Circuit capable of improving RS485 communication anti-interference effect of frequency converter

Abstract

The utility model discloses a circuit capable of improving the RS485 communication anti-interference effect of a frequency converter, which relates to the technical field of electronic circuits and comprises a communication module and an isolation module, and the communication module is connected with an upper computer through the isolation module. The communication module comprises an RS485 transceiving chip, a switch SW1 and a resistor R113, and the resistor R113 is connected between the first transceiving end and the second transceiving end of the RS485 transceiving chip through the switch SW1. The RS485 communication circuit provided by the utility model can effectively reduce RS485 communication problems caused by C-R-C filter circuit voltage drop or external noise interference.

Description

Technical Field

[0001] The utility model relates to the technical field of electronic circuits, in particular to a circuit capable of improving the anti-interference effect of RS485 communication of a frequency converter. Background Art

[0002] Figure 1 The circuit schematic diagram of the traditional RS485 communication circuit is shown in FIG. Figure 1 As shown, the RS485 communication lines of standard inverter I / O products currently on the market generally use CRC filtering circuits to filter out communication noise. Furthermore, when a single or multiple inverters communicate with a host computer (such as a PLC), external terminal resistors are required to improve communication performance. Specifically, traditional RS485 communication lines have the following drawbacks:

[0003] (1) Although external terminal resistors can improve communication performance, they will cause customers trouble in selection and application, which will invisibly increase costs and reduce the market competitiveness of products.

[0004] (2) Although the CRC filtering part in the line has a certain effect on shielding the noise of the communication front channel, the voltage drop problem of the CRC circuit itself will cause the attenuation and reduction of the communication line signal level, resulting in recognition errors of the host computer and thus causing poor communication.

[0005] (3) There is no filtering circuit at the output end of the communication chip receiver, and there is a risk of noise coupling (wireless noise, etc.) interference in data reception. Utility Model Content

[0006] In response to the above problems and technical requirements, the applicant has proposed a circuit that can improve the anti-interference effect of RS485 communication of the inverter.

[0007] The technical solution of the utility model is as follows:

[0008] A circuit capable of improving the anti-interference effect of RS485 communication of a frequency converter comprises a communication module and an isolation module, wherein the communication module is connected to a host computer via the isolation module;

[0009] The communication module includes an RS485 transceiver chip, a switch SW1 and a resistor R113. The resistor R113 is connected between a first transceiver terminal and a second transceiver terminal of the RS485 transceiver chip through the switch SW1.

[0010] A further technical solution is that the switch SW1 includes a sliding jumper switch of model CAS-220B1, and the communication module further includes a resistor R112 and a resistor R114;

[0011] The fifth pin of the switch SW1 is connected to the first transceiver terminal of the RS485 transceiver chip, and the second pin of the switch SW1 is connected to the second transceiver terminal of the RS485 transceiver chip;

[0012] The resistor R113 is connected between the first pin and the fourth pin of the switch SW1 . The first pin of the switch SW1 is grounded via the resistor R114 . The fourth pin of the switch SW1 is connected to the first power supply voltage via the resistor R112 .

[0013] A further technical solution is that the communication module further includes a resistor R115 and a capacitor C18;

[0014] The receiver output end of the RS485 transceiver chip is connected to one end of the resistor R115, and the other end of the resistor R115 is grounded via the capacitor C18.

[0015] A further technical solution is that the communication module further includes a resistor R60, and the receiver output end of the RS485 transceiver chip is connected to the first power supply voltage through the resistor R60.

[0016] A further technical solution is that the communication module further includes a resistor R116, a Schmidt inverting trigger U10A and a Schmidt inverting trigger U10B, wherein:

[0017] The receiver output end of the RS485 transceiver chip is connected to the input end of the Schmidt inverting trigger U10B, the output end of the Schmidt inverting trigger U10B is connected to the input end of the Schmidt inverting trigger U10A, and the output end of the Schmidt inverting trigger U10A is connected to the driver input end of the RS485 transceiver chip and is connected to the first power supply voltage through the resistor R116.

