electrically connected to the fifth pin of the input end of the sampling and holding circuit (5) through the resistor R13, so that the sampling voltage is transmitted to the sampling and holding circuit (5).

5. The method for driving a pulse width modulation electromagnetic lock circuit with a wide voltage input according to claim 1 is characterized in that: The current sampling circuit (4) comprises a Schottky diode D4, a capacitor C12, and a current detection chip U3; the positive electrode of the Schottky diode D4 is connected to the input voltage VIN, and the negative electrode is connected to the input of the current detection chip U3; the DC voltage D5V is electrically connected to the power supply end of the current detection chip U3, and the positive power supply end of the current detection chip U3 and the DC voltage D5V are electrically connected to the negative end of the current detection chip U3 and connected to the capacitor C12; the first and second pins of the current sampling end of the current detection chip U3 are electrically connected in parallel to the negative electrode of the Schottky diode D4, and the third and fourth pins are electrically connected in parallel to the load circuit of the MOSFET drive circuit (2), so as to obtain the load current of the MOSFET drive circuit (2).

6. The method for driving a pulse width modulation electromagnetic lock circuit with a wide voltage input according to claim 1, characterized in that: The sampling and holding circuit (5) comprises resistors R11-R14, capacitors C15-C18, Schottky diodes D2-D3, and an operational amplifier U4; one end of the resistor R13 is connected to the voltage sampling circuit (3), and the other end is connected to Pin5 of the operational amplifier U4; one end of the capacitor C17 is connected to Pin5 of the operational amplifier U4, and the other end is grounded; one end of the resistor R12 is connected to the current sampling circuit, and the other end is connected to Pin3 of the operational amplifier U4; one end of the capacitor C18 is connected to Pin3 of the operational amplifier U4, and the other end is grounded; one end of the resistor R11 is connected to Pin5 and Pin6 of the operational amplifier U4, and the other end is connected to the ADC_VOLTAGE pin of the CPU U2; one end of the resistor R14 is connected to Pin1 and Pin2 of the operational amplifier U4, and the other end is connected to the ADC_CURRENT pin of the CPU U2; one end of the capacitor C11 is connected to the ADC_CURRENT pin of the CPU U2, and the other end is grounded; one end of the capacitor C16 is connected to the CPU The cathode of Schottky diode D2 is connected to the DC voltage D5V, and the anode is connected to the ADC_CURRENT pin of CPU U2; the cathode of Schottky diode D3 is connected to the DC voltage D5V, and the anode is connected to the ADC_VOLTAGE pin of CPU U2.

7. The method for driving a pulse width modulation electromagnetic lock circuit with a wide voltage input according to claim 1, characterized in that: The alarm circuit (6) comprises a resistor R15 and an LED1. One end of the resistor R15 is connected to the LED pin of the CPU U2, and the other end is connected to the cathode of the LED1. The anode of the LED1 is connected to the DC voltage D5V.

8. The method for driving a pulse width modulation electromagnetic lock circuit with a wide voltage input according to claim 1, characterized in that: When the MOSFET driving circuit (2) drives the electromagnetic lock, when the electromagnetic lock is in the lock lifting stage, the CPU controls the duty cycle of the output pulse to provide a higher voltage to the coil, so that it completes the lock lifting action; when the electromagnetic lock pin is lifted, the voltage difference at both ends of the electromagnetic lock coil is reduced by changing the duty cycle of the CPU output pulse, thereby effectively reducing the heat generated by the coil while maintaining the lifted state, thereby extending the life of the electromagnetic lock; at the same time, the CPU can adjust the duty cycle of the output pulse in real time according to the input voltage, so as to achieve the stability of the electromagnetic lock coil voltage under a wide input voltage condition.

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