Isolated DO electrostatic protection circuit

Abstract

The utility model relates to the technical field of digital output circuits, and discloses an isolated DO electrostatic protection circuit, which comprises an isolated DO circuit, the isolated DO circuit comprises a filter capacitor bank and a voltage control type relay which are electrically connected, the voltage control type relay comprises a coil and a contact switch which are arranged in an isolated manner, and the filter capacitor bank is electrically connected with the voltage control type relay. And the output end of the voltage control type relay is connected in parallel with at least one of the capacitor C5, the piezoresistor RV1 and the transient voltage suppression diode TVS1. According to the utility model, by additionally arranging the TVS diode, the piezoresistor and other structures and carrying out simple circuit improvement, static electricity of the isolated DO can be timely dredged only by using fewer electrical elements, so that the anti-interference capability of equipment is improved, the stability and the reliability of the equipment are enhanced, a series of losses caused by static electricity faults are reduced, and the safety of the equipment is improved. The product economic benefit is further improved.

Description

Technical Field

[0001] This utility model relates to the field of digital output circuit technology, and in particular to an isolated DO electrostatic discharge protection circuit. Background Technology

[0002] DO (Digital Output) is a type of digital output circuit. In multi-system circuit design, in order to avoid mutual interference between different devices, isolated DOs are required. These can be implemented using optocouplers, relays, and other methods. In typical DO output designs, to minimize the risk of device failure, few devices are designed at the DO output, and the DO signal forms an isolated network on the circuit board.

[0003] Existing isolated DO circuits have limited consideration for electrostatic discharge (ESD) protection due to concerns about device failure risks. The existing circuit structure is shown in the attached figure. Figure 1 In this circuit, the DO output has no return path during electrostatic discharge (ESD), which can easily cause system malfunctions. If ESD is applied to the DO interface, the static electricity is not easily discharged, and the DO traces on the circuit board become a strong source of interference. If the digital output chip is coupled to this interference, it can cause device damage, uncontrolled DO ports, and other malfunctions, affecting product reliability. Utility Model Content

[0004] The purpose of this invention is to provide an electrostatic discharge protection circuit for an isolated DO. By adding structures such as TVS diodes and varistors, the electrostatic discharge effect is improved, thereby achieving effective electrostatic protection for the isolated DO.

[0005] To achieve the above objectives, this utility model provides the following solution:

[0006] An electrostatic discharge (ESD) protection circuit for an isolated DO circuit includes an isolated DO circuit, wherein the isolated DO circuit includes an electrically connected filter capacitor bank and a voltage-controlled relay, wherein the voltage-controlled relay includes an isolated coil and a contact switch, and the output terminal of the voltage-controlled relay is connected in parallel with at least one of a capacitor C5, a varistor RV1, and a transient voltage suppressor diode TVS1.

[0007] Furthermore, the output terminals of the voltage-controlled relay are two terminals connected to the contact switch, one of which is the DO output terminal DO_1, and the other terminal is the common terminal COM_DO1; one end of the capacitor C5, the varistor RV1 and / or the transient voltage suppressor diode TVS1 is connected to the DO output terminal DO_1, and the other end is connected to the common terminal COM_DO1.

[0008] Furthermore, the common terminal COM_DO1 is grounded.

[0009] Furthermore, the output terminal of the voltage-controlled relay is connected in parallel with capacitor C5, and a varistor RV1 or a transient voltage suppressor diode TVS1 is connected in parallel across the two ends of capacitor C5.

[0010] Furthermore, the output terminal of the voltage-controlled relay is connected in parallel with capacitor C5, varistor RV1, and transient voltage suppression diode TVS1.

[0011] Furthermore, the common terminal COM_DO1 is connected to the device chassis ground PGND via an RC network.

[0012] Furthermore, the RC network includes a discharge resistor R1 and a capacitor C6 connected in parallel.

[0013] Furthermore, the filter capacitor bank includes multiple capacitors connected in parallel, with one end of the filter capacitor bank grounded and the other end connected to the operating power supply.

[0014] Furthermore, one end of the coil is connected to the end of the filter capacitor bank connected to the working power supply, and the other end is the control signal input terminal.

