A high-isolation solid state relay circuit

Abstract

The application relates to the technical field of solid-state relay switch circuits, and discloses a high-isolation solid-state relay circuit, which comprises a control end circuit and an analog end circuit, wherein the control end circuit comprises three groups of gate controllers; the analog end circuit comprises three groups of solid-state relay units, and the three groups of solid-state relay units form a T-type circuit structure; each group of solid-state relay units comprises two N-type MOSFETs; the control end circuit is connected with the analog end circuit in correspondence; when the circuit is turned on, the first group of solid-state relay units and the third group of solid-state relay units are turned on, and the second group of solid-state relay units is turned off; when the circuit is turned off, the first group of solid-state relay units and the third group of solid-state relay units are turned off, and the second group of solid-state relay units is turned on. The circuit can realize switching speed in the order of ns, the turn-off isolation degree is below -120 dB under the condition of a 10 kHz frequency and a megohm-level load impedance, and AC and DC signals can be efficiently controlled.

Description

Technical Field

[0001] This application relates to the field of solid-state relay switching circuit technology, and in particular to a solid-state relay circuit with high isolation. Background Technology

[0002] Solid-state relays have crucial applications in many fields: in battery-powered systems, the extremely low power consumption of solid-state electrical switches at the control end can meet the switching requirements of low-power scenarios such as IoT devices; in industrial automation, such as PLC output modules and robot control, solid-state relays are suitable for controlling DC loads that require frequent switching (such as solenoid valves and LED lighting); in semiconductor testing, pulse power supplies, and other scenarios requiring rapid switching, solid-state relays, as a type of analog switch, can perform high-efficiency and high-isolation switching operations.

[0003] In the field of high-precision measurement of precision electronic equipment, such as precision automated measurement and radio frequency applications, automatic switching systems have important application value. The design of high-efficiency and interference-resistant automatic switching systems is widely used in related fields. Designing a long-life, high-isolation, and low-cost solid-state relay switch has become the focus of switch design. Summary of the Invention

[0004] The purpose of this application is to provide a solid-state relay circuit with high isolation to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the following technical solution is adopted:

[0006] This application provides a high-isolation solid-state relay circuit, including a control terminal circuit and an analog terminal circuit;

[0007] The control circuit includes three sets of gate controllers, each set of gate controllers is controlled by TTL digital level, and the VDD ports of the three sets of gate controllers are all connected to DC voltage source VDD and digital ground.

[0008] The analog terminal circuit includes three sets of solid-state relay units, which form a T-type circuit structure. The output terminal of the first set of solid-state relay units is connected to the input terminal of the second set of solid-state relay units and the input terminal of the third set of solid-state relay units. The output terminal of the second set of solid-state relay units is connected to the analog ground, and the output terminal of the third set of solid-state relay units is the circuit output terminal.

[0009] Each of the solid-state relay units includes two N-type MOSFETs, and the sources of the two N-type MOSFETs are connected. The signal flows in from the drain of one N-type MOSFET and flows out from the drain of the other N-type MOSFET.

[0010] The control terminal circuit is connected to the analog terminal circuit. Each group of gate controllers drives the corresponding group of solid-state relay units. When the circuit is on, the first group of solid-state relay units and the third group of solid-state relay units are on, and the second group of solid-state relay units is off. When the circuit is off, the first group of solid-state relay units and the third group of solid-state relay units are off, and the second group of solid-state relay units is on.

[0011] Preferably, in the above-mentioned high-isolation solid-state relay circuit, the N-type MOSFET is an N-type MOS transistor with high voltage resistance and low input capacitance.

[0012] Preferably, in the above-mentioned high-isolation solid-state relay circuit, in the control terminal circuit:

[0013] The first group of gate controllers is connected to the first pre-stage impedance and the first filter capacitor, and the control level is accessed through the first pre-stage impedance.

[0014] The second set of gate controllers is connected to the second pre-stage impedance and the pre-stage inverter, and the control level is accessed through the pre-stage inverter and the second pre-stage impedance.

[0015] The third gate controller is connected to the third pre-stage impedance and the third filter capacitor, and the control level is accessed through the third pre-stage impedance.

[0016] Preferably, in the above-mentioned high-isolation solid-state relay circuit, the impedance values ​​of the first pre-stage impedance, the second pre-stage impedance, and the third pre-stage impedance are the same.

[0017] Preferably, in the above-mentioned high-isolation solid-state relay circuit, in the analog terminal circuit:

[0018] The first group of solid-state relay units includes two N-type MOSFETs, whose sources are connected to the SOURCE port of the first group of gate controllers, and whose gates are connected to the GATE port of the first group of gate controllers.

