Solid-state relay power-on slow start circuit and solid-state relay

Abstract

The utility model discloses a solid-state relay power-on slow start circuit and a solid-state relay, and relates to the technical field of solid-state relay design. The slow start module is used for transmitting a control signal to a control signal output end in a delayed manner; the current limiting circuit is used for limiting the input current of the solid-state relay; the control signal output end is used for outputting a control signal to the solid-state relay; the slow start module is electrically connected with the control signal output end, and the control signal output end is electrically connected with the solid-state relay. According to the scheme, through the cooperation of the slow start module and the current limiting circuit, the current generated during fast switching of the solid-state relay is reduced by several times to dozens of times, the output current limitation of the preceding-stage DC power supply is reduced, and the type selection power of the DC power supply can be smaller; the power-on impact current of the solid-state relay is reduced, and the service life of post-stage equipment of the solid-state relay can be prolonged.

Description

Technical Field

[0001] This utility model relates to the field of solid-state relay design technology, specifically to a solid-state relay power-on soft-start circuit and a solid-state relay. Background Technology

[0002] In power system design, solid-state relays (SSRs) are often used as switching switches for power supply due to their advantages such as high reliability, long lifespan, fast response, and lack of mechanical contacts. Compared to traditional mechanical relays, solid-state relays have faster switching speeds (typically between tens and hundreds of microseconds) and are simple to operate, requiring only a 5V to 24V voltage signal to be applied to the control terminal to achieve on / off control.

[0003] However, in practical applications, especially when there are large-capacity capacitive loads (such as energy storage capacitors and filter capacitors) in the subsequent circuits, the fast turn-on characteristic of solid-state relays can lead to serious inrush current problems. When the input DC power supply has been stably powered on, and the solid-state relay suddenly closes, the large-capacity capacitor in the subsequent stage will be charged in an extremely short time (microseconds), causing the input current to surge instantaneously, potentially reaching several times or even tens of times the normal operating current. This large current surge can cause the following problems:

[0004] Input power overcurrent protection trigger: If the current limiting capability of the DC power supply is insufficient, it may cause the power supply to enter the protection state, or even damage the power supply module.

[0005] Solid-state relay overload damage: Although solid-state relays usually have a certain surge protection capability, frequent high current surges may still shorten their lifespan or cause them to fail.

[0006] Decreased system stability: Inrush current may cause the input voltage to drop, affecting the normal operation of other circuits.

[0007] Currently, common solutions to this problem include: connecting a current-limiting resistor in series at the output of the solid-state relay to slow down the capacitor charging speed, but this method introduces additional power consumption and reduces system efficiency; using a soft-start circuit (such as an NTC thermistor or MOSFET soft-start circuit), but this increases system complexity and cost; or choosing a solid-state relay with higher current tolerance, but this can only alleviate the problem and cannot fundamentally eliminate inrush current.

[0008] Therefore, how to effectively suppress the surge current caused by the large-capacity capacitor load in the downstream stage while maintaining the fast switching advantage of solid-state relays has become a key challenge in power system design. Summary of the Invention

[0009] The technical problem this invention aims to solve is to effectively suppress the inrush current caused by large-capacity capacitor loads in the downstream stage while maintaining the advantages of fast switching of solid-state relays. The purpose is to provide a power-on soft-start circuit for solid-state relays and a solid-state relay itself. Based on traditional technology, the circuit structure is improved. Through the cooperation of the soft-start module and the current limiting circuit, the current generated when the solid-state relay switches quickly is reduced by several times to tens of times, reducing the output current limit of the front-end DC power supply and allowing for a smaller power selection for the DC power supply. The reduced power-on inrush current of the solid-state relay also extends the service life of the downstream equipment.

[0010] This utility model is achieved through the following technical solution:

[0011] This solution provides a solid-state relay power-on soft-start circuit, including:

[0012] A control signal source is used to generate control signals for the solid-state relay; the control signal source is electrically connected to the soft-start module.

[0013] The soft-start module is used to delay the transmission of control signals to the control signal output terminal;

[0014] A current limiting circuit is used to limit the input current of the solid-state relay; the current limiting circuit is electrically connected to the soft-start module;

[0015] The control signal output terminal is used to output a control signal to the solid-state relay; the soft-start module is electrically connected to the control signal output terminal, and the control signal output terminal is electrically connected to the solid-state relay.