[0018] Its further technical solution is that the power supply terminal of the RS485 transceiver chip is connected to the first power supply voltage, the ground terminal of the RS485 transceiver chip is grounded, and the power supply terminal of the RS485 transceiver chip is connected to the ground terminal of the RS485 transceiver chip through a capacitor C3.

[0019] Its further technical solution is that the first transceiver end of the RS485 transceiver chip is connected to the first power supply voltage through the resistor R31, the second transceiver end of the RS485 transceiver chip is grounded through the resistor R35, and the first transceiver end and the second transceiver end of the RS485 transceiver chip are grounded through the TVS diode.

[0020] A further technical solution is that the isolation module includes a photocoupler PC6, a resistor R84, a resistor R85, a resistor R86, a resistor R87, a switch device Q1 and a switch device Q3, wherein:

[0021] The photoelectric coupler PC6 includes a dual-channel photoelectric coupler model ACSL-6210, the eighth pin of the photoelectric coupler PC6 is connected to the third electrode end of the switch device Q1 through the resistor R85, the first electrode end of the switch device Q1 is connected to the seventh pin of the photoelectric coupler PC6 and is connected to the second power supply voltage, and the second electrode end of the switch device Q1 is connected to the signal output end of the host computer;

[0022] The fifth pin of the photoelectric coupler PC6 is grounded, and the sixth pin of the photoelectric coupler PC6 is connected to the first electrode end of the switch device Q1 through the resistor R84 and is connected to the signal input end of the host computer;

[0023] The second pin of the photoelectric coupler PC6 is connected to the driver input terminal of the RS485 transceiver chip, and is connected to the first electrode terminal of the switch device Q3 through the resistor R87. The first electrode terminal of the switch device Q3 is connected to the first power supply voltage and is connected to the third pin of the photoelectric coupler PC6.

[0024] The fourth pin of the photoelectric coupler PC6 is connected to the third electrode terminal of the switch device Q3 through the resistor R86, and the second electrode terminal of the switch device Q3 is connected to the receiver output terminal of the RS485 transceiver chip.

[0025] A further technical solution is that the isolation module further includes a photocoupler PC3, a switch device Q2, a resistor R24 ​​and a resistor R20;

[0026] The anode of the primary light-emitting diode of the photoelectric coupler PC3 is connected to the second power supply voltage through the resistor R20, the cathode of the primary light-emitting diode of the photoelectric coupler PC3 is connected to the third electrode end of the switch device Q2, and the second electrode end of the switch device Q2 is connected to the enable signal end of the host computer;

[0027] The collector of the secondary-side phototransistor of the photocoupler PC3 is connected to the first power supply voltage, and the emitter of the secondary-side phototransistor of the photocoupler PC3 is grounded through the resistor R24 ​​and connected to the enable terminal of the RS485 transceiver chip driver and receiver.

[0028] The beneficial technical effects of the utility model are:

[0029] (1) Connect the terminal resistor to the transceiver end of the RS485 transceiver chip through switch SW1 to make it built-in and optional. This maintains signal stability when the circuit is connected to multiple inverters or for long-distance communication, and can also optimize communication performance when connected to a single inverter.

[0030] (2) Remove the CRC filter circuit in the traditional RS485 communication circuit and increase the signal amplitude sent to the host computer. Even if there is noise flowing in, it can be excluded and recognized as the actual signal value, avoiding the host computer's recognition error, which may cause poor communication.

[0031] (3) Set up an RC filter circuit at the output end of the RS485 transceiver chip receiver to reduce noise interference.

[0032] (4) Add a Schmitt inverting trigger for filtering to filter the noise in the idle state and maintain the stability of the communication signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is the circuit schematic diagram of the traditional RS485 communication circuit.

[0034] Figure 2 This is a circuit schematic diagram of an embodiment of the communication module provided by the utility model.

[0035] Figure 3 This is a circuit principle diagram of an embodiment of a signal input / output optical coupling isolation circuit provided by the utility model.

[0036] Figure 4 This is a circuit principle diagram of an embodiment of an enable end optical coupler isolation circuit provided by the utility model.

