A drive circuit for reducing overshoot voltage during relay opening and closing.

Abstract

This invention relates to the field of electronic circuit technology, and provides a drive circuit for reducing overshoot voltage during relay opening and closing, including an H-bridge drive circuit module and a control module. The H-bridge consists of four MOSFETs. The drains of the first and third MOSFETs are connected to the positive terminal of the power supply, and the sources of the second and fourth MOSFETs are grounded. The source of the first MOSFET and the drain of the second MOSFET are connected to the first coil terminal of the relay, and the source of the third MOSFET and the drain of the fourth MOSFET are connected to the second coil terminal of the relay. The control module inputs control signals to the gates of each MOSFET to achieve four operating modes: hold, forward pull-in, reverse pull-in, and freewheeling discharge. This invention can improve the operational stability and service life of the relay, and reduce circuit power consumption and electromagnetic interference.

Description

Technical Field

[0001] This invention relates to the field of electronic circuit technology, and more specifically, to a drive circuit for reducing overshoot voltage during relay opening and closing. Background Technology

[0002] Relays, as commonly used electrical control components, are widely used in power systems, industrial automation, and communication equipment. During relay operation, the opening and closing of circuits generates significant overshoot voltages, which can damage not only the relay contacts but also interfere with and harm other components in the circuit. Traditional relay drive circuits typically employ simple switching control methods, making it difficult to effectively suppress overshoot voltage generation. While some improvements mitigate this problem by adding buffer circuits or optimizing drive timing, these methods often increase circuit complexity and cost, with limited effectiveness.

[0003] In the process of implementing the embodiments of the present invention, the inventors have discovered that the prior art has at least the following problems or defects: traditional drive circuits are difficult to balance overshoot voltage suppression and circuit efficiency, and the control method is singular, which cannot adapt to the needs of different working conditions, resulting in poor relay operation stability, shortened lifespan, and increased electromagnetic interference and energy consumption. Summary of the Invention

[0004] This invention provides a drive circuit for reducing overshoot voltage during relay opening and closing, comprising:

[0005] The H-bridge driver circuit module consists of a first MOSFET, a second MOSFET, a third MOSFET, and a fourth MOSFET. The drains of the first and third MOSFETs are connected to the positive power supply VCC, and the sources of the second and fourth MOSFETs are connected to the power supply ground GND. The sources of the first and second MOSFETs are connected to the first coil terminal OUT1 of the relay, and the sources of the third and fourth MOSFETs are connected to the second coil terminal OUT2 of the relay.

[0006] The control module is used to input a first control signal to the gate of the first MOSFET, a second control signal to the gate of the second MOSFET, a third control signal to the gate of the third MOSFET, and a fourth control signal to the gate of the fourth MOSFET.

[0007] The drive circuit has four operating modes, including holding mode, forward pull-in mode, reverse pull-in mode, and freewheeling discharge mode; among which,

[0008] When the drive circuit is in hold mode, IN1 and IN2 are both low level, and OUT1 and OUT2 are both high impedance state;

[0009] When the drive circuit is in the forward pull-in mode, IN1 is high level, IN2 is low level, OUT1 outputs high level, and OUT2 outputs low level;

[0010] When the drive circuit is in reverse pull-in mode, IN1 is low level, IN2 is high level, OUT1 outputs low level, and OUT2 outputs high level.

[0011] When the driving circuit is in freewheeling mode, IN1 and IN2 are both high level, and OUT1 and OUT2 both output low level.

[0012] Furthermore, the control module is configured as follows:

[0013] When the relay switches from forward pull-in mode or reverse pull-in mode to holding mode, a PWM wave with a gradually decreasing duty cycle is input to IN1 and IN2, so that the current flowing through the relay coil gradually decreases from 1A to 0A over 20ms to 50ms.

[0014] Furthermore, the duty cycle of the PWM wave is gradually reduced to achieve a gradual decrease in current.

[0015] Furthermore, in the freewheeling discharge mode, the conduction state of the second MOSFET and the fourth MOSFET forms a freewheeling circuit through the second MOSFET and the fourth MOSFET, completely discharging the reverse electromotive force in the coil.

[0016] Furthermore, the drive circuit is connected to the A-channel output terminal of the AC / DC power supply, where the A-channel is a DC output terminal with feedback and the B-channel is the system power supply terminal; the A-channel output voltage is 12V and the B-channel output voltage is 12V.

