Solid-state module for forward and reverse bidirectional switching of silicon controlled rectifier

Abstract

The invention discloses a silicon controlled rectifier forward and reverse bidirectional switching solid-state module, and aims to solve the problems that an existing silicon controlled rectifier switching scheme is high in short circuit risk, high in cost and complexity and difficult to maintain, and a simple relay replacement scheme is short in service life. According to the technical scheme, the device comprises a hardware circuit structure and a single-chip microcomputer control logic part, the hardware circuit structure comprises a main loop silicon controlled rectifier unit, a relay switching unit, a single-chip microcomputer control unit, a signal acquisition unit and a power supply unit, and a mixed topological structure of three main loop silicon controlled rectifiers and a common double-pole double-throw relay is adopted. And in cooperation with closed-loop control logic of load state judgment, silicon controlled rectifier turn-off, relay switching and silicon controlled rectifier conduction, current forward and reverse safe switching is realized. Two silicon controlled rectifiers for switching are omitted, so that the risk of short circuit is thoroughly avoided; the relay is switched only when the silicon controlled rectifier has no output, so that the service life is prolonged; the circuit structure is simplified, the hardware and maintenance cost is reduced, and the anti-interference capability is remarkably improved.

Description

A solid-state module with thyristor bidirectional switching Technical Field

[0001] This invention relates to the field of power electronic control technology, and more specifically to a solid-state module with thyristor bidirectional switching. Background Technology

[0002] In the field of power electronics control, thyristors are widely used for current switching and direction control due to their unidirectional conductivity and controllable conduction characteristics. Currently, the mainstream thyristor bidirectional switching schemes on the market all adopt a structure design of 5 thyristors plus matching drive optocoupler circuits: 3 thyristors are used to form the current path of the main circuit, and the other 2 thyristors are used to control the conduction and cutoff of the forward and reverse circuits respectively. Each thyristor needs to be paired with an independent drive optocoupler to achieve signal isolation and conduction control.

[0003] However, this traditional solution has unavoidable technical flaws: high short-circuit risk. The conduction of the thyristor is affected by the dv / dt parameter. When the voltage rise rate exceeds its rated value, the thyristor may mis-conduct. Simultaneously, the drive optocoupler is susceptible to electromagnetic interference during signal transmission, causing delays or synchronization deviations in the drive signals of the forward and reverse circuits. Both of these situations can cause the forward and reverse thyristors to conduct instantaneously, resulting in a short circuit in the main circuit, burning out core components such as the thyristor and drive optocoupler, and even causing safety accidents such as equipment fires.

[0004] High cost and complexity: The five thyristors and their supporting components such as drive optocouplers, current-limiting resistors, and isolation capacitors not only increase the cost of hardware procurement, but also make the circuit structure more complex. The welding and debugging processes during production and assembly are increased, which raises the defect rate in the production process.

[0005] High maintenance difficulty: The complex circuit structure makes troubleshooting difficult. Once a problem occurs, multiple components such as thyristors and optocouplers need to be tested one by one, which prolongs equipment downtime and increases subsequent maintenance costs.

[0006] In existing technologies, although some solutions have attempted to replace thyristors with relays, these are all simple mechanical switching methods that do not consider the contact wear problem when the relay is switching under load. This results in short relay lifespan and an inability to meet the requirements for long-term stable operation, thus preventing their widespread application in practical scenarios. Summary of the Invention

[0007] To address the problems of high short-circuit risk, high cost, and difficult maintenance in existing thyristor forward / reverse switching schemes, as well as the short lifespan of simple relay alternatives, the present invention aims to provide a solid-state module for bidirectional thyristor forward / reverse switching. This module reduces cost and complexity while completely eliminating short-circuit hazards, extending component lifespan, and improving overall product reliability. The technical solution adopted by the present invention to solve its technical problems is as follows: A solid-state module for bidirectional thyristor forward / reverse switching, which achieves bidirectional current switching through a hybrid topology consisting of three main circuit thyristors and one double-pole double-throw relay, along with closed-loop control logic.

