Normally-closed bidirectional solid state relay

Abstract

The invention provides a normally-closed bidirectional solid state relay. Comprising an input circuit, an isolation driving circuit, a field effect transistor Q2 and a field effect transistor Q3, the input circuit is connected with an input positive terminal and an input negative terminal, the input end of the isolation driving circuit is connected with the input circuit, and the field effect transistor Q2 is connected with the source electrode and the grid electrode of the field effect transistor Q3 in parallel and then connected with the output end of the isolation driving circuit. The drain electrode of the field effect transistor Q2 and the drain electrode of the field effect transistor Q3 are connected with the two output terminals respectively. The turn-on voltage and the turn-off voltage of the solid relay are easier to adjust through the voltage stabilizing diode, so that the input voltage range of the solid relay is wide; input current limiting can be adjusted through the current limiting circuit; and the output realizes bidirectional switching, and meanwhile, the electromagnetic interference is reduced, and the reliability is very high.

Description

Technical Field

[0001] The invention relates to a normally closed bidirectional solid-state relay. Background Art

[0002] As solid-state relay products become more and more numerous, with complex models and various functions, the existing normally closed solid-state relay output does not have a two-way use function and cannot meet the user's requirements for two-way use; and the existing normally closed solid-state relay has a small input voltage range and cannot be used in situations with a wider range of input voltage.

[0003] For example, a normally closed solid relay disclosed in CN114465609A uses a field effect tube V2 as an output device, and its gate is connected to the output power supply + through a resistor R1 as the excitation end of the field effect tube, the drain is used as the output end to connect the load RL, and the source is used as the low power end to connect the output power supply -. When there is no input loaded on the isolation circuit, the field effect tube V2 is in the on state; when the input is loaded on the isolation circuit, the isolation circuit connects the gate of the field effect tube V2 to the output power supply -, so that the field effect tube V2 is in the off state; the entire circuit realizes the conduction of the output end of the normally closed solid relay in the state of no bias power supply. However, the positive and negative poles of the output end are fixed, and can only output in one direction.

[0004] For example, CN216751702U discloses a normally closed solid relay and its packaging structure, which uses a P-MOS tube Q2 as an output switch. When the input power is turned off and the load power is turned on, the output end of the optical isolator U1 is cut off. At this time, the source voltage of the P-MOS tube Q2 is higher than the gate voltage, the P-MOS tube Q2 is turned on, and the relay is in the on (normally closed) state. When the input power is turned on, the output end of the optical isolator U1 is turned on, the gate-source potential difference of the P-MOS tube Q2 is not enough to turn on the P-MOS tube Q2, the P-MOS tube Q2 is cut off, and the relay is in the off state, thereby realizing the normally closed function of the solid relay. And it also forms a current stabilization circuit through transistor Q1, voltage regulator D1, and resistor R1. The voltage stabilization of voltage regulator D1 makes the voltage across the optical isolator U1 and resistor R2 basically stable. The changing voltage is shared by transistor Q1. The current flowing through the optical isolator U1 is maintained at the set value, avoiding the increase of input power consumption. The stable input current allows the input voltage to work in a wider range. However, its output end can only output in one direction. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a normally closed bidirectional solid-state relay.

[0006] The present invention is achieved through the following technical solutions.

[0007] The present invention provides a normally closed bidirectional solid-state relay, comprising an input circuit, an isolation drive circuit field effect tube Q2, and a field effect tube Q3, wherein the input circuit is respectively connected to an input positive terminal and an input negative terminal, the input end of the isolation drive circuit is connected to the input circuit, the source and gate of the field effect tube Q2 and the field effect tube Q3 are respectively connected in parallel and then respectively connected to the output end of the isolation drive circuit, and the drains of the field effect tube Q2 and the field effect tube Q3 are respectively connected to two output terminals.

[0008] The input circuit includes a field effect transistor Q1, the drain of which is connected to the input positive terminal, the source and the gate of which are connected to the resistor R1 and the resistor R2 respectively, and the other ends of the resistor R1 and the resistor R2 are connected to the input positive terminal of the isolation drive circuit.