[0017] Furthermore, the control module reduces the current to keep the load change rate of channel A less than 50mA / ms, ensuring that the output voltage of channel A remains stable within the range of 12V±0.5V.

[0018] Furthermore, in the H-bridge drive circuit module, the first and third MOS transistors are P-channel MOS transistors, and the second and fourth MOS transistors are N-channel MOS transistors.

[0019] Furthermore, the timing logic of the control module is as follows:

[0020] The pull-in mode lasts 100ms, followed by a slow current descent of 50ms, and finally a follow-up discharge of 50ms.

[0021] After the continuous discharge mode ends, switch to hold mode.

[0022] Furthermore, the drive circuit omits the RC snubber circuit and TVS protection device at both ends of the relay coil.

[0023] Furthermore, the drive circuit controls the load easing and freewheeling discharge of channel A to stabilize the voltage of channel B within the range of 5V±1V, thus avoiding triggering the system power-down protection.

[0024] The embodiments of the present invention have at least the following beneficial effects: The present invention can suppress overshoot voltage during the relay opening and closing process by optimizing the control strategy of the H-bridge drive circuit, thereby improving the operating stability and service life of the relay. By designing four operating modes—holding, forward activation, reverse activation, and freewheeling discharge—it can flexibly adapt to the needs of different operating conditions, ensuring that the relay can operate smoothly under different operating states and reducing interference to other components in the circuit.

[0025] Furthermore, this invention can reduce circuit power consumption and electromagnetic interference, thereby improving the overall system reliability. By precisely controlling the turn-on and turn-off timing of the MOSFET, unnecessary energy loss can be avoided, while reducing electromagnetic radiation interference to surrounding equipment, making it suitable for applications with high requirements for circuit performance and stability. Attached Figure Description

[0026] The above and other objects, features, and advantages of exemplary embodiments of the present invention will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings. Several embodiments of the invention are illustrated in the drawings by way of example and not limitation, wherein:

[0027] Figure 1 This is a schematic diagram of the drive circuit for reducing overshoot voltage during relay opening and closing, provided in an embodiment of the present invention. Detailed Implementation

[0028] The principles and spirit of the invention will now be described with reference to several exemplary embodiments. It should be understood that these embodiments are provided merely to enable those skilled in the art to better understand and implement the invention, and are not intended to limit the scope of the invention in any way. Rather, these embodiments are provided to make the invention more thorough and complete, and to fully convey the scope of the invention to those skilled in the art.

[0029] Those skilled in the art will recognize that embodiments of the present invention can be implemented as a system, apparatus, device, method, or computer program product. Therefore, the present invention can be specifically implemented in the following forms: entirely hardware, entirely software (including firmware, resident software, microcode, etc.), or a combination of hardware and software.

[0030] It should be noted that the number of any elements in the accompanying drawings is for illustrative purposes only and not as a limitation, and any naming is for distinction only and has no limiting meaning.

[0031] The following is for reference. Figure 1 , Figure 1 This is a schematic diagram of a drive circuit for reducing overshoot voltage during relay opening and closing, provided in an embodiment of the present invention. Figure 1 As shown, a drive circuit for reducing overshoot voltage during relay opening and closing includes:

[0032] The H-bridge driver circuit module consists of a first MOSFET, a second MOSFET, a third MOSFET, and a fourth MOSFET. The drains of the first and third MOSFETs are connected to the positive power supply VCC, and the sources of the second and fourth MOSFETs are connected to the power supply ground GND. The sources of the first and second MOSFETs are connected to the first coil terminal OUT1 of the relay, and the sources of the third and fourth MOSFETs are connected to the second coil terminal OUT2 of the relay.

[0033] The control module is used to input a first control signal to the gate of the first MOSFET, a second control signal to the gate of the second MOSFET, a third control signal to the gate of the third MOSFET, and a fourth control signal to the gate of the fourth MOSFET.

[0034] The drive circuit has four operating modes, including holding mode, forward pull-in mode, reverse pull-in mode, and freewheeling discharge mode; among which,

[0035] When the drive circuit is in hold mode, IN1 and IN2 are both low level, and OUT1 and OUT2 are both high impedance state;

[0036] When the drive circuit is in the forward pull-in mode, IN1 is high level, IN2 is low level, OUT1 outputs high level, and OUT2 outputs low level;

[0037] When the drive circuit is in reverse pull-in mode, IN1 is low level, IN2 is high level, OUT1 outputs low level, and OUT2 outputs high level.