[0015] According to the specific embodiments provided by this utility model, the electrostatic discharge protection circuit for isolated DO provided by this utility model discloses the following technical effects:

[0016] The circuit structure of the isolated DO output terminal is improved by connecting the output terminal of the voltage-controlled relay in parallel with at least one of the following: capacitor C5, varistor RV1, and transient voltage suppressor diode TVS1. Static electricity can be conducted away by any one of these devices. Capacitor C5 can quickly conduct static electricity away, while varistor RV1 and transient voltage suppressor diode TVS1 can not only conduct static electricity away but also clamp the output voltage, reducing the damage of static electricity to the DO receiving device. This achieves a highly efficient electrostatic protection effect and solves the static electricity problem of isolated DO.

[0017] This invention, through simple circuit improvements, requires only a few electrical components to promptly dissipate static electricity from isolated DO devices, thereby enhancing the equipment's anti-interference capability, stability, and reliability, reducing losses caused by electrostatic discharge faults, and further improving the product's economic benefits. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of a typical isolated DO circuit structure in the prior art;

[0020] Figure 2 This is a schematic diagram of the electrostatic discharge protection circuit structure of the isolated DO in Embodiment 1 of this utility model;

[0021] Figure 3 This is a schematic diagram of the electrostatic discharge protection circuit structure of the isolated DO in Embodiment 2 of this utility model. Detailed Implementation

[0022] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0023] like Figure 1 As shown, in a typical isolated DO circuit in the prior art, VCC is the operating voltage of relay RLY1, C1, C2, C3, and C4 are the filter capacitors of VCC, RLY1 is a voltage-controlled relay, COIL1 is the control signal, and DO_1 is the relay output; GND is the digital ground, and COM_DO1 is the common ground between devices. Therefore, the front and rear ends of the relay do not share a common ground, which constitutes an isolated DO circuit.

[0024] The operating logic of the isolated DO circuit is as follows: if COIL1 is high, relay RLY1 is not working, and the output DO_1 state is the initial setting level of the peer device, which is generally also high. If COIL1 is low, relay RLY1 is working, the contact switch is energized, and the DO_1 level is pulled to the common terminal COM_DO1, which is grounded.

[0025] However, during DO_1 electrostatic discharge, since there is no electrostatic loop, the traces of DO_1 on the circuit board become an island network, generating an antenna effect. If other signals on the circuit board are coupled to this interference, it will affect the digital chips on the circuit board and cause system failure.

[0026] The purpose of this invention is to provide an electrostatic discharge protection circuit for an isolated DO (Discharge Discharge) device. This provides a new approach to solving the problem that conventional circuits cannot discharge static electricity from isolated DO devices during electrostatic discharge, which can affect the system. By using fewer components, the static electricity of the isolated DO device can be discharged in a timely manner, improving the anti-interference capability of the device and enhancing its stability and reliability.

[0027] To make the above-mentioned objectives, features and advantages of this utility model more apparent and understandable, the utility model will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] This utility model further improves upon the above-mentioned isolated DO circuit, providing an electrostatic discharge protection circuit for an isolated DO circuit, including the aforementioned isolated DO circuit. The isolated DO circuit includes an electrically connected filter capacitor bank and a voltage-controlled relay. The voltage-controlled relay includes an isolated coil and a contact switch. The output terminal of the voltage-controlled relay is connected in parallel with at least one of the following: capacitor C5, varistor RV1, and transient voltage suppression diode TVS1.

[0029] The output terminals of the voltage-controlled relay are two terminals connected to the contact switch. One terminal is the DO output terminal DO_1, and the other terminal is the common terminal COM_DO1. One end of the capacitor C5, the varistor RV1, and / or the transient voltage suppressor diode TVS1 is connected to the DO output terminal DO_1, and the other end is connected to the common terminal COM_DO1. The common terminal COM_DO1 is grounded.

[0030] Example 1

[0031] like Figure 2 As shown, in the electrostatic discharge protection circuit of the isolated DO provided in Embodiment 1 of this utility model, the output terminal of the voltage-controlled relay is connected in parallel with capacitor C5, varistor RV1 and transient voltage suppression diode TVS1.