[0019] The second group of solid-state relay units includes two N-type MOSFETs, whose sources are connected to the SOURCE port of the second group of gate controllers, and whose gates are connected to the GATE port of the second group of gate controllers.

[0020] The third group of solid-state relay units includes two N-type MOSFETs, whose sources are connected to the SOURCE port of the third group of gate controllers, and whose gates are connected to the GATE port of the third group of gate controllers.

[0021] Preferably, in the above-mentioned high-isolation solid-state relay circuit, the gate controller adopts an isolation switch gate drive scheme, and the isolation method includes capacitive isolation, optocoupler isolation, or RF signal isolation.

[0022] Preferably, in the above-mentioned high-isolation solid-state relay circuit, the circuit is normally open. When the control level is 0V, the first group of solid-state relay units and the third group of solid-state relay units are turned on, and the second group of solid-state relay units is turned off. When the control level is a TTL high level, the first group of solid-state relay units and the third group of solid-state relay units are turned off, and the second group of solid-state relay units are turned on.

[0023] Preferably, in the above-mentioned high-isolation solid-state relay circuit, when the input signal frequency is 10kHz and the load impedance is in the megohm range, the circuit's turn-off isolation reaches below -120dB.

[0024] Preferably, in the above-mentioned high-isolation solid-state relay circuit, the switching speed of the circuit is on the order of nanoseconds.

[0025] Preferably, in the above-mentioned high-isolation solid-state relay circuit, a voltage follower is connected to the circuit output terminal, and the voltage follower is used to compensate for the on-resistance of the circuit.

[0026] This application achieves the following significant technical effects:

[0027] This application provides a high-isolation solid-state relay circuit, which uses three sets of solid-state relay switches to form a T-type solid-state relay circuit. Through multi-level isolation, at a frequency of 10kHz and a load impedance of megohm, the switch turn-off isolation reaches below -120dB, and it has a switching speed on the order of nanoseconds. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In the drawings:

[0029] Figure 1 A schematic diagram of a single relay unit in a novel solid-state relay circuit according to an embodiment of this application is shown;

[0030] Figure 2 A schematic diagram of the capacitance distribution parameters of a single MOSFET and a dual MOSFET in reverse connection in the off state according to an embodiment of this application is shown;

[0031] Figure 3A schematic diagram of the conduction state of a T-type relay switch circuit according to an embodiment of this application is shown;

[0032] Figure 4 A schematic diagram of a high-isolation solid-state relay switching circuit according to an embodiment of this application is shown. Detailed Implementation

[0033] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. This application can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, unless otherwise specified, the following embodiments and features in the embodiments can be combined with each other.

[0034] The specific implementation methods of this application will be further described in detail below with reference to the accompanying drawings and embodiments.

[0035] This application provides a high-isolation solid-state relay circuit, such as... Figures 1 to 4 As shown, Figure 4 The high-isolation solid-state relay circuit is demonstrated, including three sets of control terminal digital signal circuits and their pre-stage impedances and filter capacitors, and a T-type solid-state relay switching circuit composed of three sets of solid-state relay units.

[0036] The first-stage digital circuit includes a first-group gate controller U1, a pre-stage filter capacitor C1 connected to the first group controller, and a pre-stage impedance R1; the TTL port of the first-group isolated gate controller is connected to the pre-stage impedance R1 of the first group of digital circuits. The second-stage circuit includes a second-group gate controller U2, a pre-stage inverter connected to the second group controller, and a pre-stage impedance R2; the TTL port of the second-group gate controller is connected to the pre-stage inverter of the second group of digital circuits and the pre-stage impedance R2. The third-stage circuit includes a third-group gate controller, a pre-stage filter capacitor C3 connected to the third group controller, and a pre-stage impedance R3; the TTL port of the third-group gate controller is connected to the pre-stage impedance R3 of the third group of digital circuits. All three pre-stage impedances have the same impedance value and are connected to the same control level; the VDD port of all three gate controllers is connected to the DC voltage source VDD, and the GND port is connected to digital ground.

[0037] The analog-side first-stage circuit includes a first group of solid-state relay switches Q1 and Q2 and their preceding and following stage connections; the second-stage solid-state relay switch circuit includes a second group of solid-state relay switches Q3 and Q4; and the third-stage solid-state relay switch circuit includes a third group of solid-state relay switches Q5 and Q6. In this embodiment, each group of relay switches consists of two N-type MOSFETs with their sources connected, and the signal flows in from the drain of one MOSFET and out from the drain of the other. The output contacts of the first group of solid-state relay switch units are connected to the input contacts of the second and third groups of solid-state relay switches, and the output contacts of the second group of solid-state relay switch units are connected to analog ground. In this embodiment, the source of the first group of solid-state relay switch units is connected to the first group of control port SOURCE, and the gate is connected to the first group of control port GATE. The source of the second group of solid-state relay switches is connected to the second group of control port SOURCE, and the gate is connected to the second group of control port GATE. The source of the third group of solid-state relay switches is connected to the third group of control port SOURCE, and the gate is connected to the third group of control port GATE.