[0038] When the driving circuit is in freewheeling mode, IN1 and IN2 are both high level, and OUT1 and OUT2 both output low level.

[0039] It should be noted that the H-bridge driver circuit module is a common circuit structure that controls the direction and magnitude of the current in the relay coil through the switching combination of four MOSFETs. MOSFETs are field-effect transistors, offering advantages such as fast switching speed and low on-resistance. The positive power supply terminal VCC provides the operating voltage for the driver circuit, while the power ground GND serves as the circuit's reference ground. The first two terminals, OUT1 and OUT2, of the relay coil are connected, and the relay's activation and deactivation are controlled by adjusting the voltage levels at these terminals. The control module is the core of the entire driver circuit. It sends corresponding control signals to the gates of the four MOSFETs according to different operating modes, thereby controlling the MOSFETs' on / off states. The four operating modes correspond to different relay states: the holding mode is when the relay is neither activated nor deactivated; the forward activation mode and reverse activation mode represent the relay's forward and reverse activation states, respectively; and the freewheeling mode is used to release the induced current in the relay coil.

[0040] Specifically, the selection of MOSFETs needs to be determined based on the actual drive current and voltage requirements. For example, in this circuit, the relay requires a drive current of 12V 1A, therefore the MOSFET's withstand voltage should be greater than 12V, and its conduction current should be greater than 1A. The control signal is a digital signal and can be generated by a microcontroller or other logic circuits. In hold mode, all MOSFETs are in the off state, OUT1 and OUT2 are in a high-impedance state, and no current flows through the relay coil. In forward pull-in mode, the first and fourth MOSFETs are turned on, and current flows from VCC to the relay coil and then to GND, causing the relay to pull in the forward direction. In reverse pull-in mode, the second and third MOSFETs are turned on, and the current direction is opposite to that in the forward pull-in mode, causing the relay to pull in the reverse direction. In freewheeling discharge mode, the body diodes of the second and fourth MOSFETs are turned on, forming a freewheeling circuit to release the induced current in the relay coil and prevent the reverse electromotive force from damaging the circuit.

[0041] Preferably, to improve the reliability and stability of the circuit, a protection circuit, such as a Zener diode, can be added between the gate and source of the MOSFET to prevent damage to the MOSFET due to excessive gate voltage. Simultaneously, to reduce the freewheeling discharge time, the conduction time of the MOSFET can be appropriately increased, allowing the induced current to be released more quickly. Furthermore, fault detection and protection functions can be added to the control module; when an abnormal situation is detected, the drive circuit can be shut down promptly to protect the relay and related circuit components.

[0042] In some embodiments, the control module is configured to:

[0043] When the relay switches from forward pull-in mode or reverse pull-in mode to holding mode, a PWM wave with a gradually decreasing duty cycle is input to IN1 and IN2, so that the current flowing through the relay coil gradually decreases from 1A to 0A over 20ms to 50ms.

[0044] It should be noted that when the relay switches from forward or reverse activation mode to holding mode, the control module inputs a PWM wave with a gradually decreasing duty cycle to IN1 and IN2, causing the current flowing through the relay coil to gradually decrease from 1A to 0A over 20ms to 50ms. The core of this design lies in achieving a smooth current transition through PWM wave duty cycle control, avoiding voltage overshoot caused by sudden current changes. A PWM wave is a pulse width modulation signal that controls the current magnitude by changing the high-level time of the pulse (i.e., the duty cycle). A gradually decreasing duty cycle means that the high-level time of the pulse gradually shortens, thus causing the current flowing through the relay coil to decrease gradually.

[0045] Specifically, the duty cycle control of the PWM wave is achieved through a control module. When switching modes, the control module gradually reduces the PWM wave duty cycle at preset time intervals. For example, the initial duty cycle can be set to 100%, corresponding to a rated current of 1A in the relay coil. Subsequently, the duty cycle can be reduced by 10% every 1ms until the current drops to 0A. This gradual reduction effectively avoids sudden current changes while ensuring a smooth release of energy in the relay coil. The duty cycle adjustment range can be set according to actual needs, such as gradually reducing from 100% to 0%, or selecting other suitable ranges based on the relay's characteristics.

