An isolated conversion circuit

Abstract

The utility model discloses an isolation conversion circuit, including internal external power supply switch switching circuit, internal isolation power supply circuit, isolation RS485RS422 communication circuit, dial code switch RS485RS422 switching circuit and interface ESD protection circuit, wherein, internal isolation power supply circuit is connected with internal external power supply switch switching circuit, and internal external power supply switch switching circuit is connected with isolation RS485RS422 communication circuit, and isolation RS485RS422 communication circuit connection is connected with dial code switch RS485RS422 switching circuit and interface ESD protection circuit respectively, internal external power supply switch switching circuit is connected with external power supply still. The utility model improves the anti -interference ability of system, has promoted the accuracy and reliability of data transmission, can be compatible with the communication interface of airborne computer test system, satisfies the conversion function of RS485 and RS422 interface, and the power supply of communication system can be compatible for test system internal power supply or external power supply, has reduced the quantity of component and has reduced the volume of product.

Description

Technical Field

[0001] This utility model belongs to the field of airborne computer testing technology, and specifically discloses an isolation conversion circuit. Background Technology

[0002] Most existing airborne computer testing systems require test boards to have multiple communication modes for use with products of different communication interface types. Furthermore, due to the varying power supply modes of these products, the test boards must be self-powered for communication while simultaneously providing power to the communication systems of external products, or being powered by external products. Interface circuits are often subject to numerous unpredictable interferences, making interference immunity a significant challenge.

[0003] In existing airborne computer testing systems, RS485 and RS422 are commonly used communication interface circuits. Their circuit principles are basically the same; both use differential transmission and reception, eliminating the need for a digital ground wire. Under the same data rate conditions, differential operation is the fundamental reason for the longer transmission distance. The electrical performance of RS422 is exactly the same as RS485. RS422 has four signal lines: two for transmitting (Y, Z) and two for receiving (A, B). Because RS422's transmission and reception are separate, simultaneous transmission and reception are possible. It can operate in full-duplex mode via two pairs of twisted-pair wires, with transmission and reception not interfering with each other. RS485, on the other hand, has two signal lines: one for transmitting and one for receiving. It can only operate in half-duplex mode, and transmission and reception cannot be performed simultaneously, but it only requires one pair of twisted-pair wires.

[0004] In practical applications, the devices that need to communicate may have RS422 or RS485 interfaces. Therefore, the product needs to have the ability to communicate with both RS422 and RS485 interfaces. If a separate interface space is reserved, the product size will increase, which does not meet the requirements of product miniaturization. Utility Model Content

[0005] To address the aforementioned technical problems in the existing technology, this utility model proposes an isolation switching circuit, comprising an internal / external power supply switch switching circuit, an internal isolated power supply circuit, an isolated RS485 / RS422 communication circuit, a DIP switch RS485 / RS422 switching circuit, and an interface ESD protection circuit. The internal isolated power supply circuit is connected to the internal / external power supply switch switching circuit, which is also connected to the isolated RS485 / RS422 communication circuit. The isolated RS485 / RS422 communication circuit is connected to both the DIP switch RS485 / RS422 switching circuit and the interface ESD protection circuit. The internal / external power supply switch switching circuit is also connected to an external power source.

[0006] Furthermore, in the internal and external power supply switching circuit, the output pin ISO_VOUT of the isolation power chip LTM8067 is connected to the pad of the test point, the power input pin ISO_VCC2 of the isolation communication chip ISO3086 is connected to the pad of the test point, and the input voltage pin VCCIN of the external power supply is connected to the pad of the test point. When switch 1 is closed and switch 2 is open, the isolation power chip LTM8067 is powered. When switch 1 is open and switch 2 is closed, external power supply is activated.

[0007] Furthermore, in the internal and external power supply switching circuit, the test point is connected to the connector via solder wire and plugs into the connector on the product side.

[0008] Furthermore, in the internal and external power supply switching circuit, an external power supply signal indicator is connected to one end of the common ground ISO_GND to distinguish between internal and external power supply modes.

[0009] Furthermore, in the internal and external power supply switching circuit, the test hole pads of switch 1 and switch 2 signals are connected to the switch 1 and switch 2 pads on the panel of the test equipment via wires.