[0038] This embodiment adopts a T-type circuit design. When the switch is turned on, the first group of solid-state relay switches K1 and the third group of solid-state relay switches K3 are turned on, while the second group of solid-state relay switches K2 is turned off. The on-resistance of this solid-state relay switch circuit is increased to twice that of a single group of solid-state relay switches. The on-resistance of the switch can be compensated by connecting the switch output to a voltage follower with high input impedance. This voltage follower can be set after the 2-port of the switch output.

[0039] In some embodiments, when the solid-state relay switching circuit is in the ON state, the first group of solid-state relay switches and the third group of solid-state relay switches are in the OFF state, and the second group of solid-state relay switches is in the OFF state. At this time, the input signal is input from the input terminal of the first group of solid-state relay switches through port 1, output to the input terminal of the third group of solid-state relay switches through the output terminal of the first group of solid-state relay switches, and finally output to port 2 through the output terminal of the third group of solid-state relay switches.

[0040] In some embodiments, when the solid-state relay switching circuit is in the off state, the first group of solid-state relay switches and the third group of solid-state relay switches are in the open state, and the second group of solid-state relay switches is in the closed state. Since the first group of solid-state relay switches has a turn-off capacitor, the input signal passes through V... in The port receives the input from the first group of solid-state relay switches, couples a small signal through the output of the first group of solid-state relay switches to the input of the second group of solid-state relay switches, and outputs to analog ground through the output of the second group of solid-state relay switches. At this time, since K1 and K3 are connected in series, the four transistors C... DS In series, the switching capacitor C off Reduced to single tube CDS One-quarter of it.

[0041] In some embodiments, the high-isolation solid-state relay switching circuit is a normally open solid-state relay switching circuit. When the control level is 0V, the signal input from the first group of solid-state relay switches will be output from the output terminal of the third group of solid-state relay switches. At this time, the switch is on, and the signal can be transmitted. However, the signal will be attenuated due to the on-resistance of the first and third groups of solid-state relay switches. A voltage follower can be connected in series after this switch for compensation. When the control level is a TTL high level, the signal input from the input terminal of the first group of solid-state relay switches will be blocked due to the turn-off capacitor C. off The existence of, such as Figure 3 As shown, the coupled signal flows out through the first-stage solid-state relay switch to turn off the capacitor, and then flows into the analog ground through the second-stage solid-state relay switch. The extremely small coupled signal will flow to the output terminal through the third-stage solid-state relay switch. This solid-state relay switch can ensure that the isolation between the input and output terminals reaches -120dB or less when the load impedance is high, and has a switching speed in the nanosecond range.

[0042] In some embodiments, this high-isolation solid-state relay circuit is a MOSFET relay type solid-state relay switch, which uses a MOSFET as the electronically controlled switch to control the switch turn-off. Compared to a general relay, it can achieve switching intervals on the order of nanoseconds. Figure 1 As shown, a single solid-state relay switching circuit consists of two parts: a signal terminal and a control terminal. The control terminal uses an isolated gate voltage driver to generate a certain gate control voltage with relatively low control terminal power consumption, thereby controlling the on and off of the MOSFET at the signal terminal. The control terminal isolation scheme can adopt various isolation methods such as capacitor isolation, optocoupler isolation, and RF signal isolation.

[0043] At the signal level, the single relay switch uses two N-type MOSFETs connected in reverse series. This reverse connection principle allows the switch to control both AC and DC signals. The distributed parameter models for single MOSFETs and dual MOSFETs in reverse connection are as follows: Figure 2 As shown, due to the presence of capacitance C DS Within a certain signal frequency range, C DS The inherent AC impedance weakens the switching performance and reduces the switching isolation. A single solid-state relay switch can generally only achieve a switching isolation of about -60dB, which is less than that of conventional relays and is far from the -120dB isolation requirement in high-precision measurements.

[0044] Therefore, this embodiment adopts a multi-switch combination into a T-type circuit to improve the turn-off isolation, such as... Figure 3As shown. In this T-type switch, the first-stage switch S1 and the third-stage switch S3 operate with the same logic, while the second-stage switch S2 operates with the opposite logic. When the first-stage switch S1 is off, the input signal V... s Through the first turn-off capacitor C off Coupled to the output terminal D1, at this time S2 is closed, and only a small on-resistance R exists. on The majority of the coupled signal flows to ground through switch S2, while a small amount of signal passes through the turn-off capacitor C at the three-stage switch. off Coupled to the output terminal of switch D2, the output is connected to V. o The solid-state relay switch connection method using a T-type design allows a large amount of the coupled signal to flow to ground. At the same time, it is equivalent to connecting two coupling capacitors in series, reducing the overall equivalent coupling capacitance and greatly increasing the switch's turn-off isolation.