[0008] The solid-state module includes a hardware circuit structure, which includes a main circuit thyristor unit, a relay switching unit, a microcontroller control unit, a signal acquisition unit, and a power supply unit. Each unit works together to achieve bidirectional switching of current in both directions.

[0009] The main circuit thyristor unit includes three main circuit thyristors, each equipped with a driving optocoupler to form a main path for forward and reverse current conduction, thereby isolating the microcontroller control signal from the main circuit. The rated current of the main circuit thyristor is not less than 5A and the rated voltage is not less than 600V.

[0010] The relay switching unit uses a common double-pole double-throw relay. The rated current of the double-pole double-throw relay contacts is not less than 5A, and the coil operating voltage is 24V DC. The normally closed contacts and normally open contacts of the relay are respectively connected to each phase of the three-phase power output corresponding to the thyristor. The sequence of the three-phase power is controlled by the on / off state of the relay coil to realize the switching of forward and reverse circuits.

[0011] The signal acquisition unit is a current reading circuit, which consists of a current coil transformer, a current sampling resistor, and a rectifier diode connected in series, and is finally electrically connected to the ADC acquisition pin of the microcontroller. It is used to convert the high-voltage current of the main circuit into a low-voltage signal that the microcontroller can acquire, so that the microcontroller can determine the load status.

[0012] The microcontroller control unit uses a 32-bit microcontroller to receive forward and reverse signals from the outside. When the relay needs to be activated, it first cuts off the output of the thyristor, and then switches the relay while ensuring that there is no output current. After the relay is switched, the thyristor is activated to connect the load.

[0013] The power supply unit uses a linear regulator to convert the externally input 24V power supply into 5V and 3.3V, providing a stable operating power supply for each unit.

[0014] Preferably, the hardware circuit structure is soldered on the PCB board, and the pins of the main circuit thyristor and relay are matched with the copper foil area. The copper foil width is normally not less than 2mm and the thickness is not less than 35μm to meet the 5A current carrying requirement.

[0015] Preferably, the wiring of the signal acquisition unit is set separately from the wiring of the main circuit. The main circuit can use differential wiring, and the signal acquisition line can be wrapped with shielded wire or ground wire.

[0016] Preferably, the primary winding of the current coil transformer is connected in series with the main circuit, and the secondary winding is electrically connected to both ends of the current sampling resistor to achieve electrical isolation between high voltage and low voltage.

[0017] Preferably, the voltage across the current sampling resistor is linearly proportional to the main circuit current, and the voltage signal is transmitted to the microcontroller's ADC pin after rectification and voltage division.

[0018] Preferably, the rectifier diode is an LL4148 type switching diode, whose anode is electrically connected to the output terminal of the current sampling resistor and whose cathode is electrically connected to the input terminal of the voltage divider resistor network, used to rectify the AC sampling signal into a unidirectional pulsating signal.

[0019] Preferably, the voltage divider resistor network is composed of current-limiting resistors RK13 and RK25 connected in series, and its voltage is limited to 3.3V by switching diode DK25 to match the acquisition range of the microcontroller ADC.

[0020] The microcontroller control logic of the microcontroller control unit is as follows: The microcontroller control unit acts as the control core and executes the closed-loop control logic of load status judgment, thyristor turn-off, relay switching, and thyristor turn-on in sequence; The specific control process is as follows: (1) Forward rotation state: The microcontroller controls the thyristor to turn off. After confirming that there is no load current, it controls the relay coil to turn off and finally controls the thyristor to turn on. The main circuit is in the forward conduction state; (2) Reverse rotation state: The microcontroller controls the thyristor to turn off. After confirming that there is no load current, it controls the relay coil to close and finally controls the thyristor to turn on; (3) Load status detection: The microcontroller collects the current signal through the ADC interface and calculates the load status. Calculate the main circuit current value; if the current value is less than or equal to the preset no-load current value, it is considered to be in the no-load current threshold state, and then proceed to the next step; if the current value is greater than the preset no-load current value, the microcontroller first outputs a turn-off signal to the thyristor, and after the current drops to the no-load current threshold, proceed to the next step; (4) Relay switching: The microcontroller monitors the external control signal in real time. When the external forward and reverse signals change, it first turns off the output of the thyristor, and then switches the relay on or off after confirming that there is no current passing through the load through the current detection circuit, and then turns on the output of the thyristor, thereby realizing the switching of forward and reverse, and the relay switching action when there is no load. The microcontroller performs the above operations through a set of strict logic timing and current closed-loop detection, thereby ensuring that the relay switches when there is no load.

