A surge protection circuit and method based on bidirectional thyristor

Abstract

The application discloses a surge protection circuit and method based on bidirectional thyristor, and relates to the technical field of power electronics. The circuit comprises a pressure-sensitive resistor branch, a rectification filtering branch and a TVS clamping branch connected in parallel to the bidirectional thyristor. An AC input, the bidirectional thyristor and a load are connected in series to form an AC loop, and a driving circuit is electrically connected to the control electrode of the bidirectional thyristor to realize on-off control. The pressure-sensitive resistor branch can quickly absorb large energy surge voltage in the AC loop. The rectification filtering branch rectifies the AC voltage between the two ends of the bidirectional thyristor into DC voltage through a rectifier bridge, and then filters the voltage through a filtering capacitor to reduce voltage peaks. The TVS clamping branch precisely clamps the filtered surge voltage through the series connection of a first resistor and a transient voltage suppression diode. The application improves the long-term working reliability of the bidirectional thyristor and the switching device through the cooperative protection of multiple branches, and is especially suitable for various power electronic application scenarios in which the bidirectional thyristor replaces electromagnetic relays.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, and in particular to a surge protection circuit and method based on bidirectional thyristor. Background Technology

[0002] In the field of power electronics, triacs (SCRs) are widely used as contactless switching elements in AC circuit switching, especially in applications that replace electromagnetic relays, offering advantages such as fast response and no mechanical wear. In practical applications, triacs are highly sensitive to voltage spikes, requiring not only protection against false triggering caused by voltage surges but also protection circuits to dissipate surge voltage energy and reduce overvoltage damage to the triac.

[0003] Currently, the industry typically uses RC snubber circuits connected in parallel in AC circuits to protect bidirectional thyristors. However, conventional RC snubber circuits have limited protection against various transient overvoltages of bidirectional thyristors and their related drive circuits, failing to meet the protection requirements of high-energy surge scenarios. Furthermore, the resistors in the RC circuit continuously consume energy, leading to heat generation and affecting the long-term reliability of the entire switching device. Therefore, there is an urgent need for a surge protection circuit and method that can effectively absorb surge energy, improve protection effectiveness, reduce energy loss, and enhance the long-term operational reliability of the device. Summary of the Invention

[0004] The purpose of this application is to provide a surge protection circuit and method based on bidirectional thyristors, which can effectively absorb surge energy, improve protection effect, reduce energy loss, and improve the long-term operational reliability of the device.

[0005] To achieve the above objectives, this application provides the following solution: In a first aspect, this application provides a surge protection circuit based on a bidirectional thyristor, comprising: an AC input, a load, a bidirectional thyristor, a drive circuit, and a varistor branch, a rectifier-filter branch, and a TVS clamping branch connected in parallel across the bidirectional thyristor; the AC input, the bidirectional thyristor, and the load are connected in series to form an AC loop; the drive circuit is electrically connected to the control electrode of the bidirectional thyristor to drive the switching of the bidirectional thyristor; the varistor branch contains only a varistor and is used to absorb high-energy surge voltages in the AC loop; the rectifier-filter branch includes a rectifier bridge and a filter capacitor, the AC input terminal of the rectifier bridge is connected in parallel across the bidirectional thyristor, and the filter capacitor is connected in parallel across the DC output terminal of the rectifier bridge to rectify and filter the voltage across the bidirectional thyristor to reduce voltage spikes; the TVS clamping branch includes a first resistor and a transient voltage suppression diode, the first resistor and the transient voltage suppression diode are connected in series and then connected in parallel across the DC output terminal of the rectifier bridge to clamp the filtered surge voltage.

[0006] Optionally, when the AC input is 220V, the filter capacitor is rated at 2.2μF / 450V; when the AC input is 380V, the filter capacitor is rated at 1μF / 1KV.

[0007] Optionally, the rectifier bridge is a bridge rectifier, with the AC input terminal of the bridge rectifier electrically connected to both ends of the bidirectional thyristor, and the DC output terminal of the bridge rectifier connected to the filter capacitor and the TVS clamping branch respectively.

[0008] Optionally, the varistor is a zinc oxide varistor, and the two ends of the zinc oxide varistor are directly electrically connected to the two main electrodes of the bidirectional thyristor.

