A PWM driven ac surge protection switching circuit

Abstract

The application relates to the field of circuits, in particular to an alternating current anti-surge switch circuit driven by a PWM, which comprises a driving signal module, a switch module, a driving filter module and an anti-surge protection module. The driving signal module applies a PWM pulse signal to the control electrode of each unidirectional thyristor, the switch module is composed of two unidirectional thyristors in reverse parallel connection, the driving filter module is connected between the control electrode and the cathode of the unidirectional thyristor, and the anti-surge protection module is connected in parallel between the alternating current input and the output port. The PWM pulse signal triggers the switch module, a specific duty ratio can reduce power consumption and inhibit heat generation, a pull-down resistor ensures reliable turn-off of the thyristor, a filter capacitor inhibits sharp peak interference, the anti-surge protection module guides surge energy to the output port, and a voltage-dependent resistor absorbs energy when the voltage exceeds the maximum clamping voltage, thereby realizing protection of the thyristor. The application has the technical effects of reducing power consumption, inhibiting heat generation, ensuring reliable turn-off of the thyristor, preventing mis-triggering, and effectively resisting surges.

Description

Technical Field

[0001] This application relates to the field of circuits, and in particular to a PWM-driven AC surge-resistant switch circuit. Background Technology

[0002] In the field of electronics, the development of switching power supplies is progressing rapidly, and their AC input control technology is also constantly evolving. As a crucial component of various electronic devices, the stability and reliability of the AC input control of switching power supplies directly affect the performance of the entire electronic system. With the trend towards miniaturization and intelligence in electronic devices, the requirements for AC input control of switching power supplies are becoming increasingly stringent. Efficient, fast, and stable control methods have become the industry's pursuit, which is of great significance for improving the overall performance of electronic products and the user experience.

[0003] Traditional AC input control methods for switching power supplies are mainly divided into electronic switch control and mechanical switch control, with the control circuit employing corresponding drive methods for different control types. In the industry, relays or silicon controlled rectifiers (SCRs) are commonly used to achieve switching control of the power supply input. Relay control is characterized by its simple control drive circuit and stable and reliable mechanical action; while SCR control offers advantages such as fast response speed, phase angle control capabilities, and ease of implementing soft-start functionality.

[0004] However, existing technologies have significant drawbacks. Relay control suffers from high power consumption, leading to relay overheating, momentary arcing at the contact points, contact oxidation, and ultimately, poor contact, affecting the stability and reliability of the entire switching power supply's AC input control. When using thyristor control, fixed-level drive suffers from high power consumption, poor surge protection, and susceptibility to false triggering, severely impacting the stability and reliability of the switching power supply's AC input control and failing to meet the demands of electronic devices for efficient and stable power input. Utility Model Content

[0005] To address the issues of high power consumption, poor surge protection, and susceptibility to false triggering in traditional solutions, this application provides a PWM-driven AC surge protection switch circuit.

[0006] A PWM-driven AC surge-resistant switching circuit includes: A drive signal module is used to apply PWM pulse signals to the control electrodes of each unidirectional thyristor; a switching module is composed of a first unidirectional thyristor and a second unidirectional thyristor connected in reverse parallel, wherein the anode of the first unidirectional thyristor is connected to the AC input port and the cathode is connected to the AC output port; the anode of the second unidirectional thyristor is connected to the AC output port and the cathode is connected to the AC input port. The drive filter module includes a first branch and a second branch respectively connected between the control electrode and the cathode of the first unidirectional thyristor and the second unidirectional thyristor. The first branch is composed of a first pull-down resistor and a first filter capacitor connected in parallel, and the second branch is composed of a second pull-down resistor and a second filter capacitor connected in parallel. The surge protection module, connected in parallel between the AC input port and the AC output port, includes a third resistor and a third capacitor connected in series, and a varistor connected in parallel across the series branch of the third resistor and the third capacitor.