[0021] Preferably, when switching the output state, the output of the thyristor is first turned off, then the coil of the relay is switched to be engaged or disengaged, and then the thyristor is controlled to be turned on.

[0022] Compared with the closest existing technology, the technical solution provided by the present invention has the following beneficial effects: 1. The present invention is an innovative hybrid topology, which adopts a hybrid structure of 3 main circuit thyristors and 1 relay to replace the traditional 5 thyristors, reducing 2 thyristors and matching drive optocouplers, simplifying the circuit structure and reducing hardware cost and complexity.

[0023] 2. This invention features innovative no-load switching control. By using a microcontroller to collect current signals in real time and determine the load status, it ensures that the relay switches only when there is no load, avoiding contact arcing caused by load switching and improving the service life of the relay.

[0024] 3. This invention features innovative short-circuit protection by eliminating the two thyristors used for forward and reverse switching in traditional solutions, fundamentally avoiding the short-circuit risk of simultaneous conduction of forward and reverse thyristors; at the same time, the microcontroller performs timing control on / off of the thyristors in the main circuit, further preventing false conduction. Attached Figure Description

[0025] Figure 1 is a circuit diagram of the main circuit thyristor unit of the present invention; Figure 2 is a circuit diagram of the relay switching unit of the present invention; Figure 3 is a circuit diagram of the signal acquisition unit of the present invention; Figure 4 is a circuit diagram of the current reading circuit of the present invention. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Example 1 The technical solution of this invention includes two parts: hardware circuit structure and microcontroller control logic, as follows: 1. Hardware circuit structure The hardware circuit structure includes a main circuit thyristor unit, a relay switching unit, a microcontroller control unit, a signal acquisition unit, and a power supply unit. Each unit works together to achieve bidirectional switching of current in both forward and reverse directions. The main circuit thyristor unit retains the three main circuit thyristors in the traditional scheme to form the main path for forward and reverse current conduction. Each main circuit thyristor is equipped with a driving optocoupler to achieve isolation between the microcontroller control signal and the main circuit.

[0028] The relay switching unit uses a common double-pole double-throw relay. The normally closed and normally open contacts of the relay are connected to each phase of the three-phase power output corresponding to the thyristor. The microcontroller controls the on / off state of the relay coil to adjust the sequence of the three-phase power, thereby realizing the switching of the forward and reverse circuits.

[0029] The signal acquisition unit is a current reading circuit, which consists of a current coil transformer, a current sampling resistor, and a voltage control diode connected in series, and is finally electrically connected to the ADC acquisition pin of the microcontroller. It is used to convert the high-voltage current of the main circuit into a low-voltage signal that the microcontroller can acquire, so that the microcontroller can determine the load status.

[0030] The microcontroller control unit uses a 32-bit microcontroller as the control core of the module. It accepts forward and reverse signals from the outside. When the relay needs to be activated, it first cuts off the output of the thyristor. It then switches the relay while ensuring that there is no output current. After the relay is switched, it allows the thyristor to work and connects the load.

[0031] The power supply unit uses a linear regulator to convert the external 24V power supply to 5V and 3.3V, providing operating power for the microcontroller, drive optocoupler, and relay coil, ensuring stable voltage for each unit.

