High-isolation solid-state relay circuit

Abstract

The invention 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, and is characterized in that the control end circuit comprises three groups of grid 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-shaped circuit structure; each group of solid-state relay unit comprises two N-type MOSFETs (Metal-Oxide-Semiconductor Field The control end circuit is correspondingly connected with the analog end circuit; when the circuit is conducted, the first group of solid-state relay units and the third group of solid-state relay units are conducted, and the second group of solid-state relay units are cut off; and when the circuit is cut off, the first group of solid-state relay units and the third group of solid-state relay units are cut off, and the second group of solid-state relay units are conducted. According to the circuit, the ns-order switching speed can be realized, the turn-off isolation degree is below-120dB under the conditions of 10kHz frequency and megohm-order load impedance, and alternating current and direct current signals can be efficiently controlled.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solid-state relay switching circuit, in particular to a solid-state relay circuit with high isolation degree. BACKGROUND

[0002] In many fields, solid-state relay switching is critical: in battery-powered systems, due to the extremely low energy consumption of the control end of the solid-state relay, it can meet the switching needs of low-power consumption scenarios such as Internet of Things devices; in industrial automation fields such as PLC output modules and robot control, solid-state relays can be used to control DC loads that need to be frequently switched (such as solenoid valves and LED lighting); in semiconductor testing and pulse power scenarios that require fast switching, solid-state relays can complete high-efficiency and high-isolation switching as an analog switch.

[0003] In the field of high-precision measurement of precision electronic equipment, such as precision automation measurement and radio frequency application, automatic switching system has important application value, and designing an efficient and anti-interference automatic switching system is widely used in related fields. Designing a solid-state relay switch with long service life, high isolation degree and low price has become the focus of switch design. SUMMARY

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

[0005] In order to achieve the above-mentioned purpose, the technical scheme adopted is as follows:

[0006] The present application provides a solid-state relay circuit with high isolation degree, comprising a control end circuit and an analog end circuit.

[0007] The control end circuit comprises three groups of gate controllers, each group of gate controllers is controlled by TTL digital level, and the ports VDD of the three groups of gate controllers are connected to a direct current voltage source VDD, and the ports VDD of the three groups of gate controllers are connected to digital ground.

[0008] 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; wherein the output ends of the first group of solid-state relay units are respectively connected to the input ends of the second group of solid-state relay units and the input ends of the third group of solid-state relay units, the output end of the second group of solid-state relay units is connected to analog ground, and the output end of the third group of solid-state relay units is the circuit output end.

[0009] Each of the solid-state relay units comprises two N-type MOSFETs, and the sources of the two N-type MOSFETs are connected, and 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 high-isolation solid state relay circuit, the N-type MOSFET is a high-voltage, low-input-capacitance N-type MOS tube.

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

[0013] The first group of gate controllers is connected to a first front-end impedance and a first filter capacitor, and the control level is accessed through the first front-end impedance;

[0014] The second group of gate controllers is connected to a second front-end impedance and a front-end inverter, and the control level is accessed through the front-end inverter and the second front-end impedance;

[0015] The third group of gate controllers is connected to a third front-end impedance and a third filter capacitor, and the control level is accessed through the third front-end impedance.

[0016] Preferably, in the high-isolation solid state relay circuit, the impedance values of the first front-end impedance, the second front-end impedance and the third front-end impedance are the same.

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

[0018] The first group of solid state relay units includes two N-type MOSFETs, the source is connected to the SOURCE port of the first group of gate controllers, and the gate is 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, the source is connected to the SOURCE port of the second group of gate controllers, and the gate is 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, the source is connected to the SOURCE port of the third group of gate controllers, and the gate is connected to the GATE port of the third group of gate controllers.

[0021] Preferably, in the high-isolation solid-state relay circuit, the gate controller adopts an isolated gate drive scheme, and the isolation mode includes capacitor isolation, optical coupling isolation, or RF signal isolation.

[0022] Preferably, in the 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 are turned off; when the control level is 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 high-isolation solid-state relay circuit, when the input signal frequency is 10kHz and the load impedance is megohm level, the off-isolation of the circuit reaches below-120dB.

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

[0025] Preferably, in the high-isolation solid-state relay circuit, a voltage follower is connected to the output end of the circuit, and the voltage follower is used to compensate the on-impedance of the circuit.

[0026] The application has the following significant technical effects:

[0027] The application provides a high-isolation solid-state relay circuit, which uses three groups of solid-state relays to form a T-type solid-state relay circuit, and through multi-stage isolation, when the frequency is 10kHz and the load impedance reaches megohm level, the off-isolation of the switch reaches below-120dB, and the switching speed is in the order of nanoseconds. BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the application, the following will briefly introduce the drawings needed to be used in the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the application, and for those skilled in the art, other drawings can also be obtained without creative labor. In the drawings:

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

[0030] Figure 2 A capacitor distribution parameter schematic diagram of single MOSFET and double MOSFET in off state according to an embodiment of the application is shown;

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

[0032] Figure 4 A high-isolation solid-state relay switch circuit schematic diagram according to an embodiment of the present application is shown. DETAILED DESCRIPTION

[0033] The embodiments of the present application will be described in detail with specific reference felt to the drawings. The advantages and effects of the present application can be easily understood by those skilled in the art from the description of the present application. The present application can also be implemented or applied by different specific embodiments, and the details in the description can be modified or changed based on different views and applications without departing from the spirit of the present application. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0034] The specific embodiments of the present application will be described in detail below with reference to the drawings and embodiments.