[0046] Preferably, to further optimize the current descent process, a more refined duty cycle adjustment strategy can be adopted. For example, the reduction of the duty cycle can be divided into multiple stages, with the reduction rate gradually decreasing in each stage. This better simulates the natural decay process of the current and reduces the impact on the AC / DC power supply output voltage. Furthermore, the rate of duty cycle reduction can be dynamically adjusted according to the actual load conditions. For example, under heavy loads, the rate of duty cycle reduction can be appropriately accelerated to shorten the switching time; while under light loads, the rate of duty cycle reduction can be slowed down to ensure a smooth current transition.

[0047] In some embodiments, the duty cycle of the PWM wave is gradually reduced to achieve a gradual decrease in current.

[0048] It should be noted that the duty cycle of the PWM wave gradually decreases to achieve a gradual decrease in current. This means that by progressively reducing the duty cycle of the pulse width modulation (PWM) signal, the current flowing through the relay coil decreases smoothly. PWM is a common modulation method that controls the output power or current by changing the duration of the high-level pulse (i.e., the duty cycle). In this embodiment, by adjusting the duty cycle of the PWM signal, the current in the relay coil decreases gradually, rather than being interrupted abruptly, thus avoiding voltage overshoot caused by sudden current changes.

[0049] Specifically, the duty cycle of a PWM signal refers to the proportion of high-level time within one cycle of the pulse signal. In this embodiment, the initial value of the duty cycle can be set to a high level, such as 100%, at which point the current in the relay coil reaches its maximum value of 1A. As the duty cycle of the PWM signal gradually decreases, for example, by 10% every certain period of time (e.g., 1ms), the current in the relay coil will also gradually decrease accordingly. This gradual decrease can effectively avoid sudden current changes while ensuring that the energy in the relay coil can be released smoothly. The adjustment range of the duty cycle can be set according to actual needs, such as gradually decreasing from 100% to 0%, or selecting other suitable ranges based on the characteristics of the relay.

[0050] Preferably, to further optimize the current descent process, a more refined duty cycle adjustment strategy can be adopted. For example, the reduction of the duty cycle can be divided into multiple stages, with the reduction rate gradually decreasing in each stage. This better simulates the natural decay process of the current and reduces the impact on the AC / DC power supply output voltage. Furthermore, the rate of duty cycle reduction can be dynamically adjusted according to the actual load conditions. For example, under heavy loads, the rate of duty cycle reduction can be appropriately accelerated to shorten the switching time; while under light loads, the rate of duty cycle reduction can be slowed down to ensure a smooth current transition.

[0051] In some embodiments, in the freewheeling discharge mode, the conducting state of the second MOSFET and the fourth MOSFET forms a freewheeling circuit through the second MOSFET and the fourth MOSFET, completely discharging the reverse electromotive force in the coil.

[0052] It should be noted that in the freewheeling discharge mode, the conducting states of the second and fourth MOSFETs create a freewheeling loop for the induced current in the relay coil, completely dissipating the back electromotive force in the coil. This means that in the freewheeling discharge mode, a specific MOSFET conducting state provides a circuit for the induced current in the relay coil, thereby releasing the energy stored in the coil and preventing damage to the circuit from the back electromotive force.

[0053] Preferably, to ensure the efficiency and reliability of freewheeling discharge, the conduction time of the MOSFETs can be precisely controlled. For example, a fixed time window, such as 50ms, can be set to keep the second and fourth MOSFETs conducting within this time to ensure that the induced current in the coil can be completely released. Furthermore, the conduction time can be dynamically adjusted according to the actual coil inductance and current magnitude. For example, for coils with larger inductance, the conduction time can be appropriately extended; while for coils with smaller current, the conduction time can be shortened. This further optimizes circuit performance and reduces unnecessary energy consumption.

[0054] In some embodiments, the drive circuit is connected to the A-channel output terminal of the AC / DC power supply, where the A-channel is a DC output terminal with feedback and the B-channel is a system power supply terminal; the A-channel output voltage is 12V and the B-channel output voltage is 5V.

[0055] It should be noted that the drive circuit is connected to output terminal A of the AC / DC power supply. Terminal A is a DC output terminal with feedback, while terminal B is the system power supply terminal. The output voltage of terminal A is 12V, and the output voltage of terminal B is 5V. This statement describes the power supply connection method of the drive circuit and the setting of its output voltage. An AC / DC power supply is a power supply device that converts alternating current (AC) to direct current (DC), and terminals A and B are the two output terminals of this power supply. Terminal A is a DC output terminal with a feedback mechanism, used to provide a stable 12V voltage, while terminal B provides 5V power to other parts of the system. This power supply design ensures the stable operation of the drive circuit and other parts of the system.