[0032] 2. Microcontroller Control Logic The microcontroller uses preset program logic to achieve closed-loop control of load status judgment, thyristor turn-off, relay switching, and thyristor turn-on. The specific control process is as follows: (1) Forward rotation state: The microcontroller controls the thyristor to turn off. After confirming that there is no load current, it controls the relay coil to turn off and finally controls the thyristor to turn on. The main circuit is in the forward conduction state. (2) Reverse rotation state: The microcontroller controls the thyristor to turn off. After confirming that there is no load current, it controls the relay coil to close and finally controls the thyristor to turn on. (3) Load status detection: The microcontroller collects the current signal through the ADC interface and calculates the current value of the main circuit. If the current value is less than or equal to the preset no-load current value, it is considered to be in the no-load current threshold state, and the next step is executed; if the current value is greater than the preset no-load current value, the microcontroller first outputs a turn-off signal to the thyristor, and after the current drops to the no-load current threshold, the next step is executed; (4) Relay switching: The microcontroller monitors the external control signal in real time. When the external forward and reverse signals change, the output of the thyristor is turned off first, and the current detection circuit confirms that there is no current passing through the load before switching the relay on or off, and then the output of the thyristor is turned on, thereby realizing the switching of forward and reverse, and the relay switching action when there is no load. The microcontroller performs the above operations through a set of strict logic timing and current closed-loop detection, thereby ensuring that the relay switches when there is no load.

[0033] Example 21. Circuit Connection: Following the hardware circuit structure described above, solder each component onto the PCB board, ensuring that the pins of the main circuit thyristor and relay match the copper foil area to avoid excessive current causing the copper foil to burn out; separate the wiring of the signal acquisition unit from the main circuit wiring to reduce electromagnetic interference.

[0034] 2. Programming: The pre-defined control logic program developed based on KeilMDK is burned into the microcontroller. The no-load current threshold is set in the program, and the threshold can be adjusted according to the actual load power.

[0035] 3. Debugging steps: Load testing: Connect a 4.2A rated load three-phase motor and measure the main circuit current during forward operation to confirm that it matches the load power; trigger switching and observe whether the current drops to the no-load threshold before switching the relay. After switching, the reverse current is normal and there is no short circuit or overcurrent.

[0036] Anti-interference debugging: Place the module in an electromagnetic interference environment and use an EFT burst generator to apply signal interference, power interference, and strong electrical interference to the module. Record the switching accuracy and fault conditions to ensure that the module operates stably in the interference environment.

[0037] 4. Experimental Testing: The experiment compared the module of this invention (experimental group) with five traditional thyristor modules (control group). The experimental parameters are as follows: Load: 4.2A motor load, operating voltage 380V AC; Experimental period: 4 hours of continuous operation, triggering 120 forward and reverse switching per hour; Environmental conditions: temperature 25℃±5℃, humidity 40%-60%; Electromagnetic interference intensity: power interference: 3000V, 5kHz; signal interference: 3000V, 5kHz; strong electrical interference: 4500V, 5kHz (simulating industrial environment). The experimental results above demonstrate that the solid-state module of this invention completely solves the short-circuit problem caused by mis-conduction of forward and reverse thyristors or synchronization deviation of drive signals in traditional solutions. The short-circuit failure rate is reduced to below 0.2%, which is safer and more reliable compared to the 3.2% short-circuit failure rate of traditional solutions. Its anti-interference capability is significantly superior to traditional solutions. It can operate stably under power and signal interference environments of 3000V and 5kHz, and can withstand strong electrical interference of 4500V and 5kHz in simulated complex industrial electromagnetic environments, while traditional solutions cannot function properly under similar interference at 1500V.

[0038] The above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can still make modifications or equivalent substitutions to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention are within the protection scope of the claims of the present invention pending approval.

