Control circuit based on hybrid switching timing of relays and thyristors
By using a hybrid relay and thyristor switching timing control circuit, the problems of short lifespan of mechanical relays and high cost of solid-state relays are solved, achieving high reliability and low cost load control, which is suitable for inductive loads such as AC brushed motors.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- GUANGDONG YINGKE ELECTRONICS
- Filing Date
- 2025-05-20
- Publication Date
- 2026-06-30
AI Technical Summary
In existing technologies, mechanical relays have short lifespans when frequently switching on and off large currents, and parallel connection of multiple relays increases equipment size and cost. Solid-state relays are expensive and have high heat dissipation pressure under inductive loads. Existing solutions are difficult to balance low cost, high reliability, and compatibility with inductive loads.
A hybrid relay and thyristor switching timing control circuit is adopted. The thyristor bears the load current before the relay is closed and after it is opened. Combined with zero-crossing detection and RC absorption circuit, the generation of contact arc is avoided, and soft start is performed under inductive load.
The relay lifespan has been increased from 20,000 cycles to 500,000 cycles, and the cost is only 1/3 of that of a solid-state relay. It reduces switching losses and electromagnetic interference, and is suitable for inductive loads such as AC brushed motors, improving reliability and user experience.
Smart Images
Figure CN224438962U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of automation control technology, specifically a control circuit based on a hybrid switching timing of relays and thyristors. Background Technology
[0002] In industrial automation and high-power electrical control, relays, as traditional switching elements, are widely used for load switching control due to their simple structure and low cost. However, when relays frequently switch large currents (typically 15-20A), their mechanical contacts experience a sharp decline in lifespan due to arc erosion and oxidation. Experimental data shows that conventional mechanical relays, under conditions of a rated current of 20A and a switching frequency of 10 times / minute, have an average lifespan of only 20,000 cycles (see "Low-voltage Electrical Appliance Life Test Standard GB / T 14598.1-2020"). Contact loss has become the core issue restricting their reliability.
[0003] To address this deficiency, existing technologies have proposed various improvement schemes, but all of them have significant limitations as follows.
[0004] Multi-relay parallel technology: By sharing the current through multiple contacts, the energy of a single-point arc can be reduced. Although the lifespan can be increased to about 50,000 cycles, the solution requires additional relays and complex synchronous control circuits, resulting in an increase in equipment size and cost of 30%-50%.
[0005] Solid-state relay (SSR) alternatives: These utilize the contactless nature of semiconductor devices to completely eliminate arcing, with a lifespan of up to one million cycles. However, the manufacturing cost of SSRs is approximately three times that of mechanical relays (market average price comparison data source: 2023 "China Power Electronic Components Industry Analysis Report"), and their junction temperature can reach over 80°C under high-load continuous operation (quoted from TI's application note "SSR Thermal Design Considerations"), requiring forced cooling devices, increasing system complexity and maintenance costs.
[0006] Furthermore, the above solutions are not suitable for inductive loads (such as AC brushed motors and transformers) as follows.
[0007] In parallel connection schemes of multiple relays, the contacts are prone to sticking due to back electromotive force when the inductive load is turned off.
[0008] Although SSRs can achieve soft switching, their on-state voltage drop (typically 1.2-1.5V) leads to additional power consumption and generates 24-30W of heat loss at 20A current, exacerbating the heat dissipation pressure.
[0009] Therefore, there is an urgent need in this field for a relay life optimization solution that combines low cost, high reliability, and adaptability to inductive loads, in order to resolve the performance and cost contradiction between traditional technologies and solid-state devices. Utility Model Content
[0010] This invention aims to solve at least one of the technical problems existing in the prior art. Therefore, one objective of this invention is to provide a control circuit based on a hybrid switching timing of relays and thyristors. By using thyristor TR1 to bear the load current before and after the relay is closed, and after the relay is opened, contact arcing is avoided, thereby increasing the relay lifespan from 20,000 cycles to 500,000 cycles, while the cost is only 1 / 3 that of a solid-state relay.
[0011] This utility model also provides a control circuit based on a hybrid switching timing of relays and thyristors, including the following.
[0012] Relay RL1 has its contacts connected in series in the load circuit.
[0013] Thyristor TR1 is connected in parallel across the contacts of relay RL1.
[0014] The control module is used to control the thyristor TR1 to conduct before and after the relay RL1 is closed in order to bear the load current and avoid the generation of electric arc at the contacts of the relay RL1.
[0015] The zero-crossing detection unit is used to detect the zero-crossing point of the AC power supply and control the thyristor TR1 to be triggered to turn on or off at the zero-crossing point.
[0016] Specifically, an RC snubber circuit is provided in the parallel circuit of the thyristor TR1 and the relay RL1 contacts. The RC snubber circuit includes a second resistor R2 and a safety capacitor CX connected in series.