[0032] During electrostatic discharge, any one of the following devices—capacitor C5, varistor RV1, and transient voltage suppressor diode TVS1—can conduct static electricity from the DO output terminal DO_1 to the common terminal COM_DO1, or vice versa. Capacitor C5 can quickly conduct static electricity away, while TVS1 and RV1 can not only conduct static electricity away but also clamp the voltage at the DO output terminal DO_1, reducing the damage of static electricity to the DO receiving equipment.

[0033] Example 2

[0034] Figure 2 The circuit shown provides some protection against low-level electrostatic discharge (ESD), but its protection against higher-level ESD is insufficient because the electrostatic energy is not dissipated or conducted away. Therefore, this invention further designs... Figure 3The circuit structure includes a common terminal COM_DO1 connected to the device chassis ground PGND via an RC network. This RC network includes a discharge resistor R1 and a capacitor C6 connected in parallel. The RC network provides a path to both grounds, allowing static electricity to be discharged to the device chassis ground even during high-level electrostatic discharge. In this embodiment, the device refers to the circuit board containing the electrostatic protection circuit of the isolated DO type or the chassis on which the circuit board is mounted.

[0035] Figure 3 Capacitor C6 is a safety capacitor that conducts away high-frequency electrostatic interference. R1 is a discharge resistor that dissipates the voltage across capacitor C6 after the electrostatic discharge has occurred. The capacitance of capacitor C6 should generally not be too large, for example, between 10pF and 10000pF, to avoid leakage current.

[0036] This document uses specific examples to illustrate the principles and implementation methods of this utility model. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this utility model. Furthermore, those skilled in the art will recognize that, based on the ideas of this utility model, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this utility model.

Claims

1. An electrostatic discharge (ESD) protection circuit for an isolated direct current (DO) circuit, comprising an isolated DO circuit, wherein the isolated DO circuit includes an electrically connected filter capacitor bank and a voltage-controlled relay, wherein the voltage-controlled relay includes an isolated coil and a contact switch, characterized in that, The output terminal of the voltage-controlled relay is connected in parallel with at least one of the following: capacitor C5, varistor RV1, and transient voltage suppression diode TVS1.

2. The electrostatic discharge protection circuit for an isolated DO according to claim 1, characterized in that, The output terminals of the voltage-controlled relay are two terminals connected to the contact switch, one of which is the DO output terminal DO_1, and the other terminal is the common terminal COM_DO1; one end of the capacitor C5, the varistor RV1 and / or the transient voltage suppression diode TVS1 is connected to the DO output terminal DO_1, and the other end is connected to the common terminal COM_DO1.

3. The electrostatic discharge protection circuit for an isolated DO according to claim 2, characterized in that, The common terminal COM_DO1 is grounded.

4. The electrostatic discharge protection circuit for an isolated DO according to claim 1, characterized in that, The output terminal of the voltage-controlled relay is connected in parallel with capacitor C5, and a varistor RV1 or a transient voltage suppressor diode TVS1 is connected in parallel across the two ends of capacitor C5.

5. The electrostatic discharge protection circuit for an isolated DO according to claim 1, characterized in that, The output terminal of the voltage-controlled relay is connected in parallel with capacitor C5, varistor RV1, and transient voltage suppression diode TVS1.

6. The electrostatic discharge protection circuit for an isolated DO according to claim 2, characterized in that, The common terminal COM_DO1 is connected to the device chassis ground PGND via an RC network.

7. The electrostatic discharge protection circuit for an isolated DO according to claim 6, characterized in that, The RC network includes a discharge resistor R1 and a capacitor C6 connected in parallel.

8. The electrostatic discharge protection circuit for an isolated DO according to claim 1, characterized in that, The filter capacitor bank includes multiple capacitors connected in parallel. One end of the filter capacitor bank is grounded, and the other end is connected to the power supply.

9. The electrostatic discharge protection circuit for an isolated DO according to claim 8, characterized in that, One end of the coil is connected to the end of the filter capacitor bank that is connected to the working power supply, and the other end is the control signal input terminal.

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