[0016] A further optimized solution is that the control signal source includes a control signal connector and a voltage protection circuit;

[0017] Both the first and second output terminals of the control signal connector are connected to the soft-start module.

[0018] The voltage protection circuit includes a diode D4, with the positive terminal of diode D4 connected to the second output terminal of the control signal connector and the negative terminal of diode D4 connected to the first output terminal of the control signal connector.

[0019] A further optimized solution is that the soft-start module includes a charging circuit, a discharge circuit, and a delay switch circuit that are electrically connected to each other;

[0020] The charging circuit is used to charge the delay switch circuit; the discharge circuit is used to release the stored electrical energy in the charging circuit; the delay switch circuit is used to achieve delayed conduction between the control signal source and the control signal output terminal.

[0021] A further optimized solution is that the charging circuit includes: resistor R7, resistor R8, and capacitor C2;

[0022] One end of resistor R7 is connected to the first output terminal of the control signal connector, and the other end is connected to the second output terminal of the control signal connector after being connected in series with capacitor C2.

[0023] Resistor R8 is connected in parallel across capacitor C2.

[0024] A further optimized solution is that the discharge circuit includes a resistor R6 and a diode D3;

[0025] One end of resistor R6 is connected to the first output terminal of the control signal connector, and the other end is connected to the negative terminal of diode D3. The positive terminal of diode D3 is connected between resistor R7 and capacitor C2.

[0026] A further optimized solution is that the delay switching circuit includes: PMOS transistor Q1, NMOS transistor Q2, resistor R4, resistor R3, and resistor R9;

[0027] The gate of NMOS transistor Q2 is connected between resistor R7 and capacitor C2. The source of NMOS transistor Q2 is connected to the second output terminal of the control signal connector. The drain of NMOS transistor Q2 is connected to the gate of PMOS transistor Q1 after being connected in series with resistors R9 and R3.

[0028] The source (S) terminal of PMOS transistor Q1 is connected to the first output terminal of the control signal connector, and the drain (D) terminal of PMOS transistor Q1 is connected to the first input port of the control signal output terminal.

[0029] One end of resistor R4 is connected to the first output terminal of the control signal connector, and the other end is connected between resistors R9 and R3.

[0030] A further optimization is that the delay switching circuit also includes diode D5 and diode D6;

[0031] The positive terminal of diode D5 is connected to the source (S) terminal of NMOS transistor Q2, and the negative terminal of diode D5 is connected to the gate (G) terminal of NMOS transistor Q2.

[0032] The cathode of diode D6 is connected to the source (S) of PMOS transistor Q1, and the anode of diode D6 is connected between resistors R9 and R3.

[0033] A further optimized solution is that the current limiting circuit includes resistors R1 and R2;

[0034] One end of resistor R1 is connected to the source (S) terminal of PMOS transistor Q1, and the other end is connected in series with resistor R2 to the first input port of the control signal output terminal.

[0035] A further optimized solution is to electrically connect a solid-state relay to the output side of the control signal output terminal.

[0036] This solution also provides a solid-state relay, including the aforementioned solid-state relay power-on soft-start circuit.

[0037] Compared with the prior art, this utility model has the following advantages and beneficial effects:

[0038] This solution provides a power-on soft-start circuit for a solid-state relay and a solid-state relay itself. By combining the soft-start module and the current-limiting circuit, the current generated during rapid switching of the solid-state relay is reduced by several to tens of times, thereby reducing the output current limit of the front-end DC power supply and allowing for a smaller power rating of the selected DC power supply. It also reduces the power-on inrush current of the solid-state relay and extends the service life of the downstream equipment.

[0039] This solution provides a solid-state relay power-on soft-start circuit and a solid-state relay; the circuit does not require additional power supply or control interface, and has many advantages such as fewer components, low power consumption, low cost, and small area. Attached Figure Description

[0040] The accompanying drawings, which are included to provide a further understanding of the embodiments of the present invention and form part of this application, do not constitute a limitation thereof. In the drawings:

[0041] Figure 1 A schematic diagram of the power-on soft-start circuit structure for a solid-state relay;

[0042] Figure 2 A schematic diagram illustrating the application of a power-on soft-start circuit for a solid-state relay.