[0007] By adopting the above technical solutions, the drive signal module applies PWM pulse signals to the control electrodes of each unidirectional thyristor, which reduces drive power consumption while driving the unidirectional thyristors compared to the traditional fixed-level control method. The switching module consists of unidirectional thyristors connected in reverse parallel, which can realize the control switching action of the positive and negative half-cycles of AC power, effectively controlling the conduction and cutoff of AC power. In the drive filter module, the pull-down resistor can release the residual charge between the control electrode and the cathode, ensuring that the unidirectional thyristors are reliably turned off when the PWM pulse signal is low. The filter capacitor suppresses spike interference through AC short circuit, preventing the thyristors from being falsely triggered to conduct, thereby ensuring stable circuit operation. When a surge voltage enters, the resistor and capacitor form an AC bypass path, directing the surge energy to the output port. When the capacitor is fully charged by the surge voltage, the varistor can absorb energy when the voltage across the unidirectional thyristor exceeds the limit withstand voltage, preventing the unidirectional thyristor from being over-voltage broken down, enhancing the circuit's surge resistance and effectively protecting the normal operation of the downstream circuit.

[0008] Preferably, the switching module is triggered by a PWM pulse signal. The PWM pulse signal has a preset frequency and duty cycle, which ensures reliable triggering of the unidirectional thyristor while reducing drive power consumption.

[0009] By adopting the above technical solution, the switching module is driven by a PWM pulse signal, and the PWM pulse signal has a preset frequency and duty cycle. While ensuring reliable triggering of the unidirectional thyristor, enabling the switching module to normally control the switching action during the positive and negative half-cycles of AC power, compared with the traditional fixed-level driving method, it can effectively reduce driving power consumption, reduce unnecessary energy consumption, avoid problems such as device overheating and aging caused by high driving power consumption, extend the service life of related components in the circuit, and improve the stability and reliability of the entire circuit.

[0010] Preferably, the PWM pulse signal is applied between the control electrode and the cathode.

[0011] By employing the above technical solution, a PWM pulse signal is applied between the control electrode and the cathode, triggering the first unidirectional thyristor to conduct during the positive half-cycle of the AC current and the second unidirectional thyristor to conduct during the negative half-cycle, thus achieving effective control over the positive and negative half-cycles of the AC current. Simultaneously, this application method, combined with PWM control, utilizes an optimized duty cycle, effectively driving the unidirectional thyristors while significantly reducing drive power consumption. Furthermore, when the pulse signal becomes low, the thyristors remain in the conducting state until the AC current naturally turns off at zero-crossing, achieving precise switching control.

[0012] Preferably, the PWM pulse signal applied by the drive signal module is synchronized with the AC phase, used to trigger the first unidirectional thyristor to conduct during the positive half-cycle of the AC current, and to trigger the second unidirectional thyristor to conduct during the negative half-cycle of the AC current.

[0013] By adopting the above technical solution, the PWM pulse signal is synchronized with the AC phase, which can trigger the first unidirectional thyristor to conduct during the positive half-cycle of the AC current and the second unidirectional thyristor to conduct during the negative half-cycle, thereby realizing effective control of the switching action during the positive and negative half-cycles of the AC current. Combined with the technical means of applying PWM pulse signals to the control electrode of each unidirectional thyristor by the drive signal module, the switching module consisting of two unidirectional thyristors connected in reverse parallel, the drive filter module connected between the control electrode and the cathode, and the surge protection module connected in parallel between the AC input and output ports, the drive power can be reduced, the surge resistance can be enhanced, the thyristor can be prevented from being falsely triggered to conduct, the unidirectional thyristors can be reliably turned off, the switching transistor can be prevented from being broken down by surge voltage and from being accidentally falsely turned on, and the downstream circuit can be protected to operate normally.

[0014] Preferably, the control logic of the PWM pulse signal is as follows: when a high-level pulse is applied, the corresponding unidirectional thyristor is triggered to turn on; when the pulse signal becomes low-level, the thyristor remains in the on state until the AC current naturally turns off at the zero-crossing point.