[0009] The isolation driving circuit includes a light-emitting diode D1 and a photovoltaic E1. The positive electrode of the light-emitting diode D1 is connected to the input circuit, and the negative electrode is connected to the input negative terminal; the positive electrode of the photovoltaic E1 is connected to the source of the field effect transistor Q2 and the field effect transistor Q3, and the negative electrode is connected to the gate of the field effect transistor Q2 and the field effect transistor Q3.

[0010] A switching diode D2 and a voltage regulator diode D3 are connected in sequence between the cathode of the light emitting diode D1 and the negative input terminal.

[0011] The beneficial effects of the present invention are: the on-voltage and off-voltage of the solid-state relay are easier to adjust through the voltage-stabilizing diode, so that its input voltage range is wide; the input current limiting circuit makes the input current limiting adjustable; and the output realizes a bidirectional switch, while reducing electromagnetic interference and having high reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a schematic diagram of the principle of the present invention;

[0013] Figure 2 It is a schematic diagram of the circuit principle of the present invention;

[0014] Figure 3 This is a schematic diagram of the structure of Embodiment 1 of the present invention;

[0015] Figure 4 This is a schematic diagram of the structure of Example 2 of the present invention. DETAILED DESCRIPTION

[0016] The technical solution of the present invention is further described below, but the scope of protection claimed is not limited to the description.

[0017] The present invention provides a normally closed bidirectional solid-state relay, comprising an input circuit, an isolation drive circuit field effect tube Q2, and a field effect tube Q3, wherein the input circuit is connected to an input positive terminal and an input negative terminal respectively, the input end of the isolation drive circuit is connected to the input circuit, the source and gate of the field effect tube Q2 and the field effect tube Q3 are respectively connected in parallel and then connected to the output end of the isolation drive circuit respectively, and the drains of the field effect tube Q2 and the field effect tube Q3 are respectively connected to two output terminals. When no voltage or control signal is applied between the positive and negative inputs of the solid-state relay, the gate voltages of the field effect tubes Q2 and Q3 are zero, and since the field effect tubes Q2 and Q3 are depletion-type field effect tubes, the field effect tubes Q2 and Q3 are bidirectionally conductive. When a given voltage or control signal is applied between the positive and negative inputs of the solid-state relay, the input current is supplied to the light-emitting diode D1 through the current limiting circuit composed of the field effect tube Q1, the resistor R1, and the resistor R2, and then flows back through the switching diode D2 and the voltage-stabilizing diode D3; the light-emitting diode D1 emits infrared light to illuminate the photovoltaic E1, and at this time the photovoltaic output voltage and current are supplied to the gates of the field effect tubes Q2 and Q3, so that the gates of the field effect tubes Q2 and Q3 generate negative voltages, and at the same time the drain and source of the field effect tubes Q2 and Q3 are turned off.

[0018] Furthermore, the input circuit includes a field effect transistor Q1, the drain of the field effect transistor Q1 is connected to the input positive terminal, the source and the gate are connected to the resistor R1 and the resistor R2 respectively, and the other ends of the resistor R1 and the resistor R2 are connected to the input positive terminal of the isolation drive circuit. The current limiting circuit composed of the field effect transistor Q1, the resistor R1 and the resistor R2 can adapt to a relatively wide input voltage range, and the current can be limited within a set range.

[0019] Furthermore, the isolated driving circuit includes a light emitting diode D1 and a photovoltaic E1, wherein the positive electrode of the light emitting diode D1 is connected to the input circuit, and the negative electrode is connected to the input negative terminal; the positive electrode of the photovoltaic E1 is connected to the source electrode of the field effect transistor Q2 and the field effect transistor Q3, and the negative electrode is connected to the gate electrode of the field effect transistor Q2 and the field effect transistor Q3. The light emitting diode D1 and the photovoltaic E1 form an isolated driving circuit. Multiple groups of isolated driving circuits can also be used to form an isolated driving circuit to output a larger driving current.

[0020] Furthermore, a switch diode D2 and a voltage regulator diode D3 are sequentially connected between the cathode of the light emitting diode D1 and the input negative terminal. The reverse cut-off voltage of the switch diode protects the input circuit to prevent the input voltage from damaging the input circuit in reverse.