[0056] Specifically, the A-channel output of the AC / DC power supply maintains a stable 12V output voltage through a feedback mechanism. This feedback mechanism means that the power supply detects changes in the output voltage and adjusts the output accordingly to ensure voltage stability. The B-channel output provides a 5V DC voltage to power other electronic components in the system. This dual-output design can meet the voltage requirements of different parts. For example, the 12V voltage from channel A can be used to drive devices requiring higher voltages, such as relays, while the 5V voltage from channel B can power low-voltage devices such as microcontrollers and sensors.

[0057] Preferably, to further improve the stability and reliability of the power supply, overvoltage protection and undervoltage protection functions can be added to the AC / DC power supply. Overvoltage protection automatically cuts off the power output when the output voltage exceeds a set value to prevent circuit damage; undervoltage protection cuts off the power supply when the voltage falls below a set value to prevent the circuit from operating under unstable voltage conditions. Furthermore, isolation measures, such as using a transformer or optocoupler, can be added between circuits A and B to prevent interference between the two circuits and ensure stable system operation.

[0058] In some embodiments, the control module reduces the current to ensure that the load change rate of channel A is less than 50mA / ms, thereby ensuring that the output voltage of channel A remains stable within the range of 12V±0.5V.

[0059] It should be noted that the control module reduces the load change rate of channel A to less than 50mA / ms by gradually decreasing the current, ensuring that the output voltage of channel A remains stable within the range of 12V±0.5V. This means that by gradually decreasing the current through the control module, the rate of change of the load current in channel A is limited, thereby guaranteeing the stability of the output voltage of channel A. The load change rate refers to the rate at which the load current changes per unit time, while the 12V±0.5V range refers to the allowable fluctuation range of the output voltage of channel A. This method effectively avoids output voltage fluctuations caused by sudden changes in load current.

[0060] Specifically, the control module achieves a gradual decrease in current by adjusting the duty cycle of the PWM signal. In relay switching mode, the control module gradually reduces the duty cycle of the PWM signal, causing the current flowing through the relay coil to decrease slowly. For example, with an initial current of 1A, the control module can gradually reduce the current to 0A within 20ms to 50ms. During this process, the rate of change of the load current is strictly controlled to be less than 50mA / ms. Thus, the fluctuation range of the A-channel output voltage can be controlled within 12V ± 0.5V. For example, when the load current gradually decreases from 1A to 0A, the A-channel output voltage will not exceed 12.5V or fall below 11.5V.

[0061] Preferably, to further optimize the current fading process, a more refined control strategy can be adopted. For example, the current fading process can be divided into multiple stages, with the current decrease rate gradually decreasing in each stage. This allows for a smoother current transition and reduces the impact on the A-channel output voltage. Furthermore, the current fading time can be dynamically adjusted according to the actual load conditions. For example, for scenarios with rapid load changes, the current fading time can be appropriately extended; while for scenarios with slow load changes, the current fading time can be shortened. This better adapts to different operating conditions and ensures the stability of the A-channel output voltage.

[0062] In some embodiments, in the H-bridge drive circuit module, the first MOSFET and the third MOSFET are P-channel MOSFETs, and the second MOSFET and the fourth MOSFET are N-channel MOSFETs.

[0063] It should be noted that in the H-bridge driver circuit module, the first and third MOSFETs are P-channel MOSFETs, while the second and fourth MOSFETs are N-channel MOSFETs. This statement clarifies the selection of MOSFET types in the H-bridge driver circuit. MOSFETs are divided into two types: P-channel and N-channel. P-channel MOSFETs carry holes and are typically used for high-level conduction; N-channel MOSFETs carry electrons and are typically used for low-level conduction. In the H-bridge circuit, appropriately selecting the type of MOSFET can optimize circuit performance, improve efficiency, and reduce power consumption.

[0064] Specifically, the selection of P-channel and N-channel MOSFETs is based on the circuit's operating principle and requirements. In an H-bridge circuit, the first and third MOSFETs are connected to the positive terminal VCC, so P-channel MOSFETs are chosen. This allows them to conduct under low-level signals, enabling current to flow from VCC to the relay coil. The second and fourth MOSFETs are connected to ground GND, so N-channel MOSFETs are chosen. This allows them to conduct under high-level signals, enabling current to flow from the relay coil to GND. This combination ensures that current flows correctly to the relay coil under different operating modes, while avoiding short circuits or malfunctions. Furthermore, the on-resistance (Rds(on)) of the P-channel and N-channel MOSFETs also needs to be selected according to the actual current requirements to ensure circuit efficiency.