[0037] Figure 5 This is a pin diagram of the CPU provided by the utility model.

[0038] Figure 6 It is the waveform diagram of the simulated signal transmitted to the host computer by the traditional communication circuit when the input signals are the same.

[0039] Figure 7 It is a waveform diagram of the simulation signal transmitted to the host computer by the communication circuit provided by the utility model when the input signals are the same.

[0040] Figure 8 This is the simulated signal waveform diagram of the inverter input to the traditional communication circuit when the host computer receives the same signal.

[0041] Figure 9 It is a simulation signal waveform diagram of the frequency converter input to the communication circuit provided by the utility model when the host computer receives the same signal.

[0042] Figure 10 This is the signal noise waveform of a traditional communication circuit in idle state.

[0043] Figure 11 This is a signal noise waveform diagram of a communication circuit in an idle state provided by the utility model. DETAILED DESCRIPTION

[0044] The specific implementation of the present utility model will be further described below with reference to the accompanying drawings.

[0045] The utility model provides a circuit capable of improving the anti-interference effect of RS485 communication of a frequency converter, comprising a communication module and an isolation module, wherein the communication module is connected to a host computer via the isolation module;

[0046] The communication module includes an RS485 transceiver chip, a switch SW1 and a resistor R113. The resistor R113 is connected between a first transceiver terminal and a second transceiver terminal of the RS485 transceiver chip through the switch SW1.

[0047] Specifically, resistor R113 is a terminal resistor used to improve communication performance when a single or multiple inverters communicate with a host computer via a communication circuit. Connecting the terminal resistor between the first and second transceiver terminals of the RS485 transceiver chip via switch SW1 makes it a built-in, optional feature. This reduces application costs compared to external terminal resistors, while maintaining signal stability and optimizing communication performance. Furthermore, the CRC filter circuit between the communication circuit and the communication bus in traditional communication circuits is removed, reducing line resistance and avoiding the problem of signal level attenuation and degradation in the communication line caused by the CRC filter circuit, ensuring that the host computer can accurately identify high and low level signals.

[0048] Figure 1 A circuit schematic diagram of an embodiment of a communication module is shown. In this embodiment, the RS485 transceiver chip is model 75176B, the switch SW1 is a CAS-220B1 sliding jumper switch, and the communication module also includes resistors R112 and R114. The fifth pin of the switch SW1 is connected to the first transceiver terminal of the RS485 transceiver chip, i.e., the sixth pin of the RS485 transceiver chip, and the second pin of the switch SW1 is connected to the second transceiver terminal of the RS485 transceiver chip, i.e., the seventh pin of the RS485 transceiver chip. Resistor R113 is connected between the first and fourth pins of the switch SW1. The first pin of the switch SW1 is grounded via resistor R114, and the fourth pin of the switch SW1 is connected to the first power supply voltage via resistor R112. The third and sixth pins of the switch SW1 are left unconnected. The functions of the pins of the RS485 transceiver chip and the sliding jumper switch are consistent with those of the prior art.

[0049] Furthermore, the communication module further includes a resistor R115 and a capacitor C18;

[0050] The receiver output end of the RS485 transceiver chip is connected to one end of the resistor R115, and the other end of the resistor R115 is grounded via the capacitor C18.

[0051] Specifically, resistor R115 and capacitor C18 form an RC filter circuit for filtering out signal noise. In this embodiment, the RC filter circuit has a filtering time constant of approximately 2.07 μs. The communication module also includes a resistor R60. The receiver output terminal of the RS485 transceiver chip, i.e., the first pin of the RS485 transceiver chip, is connected to the first power supply voltage through resistor R60.