[0043] Figure 3 This is a schematic diagram of a solid-state relay. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of this utility model are only used to explain this utility model and are not intended to limit this utility model.

[0045] Maintaining the fast switching advantage of solid-state relays while effectively suppressing inrush current from large-capacity capacitor loads in the downstream stage has become a key challenge in power system design. Therefore, this solution provides the following embodiments to address the aforementioned technical problems: Example

[0046] This embodiment provides a power-on soft-start circuit for a solid-state relay, such as... Figure 1 and Figure 2 As shown, it includes:

[0047] A control signal source is used to generate control signals for the solid-state relay; the control signal source is electrically connected to the soft-start module.

[0048] The soft-start module is used to delay the transmission of control signals to the control signal output terminal;

[0049] A current limiting circuit is used to limit the input current of the solid-state relay; the current limiting circuit is electrically connected to the soft-start module;

[0050] The control signal output terminal is used to output a control signal to the solid-state relay; the soft-start module is electrically connected to the control signal output terminal, and the control signal output terminal is electrically connected to the solid-state relay.

[0051] The control signal source includes a control signal connector and a voltage protection circuit;

[0052] Both the first and second output terminals of the control signal connector are connected to the soft-start module.

[0053] The voltage protection circuit includes a diode D4, with the positive terminal of diode D4 connected to the second output terminal of the control signal connector and the negative terminal of diode D4 connected to the first output terminal of the control signal connector.

[0054] The soft-start module includes a charging circuit, a discharge circuit, and a time-delay switch circuit that are electrically connected to each other.

[0055] The charging circuit is used to charge the delay switch circuit; the discharge circuit is used to release the stored electrical energy in the charging circuit; the delay switch circuit is used to achieve delayed conduction between the control signal source and the control signal output terminal.

[0056] The charging circuit includes: resistor R7, resistor R8, and capacitor C2;

[0057] One end of resistor R7 is connected to the first output terminal of the control signal connector, and the other end is connected to the second output terminal of the control signal connector after being connected in series with capacitor C2.

[0058] Resistor R8 is connected in parallel across capacitor C2.

[0059] The discharge circuit includes a resistor R6 and a diode D3;

[0060] One end of resistor R6 is connected to the first output terminal of the control signal connector, and the other end is connected to the negative terminal of diode D3. The positive terminal of diode D3 is connected between resistor R7 and capacitor C2.

[0061] The delay switching circuit includes: PMOS transistor Q1, NMOS transistor Q2, resistor R4, resistor R3 and resistor R9;

[0062] The gate of NMOS transistor Q2 is connected between resistor R7 and capacitor C2. The source of NMOS transistor Q2 is connected to the second output terminal of the control signal connector. The drain of NMOS transistor Q2 is connected to the gate of PMOS transistor Q1 after being connected in series with resistors R9 and R3.

[0063] The source (S) terminal of PMOS transistor Q1 is connected to the first output terminal of the control signal connector, and the drain (D) terminal of PMOS transistor Q1 is connected to the first input port of the control signal output terminal.

[0064] One end of resistor R4 is connected to the first output terminal of the control signal connector, and the other end is connected between resistors R9 and R3.

[0065] The delay switching circuit also includes diodes D5 and D6;

[0066] The positive terminal of diode D5 is connected to the source (S) terminal of NMOS transistor Q2, and the negative terminal of diode D5 is connected to the gate (G) terminal of NMOS transistor Q2.

[0067] The cathode of diode D6 is connected to the source (S) of PMOS transistor Q1, and the anode of diode D6 is connected between resistors R9 and R3.

[0068] The current limiting circuit includes resistors R1 and R2;

[0069] One end of resistor R1 is connected to the source (S) terminal of PMOS transistor Q1, and the other end is connected in series with resistor R2 to the first input port of the control signal output terminal.

[0070] The output side of the control signal output terminal is electrically connected to a solid-state relay.

[0071] The control signal output terminal also includes a resistor R5 and a capacitor C1; one end of the resistor R5 is connected to the second input port of the control signal output terminal, and the other end is connected to the first input port of the control signal output terminal, and the capacitor C1 is connected in parallel on both sides of the resistor R5.