[0009] Optionally, the transient voltage suppressor diode is a unidirectional transient voltage suppressor diode. The positive output terminal of the rectifier bridge is electrically connected to one end of the first resistor, the other end of the first resistor is electrically connected to the negative terminal of the unidirectional transient voltage suppressor diode, and the positive terminal of the unidirectional transient voltage suppressor diode is electrically connected to the negative output terminal of the rectifier bridge.

[0010] Optionally, the AC input is a 220V AC mains input, and the two output terminals of the AC input are respectively connected to the load and the main electrode of the bidirectional thyristor to form a single-phase AC circuit.

[0011] Secondly, this application provides a surge protection method based on a bidirectional thyristor, using the surge protection circuit based on a bidirectional thyristor as described above. The surge protection method based on a bidirectional thyristor includes the following steps: A varistor connected in parallel across the bidirectional thyristor absorbs large-energy surge voltages in the AC circuit, reducing the peak energy of the surge voltage.

[0012] The AC surge voltage across the bidirectional thyristor is rectified into DC voltage by a rectifier bridge, and then the DC surge voltage is filtered and buffered by a filter capacitor connected in parallel to the output of the rectifier bridge to reduce voltage spikes.

[0013] The filtered DC surge voltage is quickly clamped by the series branch of the first resistor and the transient voltage suppression diode, limiting the voltage across the bidirectional thyristor to within a safe threshold.

[0014] According to the specific embodiments provided in this application, the following technical effects are disclosed: This application provides a surge protection circuit and method based on a bidirectional thyristor, including: an AC input, a load, a bidirectional thyristor, a drive circuit, and a varistor branch, a rectifier-filter branch, and a TVS clamping branch connected in parallel across the bidirectional thyristor. The AC input, the bidirectional thyristor, and the load are connected in series to form an AC loop, thereby constructing a complete power transmission path and providing a stable circuit foundation for surge protection. The drive circuit is electrically connected to the control electrode of the bidirectional thyristor to drive the switching of the bidirectional thyristor, achieving precise control of the AC loop and ensuring the reliability of the load operation. The varistor branch contains only a varistor, used to absorb high-energy surge voltages in the AC loop. Its nonlinear resistance characteristics allow for rapid surge response, significantly reducing the peak energy of the surge and preventing damage to the bidirectional thyristor due to high-energy impacts. Simultaneously, it has no continuously consuming components, solving the problem of traditional RC circuits. Overheating issues; the rectifier-filter branch includes a rectifier bridge and a filter capacitor. The AC input terminal of the rectifier bridge is connected in parallel across the bidirectional thyristor, and the filter capacitor is connected in parallel across the DC output terminal of the rectifier bridge. This is used to rectify and filter the voltage across the bidirectional thyristor to reduce voltage spikes. By converting AC surges to DC and filtering them, the risk of false triggering of the bidirectional thyristor due to voltage surges is effectively eliminated, improving circuit stability. The TVS clamping branch includes a first resistor and a transient voltage suppressor diode. The first resistor and the transient voltage suppressor diode are connected in series and then in parallel across the DC output terminal of the rectifier bridge. This is used to clamp the filtered surge voltage. The first resistor limits the current when the transient voltage suppressor diode is conducting, preventing it from being damaged by overcurrent. The transient voltage suppressor diode can quickly clamp the surge voltage within a safe threshold, ensuring that the voltage across the bidirectional thyristor is always within the rated operating range, achieving precise protection. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a circuit diagram of a surge protection circuit based on a bidirectional thyristor applied in a 220V voltage scenario, as provided in one embodiment of this application.

[0017] Figure 2 This is a circuit diagram of a surge protection circuit based on a bidirectional thyristor applied in a 380V voltage scenario, as provided in one embodiment of this application. Detailed Implementation

[0018] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0019] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0020] This application provides a surge protection circuit based on a bidirectional thyristor. In one exemplary embodiment, such as... Figure 1 As shown, it includes: AC input (220V AC), load, triac (model BTA41-800BW), drive circuit (Triac_Drive), and varistor branch, rectifier filter branch and TVS clamping branch connected in parallel across the triac.

[0021] An AC input, a bidirectional thyristor, and a load are connected in series to form an AC circuit. In this embodiment, the AC input is a 220V AC mains input, and the two output terminals of the AC input are connected to the load and the main electrode of the bidirectional thyristor, respectively, to form a single-phase AC circuit.