[0052] At the same time, the communication module also includes capacitor C3, resistor R31, resistor R35 and TVS diode, and the power supply terminal of the RS485 transceiver chip accesses the first power supply voltage, and the ground terminal of the RS485 transceiver chip is grounded, and the power supply terminal of the RS485 transceiver chip is connected with the ground terminal of the RS485 transceiver chip by capacitor C3. The first transceiver end of the RS485 transceiver chip accesses the first power supply voltage by resistor R31, and the second transceiver end of the RS485 transceiver chip is grounded by resistor R35, and the first transceiver end and the second transceiver end of the RS485 transceiver chip are grounded by TVS diode. In the present embodiment, the TVS diode is a multi-channel TVS diode using model PG712FBS23, for protecting subsequent circuits from the influence of transient voltage and transient current. The first pin of the TVS diode is connected with the first transceiver end of the RS485 transceiver chip, and the second pin of the TVS diode is connected with the second transceiver end of the RS485 transceiver chip, and the ground terminal of the TVS diode is grounded.

[0053] Furthermore, the communication module further includes a resistor R116, a Schmitt inverting trigger U10A, and a Schmitt inverting trigger U10B.

[0054] The Schmidt inverting trigger U10A and the Schmidt inverting trigger U10B are used to filter idle noise and maintain the stability of the communication signal. The receiver output of the RS485 transceiver chip is connected to the input of the Schmidt inverting trigger U10B, the output of the Schmidt inverting trigger U10B is connected to the input of the Schmidt inverting trigger U10A, and the output of the Schmidt inverting trigger U10A is connected to the driver input of the RS485 transceiver chip, i.e., the fourth pin of the RS485 transceiver chip, and is connected to the first power supply voltage through resistor R116.

[0055] Furthermore, the isolation module includes a signal input / output optocoupler isolation circuit formed by a photoelectric coupler PC6, a resistor R84, a resistor R85, a resistor R86, a resistor R87, a switch device Q1, and a switch device Q3, to achieve optoelectronic isolation between the RS485 chip driver input and receiver output and the host computer.

[0056] like Figure 3As shown, in this embodiment, the photocoupler PC6 adopts a dual-channel photocoupler model ACSL-6210. The eighth pin of the photocoupler PC6 is connected to the third electrode terminal of the switch device Q1 through a resistor R85. The first electrode terminal of the switch device Q1 is connected to the seventh pin of the photocoupler PC6 and is connected to the second power supply voltage. The second electrode terminal of the switch device Q1 is connected to the signal output terminal of the host computer. The fifth pin of the photocoupler PC6 is grounded. The sixth pin of the photocoupler PC6 is connected to the first electrode terminal of the switch device Q1 through a resistor R84 and is connected to the signal input terminal of the host computer. The second pin of the photocoupler PC6 is connected to the driver input terminal of the RS485 transceiver chip and is connected to the first electrode terminal of the switch device Q3 through a resistor R87. The first electrode terminal of the switch device Q3 is connected to the first power supply voltage and is connected to the third pin of the photocoupler PC6. The fourth pin of the photocoupler PC6 is connected to the third electrode terminal of the switch device Q3 through a resistor R86. The second electrode terminal of the switch device Q3 is connected to the receiver output terminal of the RS485 transceiver chip. The functions of the pins of the photoelectric coupler PC6 are consistent with those in the prior art.

[0057] Furthermore, the isolation module further includes an enable end optocoupler isolation circuit formed by a photocoupler PC3, a switch device Q2, a resistor R24 ​​and a resistor R20.

[0058] like Figure 4 The model of the photoelectric coupler PC3 in this embodiment is ACPL-217. The anode of the primary light-emitting diode of the photoelectric coupler PC3 is connected to the second power supply voltage through the resistor R20. The cathode of the primary light-emitting diode of the photoelectric coupler PC3 is connected to the third electrode end of the switch device Q2. The second electrode end of the switch device Q2 is connected to the enable signal end of the host computer. The collector of the secondary phototransistor of the photoelectric coupler PC3 is connected to the first power supply voltage. The emitter of the secondary phototransistor of the photoelectric coupler PC3 is grounded through the resistor R24 ​​and connected to the enable end of the RS485 transceiver chip driver and the enable end of the receiver. The enable end of the RS485 transceiver chip driver is Figure 2 The third pin of the RS485 transceiver chip is the enable pin of the RS485 transceiver chip receiver. Figure 2 In this embodiment, the host computer uses a CPU of model TMS320F28035, and the first power supply voltage is 5.5V, and the second power supply voltage is 3.3V.