[0010] Furthermore, in the internal isolated power supply circuit, when switch 1 is closed and switch 2 is open, the power output signal pin ISO_VOUT of the LTM8067 chip is connected to the power supply pin ISO_VCC2 of ISO3086 chip D2 and ISO3086 chip D4; when switch 2 is closed and switch 1 is open, the power output signal pin ISO_VOUT of the LTM8067 chip is connected to the input voltage pin VCCIN of the external power supply.

[0011] Furthermore, in the isolated RS485 / RS422 communication circuit, when the input enable RE of the ISO3086 chip is low, the control data output is valid; when the output enable DE of the ISO3086 chip is high, the data input is valid.

[0012] Furthermore, in the RS485 / RS422 DIP switch switching circuit, With DIP switch D1 off, the positive data transmit signal and the positive data receive signal are connected, the negative data transmit signal and the negative data receive signal are connected, the positive clock transmit signal and the positive clock receive signal are connected, and the negative clock transmit signal and the negative clock receive signal are connected. The two clock transmit and receive signal lines and the two data transmit and receive signal lines are connected to the two ISO3086 chips respectively. Pins 14 and 12 on ISO3086 chip D2 are connected, pins 13 and 11 on ISO3086 chip D2 are connected, pins 14 and 12 on ISO3086 chip D4 are connected, and pins 13 and 11 on ISO3086 chip D4 are connected. With DIP switch D1 open, the positive data transmit signal is disconnected from the positive data receive signal, the negative data transmit signal is disconnected from the negative data receive signal, the positive clock transmit signal is disconnected from the positive clock receive signal, and the negative clock transmit signal is disconnected from the negative clock receive signal. The two data transmit signals are connected to pins 12 and 11 on the ISO3086 chip D2, the two data receive signals are connected to pins 14 and 13 on the ISO3086 chip D2, the two clock transmit signals are connected to pins 12 and 11 on the ISO3086 chip D4, and the two clock receive signals are connected to pins 14 and 13 on the ISO3086 chip D4.

[0013] Furthermore, in the interface ESD protection circuit, the transient voltage suppressor is connected to the interface signals of ISO3086 chip D2 and ISO3086 chip D4.

[0014] Furthermore, in the interface ESD protection circuit, the transient voltage suppressor is model ESD101-B1-02EL.

[0015] This invention can be configured for either external or internal power supply, improving the overall system's anti-interference capability and enhancing the accuracy and reliability of data transmission. It is compatible with the communication interface of airborne computer testing systems, fulfilling the conversion function between RS485 and RS422 interfaces. Furthermore, the power supply for the communication system can be compatible with either internal or external power supply for the testing system, effectively reducing the number of components and the size of the product. Attached Figure Description

[0016] Figure 1 This is the circuit schematic diagram of this utility model; Figure 2 This is a circuit diagram of the internal and external power supply switch switching in this utility model; Figure 3 This is a circuit diagram of the internal isolation power supply in this utility model; Figure 4This is a circuit diagram of the isolated RS485 / RS422 communication circuit in this utility model; Figure 5 This is the circuit diagram for the RS485 / RS422 DIP switch in this utility model; Figure 6 This is a circuit diagram of the interface ESD protection circuit in this utility model. Detailed Implementation

[0017] To better understand the purpose, technical solution, and function of this utility model, a more detailed description is provided below with reference to the accompanying drawings. However, this utility model can be implemented in many different ways as defined and covered by the claims. The accompanying drawings, which constitute a part of this utility model, are used to provide a further understanding of this utility model. The illustrative embodiments of this utility model and their descriptions are used to explain this utility model and do not constitute an improper limitation of this utility model.

[0018] This invention enables automatic data transmission and reception. It employs an isolated communication chip to achieve a "receive / drive—isolation—receive / drive" working mode. An isolated DC / DC converter is added to the isolated communication chip to reduce interference from external system circuits. An ESD protection diode circuit with surge voltage protection is added to the signal receiving port for electrostatic discharge (ESD) protection of the interface circuit, which can improve electromagnetic compatibility. In addition, since RS485 and RS422 are half-duplex and full-duplex respectively, a DIP switch is used in the circuit to switch between RS485 and RS422 data transmission and reception. A dual-switch mode is used in the isolated power supply to switch between external and internal power supply.