[0065] Preferably, to further optimize circuit performance, a MOSFET with low on-resistance can be selected to reduce power loss in the circuit. For example, for applications requiring 1A drive current, a MOSFET with an on-resistance of less than 0.1Ω can be selected. Furthermore, a suitable MOSFET can be selected based on the circuit's operating frequency, as high-frequency applications require MOSFETs with faster switching speeds. In practical applications, the MOSFET's voltage rating should also be considered to ensure it can withstand the power supply voltage and potential voltage fluctuations. For example, for a 12V power supply, the MOSFET's voltage rating should be selected above 20V to provide sufficient safety margin.

[0066] In some embodiments, the timing logic of the control module is as follows:

[0067] After the positive pull-in mode lasts for 100ms, the current is gradually reduced for 50ms, and then the current is switched to the freewheeling discharge mode for 10ms.

[0068] After the continuous discharge mode ends, switch to hold mode.

[0069] It should be noted that the timing logic of the control module is as follows: after a 100ms forward pull-in mode, the current gradually decreases for 50ms, then switches to a freewheeling discharge mode for 10ms; after the freewheeling discharge mode ends, it switches to a holding mode. This describes the specific timing logic of the control module switching between different operating modes. Timing logic refers to the order in which the circuit performs operations at different points in time. This logic ensures that the relay can smoothly transition when switching modes, avoiding problems caused by sudden current changes or voltage overshoots.

[0070] Specifically, the forward pull-in mode refers to the relay coil being energized and generating a magnetic field, causing the relay contacts to close. In this mode, the control module sends a control signal to the MOSFETs, allowing current to flow through the relay coil. The forward pull-in mode lasts for 100ms, which is sufficient time for the relay contacts to stably close. Subsequently, the control module switches to the freewheeling discharge mode, which lasts for 10ms. In this mode, the induced current in the relay coil forms a freewheeling loop through the second and fourth MOSFETs, releasing the energy in the coil. Finally, after the freewheeling discharge mode ends, the control module switches to the holding mode, at which point no current flows through the relay coil, and the relay remains in its current state. This timing logic design effectively prevents the back electromotive force generated by the relay during mode switching from damaging the circuit.

[0071] Preferably, to further optimize the timing logic, the duration of each mode can be adjusted according to the specific characteristics of the relay and the actual application requirements. For example, if the relay's pull-in speed is fast, the duration of the forward pull-in mode can be appropriately shortened; if the relay's coil inductance is large, the duration of the freewheeling discharge mode may need to be extended to ensure that the induced current is fully released. Furthermore, a real-time monitoring function can be added to the control module to dynamically adjust the timing logic based on the monitored current and voltage conditions. For example, when it is detected that the current in the coil has not been fully released, the duration of the freewheeling discharge mode can be appropriately extended to ensure the safe and stable operation of the circuit.

[0072] In some embodiments, the drive circuit omits the RC snubber circuit and TVS protection device at both ends of the relay coil.

[0073] It should be noted that the RC snubber circuit and TVS protection device at both ends of the relay coil are omitted from the described drive circuit. This indicates that by optimizing the design of the drive circuit, the RC snubber circuit and TVS protection device, which were originally used to suppress the back electromotive force of the relay coil, are no longer needed. The RC snubber circuit is a circuit composed of resistors and capacitors used to absorb the back electromotive force generated when the relay coil is de-energized; the TVS protection device is a transient voltage suppressor used to protect the circuit from overvoltage damage. Omitting these components simplifies the circuit structure and reduces cost and power consumption.

[0074] Specifically, an RC snubber circuit typically consists of a resistor and a capacitor connected in parallel across the relay coil. When the relay coil is de-energized, the energy stored in the coil is released through the RC circuit, thereby suppressing the back electromotive force (EMF). A TVS (Transient Voltage Suppressor) device is a diode that quickly conducts when an overvoltage occurs in the circuit, clamping the overvoltage within a safe range. In this drive circuit, by employing an H-bridge drive circuit and optimized timing control logic, the back EMF in the relay coil can be effectively released through freewheeling discharge mode, thus eliminating the need for an additional RC snubber circuit and TVS protection device. This design not only simplifies the circuit structure but also reduces cost and power consumption.