[0059] Furthermore, the switching device Q1 , the switching device Q2 and the switching device Q3 are triodes.

[0060] In this embodiment, the switching device Q1 and the switching device Q3 are PNP transistors, and the switching device Q2 is an NPN transistor. For the transistors, the first electrode terminal of the switching device Q1, the switching device Q2, and the switching device Q3 is the emitter terminal, the second electrode terminal is the base terminal, and the third electrode terminal is the collector terminal. In specific implementations, the switching device Q1, the switching device Q2, and the switching device Q3 may also be other power devices with switching functions. It should be noted that Figure 3 and Figure 4 In the symbols of the switching device Q1, the switching device Q2 and the switching device Q3, the base terminal resistance and the resistance between the emitter and the base terminal represent the internal resistance of the transistor.

[0061] The utility model conducts a performance simulation test on the traditional communication circuit and the improved communication circuit. Figure 6 and Figure 7 When the input signals are the same, the traditional communication circuit and the improved communication circuit transmit the signal waveforms to the host computer, such as Figure 6 and Figure 7 As shown in the figure, when the communication circuit receives the same signal from the inverter, the traditional communication circuit will attenuate the signal level transmitted to the host computer due to the existence of the CRC filter circuit voltage divider. Figure 7 As shown, under the same input signal, the signal level transmitted to the host computer by the improved communication circuit provided by the present invention is significantly higher than that of the traditional communication circuit, which can prevent the host computer from identifying errors and improve the stability of communication. Figure 8 and Figure 9 The following are the signal waveforms of the inverter input to the traditional communication circuit and the improved communication circuit when the host computer receives the same signal. Figure 8 and Figure 9 It can be seen that if the host computer receives signals of the same signal level, a higher voltage must be provided using a traditional communication circuit. Figure 10 and Figure 11 They are the signal noise waveforms of the traditional communication circuit and the improved communication circuit in the idle state, respectively. Figure 10 and Figure 11 It can be seen that the improved communication circuit can filter noise and reduce noise interference.

[0062] In summary, the RS485 communication circuit provided by the utility model can effectively reduce RS485 communication problems caused by CRC filter circuit voltage drop or external noise interference, improve communication anti-interference effect, reduce communication failure rate, and provide built-in optional terminal resistors to reduce application costs.

[0063] The above description is only a preferred embodiment of the present invention, and the present invention is not limited to the above embodiment. It is understood that other improvements and variations directly derived or imagined by those skilled in the art without departing from the spirit and concept of the present invention should be considered to be included in the scope of protection of the present invention.

Claims

1. A circuit that can improve the anti-interference effect of RS485 communication of a frequency converter, characterized in that: It includes a communication module and an isolation module, wherein the communication module is connected to the host computer through the isolation module; The communication module includes an RS485 transceiver chip, a switch SW1 and a resistor R113. The resistor R113 is connected between a first transceiver terminal and a second transceiver terminal of the RS485 transceiver chip through the switch SW1.

2. The circuit for improving the anti-interference effect of RS485 communication of the frequency converter according to claim 1, characterized in that: The switch SW1 includes a sliding jumper switch of model CAS-220B1, and the communication module also includes a resistor R112 and a resistor R114; The fifth pin of the switch SW1 is connected to the first transceiver terminal of the RS485 transceiver chip, and the second pin of the switch SW1 is connected to the second transceiver terminal of the RS485 transceiver chip; The resistor R113 is connected between the first pin and the fourth pin of the switch SW1 . The first pin of the switch SW1 is grounded via the resistor R114 . The fourth pin of the switch SW1 is connected to the first power supply voltage via the resistor R112 .

3. The circuit for improving the anti-interference effect of RS485 communication of the frequency converter according to claim 1, characterized in that: The communication module also includes a resistor R115 and a capacitor C18; The receiver output end of the RS485 transceiver chip is connected to one end of the resistor R115, and the other end of the resistor R115 is grounded via the capacitor C18.