[0022] The drive circuit is electrically connected to the control electrode of the bidirectional thyristor and is used to output a drive signal to control the switching of the bidirectional thyristor. The varistor branch contains only varistor R2 (model RV10D471 / I) and no other series components. It is used to absorb large-energy surge voltages in the AC circuit. When a large-energy surge voltage occurs in the AC circuit, the resistance of the zinc oxide varistor decreases sharply as the voltage increases, quickly absorbing the peak energy of the surge and reducing the impact of the surge voltage on the bidirectional thyristor. In this embodiment, the varistor R2 is a zinc oxide varistor, and its two ends are directly electrically connected to the two main electrodes of the bidirectional thyristor.

[0023] The rectifier-filter branch includes a rectifier bridge BR1 (model ABS10) and a filter capacitor C1. The AC input terminal of the rectifier bridge is connected in parallel across the bidirectional thyristor, and the filter capacitor C1 is connected in parallel across the DC output terminal of the rectifier bridge. This filter capacitor rectifies and filters the voltage across the bidirectional thyristor to reduce voltage spikes. In this embodiment, the rectifier bridge BR1 is a bridge rectifier. The AC input terminal of the bridge rectifier is electrically connected to the bidirectional thyristor, and the DC output terminal is connected to the filter capacitor C1 and the TVS clamping branch. The filter capacitor C1 has a specification of 2.2μF / 450V. The bridge rectifier rectifies the AC surge voltage across the bidirectional thyristor into a DC voltage, and the filter capacitor C1 improves the response speed of the filter buffer, quickly reducing voltage spikes in the DC voltage and preventing false triggering of the bidirectional thyristor due to voltage fluctuations.

[0024] The TVS clamping branch includes a first resistor R1 (model R220) and a transient voltage suppressor diode D1 (model SMAJ400A). The first resistor R1 and the transient voltage suppressor diode D1 are connected in series and then in parallel to the DC output terminal of the rectifier bridge to clamp the filtered surge voltage. In this embodiment, the transient voltage suppressor diode D1 is a unidirectional transient voltage suppressor diode. The positive output terminal of the rectifier bridge BR1 is electrically connected to one end of the first resistor R1, and the other end of the first resistor R1 is electrically connected to the negative terminal of the unidirectional transient voltage suppressor diode. The positive terminal of the unidirectional transient voltage suppressor diode is electrically connected to the negative output terminal of the rectifier bridge BR1. The first resistor R1 provides current limiting protection, preventing the transient voltage suppressor diode from being damaged by overcurrent. The transient voltage suppressor diode D1 conducts rapidly when the voltage exceeds its breakdown voltage, clamping the voltage at the bridge rectifier output terminal within a safe threshold, thus achieving precise protection against the filtered surge voltage.

[0025] certainly, Figure 1 The architecture shown is merely exemplary; it can be omitted as needed when implementing different functionalities. Figure 1 One or at least two components of the system shown.

[0026] As in Figure 2 In another exemplary embodiment, when the AC input is 380V, the filter capacitor C1 has a specification of 1μF / 1KV / CBB / I. In this scenario, the bidirectional thyristor is model BTA41-1200BW, the varistor R2 has a specification of RV10D821 / I, and an additional transient voltage suppressor diode D2 is added in series after the transient voltage suppressor diode D1 in the TVS clamping branch. In other embodiments, the anode of the unidirectional transient voltage suppressor diode is electrically connected to one end of the first resistor R1, and the cathode of the unidirectional transient voltage suppressor diode is electrically connected to the positive output terminal of the rectifier bridge.

[0027] Based on the same inventive concept, this application also provides a surge protection method using the surge protection circuit based on a bidirectional thyristor described above. The solution provided by this method is similar to the implementation described above. In an exemplary embodiment, a surge protection method based on a bidirectional thyristor is provided, including the following steps: S1. The varistor connected in parallel across the bidirectional thyristor absorbs the large energy surge voltage in the AC circuit, reducing the peak energy of the surge voltage.

[0028] S2. The AC surge voltage across the bidirectional thyristor is rectified into DC voltage using a rectifier bridge. Then, a filter capacitor connected in parallel to the output of the rectifier bridge filters and buffers the DC surge voltage, reducing voltage spikes. Rectification, filtering, and peak clipping can eliminate the triggering interference of voltage sudden changes on the bidirectional thyristor.

