Low-cost wide-voltage power supply RS485 signal isolator

Abstract

The invention discloses a low-cost wide-voltage power supply RS485 signal isolator, which is applied to the technical field of signal isolators and comprises a wide-voltage input circuit, a DC5V isolation circuit, an RS485 level to TTL level circuit, a TTL level to RS485 level circuit and a TTL level isolation chip. After entering the power supply chip U6 through a DC6V-30V power supply, the input voltage can be converted into stable DC5V through the power supply chip U6. And at the moment, the DC5V is isolated by the power supply isolation chip U1 to generate DC5VO for power supply setting. Therefore, the limitation that the RS485 isolation module can only use DC5V power supply can be well solved, DC6V-30V wide-range power supply can be realized, and operators and an RS485 communication board card are effectively protected; the diode D6 is arranged to realize positive and negative connection protection of power supply of the power supply terminal. And meanwhile, the TVS tube and the fuse are arranged, so that the power supply part can be prevented from static electricity, surge, overvoltage and short circuit, and the interface card is prevented from being damaged by static electricity, surge and large-current signals which are serially connected by external signals.

Description

Technical Field

[0001] The invention belongs to the technical field of signal isolators, and in particular relates to a low-cost, wide-voltage power supply RS485 signal isolator. Background Art

[0002] RS485 isolator is a device used to protect RS485 communication system. It effectively isolates electrical noise, electromagnetic interference and ground loop by adding an isolation layer to the RS485 communication line, thereby improving the stability and reliability of the communication system.

[0003] At present, the Chinese invention with the announcement number: CN111817709B discloses a digital isolator circuit and digital isolator based on Efficient-OOK. The existing RS485 isolator has certain defects in use: first, when the communication interface of the S485 isolator is connected to the communication interface of the high-voltage equipment, it can only be powered by DC5V, so it is easy to damage the circuit on the RS485 isolator motherboard card. Secondly, the power supply voltage range is narrow. And because the isolation voltage is high, the operator is prone to electric shock at the end of use. Moreover, the RS485 isolator uses an optocoupler isolation solution to make the RS485 isolator with many components, which is not only large in size, but also has a high failure rate. At the same time, the load end protection measures of the RS485 isolator are relatively few, and it is impossible to form effective protection against lightning strikes, surges, etc. The static electricity, surges, and high current signals of the external signals are easy to damage the interface card. Finally, the level conversion chip in the RS485 isolator has a large load on the transceiver control pin, and it is troublesome when the controlled end needs to connect a 120Ω matching resistor. Summary of the invention

[0004] The purpose of the present invention is to provide a low-cost wide-voltage power supply RS485 signal isolator, which has the advantages of realizing DC6V-30V wide range power supply, effectively protecting operators and RS485 communication boards; at the same time, preventing static electricity, surges, and high current signals from external signals from damaging the interface card and making it more convenient for the controlled end to connect to a 120Ω matching resistor.

[0005] The above technical purpose of the present invention is achieved through the following technical scheme: a low-cost wide-voltage powered RS485 signal isolator, comprising a wide-voltage input circuit, a DC5V isolation circuit, an RS485 level conversion TTL level circuit, a TTL level conversion RS485 level circuit, and a TTL level isolation chip, wherein the TTL level isolation chip is arranged between the RS485 level conversion TTL level circuit and the TTL level conversion RS485 level circuit, the input end of the wide-voltage input circuit is electrically connected to a DC6V-30V power supply, the wide-voltage input circuit is electrically connected to the DC5V isolation circuit and the RS485 level conversion TTL level circuit, and the DC5V isolation circuit is electrically connected to the TTL level isolation chip and the TTL level conversion RS485 level circuit.

[0006] With the above technical solution, after the DC6V-30V power supply enters the power chip U6, the input voltage will be converted into a stable DC5V after passing through the power chip U6. At this time, the DC5V is isolated by the power isolation chip U1 to generate DC5VO for power supply. This can well solve the limitation that the RS485 isolation module can only use DC5V for power supply, and can achieve DC6V-30V wide range power supply. And it can physically isolate the control end and the device end, where the signal isolation chip U3 isolation voltage is 3000V, and the power isolation chip U1 isolation voltage is 1500V, which effectively protects the operator and the RS485 communication board; by setting the diode D6, the power supply terminal power supply positive and negative reverse connection protection can be achieved. At the same time, the TVS tube and fuse can be set to realize that the power supply part can be anti-static, surge, overvoltage, and short circuit, and prevent the static electricity, surge, and high current signal of the external signal from damaging the interface card; by setting the inverter U2 and the inverter U4, the TTL level can be automatically controlled to the RS485 level, and the common mode inductor can suppress the common mode interference. And if the controlled end needs to be connected to a 120Ω matching resistor, just short-circuit pins 1 and 3 of the CON1 connector externally, so that the controlled end can be more conveniently connected to the 120Ω matching resistor.