4. The circuit for improving the anti-interference effect of RS485 communication of a frequency converter according to claim 1, wherein: The communication module further includes a resistor R60 , and the receiver output end of the RS485 transceiver chip is connected to the first power supply voltage through the resistor R60 .

5. The circuit for improving the anti-interference effect of RS485 communication of a frequency converter according to claim 1, characterized in that: The communication module further includes a resistor R116, a Schmidt inverting trigger U10A and a Schmidt inverting trigger U10B, wherein: The receiver output end of the RS485 transceiver chip is connected to the input end of the Schmidt inverting trigger U10B, the output end of the Schmidt inverting trigger U10B is connected to the input end of the Schmidt inverting trigger U10A, and the output end of the Schmidt inverting trigger U10A is connected to the driver input end of the RS485 transceiver chip and is connected to the first power supply voltage through the resistor R116.

6. The circuit for improving the anti-interference effect of RS485 communication of a frequency converter according to claim 1, characterized in that: The power supply terminal of the RS485 transceiver chip is connected to the first power supply voltage, the ground terminal of the RS485 transceiver chip is grounded, and the power supply terminal of the RS485 transceiver chip is connected to the ground terminal of the RS485 transceiver chip through the capacitor C3.

7. The circuit for improving the anti-interference effect of RS485 communication of a frequency converter according to claim 1, characterized in that: The first transceiver terminal of the RS485 transceiver chip is connected to the first power supply voltage through the resistor R31, the second transceiver terminal of the RS485 transceiver chip is grounded through the resistor R35, and the first transceiver terminal and the second transceiver terminal of the RS485 transceiver chip are grounded through the TVS diode.

8. The circuit for improving the anti-interference effect of RS485 communication of a frequency converter according to claim 1, characterized in that: The isolation module includes a photoelectric coupler PC6, a resistor R84, a resistor R85, a resistor R86, a resistor R87, a switch device Q1 and a switch device Q3, wherein: The photoelectric coupler PC6 includes a dual-channel photoelectric coupler model ACSL-6210, the eighth pin of the photoelectric coupler PC6 is connected to the third electrode end of the switch device Q1 through the resistor R85, the first electrode end of the switch device Q1 is connected to the seventh pin of the photoelectric coupler PC6 and is connected to the second power supply voltage, and the second electrode end of the switch device Q1 is connected to the signal output end of the host computer; The fifth pin of the photoelectric coupler PC6 is grounded, and the sixth pin of the photoelectric coupler PC6 is connected to the first electrode end of the switch device Q1 through the resistor R84 and is connected to the signal input end of the host computer; The second pin of the photoelectric coupler PC6 is connected to the driver input terminal of the RS485 transceiver chip, and is connected to the first electrode terminal of the switch device Q3 through the resistor R87. The first electrode terminal of the switch device Q3 is connected to the first power supply voltage and is connected to the third pin of the photoelectric coupler PC6. The fourth pin of the photoelectric coupler PC6 is connected to the third electrode terminal of the switch device Q3 through the resistor R86, and the second electrode terminal of the switch device Q3 is connected to the receiver output terminal of the RS485 transceiver chip.

9. The circuit for improving the anti-interference effect of RS485 communication of a frequency converter according to claim 8, characterized in that: The isolation module further includes a photocoupler PC3, a switch device Q2, a resistor R24 ​​and a resistor R20; The anode of the primary light-emitting diode of the photoelectric coupler PC3 is connected to the second power supply voltage through the resistor R20, the cathode of the primary light-emitting diode of the photoelectric coupler PC3 is connected to the third electrode end of the switch device Q2, and the second electrode end of the switch device Q2 is connected to the enable signal end of the host computer; The collector of the secondary-side phototransistor of the photocoupler PC3 is connected to the first power supply voltage, and the emitter of the secondary-side phototransistor of the photocoupler PC3 is grounded through the resistor R24 ​​and connected to the enable terminal of the RS485 transceiver chip driver and receiver.

10. The circuit capable of improving the anti-interference effect of RS485 communication of a frequency converter according to claim 9, characterized in that: The switching device Q1 , the switching device Q2 and the switching device Q3 are triodes.

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