[0021] When the input end of the solid relay is not powered, the gates of the output depletion-type field effect transistors Q2 and Q3 have no voltage. At this time, the drain-source of the depletion-type field effect transistors Q2 and Q3 is in the on state, that is, the drain of the depletion-type field effect transistor Q2 and the drain of Q3 are in the on state. When the input voltage is added, after passing through the current limiting circuit composed of the field effect transistor Q1, the resistor R1 and the resistor R2, the current flows back through the light-emitting diode D1, the switching diode D2 and the voltage-stabilizing diode D3. Among them, the switching diode D2 can prevent the damage to the input circuit after the input voltage is reversed, and the voltage-stabilizing diode D3 is used to adjust the on-voltage and off-voltage of the solid relay; the light-emitting diode D1 and the photovoltaic E1 form an optical isolation driving circuit. When the light-emitting diode D1 passes the current, it emits infrared light, which irradiates the photovoltaic E1, so that the photovoltaic E1 generates voltage and current to drive the field effect transistors Q2 and Q3. At this time, the gates of the depletion-type field effect transistors Q2 and Q3 have voltage, and the drain-source of the depletion-type field effect transistors Q2 and Q3 is closed, that is, the solid relay is in the off state.

[0022] Example 1: Figure 3 As shown, the input control voltage or control signal is added to the input end, and the output power supply and output load RL are added to the output. When no power supply or control signal is added to the input, the output power supply forms a conduction path through the field effect tubes Q2, Q3 and the load resistor RL of the normally closed optical isolation bidirectional solid-state relay, and the current passes through the load resistor RL. At this time, the output current flows back from the positive output power supply, the field effect tubes Q2 and Q3 of the solid-state relay to the negative output power supply and the load resistor RL to form a loop; when the input applies power or control signal, the gates of the field effect tubes Q2 and Q3 of the normally closed optical isolation bidirectional solid-state relay will have a driving voltage, and at this time, the drain and source of the field effect tubes Q2 and Q3 are closed, so no current flows through the load RL, and the load does not work.

[0023] Example 2: Figure 4 As shown, the input control voltage or control signal is added to the input end, and the output power supply and output load RL are added to the output. When no power supply or control signal is added to the input, the output power supply forms a conduction path through the load resistor RL and the field effect tubes Q2 and Q3 of the normally closed optical isolation bidirectional solid-state relay. At this time, the load resistor RL passes the current, and the output current flows back from the positive output power supply, the load resistor RL, the field effect tubes Q2 and Q3 of the solid-state relay to the negative output power supply to form a loop; when the input applies power or control signal, the gates of the field effect tubes Q2 and Q3 of the normally closed optical isolation bidirectional solid-state relay will have a driving voltage, and at this time, the drain and source of the field effect tubes Q2 and Q3 are closed, so no current flows through the load RL, and the load does not work.

Claims

1. A normally closed bidirectional solid-state relay, characterized in that: It includes an input circuit, an isolation drive circuit field effect transistor Q2, and a field effect transistor Q3. The input circuit is connected to the input positive terminal and the input negative terminal respectively, the input end of the isolation drive circuit is connected to the input circuit, the source and gate of the field effect transistor Q2 and the field effect transistor Q3 are respectively connected in parallel and then connected to the output end of the isolation drive circuit respectively, and the drains of the field effect transistor Q2 and the field effect transistor Q3 are respectively connected to the two output terminals.

2. The normally closed bidirectional solid-state relay according to claim 1, characterized in that: The input circuit includes a field effect transistor Q1, the drain of which is connected to the input positive terminal, the source and the gate of which are connected to the resistor R1 and the resistor R2 respectively, and the other ends of the resistor R1 and the resistor R2 are connected to the input positive terminal of the isolation drive circuit.

3. The normally closed bidirectional solid-state relay according to claim 1, characterized in that: The isolation driving circuit includes a light-emitting diode D1 and a photovoltaic E1. The positive electrode of the light-emitting diode D1 is connected to the input circuit, and the negative electrode is connected to the input negative terminal; the positive electrode of the photovoltaic E1 is connected to the source of the field effect transistor Q2 and the field effect transistor Q3, and the negative electrode is connected to the gate of the field effect transistor Q2 and the field effect transistor Q3.

4. The normally closed bidirectional solid-state relay according to claim 3, characterized in that: A switching diode D2 and a voltage regulator diode D3 are connected in sequence between the cathode of the light emitting diode D1 and the negative input terminal.

Images