[0007] The present invention is further configured as follows: PW1+, PW1-, and a power chip U6 are provided inside the wide voltage input circuit, the power chip U6 is a BUCK type power chip U6 LV2842XLVDDCR, the PW1+ and PW1- are electrically connected to the positive and negative poles of a DC6V-30V power supply, respectively, and a diode D6, a fuse F5, a TVS tube D7, and a common mode inductor L5 are also electrically connected between the PW1+ and PW1- and the power chip U6, respectively.

[0008] The above technical solution is adopted: by setting a diode D6 that can prevent reverse power supply, the power supply terminal can be protected from reverse positive and negative power supply; the power supply part can use fuse F5 and TVS tube D7 to prevent static electricity, surge, overvoltage, and short circuit, and the common mode inductor L5 can suppress common mode interference.

[0009] The present invention is further configured as follows: a power isolation chip U1 is provided inside the DC5V isolation circuit, and the power isolation chip U1 is a power isolation chip U1 B0505S-1W type.

[0010] The present invention is further configured as follows: a level conversion chip IC2, a CON2 connector, an inverter U4, a resistor R14, and a resistor R15 are provided inside the RS485 level-to-TTL level circuit; the level conversion chip IC2 is a level conversion chip IC2SP3485 type; a fuse F3, a fuse F4, a common-mode inductor L6, a TVS tube D8, a TVS tube D9, and a TVS tube D10 are electrically connected between the CON2 connector and the level conversion chip IC2, respectively.

[0011] The above technical solution is adopted: TVS tubes D8, D9 and D10 are used to protect against external static electricity and surge, and fuses F3 and F4 are used to protect against external large current; thus, static electricity, surge and large current signals from external signals are further prevented from damaging the interface card. At the same time, common mode inductor L6 is set to better suppress common mode interference.

[0012] The present invention is further configured as follows: a level conversion chip IC1, a CON1 connector, an inverter U2, a resistor R7, and a resistor R8 are provided inside the TTL level to RS485 level circuit; the level conversion chip IC1 is a level conversion chip IC1SP3485 type; a fuse F1, a fuse F2, a common mode inductor L3, a TVS tube D1, a TVS tube D2, and a TVS tube D3 are electrically connected between the CON1 connector and the level conversion chip IC1, respectively.

[0013] The above technical solution is adopted: TVS tubes D1, D2 and D3 are used to protect against external static electricity and surges, and fuses F1 and F2 are used to protect against external large currents; thereby further preventing static electricity, surges and large current signals from external signals from damaging the interface card. At the same time, common mode inductor L3 is set to further improve the ability to suppress common mode interference.

[0014] The present invention is further configured as follows: the TTL level isolation chip is a TTL level isolation chip U3π122m31 type.

[0015] The present invention is further configured as follows: LED2 is further provided inside the DC5V isolation circuit, LED3 is further provided inside the RS485 level conversion circuit, and LED1 is further provided inside the TTL level conversion circuit, and LED2 and LED3 are green and blue respectively.

[0016] By adopting the above technical solution, the power indicator LED2 is added to make it easier to eliminate power failures; at the same time, the control end signal sending indicator LED3 and the controlled end signal sending indicator LED1 are added to make it easier to judge the signal sending status.

[0017] In summary, the present invention has the following beneficial effects: 1. After the DC6V-30V power supply enters the power chip U6, the input voltage will be converted into a stable DC5V after passing through the power chip U6. At this time, the DC5V is isolated by the power isolation chip U1 to generate DC5VO for power supply. This can well solve the limitation that the RS485 isolation module can only use DC5V for power supply, and can achieve a wide range of DC6V-30V power supply. And it can physically isolate the control end and the device end, where the isolation voltage of the signal isolation chip U3 is 3000V, and the isolation voltage of the power isolation chip U1 is 1500V, which effectively protects the operator and the RS485 communication board; 2. By setting the diode D6, the power supply terminal can be protected from reverse connection of positive and negative. At the same time, the TVS tube and fuse can be set to prevent static electricity, surge, overvoltage, and short circuit in the power supply part, and prevent static electricity, surge, and high current signals from external signals from damaging the interface card; 3. By setting inverter U2 and inverter U4, TTL level can be automatically converted to RS485 level for control, and common mode inductance can suppress common mode interference. And if the controlled end needs to be connected to a 120Ω matching resistor, just short-circuit pin 1 and pin 3 of the CON1 connector externally, so that the controlled end can be more conveniently connected to a 120Ω matching resistor. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is the circuit composition principle diagram of the present invention; Figure 2 It is the principle diagram of the wide voltage input circuit of the present invention; Figure 3 This is the principle diagram of the DC5V isolation circuit of the present invention; Figure 4 This is the schematic diagram of the control end RS485 to TTL level and inverter circuit of the present invention; Figure 5 This is the schematic diagram of the load-end RS485 to TTL level and inverter circuit of the present invention; Figure 6The figure is a schematic diagram of a TTL level signal isolation circuit of the present invention. DETAILED DESCRIPTION

[0019] The present invention is further described in detail below in conjunction with the accompanying drawings.