[0072] In this embodiment, the solid-state relay is powered by 24V, the equivalent capacitance at the load end is 2000μF, and the current can be reduced from 118A to about 20A; capacitor C1 is 2.2nF, capacitor C2 is 4.7nF, diode D3 is a DSS310, diode D4 is a PTVS30VS1UR115; diodes D5 and D6 are BZT52C15; resistors R1 and R2 are both 1.1kΩ; resistors R4, R9, and R8 are all 10 kΩ; resistor R5 is 22kΩ; resistor R6 is 100Ω; and resistor R7 is 51kΩ.

[0073] Solid-state relay principle as follows Figure 3 As shown, the solid-state relay internally consists of a linear optocoupler and a transistor amplifier circuit. The optocoupler input current I...F Once the turn-on current is reached, the collector and emitter terminals of the transistor will conduct and exhibit a certain impedance R. CE Optocoupler input current I F When the solid-state relay reaches its turn-on current threshold, the transistor is in amplification mode within a certain range. At this time, transistor R... CE Relatively large; when the input current I F As the transistor continues to grow, it will reach a certain value before it enters a saturated conduction state. At this point, R... CE The resistance will become extremely small.

[0074] In the solid-state relay power-on soft-start circuit, the control signal is input through control signal connector J1 and output to the solid-state relay's control interface through control signal output connector J2. A current-limiting circuit composed of resistors R1 and R2 limits the input current I of the solid-state relay during the initial power-on phase. F Because the gate-source drive voltage of NMOS transistor Q2 has a threshold value V. gsTH The input signal is charged to V through the charging circuit (resistor R7, capacitor C2 and resistor R8). gsTH Delay time T d Delay time T d Afterwards, NMOS transistor Q2 turns on, and resistors R4 and R9 generate a voltage divider to provide a negative voltage drive signal to the gate-source (GS) junction of PMOS transistor Q1. Then, PMOS transistor Q1 turns on, and its internal resistance R... dson Approximately 0Ω, resistors R1 and R2 are short-circuited, stopping the limiting of the solid-state relay's input current and allowing it to operate in saturation conduction. Diode D4 provides protection against abnormal control signal voltages, while diodes D5 and D6 limit the gate-source (GS) drive voltages of NMOS transistor Q2 and PMOS transistor Q1, respectively. The bleeder circuit composed of resistor R6 and diode D3 quickly releases the voltage across capacitor C2. Capacitor C1 filters the output signal; when interference exists in the control signal input, capacitor C1 can perform conditional filtering. Resistor R5 is the matching resistor for the solid-state relay's input, providing anti-interference capabilities. Simultaneously, when powered down, resistor R5 also serves to bleed voltage from capacitor C1.

[0075] The control signal from control signal connector J1 rises rapidly, but PMOS transistor Q1 does not immediately turn on. After being current-limited by resistors R1 and R2, the control signal is given to the input terminal of the solid-state relay, limiting the input current I of the solid-state relay. F At this time, the solid-state relay transistor is in amplification mode, R CE The resistance is relatively large. The R value is relatively large. CE This will limit the current supplied by the DC power supply at the front end of the solid-state relay to charge the downstream load capacitor Cload. This is because the gate-source drive voltage of the NMOS transistor Q2 has a threshold voltage V.gsTH The input signal is charged to V through resistor R7, capacitor C2, and resistor R8. gsTH The time is T d After T d After a certain time, NMOS transistor Q2 turns on, and the voltage divider between resistors R4 and R9 provides a sufficient drive voltage for PMOS transistor Q1 to turn on. Afterward, PMOS transistor Q1 saturates and conducts. The on-resistance R of PMOS transistor Q1... dson The current is almost 0Ω, and resistors R1 and R2 are short-circuited. After this, the drive current of the solid-state relay is no longer externally limited, and the solid-state relay is in a saturated conduction state, no longer limiting the supply current from the preceding DC power supply to the following stage. When the control signal is turned off, the bleeder circuit composed of resistor R6 and diode D3 quickly releases the voltage across capacitor C2, enabling the control circuit to achieve a normal restart with rapid power-on and power-off cycles.