[0015] By adopting the above technical solution, the unidirectional thyristor is controlled by a PWM pulse signal to turn on and off. When a high-level pulse is applied, the corresponding unidirectional thyristor can be precisely triggered to turn on, thus achieving effective control of the AC circuit. When the pulse signal becomes low-level, the thyristor can maintain the conducting state until the AC current naturally turns off at the zero-crossing point. This control logic avoids the continuous high-level drive under traditional control methods, greatly reducing drive power consumption and reducing the problem of thyristor heating and aging. At the same time, by utilizing the characteristic of natural turn-off at the zero-crossing point of AC current, the turn-off process of the thyristor is made more stable and reliable, which helps to improve the stability and reliability of the entire AC switching circuit, reduce the occurrence of malfunctions, ensure the normal operation of the circuit, and extend the service life of each component in the circuit.

[0016] Preferably, the first pull-down resistor and the second pull-down resistor are used to release the residual charge between the control electrode and the cathode to ensure reliable turn-off, and to ensure that the unidirectional thyristor is reliably turned off when the PWM pulse signal is low.

[0017] By adopting the above technical solution, the first pull-down resistor and the second pull-down resistor can release the residual charge between the control electrode and the cathode, preventing the residual charge from affecting the turn-off state of the unidirectional thyristor. When the PWM pulse signal goes low, it ensures that the unidirectional thyristor is reliably turned off, preventing the thyristor from failing to turn off properly due to residual charge. This ensures the stability and reliability of the circuit during the low-level pulse signal period, avoids circuit failures that may be caused by thyristor mis-turn-on, and improves the working performance and safety of the entire surge-resistant PWM AC switching circuit.

[0018] Preferably, the first filter capacitor and the second filter capacitor suppress spike interference by AC short-circuiting to prevent the thyristor from being falsely triggered and turned on.

[0019] By employing the above technical solution, the first and second filter capacitors effectively suppress spike interference signals through AC short-circuiting. Spike interference signals, as high-frequency, short-duration interference pulses, can cause the thyristor to conduct unexpectedly, thus affecting the normal operation of the entire AC switching circuit. The first and second filter capacitors act as AC short-circuiters for spike interference signals, guiding these interference signals to ground and preventing them from affecting the voltage difference between the control electrode and cathode of the thyristor. This reliably prevents the thyristor from being falsely triggered, ensuring the stability and reliability of the AC switching circuit and reducing potential faults and safety hazards caused by thyristor false triggering.

[0020] Preferably, when a surge voltage occurs, the third resistor and the third capacitor form an AC bypass path to direct the surge energy to the output port.

[0021] By adopting the above technical solution, when a surge voltage occurs, the third resistor and the third capacitor can form an AC bypass path, directing the surge energy to the output port. This process effectively reduces the direct impact of the surge voltage on key components such as the unidirectional thyristor in the switching circuit, preventing excessive accumulation of surge energy in the circuit and subsequent component damage. This allows the circuit to promptly guide excess energy to the output port when facing surge voltages, ensuring circuit stability and reliability, reducing the risk of faults and damage caused by surge impacts, and extending the circuit's lifespan.

[0022] Preferably, when the third capacitor is fully charged by the surge voltage, a superimposed voltage is formed across the first unidirectional thyristor and the second unidirectional thyristor; the varistor is used to absorb energy when the superimposed voltage exceeds the withstand voltage limit of the first unidirectional thyristor and the second unidirectional thyristor.

[0023] By employing the above technical solution, when a surge voltage enters the circuit and the third capacitor is fully charged, a superimposed voltage will be formed across the first and second unidirectional thyristors. Without effective protection measures, if this superimposed voltage exceeds the withstand voltage limits of the first and second unidirectional thyristors, it will cause these two unidirectional thyristors to break down and short-circuit, thus preventing the entire circuit from functioning properly or even causing damage. The presence of the varistor allows it to absorb energy in time when the superimposed voltage exceeds the withstand voltage limits of the first and second unidirectional thyristors. This not only prevents the first and second unidirectional thyristors from breaking down due to overvoltage, ensuring the safety of these two critical components, but also ensures that the entire surge-resistant PWM AC switching circuit can still operate stably and reliably under the impact of surge voltage, preventing circuit failures caused by surge voltage, improving circuit stability and reliability, and extending the circuit's lifespan.

[0024] Preferably, the maximum clamping voltage generated by the varistor when subjected to the maximum expected surge current is less than the rated reverse breakdown voltage of the first unidirectional thyristor and the second unidirectional thyristor, so as to ensure that the thyristor is preferentially turned on to absorb energy when the surge voltage exceeds the withstand voltage of the unidirectional thyristor.