[0017] Specifically, the control module includes an optocoupler isolation unit U1, whose input terminal is connected to the external control signal Control terminal and whose output terminal is connected to the trigger electrode G pin of the thyristor TR1, for the purpose of realizing electrical isolation control.
[0018] Specifically, when the device is applied to an AC brushed motor inductive load, the control module is further configured to: perform a soft start through the thyristor TR1 before the relay RL1 is closed, so that the load current gradually increases at the zero crossing point; and close the relay RL1 after the load current stabilizes to take over the current path.
[0019] Specifically, the turn-on and turn-off sequence of the thyristor TR1 is as follows: before the relay RL1 is closed, the thyristor TR1 is turned on and maintained until the relay RL1 is fully closed; after the relay RL1 is opened, the thyristor TR1 is turned on and maintained until the relay RL1 is fully opened, and then the thyristor TR1 is turned off.
[0020] Furthermore, the control module also includes a first current-limiting resistor R1 and a filter capacitor C1 connected to the optocoupler isolation unit, which are used to optimize the stability and anti-interference capability of the trigger signal.
[0021] Specifically, the optocoupler isolation unit U1 is connected to a first current-limiting resistor R3.
[0022] Specifically, pin 1 of the optocoupler isolation unit U1 is connected to a fourth resistor R4.
[0023] Specifically, the fourth resistor R4 is connected to a +5V terminal.
[0024] The beneficial effects of this utility model are as follows.
[0025] 1. Before relay RL1 is closed / after it is opened, the current is carried by thyristor TR1 to avoid contact arcing and to prevent electromagnetic interference caused by arcing.
[0026] 2. The thyristor TR1 is triggered only at the AC zero-crossing point, reducing switching losses and EMI.
[0027] Third, the lifespan of the RL1 relay has been increased from 20,000 cycles to 500,000 cycles, while the cost is only 1 / 3 of that of a solid-state relay.
[0028] Fourth, when used with AC brushed motors and inductive loads, the zero-crossing point can be combined to give the load a soft start first, and then the relay RL1 can take over the current path. This reduces the impact of sudden large current on components and load, and the motor starting torque can be increased gradually without sudden excessive force, making the user experience better. Attached Figure Description
[0029] The above and / or additional aspects and advantages of this invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings.
[0030] Figure 1 This is the circuit diagram of this utility model.
[0031] Figure 2 This is the first operation flow logic diagram of this utility model.
[0032] Figure 3 This is the second operation flow logic diagram of this utility model. Detailed Implementation
[0033] The embodiments of this utility model are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this utility model, and should not be construed as limiting this utility model.
[0034] The following is for reference. Figures 1 to 3 A control circuit based on a hybrid switching timing of relays and thyristors according to an embodiment of the present invention is described below.
[0035] Relay RL1 has its contacts connected in series in the load circuit.
[0036] Thyristor TR1 is connected in parallel across the contacts of relay RL1.
[0037] The control module is used to control the thyristor TR1 to conduct before and after the relay RL1 is closed in order to bear the load current and avoid the generation of electric arc at the contacts of the relay RL1.
[0038] The zero-crossing detection unit is used to detect the zero-crossing point of the AC power supply and control the thyristor TR1 to be triggered to turn on or off at the zero-crossing point. The zero-crossing detection unit uses a voltage comparator LM393, which monitors the AC voltage waveform in real time through a voltage divider resistor network. When a zero-crossing is detected, it outputs a trigger signal to the control module.
[0039] Specifically, an RC snubber circuit is provided in the parallel circuit of the thyristor TR1 and the relay RL1 contacts. The RC snubber circuit includes a second resistor R2 and a safety capacitor CX connected in series.
[0040] Specifically, the control module includes an optocoupler isolation unit U1, whose input terminal is connected to the external control signal Control terminal and whose output terminal is connected to the trigger electrode G pin of the thyristor TR1, for the purpose of realizing electrical isolation control.
[0041] Specifically, when the device is applied to an inductive load of an AC brushed motor, the control module is further configured to: perform a soft start via the thyristor TR1 before the relay RL1 is closed, causing the load current to gradually increase at the zero-crossing point; and close the relay RL1 after the load current stabilizes to take over the current path. The soft start is achieved by gradually increasing the conduction angle of the thyristor TR1 at the zero-crossing point to gradually increase the load current.
[0042] Specifically, the turn-on and turn-off sequence of the thyristor TR1 is as follows: before the relay RL1 is closed, the thyristor TR1 is turned on and maintained until the relay RL1 is fully closed; after the relay RL1 is opened, the thyristor TR1 is turned on and maintained until the relay RL1 is fully open, and then the thyristor TR1 is turned off. The optocoupler isolation unit U1 is a PC817 type optocoupler, with a current-limiting resistor R3 (1kΩ) connected in series at its input terminal, and its output terminal connected to the trigger pin G of the thyristor TR1, with an isolation voltage of 5000Vrms.