[0075] Preferably, to further improve the reliability and safety of the circuit, a real-time monitoring function for the relay coil voltage can be added after omitting the RC snubber circuit and TVS protection device. For example, by setting a voltage monitoring circuit across the relay coil, the voltage change across the coil can be monitored in real time. Once an abnormal voltage is detected, such as excessively high back electromotive force, a protection mechanism can be immediately triggered, such as cutting off the power supply or entering a safe mode. In addition, an overcurrent protection function can be added to the circuit to prevent excessive current caused by short circuits or other faults in the relay coil. Through these alternatives, the safe operation of the circuit can be ensured while omitting traditional protection components.

[0076] In some embodiments, the drive circuit controls the load easing and freewheeling discharge of channel A to stabilize the voltage of channel B within the range of 5V±1V, thereby avoiding triggering the system power-down protection.

[0077] It should be noted that the drive circuit stabilizes the voltage of the B circuit within the range of 5V±1V by controlling the load reduction and freewheeling discharge of the A circuit, thus preventing the system from triggering power-down protection. This statement illustrates that the drive circuit ensures the stability of the system power supply by optimizing the current control strategy. The A circuit is the feedback DC output terminal of the AC / DC power supply, providing drive current to the relay; the B circuit is the system power supply terminal, providing a stable 5V voltage to other electronic components. By controlling the load current reduction and freewheeling discharge of the A circuit, voltage fluctuations in the B circuit caused by sudden load changes can be avoided, thereby preventing the system from triggering power-down protection due to excessively low voltage.

[0078] Specifically, load easing in channel A refers to gradually reducing the current flowing through the relay coil during relay switching, rather than directly cutting off the power. This avoids a rise in the output voltage of channel A due to sudden current changes, which could then affect the voltage of channel B. Freewheeling discharge utilizes a loop formed by the conduction of the second and fourth MOSFETs to provide a release path for the induced current in the relay coil, preventing the back electromotive force from raising the voltage of channel A. These two control strategies ensure that the voltage of channel B remains stable within the range of 5V ± 1V, i.e., between 4V and 6V. For example, when the load current in channel A gradually decreases from 1A to 0A, the voltage of channel B will not fall below 4V or rise above 6V, thus avoiding triggering the system's power-down protection mechanism.

[0079] Preferably, to further optimize the stability of the B-channel voltage, a more refined control strategy can be adopted. For example, a voltage feedback mechanism can be added to the control module to monitor changes in the B-channel voltage in real time and dynamically adjust the rate of decrease of the load current in the A-channel and the freewheeling discharge time based on the monitoring results. Furthermore, a filter capacitor can be added to the B-channel power supply terminal to smooth voltage fluctuations. For example, a large-capacity electrolytic capacitor or solid-state capacitor can be selected, and its capacity can be adjusted according to the load characteristics of the B-channel to ensure the stability of the B-channel voltage during sudden load changes. Through these optimization measures, the reliability and stability of the system can be further improved.

[0080] The various embodiments of the present invention have the following beneficial effects: The present invention can optimize the control strategy of the H-bridge drive circuit, effectively suppress overshoot voltage during the relay opening and closing process, thereby improving the relay's operational stability and service life. By designing four operating modes—holding, forward activation, reverse activation, and freewheeling discharge—it can flexibly adapt to the needs of different operating conditions, ensuring that the relay can operate smoothly under different operating states and reducing interference to other components in the circuit. Furthermore, the present invention can reduce circuit power consumption and electromagnetic interference, improving the overall system reliability. By precisely controlling the turn-on and turn-off timing of the MOSFET, unnecessary energy loss can be avoided, while reducing electromagnetic radiation interference to surrounding equipment, making it suitable for applications with high requirements for circuit performance and stability.

[0081] This invention further enhances the response speed and operational accuracy of relays through multi-level drive voltage control and adaptive adjustment technology. By monitoring the relay's operating status in real time, drive parameters can be dynamically adjusted to ensure efficient and stable control under various load conditions. Simultaneously, this invention simplifies the circuit structure, reduces manufacturing costs, and facilitates mass production and application. Through integrated design and modular layout, the reliability and maintainability of the circuit can be improved, meeting the modern industrial demands for high efficiency, energy saving, and environmental protection.