[0025] By adopting the above technical solution, the maximum clamping voltage generated by the varistor when subjected to the maximum expected surge current is set to be less than the rated reverse breakdown voltage of the first and second unidirectional thyristors. When the surge voltage exceeds the withstand voltage of the unidirectional thyristors, the varistor can preferentially conduct. In this way, the varistor can absorb surge energy in time, preventing the unidirectional thyristors from breaking down and short-circuiting due to overvoltage caused by the surge voltage. This effectively protects the first and second unidirectional thyristors, ensures the normal operation of the switching module, enhances the stability and reliability of the entire surge-resistant PWM AC switching circuit when facing surge voltage, reduces the risk of damage to the circuit caused by surge impact, and extends the service life of key components such as unidirectional thyristors in the circuit.

[0026] In summary, this application includes at least one of the following beneficial technical effects: 1. By using a PWM pulse signal to drive the thyristor, the average driving power consumption is reduced, thereby reducing power consumption and suppressing circuit heating; 2. The pull-down resistor releases the residual charge between the control electrode and the cathode, ensuring that the thyristor is reliably turned off when the PWM is low; 3. The filter capacitor suppresses spike interference through AC short circuit, the third resistor and the third capacitor form an AC bypass path, and the varistor absorbs surge energy, which can prevent the thyristor from being falsely triggered and enhance the circuit's surge protection capability. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure of a PWM-driven AC surge protection switch circuit provided in an embodiment of this application.

[0028] Figure 2 This is a circuit diagram of a PWM-driven AC surge protection switch circuit provided in an embodiment of this application; Explanation of reference numerals in the attached diagram: 1. Drive signal module; 2. Switch module; 3. Drive filter module; 4. Surge protection module; 5. AC input port; 6. AC output port; SCR1, First unidirectional thyristor; SCR2, Second unidirectional thyristor; INV_R, AC input port; OP_R, AC output port; R1, First pull-down resistor; C1, First filter capacitor; R2, Second pull-down resistor; C2, Second filter capacitor; R3, Third resistor; C3, Third capacitor; MOV1: Varistor; SCR1-G, PWM pulse signal; SCR2-G, PWM pulse signal. Detailed Implementation

[0029] This application mainly adopts PWM control and adds a surge protection module, which achieves the effect of reducing drive power consumption and enhancing surge resistance. The following will describe this application in further detail with reference to the accompanying drawings.

[0030] The surge-resistant PWM AC switching circuit provided in this application includes a drive signal module, a switch module, a drive filter module, and a surge protection module. The drive signal module applies a PWM pulse signal to the switch module, the drive filter module is connected between the control electrode and the cathode of the switch module, and the surge protection module is connected in parallel between the AC input port and the AC output port. This achieves the effects of reducing drive power consumption, enhancing surge resistance, and preventing thyristor mis-conduction. This is because the drive filter module can filter interference signals, the surge protection module can absorb surge energy, and the PWM pulse signal drive can reduce power consumption.

[0031] Specifically, the drive signal module includes components such as a signal generator. The signal generator can be a dedicated PWM pulse signal generation chip, characterized by its ability to generate PWM pulse signals according to set parameters, such as a PWM pulse signal with a frequency of 19kHz, a duty cycle of 15%, and an amplitude of 1.5V. Alternatively, it can be implemented using microcontroller programming to generate the PWM pulse signal, with parameters such as pulse frequency, duty cycle, and amplitude adjusted via software settings. The PWM pulse signal generated by the signal generator is synchronized with the AC current phase. Its connection to the switching module involves applying the signal between the control electrode and cathode of a unidirectional thyristor in the switching module. This triggers the first unidirectional thyristor to conduct during the positive half-cycle of the AC current and the second unidirectional thyristor to conduct during the negative half-cycle.

