Low-cost isolated 485 communication circuit
By combining a common non-isolated RS485 transceiver control chip with high-speed optocouplers and transistor circuits, the problem of high electrical isolation cost in industrial applications of RS485 communication is solved, achieving low-cost and high-speed electrical isolation.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- XINAN JIANGSU ELECTRIC APPLIANCE CO LTD
- Filing Date
- 2025-06-23
- Publication Date
- 2026-05-29
AI Technical Summary
Existing RS485 communication requires electrical isolation in industrial applications and is costly, especially when using foreign isolation chips, which increases costs.
It adopts a common non-isolated 485 transceiver control chip combined with a high-speed optocoupler and transistor circuit, and uses a combination of common-mode filter inductor and capacitor diode for signal processing to achieve electrical isolation and high-low level conversion, thereby reducing costs.
It achieves low-cost electrical isolation while increasing the communication rate to 10 Mbps, meeting the isolation and speed requirements of industrial applications.
Smart Images
Figure CN224305757U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of communication circuit technology, specifically a low-cost isolated 485 communication circuit. Background Technology
[0002] In the power industry and industrial applications, RS485 communication is the most common communication method. Generally, when devices communicate directly using RS485, they are required to be isolated from each other. This is to reduce the risk of damage and to increase the ability to resist interference.
[0003] Due to the rapid development of industrial applications in recent years, related industries have also made great strides, and the application of 485 communication has become increasingly common. Industrial applications usually require electrical isolation, and 485 communication has a high speed, so foreign 485 isolation chips are often used to achieve this, but the cost is high. Utility Model Content
[0004] The purpose of this invention is to provide a low-cost isolated 485 communication circuit to solve the problems raised in the prior art.
[0005] To achieve the above objectives, this utility model provides the following technical solution:
[0006] A low-cost isolated 485 communication circuit includes a communication circuit and an isolation circuit. The communication circuit includes a 485 transceiver control chip U50. The input terminal of the 485 transceiver control chip U50 is connected to capacitors C196 and C197, diode D24, and diode D25 connected in parallel. The parallel connection of capacitors C196, C197, D24, and D25 is then connected to a common-mode filter inductor L1. The common-mode filter inductor L1 is connected to the signal input terminal through a fuse F. The output terminal of the communication circuit is connected to the isolation circuit. The isolation circuit includes a high-speed optocoupler U49. A transistor Q17 is disposed between the high-speed optocoupler U49 and the 485 transceiver control chip U50. The transistor Q17 is connected in series with resistors R247 and R250.
[0007] In a preferred embodiment, the input terminal of the 485 transceiver control chip U50 is connected to an interface H10, and the interface H10 is connected in parallel with resistors R251, R252, R253 and R255, and the resistors R251, R252, R253 and R255 are connected in series.
[0008] In a preferred embodiment, the input terminal of the 485 transceiver control chip U50 is connected to capacitors C192 and C194 connected in parallel.
[0009] In a preferred embodiment, the transistor Q17 is a PNP transistor, the resistor R247 is connected in series with a resistor R244, and the resistor R244 is connected in parallel with capacitors C190 and C193.
[0010] In a preferred embodiment, the input terminal of the high-speed optocoupler U49 is connected to resistors R254 and R256, capacitor C200 and capacitor C201.
[0011] In a preferred embodiment, the output terminal of the high-speed optocoupler U49 is connected to resistors R248 and R249, and the output terminal of the high-speed optocoupler U49 is connected to capacitors C189 and C191 connected in parallel. After capacitors C189 and C191 are connected in parallel, resistors R245 and R246 are connected in parallel. Resistor R245 is connected in series with capacitor C198, and resistor R246 is connected in series with capacitor C199.
[0012] Compared with the prior art, the beneficial effects of this utility model are:
[0013] 1. This utility model combines a high-speed isolation optocoupler in an isolation circuit with a common non-isolated 485 transceiver control chip, and then uses transistors and other circuits to make the circuit meet the requirements of 485 communication and the purpose of electrical isolation. It is also cheaper than an isolated 485 chip, and the isolation circuit has the function of logic level switching to realize high and low level conversion.
[0014] 2. The communication rate of a typical single-chip isolated 485 transceiver control chip is 500k-1M, while this solution can achieve a communication rate of 10M, which is higher. Attached Figure Description
[0015] Fig. 1 This is a schematic diagram of the communication circuit of this utility model;
[0016] Fig. 2 This is a schematic diagram of the isolation circuit of this utility model. Detailed Implementation
[0017] 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.
[0018] Example: Please refer to Figs. 1-2 This utility model provides a low-cost isolated 485 communication circuit, the technical solution of which is as follows:
[0019] A low-cost isolated 485 communication circuit includes a communication circuit and an isolation circuit. The communication circuit includes a 485 transceiver control chip U50. The input terminal of the 485 transceiver control chip U50 is connected to capacitors C196 and C197, diode D24, and diode D25 connected in parallel. The parallel connection of capacitors C196, C197, D24, and D25 is then connected to a common-mode filter inductor L1. The common-mode filter inductor L1 is connected to the signal input terminal through a fuse F. The output terminal of the communication circuit is connected to the isolation circuit. The isolation circuit includes a high-speed optocoupler U49. A transistor Q17 is disposed between the high-speed optocoupler U49 and the 485 transceiver control chip U50. The transistor Q17 is connected in series with resistors R247 and R250.