Claims

1. A solid-state module with thyristor bidirectional switching, comprising a hardware circuit structure, characterized in that, The hardware circuit structure includes a main circuit thyristor unit, a relay switching unit, a microcontroller control unit, a signal acquisition unit, and a power supply unit. These units work together to achieve bidirectional current switching. The main circuit thyristor unit includes three main circuit thyristors, each paired with a driver optocoupler, forming the main path for forward and reverse current conduction, thus isolating the microcontroller control signal from the main circuit. The relay switching unit uses a standard double-pole double-throw relay. The normally closed and normally open contacts of the relay are connected to two phases of the three-phase output corresponding to the thyristor, respectively. The relay coil's on / off state controls the three-phase sequence, achieving forward and reverse circuit switching. The signal acquisition unit is for current reading. The circuit is constructed by sequentially connecting a current coil transformer, a current sampling resistor, a rectifier diode, and a voltage divider network in series, ultimately connecting to the ADC acquisition pin of the microcontroller. This converts the high-voltage current of the main circuit into a low-voltage signal that the microcontroller can acquire, allowing the microcontroller to determine the load status. The microcontroller control unit uses a 32-bit microcontroller that accepts forward and reverse signals from the outside. When a relay operation is required, it first cuts off the output of the thyristor, switches the relay while ensuring there is no output current, and then allows the thyristor to operate and connect the load after the relay switching is complete. The power supply unit uses a linear regulator to convert the external 24V power supply into 5V and 3.3V, providing a stable operating power for each unit.

2. The solid-state module with thyristor bidirectional switching according to claim 1, characterized in that, The hardware circuit structure is soldered onto the PCB board, and the pins of the main circuit thyristor and relay are matched with the copper foil area.

3. The solid-state module with thyristor bidirectional switching according to claim 1, characterized in that, The wiring of the signal acquisition unit is set separately from the main circuit wiring.

4. The solid-state module with thyristor bidirectional switching according to claim 1, characterized in that, The rated current of the main circuit thyristor is not less than 5A, and the rated voltage is not less than 600V; the rated current of the contacts of the double-pole double-throw relay is not less than 5A, and the coil operating voltage is 24V DC.

5. The solid-state module with thyristor bidirectional switching according to claim 1, characterized in that, The primary winding of the current transformer is connected in series with the main circuit, and the secondary winding is electrically connected to the two ends of the current sampling resistor. The voltage across the current sampling resistor is linearly proportional to the current in the main circuit. The voltage signal is rectified and divided before being transmitted to the ADC pin of the microcontroller. The rectifier diode is an LL4148 type switching diode. Its anode is electrically connected to the output terminal of the current sampling resistor, and its cathode is electrically connected to the input terminal of the voltage divider resistor network. It is used to rectify the AC sampling signal into a unidirectional pulsating signal. The voltage divider resistor network is composed of current-limiting resistors RK13 and RK25 connected in series. Its output voltage is limited to the range of 0~3.3V by diode DK25.

6. The solid-state module with thyristor bidirectional switching according to claim 1, characterized in that, The microcontroller control logic of the microcontroller control unit is as follows: The microcontroller control unit acts as the control core and executes closed-loop control logic of load status judgment, thyristor turn-off, relay switching, and thyristor turn-on in sequence; The specific control process is as follows: (1) Forward rotation state: The microcontroller controls the thyristor to turn off. After confirming that there is no load current, it controls the relay coil to turn off and finally controls the thyristor to turn on. The main circuit is in the forward conduction state; (2) Reverse rotation state: The microcontroller controls the thyristor to turn off. After confirming that there is no load current, it controls the relay coil to close and finally controls the thyristor to turn on; (3) Load status detection: The microcontroller collects the current signal through the ADC interface. Calculate the main circuit current value; if the current value is less than or equal to the preset no-load current value, it is considered to be in the no-load current threshold state, and then proceed to the next step; if the current value is greater than the preset no-load current value, the microcontroller first outputs a turn-off signal to the thyristor, and after the current drops to the no-load current threshold, proceed to the next step; (4) Relay switching: the microcontroller monitors the external control signal in real time. When the external forward and reverse signals change, the thyristor output is turned off first, and the current detection circuit confirms that there is no current passing through the load before switching the relay on or off, and then the thyristor output is turned on, thereby realizing the switching of forward and reverse, and the relay switching action when there is no load.

Images