[0032] Specifically, the switching module consists of a first unidirectional thyristor SCR1 and a second unidirectional thyristor SCR2 connected in reverse parallel. The first and second unidirectional thyristors are semiconductor devices with three electrodes: a control electrode, an anode (A), and a cathode. Their design allows them to control conduction and cutoff based on the voltage signal between the control electrode and the cathode. During the positive half-cycle of the AC current, the first unidirectional thyristor operates, and during the negative half-cycle, the second unidirectional thyristor operates. Applying a PWM pulse to the cathode triggers the unidirectional thyristor to conduct. To turn it off, the drive signal is changed to a low level, allowing it to turn off naturally during the AC zero-crossing commutation. An alternative feature is the use of a bidirectional thyristor to replace the two unidirectional thyristors. The bidirectional thyristor can achieve conduction control in both the positive and negative half-cycles of the AC current, simplifying the circuit structure. The anode of the first unidirectional thyristor is connected to the AC input port INV_R, and the cathode is connected to the AC output port OP_R; the anode of the second unidirectional thyristor is connected to the AC output port OP_R, and the cathode is connected to the AC input port INV_R. This connection method enables the switching module to control the switching action during the positive and negative half-cycles of the AC current.

[0033] Specifically, the drive filter module includes a first branch and a second branch, which are respectively connected between the control electrode and the cathode of the first unidirectional thyristor and the second unidirectional thyristor.

[0034] The first branch circuit consists of a first pull-down resistor R1 connected in parallel with a first filter capacitor C1, and the second branch circuit consists of a second pull-down resistor R2 connected in parallel with a second filter capacitor C2. These two types of pull-down resistors are typically carbon film resistors or metal film resistors, but wire-wound resistors can also be used as alternatives. Their function is to act as a lower bias for the switching transistor and simultaneously release residual charge between the control electrode and cathode of the corresponding thyristor, ensuring reliable turn-off of the unidirectional thyristor. The two types of filter capacitors are generally ceramic capacitors or mica capacitors, but thin-film capacitors can also be used as alternatives. They have good high-frequency characteristics and can suppress spike interference through AC short circuit, preventing false triggering of the thyristor. The first pull-down resistor R1 and the first filter capacitor C1 are connected in parallel between the control electrode and cathode of the first unidirectional thyristor, forming a filtering circuit for the first control signal: the first pull-down resistor R1 is used to release residual charge between the control electrode and cathode of the first thyristor, ensuring reliable turn-off when the PWM pulse signal is low; the first filter capacitor C1 is used to suppress spike interference and prevent false triggering. Similarly, the second pull-down resistor R2 and the second filter capacitor C2 are connected in parallel between the control electrode and the cathode of the second unidirectional thyristor to achieve the corresponding filtering and protection functions for the second control signal.

[0035] Specifically, the surge protection module is connected in parallel between the AC input port INV_R and the AC output port OP_R. It includes a third resistor R3 and a third capacitor C3 connected in series, and a varistor MOV1 connected in parallel across the series branch of the third resistor R3 and the third capacitor C3. The third resistor R3 can be a power resistor, designed to withstand a certain amount of power and function as a current limiter in the circuit. A cement resistor can be used as an alternative. The third capacitor C3 can be an electrolytic capacitor or a non-polarized capacitor, and its function is to form an AC bypass path with the third resistor R3. The varistor MOV1 is a nonlinear resistive element. When subjected to the maximum expected surge current, the maximum clamping voltage it generates is less than the rated reverse breakdown voltage of the first unidirectional thyristor SCR1 and the second unidirectional thyristor SCR2. When a surge voltage occurs, the third resistor R3 and the third capacitor C3 form an AC bypass path to guide the surge energy to the output port. When the third capacitor C3 is fully charged by the surge voltage, a superimposed voltage is formed across the first and second unidirectional thyristors. The varistor MOV1 is used to absorb energy when this superimposed voltage exceeds the unidirectional thyristor's withstand voltage limit, ensuring that the unidirectional thyristor will not be over-voltage broken down.

[0036] The implementation principle of this embodiment is as follows: This circuit drives the switching module by applying a PWM pulse signal synchronized with the AC phase through the drive signal module, realizing the control of the positive and negative half-cycles of the AC current. Simultaneously, the PWM control method reduces drive power consumption. The pull-down resistor in the drive filter module releases residual charge between the control electrode and the cathode, ensuring reliable turn-off of the thyristor. The filter capacitor suppresses spike interference, preventing false triggering of the thyristor. When a surge voltage intrudes, the surge protection module directs the surge energy to the output port through an AC bypass path formed by a resistor and capacitor. The varistor MOV1 absorbs voltages exceeding the thyristor's withstand voltage, protecting the thyristor from breakdown. Compared to traditional control methods, this circuit significantly improves drive power consumption, enhances surge resistance, and prevents false turn-on of the thyristor, thus improving circuit stability and reliability.