[0076] When a solid-state relay is powered on, the already powered-on DC power supply causes a significant current surge during the rapid charging of the downstream capacitive load. This solution, through reasonable adjustment of component parameters, can reduce the current generated during the rapid switching of the solid-state relay by several to tens of times, lowering the output current limit of the upstream DC power supply and allowing for the selection of a smaller power supply. The reduced power-on inrush current also extends the lifespan of the downstream equipment. Furthermore, the improved circuitry does not require additional power supply or control interfaces, offering advantages such as fewer components, lower power consumption, lower cost, and smaller footprint. Example

[0077] This embodiment provides a solid-state relay, including the power-on soft-start circuit of the solid-state relay described in Embodiment 1.

[0078] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of this utility model. It should be understood that the above description is only a specific embodiment of this utility model and is not intended to limit the scope of protection of this utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the scope of protection of this utility model.

Claims

1. A solid state relay soft start circuit, comprising: include: A control signal source is used to generate control signals for solid-state relays; The control signal source is electrically connected to the soft start module; The soft-start module is used to delay the transmission of control signals to the control signal output terminal; A current limiting circuit is used to limit the input current of the solid-state relay; the current limiting circuit is electrically connected to the soft-start module; The control signal output terminal is used to output a control signal to the solid-state relay; the soft-start module is electrically connected to the control signal output terminal, and the control signal output terminal is electrically connected to the solid-state relay.

2. A solid state relay soft start circuit according to claim 1, wherein The control signal source includes a control signal connector and a voltage protection circuit; Both the first and second output terminals of the control signal connector are connected to the soft-start module. The voltage protection circuit includes a diode D4, with the positive terminal of diode D4 connected to the second output terminal of the control signal connector and the negative terminal of diode D4 connected to the first output terminal of the control signal connector.

3. A solid state relay soft start circuit according to claim 2, wherein The soft-start module includes a charging circuit, a discharge circuit, and a time-delay switch circuit that are electrically connected to each other. The charging circuit is used to charge the delay switch circuit; the discharge circuit is used to release the stored electrical energy in the charging circuit; the delay switch circuit is used to achieve delayed conduction between the control signal source and the control signal output terminal.

4. The solid state relay soft start circuit of claim 3, wherein, The charging circuit includes: resistor R7, resistor R8, and capacitor C2; One end of resistor R7 is connected to the first output terminal of the control signal connector, and the other end is connected to the second output terminal of the control signal connector after being connected in series with capacitor C2. Resistor R8 is connected in parallel across capacitor C2.

5. A solid state relay soft start circuit according to claim 4, wherein The discharge circuit includes a resistor R6 and a diode D3; One end of resistor R6 is connected to the first output terminal of the control signal connector, and the other end is connected to the negative terminal of diode D3. The positive terminal of diode D3 is connected between resistor R7 and capacitor C2.

6. A solid state relay soft start circuit according to claim 5, wherein, The delay switch circuit includes: PMOS transistor Q1, NMOS transistor Q2, resistor R4, resistor R3 and resistor R9; The gate of NMOS transistor Q2 is connected between resistor R7 and capacitor C2. The source of NMOS transistor Q2 is connected to the second output terminal of the control signal connector. The drain of NMOS transistor Q2 is connected to the gate of PMOS transistor Q1 after being connected in series with resistors R9 and R3. The source (S) terminal of PMOS transistor Q1 is connected to the first output terminal of the control signal connector, and the drain (D) terminal of PMOS transistor Q1 is connected to the first input port of the control signal output terminal. One end of resistor R4 is connected to the first output terminal of the control signal connector, and the other end is connected between resistors R9 and R3.

7. A solid state relay soft start circuit according to claim 6, wherein The delay switch circuit also includes diode D5 and diode D6; The positive terminal of diode D5 is connected to the source (S) terminal of NMOS transistor Q2, and the negative terminal of diode D5 is connected to the gate (G) terminal of NMOS transistor Q2. The cathode of diode D6 is connected to the source (S) of PMOS transistor Q1, and the anode of diode D6 is connected between resistors R9 and R3.

8. The solid state relay soft start circuit of claim 6, wherein, The current limiting circuit includes resistors R1 and R2; One end of resistor R1 is connected to the source (S) terminal of PMOS transistor Q1, and the other end is connected in series with resistor R2 to the first input port of the control signal output terminal.

9. The solid state relay soft start circuit of claim 6, wherein, The output side of the control signal output terminal is electrically connected to a solid-state relay.

10. A solid state relay characterized by, Includes the solid-state relay power-on soft-start circuit as described in any one of claims 1-9.

Images