[0019] Specifically, this utility model circuit comprises five parts: the first part is an internal / external power supply switch switching circuit; the second part is an internal isolated power supply circuit; the third part is an isolated RS485 / RS422 communication circuit; the fourth part is a DIP switch RS485 / RS422 switching circuit; and the fifth part is an interface ESD protection circuit. The overall connection relationship of the circuit is as follows: Figure 1 As shown, circuits with the same signal name are connected together. The following provides a detailed description and explanation of each circuit in this invention.

[0020] Part 1: Internal / External Power Supply Switching Circuit. For example... Figure 2As shown, ISO_VOUT is the internal isolated power supply output pin, ISO_VCC2 is the power input pin of the isolated communication chip, and VCCIN provides power to the external product. The output voltage ISO_VOUT of the isolated power supply chip LTM8067 is connected to the test pad (the circuit will route the signal to the pad to be tested), the voltage input pin ISO_VCC2 of the isolated communication chip ISO3086 is connected to the test pad, and the input voltage VCCIN from the external product is connected to the test pad. These three power supplies share a common ground, ISO_GND.

[0021] When switch 1 is closed and switch 2 is open, the internal isolated power supply LTM8067 provides power; when switch 1 is open and switch 2 is closed, power can be supplied through the power system on the external product. This test point can be connected to a connector via soldering wires to interlock with the connector on the product side, allowing for both internal power supply and external power supply simultaneously. HL1 is an external power supply signal indicator, effectively distinguishing between internal and external power supply modes.

[0022] The test pads for switch 1 and switch 2 signals can be connected to the switch 1 and switch 2 pads on the test equipment panel via wires. This facilitates the switching function on the test equipment housing panel, enabling switching between internal and external power supply.

[0023] Part Two: Internal Isolated Power Supply Circuit. For example... Figure 3 As shown, the power supply uses the LTM8067 chip, a DC-DC isolated converter that enables power supply isolation for different components. The package includes a switch controller, power switch, transformer, and all auxiliary components. The input voltage range is 3V to 40V, and it supports an output voltage range of 2.5V to 24V, set by a single resistor. Only output and input capacitors are required, significantly reducing the size of the heatsink. It also features comprehensive internal protection circuitry. The LTM8067 has a rated electrical isolation of 2kVAC, suppressing electromagnetic interference and eliminating ground loops, protecting the RS485 / RS422 controller from external network interference, and improving the protocol converter's anti-interference capability.

[0024] The circuit of LTM8067 is as follows Figure 3 As shown, the power output signal is ISO_VOUT, and the ground signal is ISO_GND. With switch 1 closed and switch 2 open, ISO_VOUT is connected to the power supply pin ISO_VCC2 of ISO3086 chip D2 and ISO3086 chip D4. With switch 2 closed and switch 1 open, ISO_VOUT is connected to the external power supply VCCIN.

[0025] Part Three: Isolate RS485 / RS422 communication circuits. For example... Figure 4 As shown, the communication circuit uses the ISO3086 chip. The ISO3086 chip is an isolated full-duplex differential line driver and receiver with a high-level active driver enable and a low-level active receiver enable for controlling data flow, suitable for data transmission up to 20 Mbps. Due to the open ground loop, the ISO3086 chip can operate over a wide common-mode voltage range, making it ideal for long-distance transmission lines. The ISO3086 chip is rated to provide up to 2500 VRMS of electrical isolation over 60 seconds. Typically, all wired I / O is susceptible to transient noise from various signal sources. If this transient noise has sufficient amplitude and duration, it can damage the transceiver or nearby sensitive circuitry. The ISO3086 chip significantly improves protection levels and reduces the risk of damage to expensive control circuitry.

[0026] When the input enable RE of the ISO3086 chip is low, the control data output is valid; when the output enable DE of the ISO3086 chip is high, the data input is valid. This invention uses pull-up and pull-down switches to define the initial operating states of the output enable DE and input enable RE, meaning that the input and output are enabled immediately upon power-up.

[0027] The circuit of ISO3086 is as follows Figure 4 As shown, the power output signal is ISO_VCC2, and the ground signal is ISO_GND.