[0043] Furthermore, the control module also includes a first current-limiting resistor R1 and a filter capacitor C1 connected to the optocoupler isolation unit, which are used to optimize the stability and anti-interference capability of the trigger signal.
[0044] Specifically, the optocoupler isolation unit U1 is connected to a first current-limiting resistor R3. Pin 1 of the optocoupler isolation unit U1 is connected to a fourth resistor R4. The fourth resistor R4 is connected to a +5V terminal.
[0045] The circuit structure is as follows: thyristor TR1 is connected in parallel to the output of relay RL1, and an RC snubber circuit is added; the control unit drives thyristor TR1 through optocoupler isolation and detects AC zero-crossing for precise triggering. The second resistor R2 of the RC snubber circuit has a resistance of 10kΩ±5%, and the safety capacitor CX has a capacitance of 0.1μF / 630V, which is used to suppress voltage spikes during the switching process of thyristor TR1.
[0046] Closing process: After detecting a zero crossing, thyristor TR1 is triggered to conduct, and relay RL1 is closed after the current stabilizes; Opening process: Thyristor TR1 is triggered to conduct, relay RL1 is opened, and thyristor TR1 is turned off after relay RL1 is completely disconnected.
[0047] Soft-start function: For inductive loads (such as motors), the thyristor TR1 gradually increases its conduction angle at zero crossings to achieve smooth starting and reduce current surges. For inductive loads, the control module achieves soft starting by gradually increasing the conduction angle of thyristor TR1: at each AC zero crossing, the conduction angle is gradually increased from 0° to 180°, increasing by 10° each time, until the load current stabilizes. Then, relay RL1 is closed to take over the current path.
[0048] Although embodiments of the present invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the claims and their equivalents.
Claims
1. A control circuit based on a hybrid switching sequence of relays and thyristors, characterized in that, include: Relay RL1, whose contacts are connected in series in the load circuit; Thyristor TR1 is connected in parallel across the contacts of relay RL1; The control module is used to control the thyristor TR1 to conduct before and after the relay RL1 is closed in order to bear the load current and avoid the generation of electric arc at the contacts of the relay RL1. The zero-crossing detection unit is used to detect the zero-crossing point of the AC power supply and control the thyristor TR1 to be triggered to turn on or off at the zero-crossing point.
2. The control circuit based on the hybrid switching timing of relays and thyristors according to claim 1, characterized in that, An RC snubber circuit is provided in the parallel circuit between the contacts of the thyristor TR1 and the relay RL1. The RC snubber circuit includes a second resistor R2 and a safety capacitor CX connected in series.
3. The control circuit based on the hybrid switching timing of relays and thyristors according to claim 1, characterized in that, The control module includes an optocoupler isolation unit U1, whose input terminal is connected to the external control signal Control terminal and whose output terminal is connected to the trigger electrode G pin of the thyristor TR1, for the purpose of realizing electrical isolation control.
4. The control circuit based on the hybrid switching timing of relays and thyristors according to claim 1, characterized in that, When the device is applied to an inductive load of an AC brushed motor, the control module is further configured to: perform a soft start through the thyristor TR1 before the relay RL1 is closed, so that the load current gradually increases at the zero crossing point; and close the relay RL1 to take over the current path after the load current stabilizes.
5. The control circuit based on a hybrid switching sequence of relays and thyristors according to claim 1, characterized in that, The turn-on and turn-off sequence of the thyristor TR1 is as follows: before the relay RL1 is closed, the thyristor TR1 is turned on and maintained until the relay RL1 is fully closed; after the relay RL1 is opened, the thyristor TR1 is turned on and maintained until the relay RL1 is fully opened, and then the thyristor TR1 is turned off.
6. The control circuit based on the hybrid switching timing of relays and thyristors according to claim 1, characterized in that, The control module also includes a first current-limiting resistor R1 and a filter capacitor C1 connected to the optocoupler isolation unit U1, which are used to optimize the stability and anti-interference capability of the trigger signal.
7. The control circuit based on a hybrid switching sequence of relays and thyristors according to claim 6, characterized in that, The optocoupler isolation unit U1 is connected to a first current-limiting resistor R3.
8. The control circuit based on a hybrid switching sequence of relays and thyristors according to claim 6 or 7, characterized in that, The fourth resistor R4 is connected to pin 1 of the optocoupler isolation unit U1.
9. The control circuit based on a hybrid switching sequence of relays and thyristors according to claim 8, characterized in that, The fourth resistor R4 is connected to a +5V terminal.