[0020] In a preferred embodiment, the input terminal of the 485 transceiver control chip U50 is connected to an interface H10, and the interface H10 is connected in parallel with resistors R251, R252, R253 and R255, and the resistors R251, R252, R253 and R255 are connected in series.
[0021] In a preferred embodiment, the input terminal of the 485 transceiver control chip U50 is connected to capacitors C192 and C194 connected in parallel.
[0022] In a preferred embodiment, the transistor Q17 is a PNP transistor, the resistor R247 is connected in series with a resistor R244, and the resistor R244 is connected in parallel with capacitors C190 and C193.
[0023] In a preferred embodiment, the input terminal of the high-speed optocoupler U49 is connected to resistors R254 and R256, capacitor C200 and capacitor C201.
[0024] In a preferred embodiment, the output terminal of the high-speed optocoupler U49 is connected to resistors R248 and R249, and the output terminal of the high-speed optocoupler U49 is connected to capacitors C189 and C191 connected in parallel. After capacitors C189 and C191 are connected in parallel, resistors R245 and R246 are connected in parallel. Resistor R245 is connected in series with capacitor C198, and resistor R246 is connected in series with capacitor C199.
[0025] The working principle of this utility model:
[0026] After passing through fuses F1 / F2, the input signal is filtered by common-mode filter inductor L1. Port spike suppression and absorption are achieved through capacitors C196 and C197, diodes D24 and D25. The signal then enters the general non-isolated 485 transceiver control chip U50 for analysis. Simultaneously, matching resistors R252, R253, R251, and R255 are added to increase the 485 communication matching resistance. After analyzing the signal, the 485 transceiver control chip U50 outputs the 485RX1 signal.
[0027] The 485RX1 signal, parsed by the 485 transceiver control chip U50, is transmitted to the base of transistor Q17 via resistor R250. Transistor Q17 is a PNP transistor. The switching on and off of transistor Q17 controls the conduction and switching off of the upper LED of the high-speed optocoupler U49, causing the receiving end DSP_485RX1 to receive different level signals. Furthermore, the level of DSP_485RX1 is consistent with the level of 485RX1, thus achieving the goal of matching the level of the isolated 485 chip at the MCU end. The 485TX1 signal works similarly. This invention uses a common transceiver control chip U50 for transmitting and receiving 485 communication information, uses a high-speed optocoupler U49 for electrical signal isolation, and uses a combination of transistors to change the signal level, achieving the goal of matching the level of the isolated 485 communication at the MCU receiving end, while also being lower in cost and higher in speed.
[0028] It will be apparent to those skilled in the art that this invention is not limited to the details of the exemplary embodiments described above, and that it can be implemented in other specific forms without departing from the spirit or essential characteristics of this invention. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of this invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within this invention. No reference numerals in the claims should be construed as limiting the scope of the claims.
Claims
1. A low-cost isolated 485 communication circuit, comprising a communication circuit and an isolation circuit, characterized in that: The communication circuit includes a 485 transceiver control chip U50. The input terminal of the 485 transceiver control chip U50 is connected to capacitors C196 and C197, diode D24, and diode D25 connected in parallel. These capacitors are then connected to a common-mode filter inductor L1. The common-mode filter inductor L1 is connected to the signal input terminal via a fuse F. The output terminal of the communication circuit is connected to an isolation circuit. The isolation circuit includes a high-speed optocoupler U49. A transistor Q17 is positioned between the high-speed optocoupler U49 and the 485 transceiver control chip U50. The transistor Q17 is connected in series with resistors R247 and R250.
2. The low-cost isolated 485 communication circuit according to claim 1, characterized in that: The input terminal of the 485 transceiver control chip U50 is connected to an interface H10. The interface H10 is connected in parallel with resistors R251, R252, R253 and R255, and the resistors R251, R252, R253 and R255 are connected in series.
3. The low-cost isolated 485 communication circuit according to claim 1, characterized in that: The input terminal of the 485 transceiver control chip U50 is connected to capacitors C192 and C194, which are set in parallel.
4. The low-cost isolated 485 communication circuit according to claim 1, characterized in that: The transistor Q17 is a PNP transistor, the resistor R247 is connected in series with resistor R244, and the resistor R244 is connected in parallel with capacitors C190 and C193.
5. The low-cost isolated 485 communication circuit according to claim 1, characterized in that: The input terminal of the high-speed optocoupler U49 is connected to resistors R254 and R256, capacitors C200 and C201.
6. The low-cost isolated 485 communication circuit according to claim 1, characterized in that: The output terminal of the high-speed optocoupler U49 is connected to resistors R248 and R249. The output terminal of the high-speed optocoupler U49 is connected to capacitors C189 and C191 connected in parallel. After capacitors C189 and C191 are connected in parallel, resistors R245 and R246 are connected in parallel. Resistor R245 is connected in series with capacitor C198, and resistor R246 is connected in series with capacitor C199.