[0082] Furthermore, the storage medium in the embodiments of this application stores program instructions capable of implementing all the above methods. These program instructions can be stored in the storage medium in the form of a software product, including several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) or processor to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks, or terminal devices such as computers, servers, mobile phones, and tablets.

[0083] The above description is merely an explanation of some preferred embodiments of the present invention and the technical principles employed. Those skilled in the art should understand that the scope of the invention as described in the embodiments of the present invention is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the above-described inventive concept. For example, technical solutions formed by substituting the above-described features with (but not limited to) technical features with similar functions disclosed in the embodiments of the present invention.

Claims

1. A drive circuit for reducing overshoot voltage during relay opening and closing, characterized in that, include: The H-bridge driver circuit module consists of a first MOSFET, a second MOSFET, a third MOSFET, and a fourth MOSFET. The drains of the first and third MOSFETs are connected to the positive power supply VCC, and the sources of the second and fourth MOSFETs are connected to the power supply ground GND. The sources of the first and second MOSFETs are connected to the first coil terminal OUT1 of the relay, and the sources of the third and fourth MOSFETs are connected to the second coil terminal OUT2 of the relay. The control module is used to input a first control signal to the gate of the first MOSFET, a second control signal to the gate of the second MOSFET, a third control signal to the gate of the third MOSFET, and a fourth control signal to the gate of the fourth MOSFET. The drive circuit has four operating modes, including holding mode, forward pull-in mode, reverse pull-in mode, and freewheeling discharge mode; among them, When the drive circuit is in hold mode, no current flows through the relay coil, IN1 and IN2 are both low level, OUT1 and OUT2 are both high impedance state, and the first MOSFET, second MOSFET, third MOSFET and fourth MOSFET are all cut off; When the drive circuit is in the forward energizing mode, the relay is forward energized, IN1 is at a high level, IN2 is at a low level, OUT1 outputs a high level, OUT2 outputs a low level, and the first MOSFET and the fourth MOSFET are turned on. When the drive circuit is in reverse energizing mode, the relay is energized in reverse, IN1 is low level, IN2 is high level, OUT1 outputs low level, OUT2 outputs high level, and the second MOSFET and the third MOSFET are turned on. When the drive circuit is in freewheeling mode, the induced current in the relay coil is released, IN1 and IN2 are both high level, OUT1 and OUT2 both output low level, and the second MOSFET and the fourth MOSFET are turned on. The timing logic of the control module is as follows: after the forward pull-in mode or reverse pull-in mode lasts for 100ms, the current is gradually reduced for 50ms, and then it switches to the freewheeling discharge mode for 10ms; after the freewheeling discharge mode ends, it switches to the holding mode. The control module is further configured as follows: When the relay switches from forward pull-in mode or reverse pull-in mode to holding mode, a PWM wave with a gradually decreasing duty cycle is input to IN1 and IN2, so that the current flowing through the relay coil gradually decreases from 1A to 0A over 20ms to 50ms.

2. The driving circuit according to claim 1, characterized in that, In the freewheeling discharge mode, the conducting state of the second MOSFET and the fourth MOSFET forms a freewheeling circuit through the second MOSFET and the fourth MOSFET, completely discharging the reverse electromotive force in the coil.

3. The driving circuit according to claim 1, characterized in that, The drive circuit is connected to the A-channel output terminal of the AC / DC power supply. The AC / DC power supply includes an A-channel output terminal and a B-channel output terminal. The A-channel output terminal is a DC output terminal with feedback, and the B-channel output terminal is the system power supply terminal. The output voltage of channel A is 12V, and the output voltage of channel B is 5V.

4. The driving circuit according to claim 3, characterized in that, The control module reduces the current to keep the load change rate of channel A less than 50mA / ms, ensuring that the output voltage of channel A remains stable within the range of 12V±0.5V.

5. The driving circuit according to claim 1, characterized in that, In the H-bridge drive circuit module, the first and third MOSFETs are P-channel MOSFETs, and the second and fourth MOSFETs are N-channel MOSFETs.

6. The driving circuit according to claim 1, characterized in that, The drive circuit omits the RC snubber circuit and TVS protection device at both ends of the relay coil.

7. The driving circuit according to claim 3, characterized in that, The drive circuit controls the load reduction and freewheeling discharge of channel A to stabilize the voltage of channel B within the range of 5V±0.2V, thus avoiding triggering the system power-down protection.

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