[0028] Part Four: RS485 / RS422 DIP switch switching circuit. (For example...) Figure 5 As shown, the on / off function of the DIP switch is used to achieve the conversion between RS485 and RS422 modes.

[0029] D1 is a DIP switch. When the DIP switch is off, pins 1 and 8, 2 and 7, 3 and 6, and 4 and 5 of D1 are connected. In this state, the positive data transmit signal is connected to the positive data receive signal, and the negative data transmit signal is connected to the negative data receive signal. Similarly, the positive clock transmit signal is connected to the positive clock receive signal, and the negative clock transmit signal is connected to the negative clock receive signal. Two clock transmit and receive signal lines and two data transmit and receive signal lines are connected to two ISO3086 chips respectively. On ISO3086 chip D2, pins A and Z are connected together; on ISO3086 chip D2, pins B and Y are connected together; on ISO3086 chip D4, pins A and Z are connected together; on ISO3086 chip D4, pins B and Y are connected together. That is, on ISO3086 chip D2, pins 14 and 12 are connected together; on ISO3086 chip D2, pins 13 and 11 are connected together; on ISO3086 chip D4, pins 14 and 12 are connected together; and on ISO3086 chip D4, pins 13 and 11 are connected together. It can only operate in half-duplex mode, and the communication mode is RS485.

[0030] D1 is a DIP switch. When the DIP switch is in the open state, that is, pins 1 and 8, 2 and 7, 3 and 6, and 4 and 5 of DIP switch D1 are not conducting. At this time, the positive data transmit signal is disconnected from the positive data receive signal, the negative data transmit signal is disconnected from the negative data receive signal, the positive clock transmit signal is disconnected from the positive clock receive signal, and the negative clock transmit signal is disconnected from the negative clock receive signal. The four clock transmit (Z, Y) and receive (A, B) signal lines and the four data transmit (Z, Y) and receive (A, B) signal lines are connected to two ISO3086 chips respectively. That is, the two data transmit signals are connected to pins 12 and 11 on ISO3086 chip D2, and the two data receive signals are connected to pins 14 and 13 on ISO3086 chip D2. Two clock transmit signals are connected to pins 12 and 11 on the ISO3086 chip D4, and two clock receive signals are connected to pins 14 and 13 on the ISO3086 chip D4. In this way, the A, B, Z, and Y axes of the two ISO3086 chips are separated, and the transmit and receive operations are independent, allowing simultaneous transmission and reception in full-duplex mode. This communication mode is RS422.

[0031] Part 5: Interface ESD Protection Circuit. For example... Figure 6As shown, V1~V8 are transient voltage suppressors ESD101-B1-02EL, which are high-efficiency protection devices in diode form. These bipolar devices are mainly used in electrostatic discharge protection circuits, adding surge voltage protection circuitry at the ports to improve electromagnetic compatibility. The chip uses transient suppression diodes at its input and output terminals to prevent surge voltages from the PC side from entering the circuit board, protecting the circuit from damage caused by surge pulses generated by electrostatic discharge, electrical fast transients, or lightning strikes. This effectively protects the precision components in the electronic circuitry and ensures stable operation in wireless transmitting stations susceptible to lightning strikes.

[0032] V1~V8 are connected to the interface signals of ISO3086 chip D2 and D4. Each of the output terminals of ISO3086 chip D2 and D4 has four pins, which serve to protect the interface chip.

[0033] The power supply chip and communication chip in this circuit utilize isolation chips, significantly improving the overall circuit performance. This ensures data isolation and guarantees the accuracy and reliability of data transmission. Surge voltage protection circuits are added at the ports, enhancing the system's electromagnetic compatibility.

[0034] This utility model circuit has been fully verified on multiple airborne computer test boards, and is especially suitable for compatibility with the communication interface of airborne computer test systems. It meets the conversion function of RS485 and RS422 interfaces, and can be compatible with the power supply of the communication system for either internal or external power supply of the test system. This can effectively reduce the number of components used in the design and reduce the size of the product.

[0035] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Those skilled in the art can make various changes or modifications within the scope of the claims, all of which should be included within the protection scope of the present utility model.