[0045] In summary, this application can significantly improve the switching speed while maintaining the turn-off isolation required for high-precision impedance measurement compared to mechanical relay switches. Applying this high-isolation solid-state relay switch to a digital sampling bridge can greatly improve measurement speed while preventing imbalance fluctuations in the stable bridge circuit during the switching process.

[0046] The above embodiments are only used to illustrate this application and are not intended to limit this application. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of this application. Therefore, all equivalent technical solutions also fall within the scope of this application, and the patent protection scope of this application should be defined by the claims.

Claims

1. A high-isolation solid-state relay circuit, characterized in that, Includes control circuitry and analog circuitry; The control circuit includes three sets of gate controllers, each set of gate controllers is controlled by TTL digital level, and the VDD ports of the three sets of gate controllers are all connected to DC voltage source VDD and digital ground. The analog terminal circuit includes three sets of solid-state relay units, which form a T-type circuit structure. The output terminal of the first set of solid-state relay units is connected to the input terminal of the second set of solid-state relay units and the input terminal of the third set of solid-state relay units. The output terminal of the second set of solid-state relay units is connected to the analog ground, and the output terminal of the third set of solid-state relay units is the circuit output terminal. Each of the solid-state relay units includes two N-type MOSFETs, and the sources of the two N-type MOSFETs are connected. The signal flows in from the drain of one N-type MOSFET and flows out from the drain of the other N-type MOSFET. The control terminal circuit is connected to the analog terminal circuit. Each group of gate controllers drives the corresponding group of solid-state relay units. When the circuit is on, the first group of solid-state relay units and the third group of solid-state relay units are on, and the second group of solid-state relay units is off. When the circuit is off, the first group of solid-state relay units and the third group of solid-state relay units are off, and the second group of solid-state relay units is on.

2. The high isolation solid-state relay circuit according to claim 1, characterized in that, The N-type MOSFET is a high-voltage, low-input-capacitance N-type MOS transistor.

3. The high isolation solid-state relay circuit according to claim 1, characterized in that, In the control circuit: The first group of gate controllers is connected to the first pre-stage impedance and the first filter capacitor, and the control level is accessed through the first pre-stage impedance. The second set of gate controllers is connected to the second pre-stage impedance and the pre-stage inverter, and the control level is accessed through the pre-stage inverter and the second pre-stage impedance. The third gate controller is connected to the third pre-stage impedance and the third filter capacitor, and the control level is accessed through the third pre-stage impedance.

4. The high isolation solid-state relay circuit according to claim 3, characterized in that, The impedance values ​​of the first preamplifier, the second preamplifier, and the third preamplifier are the same.

5. The high isolation solid-state relay circuit according to claim 1, characterized in that, In the analog terminal circuit: The first group of solid-state relay units includes two N-type MOSFETs, whose sources are connected to the SOURCE port of the first group of gate controllers, and whose gates are connected to the GATE port of the first group of gate controllers. The second group of solid-state relay units includes two N-type MOSFETs, whose sources are connected to the SOURCE port of the second group of gate controllers, and whose gates are connected to the GATE port of the second group of gate controllers. The third group of solid-state relay units includes two N-type MOSFETs, whose sources are connected to the SOURCE port of the third group of gate controllers, and whose gates are connected to the GATE port of the third group of gate controllers.

6. The high isolation solid-state relay circuit according to claim 1, characterized in that, The gate controller adopts an isolated switch gate drive scheme, and the isolation methods include capacitive isolation, optocoupler isolation, or RF signal isolation.

7. The high-isolation solid-state relay circuit according to claim 1, characterized in that, The circuit is normally open. When the control level is 0V, the first and third solid-state relay units are turned on, and the second solid-state relay unit is turned off. When the control level is TTL high level, the first and third solid-state relay units are turned off, and the second solid-state relay unit is turned on.

8. The high-isolation solid-state relay circuit according to any one of claims 1 to 7, characterized in that, When the input signal frequency is 10kHz and the load impedance is in the megohm range, the circuit's turn-off isolation reaches below -120dB.

9. The high isolation solid-state relay circuit according to claim 1, characterized in that, The switching speed of the circuit is on the order of nanoseconds.

10. The high-isolation solid-state relay circuit according to claim 1, characterized in that, A voltage follower is connected to the circuit output terminal, which is used to compensate for the circuit's on-resistance.

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