[0035] An embodiment of the present application provides a high-isolation solid-state relay circuit, as shown in Figures 1 to 4 Figure 4 The high-isolation solid-state relay circuit is shown, which includes three groups of control end digital signal circuits and their front-stage impedance, filter capacitor, and three groups of solid-state relay units to form a T-type solid-state relay switch circuit.

[0036] The first-stage circuit of the digital end includes a first group of gate controllers U1 and a front-stage filter capacitor C1 and a front-stage impedance R1 connected to the first group of controllers; the first group of isolation type gate controller ports TTL are connected to the first group of digital circuit front-stage impedance R1. The second-stage circuit includes a second group of gate controllers U2 and a front-stage inverter and a front-stage impedance R2 connected to the second group of controllers; the second group of gate controller ports TTL are connected to the second group of digital circuit front-stage inverter and front-stage impedance R2. The third-stage circuit includes a third group of gate controllers and a front-stage filter capacitor C3 and a front-stage impedance R3 connected to the third group of controllers; the third group of gate controller ports TTL are connected to the third group of digital circuit front-stage impedance R3. The three groups of front-stage impedance have the same impedance value and are connected to the same control level; the third group of gate controller ports VDD are connected to a direct current voltage source VDD, and the port GND is connected to a digital ground.

[0037] ​The first-stage circuit of the analog end comprises a first group of solid-state relay switches Q1 and Q2 and the connection circuit before and after the first group of solid-state relay switches; the second-stage solid-state relay switch circuit comprises a second group of solid-state relay switches Q3 and Q4; and the third-stage solid-state relay switch circuit comprises a third group of solid-state relay switches Q5 and Q6. In the embodiment, each group of relay switches is composed of two N-type MOSFETs with their source electrodes connected, and the signal flows in from the drain electrode of one tube and flows out from the drain electrode of the other tube. The output contact of the first group of solid-state relay switch units is connected to the input contact of the second group and the third group of solid-state relay switches, and the output contact of the second group of solid-state relay switch units is connected to the analog ground. In the embodiment, the source electrode of the first group of solid-state relay switch units is connected to the first group of control end ports SOURCE, and the gate electrode is connected to the first group of control end ports GATE. The source electrode of the second group of solid-state relay switches is connected to the second group of control end ports SOURCE, and the gate electrode is connected to the second group of control end ports GATE. The source electrode of the third group of solid-state relay switches is connected to the third group of control end ports SOURCE, and the gate electrode is connected to the third group of control end ports GATE.

[0038] In the embodiment, a T-type circuit design is adopted. 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, and the second group of solid-state relay switches K2 is turned off. The on-state impedance of the solid-state relay switch circuit is doubled, and the on-state impedance of the switch can be compensated by connecting the switch output to a voltage follower with high input impedance. The voltage follower can be arranged after the 2 port of the switch output.

[0039] In some embodiments, when the solid-state relay switch 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 closed state, and the second group of solid-state relay switches is in the open state. At this time, the input signal is input from the first group of solid-state relay switch input terminals through the 1 port, output to the third group of solid-state relay switch input terminals through the first group of solid-state relay switch output terminals, and finally output to the 2 port through the third group of solid-state relay switch output terminals.

[0040] In some embodiments, when the solid-state relay switch 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. At this time, the input signal is input from the first group of solid-state relay switch input terminals through the V in port, coupled to the second group of solid-state relay switch input terminals through the coupling part of the first group of solid-state relay switch output terminals, and output to the analog ground through the second group of solid-state relay switch output terminals. At this time, K1 and K3 are connected in series, and four tubes C DS are connected in series. The turn-off capacitance C off of the switch is reduced to a 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 uses a multi-switch combination to form a T-type circuit to improve the turn-off isolation, such as... Figure 3The first stage switch S1 and the third stage switch S3 take the same logic, and the second stage switch S2 takes opposite logic. When the first stage switch S1 is in the off state, the input signal V s The first stage switch S1 and the third stage switch S3 take the same logic, and the second stage switch S2 takes opposite logic. When the first stage switch S1 is in the off state, the input signal V off Coupled to the output end D1, at this time S2 is closed, and only a trace of on impedance R on The majority of the coupled signal flows into the ground through the S2 switch, and a trace of the signal flows through the off capacitor C off Coupled to the output end D1, at this time S2 is closed, and only a trace of on impedance R o The T-type design of the solid-state relay switch connection mode makes the coupled signal flow to the ground in a large amount, and is equivalent to connecting two coupling capacitors in series, thereby reducing the overall equivalent coupling capacitor and greatly increasing the off isolation degree of the switch.

[0045] In summary, the application can significantly improve the switching speed of the switch, and can also maintain the off isolation degree that meets the high-precision impedance measurement compared with the mechanical relay switch. The high-isolation solid-state relay switch is applied to the digital sampling bridge, which can greatly improve the measurement speed and prevent the switching process of the switch from causing unbalanced fluctuations in the stable bridge.

[0046] The above embodiments are only used to illustrate the application, and are not intended to limit the application. Those skilled in the related technical field can make various changes and modifications without departing from the spirit and scope of the application. Therefore, all equivalent technical solutions belong to the scope of the application, and the patent protection scope of the 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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