[0029] S3. The filtered DC surge voltage is quickly clamped by the series branch of the first resistor and the transient voltage suppression diode, limiting the voltage across the bidirectional thyristor within a safe threshold. When the voltage exceeds the breakdown voltage of the transient voltage suppression diode, the transient voltage suppression diode quickly conducts, clamping the voltage at the rectifier bridge output within a safe threshold, ensuring that the voltage across the bidirectional thyristor is always within its rated operating range.

[0030] Steps S1, S2, and S3 are executed synchronously. The varistor branch, rectifier filter branch, and TVS clamping branch form a collaborative protection system, achieving full-dimensional surge protection for the bidirectional thyristor from three dimensions: energy absorption, spike reduction, and voltage clamping. Moreover, the entire protection circuit has no continuously consuming resistors, avoiding the heating problem of conventional RC circuits and significantly improving the long-term operational reliability of the bidirectional thyristor and the entire switching device.

[0031] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0032] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A surge protection circuit based on a bidirectional thyristor, characterized in that, include: The system comprises an AC input, a load, a bidirectional thyristor (SCR), a drive circuit, and a varistor branch, a rectifier-filter branch, and a TVS clamping branch connected in parallel across the SCR. The AC input, SCR, and load are connected in series to form an AC loop. The drive circuit is electrically connected to the control electrode of the SCR to drive the SCR's switching on and off. The varistor branch contains only a varistor and is used to absorb large-energy surge voltages in the AC loop. The rectifier-filter branch includes a rectifier bridge and a filter capacitor. The AC input terminal of the rectifier bridge is connected in parallel across the SCR, and the filter capacitor is connected in parallel across the DC output terminal of the rectifier bridge to rectify and filter the voltage across the SCR to reduce voltage spikes. The TVS clamping branch includes a first resistor and a transient voltage suppressor diode. The first resistor and the transient voltage suppressor diode are connected in series and then in parallel across the DC output terminal of the rectifier bridge to clamp the filtered surge voltage.

2. The surge protection circuit based on bidirectional thyristor according to claim 1, characterized in that, When the AC input is 220V, the filter capacitor has a specification of 2.2μF / 450V; when the AC input is 380V, the filter capacitor has a specification of 1μF / 1KV.

3. The surge protection circuit based on bidirectional thyristor according to claim 1, characterized in that, The rectifier bridge is a bridge rectifier. The AC input terminal of the bridge rectifier is electrically connected to the two ends of the bidirectional thyristor. The DC output terminal of the bridge rectifier is connected to a filter capacitor and a TVS clamping branch, respectively.

4. The surge protection circuit based on bidirectional thyristor according to claim 1, characterized in that, The varistor is a zinc oxide varistor, and its two ends are directly electrically connected to the two main electrodes of the bidirectional thyristor.

5. The surge protection circuit based on bidirectional thyristor according to claim 1, characterized in that, The transient voltage suppression diode is a unidirectional transient voltage suppression diode. The positive output terminal of the rectifier bridge is electrically connected to one end of the first resistor, the other end of the first resistor is electrically connected to the negative terminal of the unidirectional transient voltage suppression diode, and the positive terminal of the unidirectional transient voltage suppression diode is electrically connected to the negative output terminal of the rectifier bridge.

6. The surge protection circuit based on bidirectional thyristor according to claim 1, characterized in that, The AC input is a 220V AC mains input, and the two output terminals of the AC input are respectively connected to the load and the main electrode of the bidirectional thyristor to form a single-phase AC circuit.

7. A surge protection method based on bidirectional thyristors, characterized in that, The surge protection circuit based on a bidirectional thyristor as described in any one of claims 1-6 is used, wherein the surge protection method based on the bidirectional thyristor includes: The peak energy of the surge voltage is reduced by absorbing the large energy surge voltage in the AC circuit through the varistor connected in parallel across the two ends of the bidirectional thyristor. The AC surge voltage across the bidirectional thyristor is rectified into DC voltage by a rectifier bridge, and then the DC surge voltage is filtered and buffered by a filter capacitor connected in parallel to the output of the rectifier bridge to reduce voltage spikes. The filtered DC surge voltage is quickly clamped by the series branch of the first resistor and the transient voltage suppression diode, limiting the voltage across the bidirectional thyristor to within a safe threshold.

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