Claims

1. An isolation switching circuit, characterized in that, It includes an internal / external power supply switch circuit, an internal isolated power supply circuit, an isolated RS485 / RS422 communication circuit, a DIP switch RS485 / RS422 switching circuit, and an interface ESD protection circuit. The internal isolated power supply circuit is connected to the internal / external power supply switch circuit, which is also connected to the isolated RS485 / RS422 communication circuit. The isolated RS485 / RS422 communication circuit is connected to both the DIP switch RS485 / RS422 switching circuit and the interface ESD protection circuit. The internal / external power supply switch circuit is also connected to an external power source.

2. The isolation switching circuit according to claim 1, characterized in that, In the internal and external power supply switching circuit, the output pin ISO_VOUT of the isolation power chip LTM8067 is connected to the pad of the test point, the power input pin ISO_VCC2 of the isolation communication chip ISO3086 is connected to the pad of the test point, and the input voltage pin VCCIN of the external power supply is connected to the pad of the test point. When switch 1 is closed and switch 2 is open, the isolation power chip LTM8067 is powered. When switch 1 is open and switch 2 is closed, external power supply is activated.

3. The isolation switching circuit according to claim 2, characterized in that, In the internal and external power supply switching circuit, the test point is connected to the connector via solder wire and plugs into the connector on the product side.

4. The isolation switching circuit according to claim 2, characterized in that, In the internal and external power supply switching circuit, an external power supply signal indicator is connected to the common ground ISO_GND terminal to distinguish between internal and external power supply modes.

5. An isolation switching circuit according to claim 2, characterized in that, In the internal and external power supply switching circuit, the test hole pads of switch 1 and switch 2 signals are connected to the switch 1 and switch 2 pads on the panel of the test equipment via wires.

6. The isolation switching circuit according to claim 1, characterized in that, In the internal isolated power supply circuit, when switch 1 is closed and switch 2 is open, the power output signal pin ISO_VOUT of the LTM8067 chip is connected to the power supply pin ISO_VCC2 of the ISO3086 chip D2 and ISO3086 chip D4; when switch 2 is closed and switch 1 is open, the power output signal pin ISO_VOUT of the LTM8067 chip is connected to the input voltage pin VCCIN of the external power supply.

7. The isolation switching circuit according to claim 1, characterized in that, In the isolated RS485 / RS422 communication circuit, when the input enable RE of the ISO3086 chip is low, the control data output is valid; when the output enable DE of the ISO3086 chip is high, the data input is valid.

8. An isolation switching circuit according to claim 1, characterized in that, In the RS485 / RS422 DIP switch switching circuit With DIP switch D1 off, the positive data transmit signal and the positive data receive signal are connected, the negative data transmit signal and the negative data receive signal are connected, the positive clock transmit signal and the positive clock receive signal are connected, and the negative clock transmit signal and the negative clock receive signal are connected. The two clock transmit and receive signal lines and the two data transmit and receive signal lines are connected to the two ISO3086 chips respectively. Pins 14 and 12 on ISO3086 chip D2 are connected, pins 13 and 11 on ISO3086 chip D2 are connected, pins 14 and 12 on ISO3086 chip D4 are connected, and pins 13 and 11 on ISO3086 chip D4 are connected. With DIP switch D1 open, the positive data transmit signal is disconnected from the positive data receive signal, the negative data transmit signal is disconnected from the negative data receive signal, the positive clock transmit signal is disconnected from the positive clock receive signal, and the negative clock transmit signal is disconnected from the negative clock receive signal. The two data transmit signals are connected to pins 12 and 11 on the ISO3086 chip D2, the two data receive signals are connected to pins 14 and 13 on the ISO3086 chip D2, the two clock transmit signals are connected to pins 12 and 11 on the ISO3086 chip D4, and the two clock receive signals are connected to pins 14 and 13 on the ISO3086 chip D4.

9. An isolation switching circuit according to claim 1, characterized in that, In the interface ESD protection circuit, the transient voltage suppressor is connected to the interface signals of ISO3086 chip D2 and ISO3086 chip D4.

10. An isolation switching circuit according to claim 9, characterized in that, The transient voltage suppressor in the interface ESD protection circuit is model ESD101-B1-02EL.

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