[0037] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A PWM-driven AC surge-resistant switching circuit, characterized in that, include: The drive signal module is used to apply PWM pulse signals to the control electrode of each unidirectional thyristor. The switching module consists of a first unidirectional thyristor (SCR1) and a second unidirectional thyristor (SCR2) connected in reverse parallel. The anode of the first unidirectional thyristor (SCR1) is connected to the AC input port (INV_R), and the cathode is connected to the AC output port (OP_R). The anode of the second unidirectional thyristor (SCR2) is connected to the AC output port (OP_R), and the cathode is connected to the AC input port (INV_R). The drive filter module includes a first branch and a second branch connected between the control electrode and the cathode of the first unidirectional thyristor (SCR1) and the second unidirectional thyristor (SCR2), respectively. The first branch is composed of a first pull-down resistor (R1) and a first filter capacitor (C1) connected in parallel, and the second branch is composed of a second pull-down resistor (R2) and a second filter capacitor (C2) connected in parallel. The surge protection module, connected in parallel between the AC input port (INV_R) and the AC output port (OP_R), includes a third resistor (R3) and a third capacitor (C3) connected in series, and a varistor (MOV1) connected in parallel across the series branch of the third resistor (R3) and the third capacitor (C3).

2. The circuit according to claim 1, characterized in that: The switching module is triggered by a PWM pulse signal. The PWM pulse signal has a preset frequency and duty cycle, which ensures reliable triggering of the unidirectional thyristor while reducing drive power consumption.

3. The circuit according to claim 2, characterized in that: The PWM pulse signal is applied between the control electrode and the cathode.

4. The circuit according to claim 1, characterized in that: The PWM pulse signal applied by the drive signal module is synchronized with the AC phase, and is used to trigger the first unidirectional thyristor (SCR1) to conduct during the positive half-cycle of the AC current, and to trigger the second unidirectional thyristor (SCR2) to conduct during the negative half-cycle of the AC current.

5. The circuit according to claim 1, characterized in that: When the PWM pulse signal is a high-level pulse, it triggers the corresponding unidirectional thyristor to turn on. When the pulse signal becomes low-level, the unidirectional thyristor remains on until the AC current naturally turns off at the zero-crossing point.

6. The circuit according to claim 1, characterized in that: The first pull-down resistor (R1) and the second pull-down resistor (R2) are used to release the residual charge between the control electrode and the cathode to ensure reliable turn-off, and to ensure that the unidirectional thyristor is reliably turned off when the PWM pulse signal is low.

7. The circuit according to claim 1, characterized in that: The first filter capacitor (C1) and the second filter capacitor (C2) suppress spike interference through AC short circuit to prevent the unidirectional thyristor from being falsely triggered and turned on.

8. The circuit according to claim 1, characterized in that: When a surge voltage occurs, the third resistor (R3) and the third capacitor (C3) form an AC bypass path, directing the surge energy to the AC output port (OP_R).

9. The circuit according to claim 1, characterized in that: When the third capacitor (C3) is fully charged by the surge voltage, a superimposed voltage is formed across the first unidirectional thyristor (SCR1) and the second unidirectional thyristor (SCR2); the varistor (MOV1) is used to absorb energy when the superimposed voltage exceeds the ultimate withstand voltage of the first unidirectional thyristor (SCR1) and the second unidirectional thyristor (SCR2).

10. The circuit according to claim 9, characterized in that: The maximum clamping voltage generated by the varistor (MOV1) when subjected to the maximum expected surge current is less than the rated reverse breakdown voltage of the first unidirectional thyristor (SCR1) and the second unidirectional thyristor (SCR2), to ensure that the surge voltage exceeds the withstand voltage of the unidirectional thyristor and preferentially conducts to absorb energy.

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