[0020] Embodiment 1: refer to Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6A low-cost wide-voltage powered RS485 signal isolator comprises a wide-voltage input circuit, a DC5V isolation circuit, an RS485 level conversion TTL level circuit, a TTL level conversion RS485 level circuit, and a TTL level isolation chip. The TTL level isolation chip is arranged between the RS485 level conversion TTL level circuit and the TTL level conversion RS485 level circuit. The input end of the wide-voltage input circuit is electrically connected to a DC6V-30V power supply. The wide-voltage input circuit is electrically connected to the DC5V isolation circuit and the RS485 level conversion TTL level circuit respectively. The DC5V isolation circuit is electrically connected to the TTL level isolation chip and the TTL level conversion RS485 level circuit respectively. PW1+, PW1-, and a power chip U6 are arranged inside the wide-voltage input circuit. The power chip U6 is a BUCK type power chip U6. LV2842XLVDDCR, the PW1+ and PW1- are electrically connected to the positive and negative poles of the DC6V-30V power supply, respectively, and the diode D6, the fuse F5, the TVS tube D7, and the common mode inductor L5 are electrically connected between the PW1+ and PW1- and the power chip U6, respectively; the DC5V isolation circuit is provided with a power isolation chip U1, and the power isolation chip U1 is a power isolation chip U1 B0505S-1W type; the RS485 level to TTL level circuit is provided with a level conversion chip IC2, a CON2 connector, an inverter U4, a resistor R14, and a resistor R15, and the level conversion chip IC2 is a level conversion chip IC2 SP3485 type, fuse F3, fuse F4, common mode inductor L6, TVS tube D8, TVS tube D9, TVS tube D10 are electrically connected between the CON2 connector and the level conversion chip IC2 respectively; the TTL level to RS485 level circuit is provided with a level conversion chip IC1, a CON1 connector, an inverter U2, a resistor R7, and a resistor R8 inside, the level conversion chip IC1 is a level conversion chip IC1 SP3485 type, fuse F1, fuse F2, common mode inductor L3, TVS tube D1, TVS tube D2, TVS tube D3 are electrically connected between the CON1 connector and the level conversion chip IC1 respectively; the TTL level isolation chip is a TTL level isolation chip U3 π122m31 type; LED2 is also provided inside the DC5V isolation circuit, LED3 is also provided inside the RS485 level to TTL level circuit, and LED1 is also provided inside the TTL level to RS485 level circuit, and the LED2 and LED3 are green and blue respectively.

[0021] Embodiment 2: refer to Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 , a low-cost wide-voltage powered RS485 signal isolator, including a wide-voltage input circuit, a DC5V isolation circuit, an RS485 level conversion TTL level circuit, a TTL level conversion RS485 level circuit, and a TTL level isolation chip. The TTL level isolation chip is arranged between the RS485 level conversion TTL level circuit and the TTL level conversion RS485 level circuit. The input end of the wide-voltage input circuit is electrically connected to a DC6V-30V power supply. The wide-voltage input circuit is electrically connected to the DC5V isolation circuit and the RS485 level conversion TTL level circuit respectively. The DC5V isolation circuit is electrically connected to the TTL level isolation chip and the TTL level conversion RS485 level circuit respectively. After entering the power chip U6 through the DC6V-30V power supply, the input voltage will be converted into a stable DC5V after passing through the power chip U6. At this time, the DC5V is isolated by the power isolation chip U1 to generate a DC5VO for power supply. Thereby, the limitation that the RS485 isolation module can only use DC5V for power supply can be well solved, and a wide range of DC6V-30V power supply can be realized. And it can physically isolate the control end from the device end, where the signal isolation chip U3 isolation voltage is 3000V, and the power isolation chip U1 isolation voltage is 1500V, which effectively protects the operator and the RS485 communication board; by setting the diode D6, the power supply terminal can be protected from positive and negative power supply. At the same time, the TVS tube and fuse can be set to prevent static electricity, surge, overvoltage, and short circuit in the power supply part, and prevent static electricity, surge, and high current signals from external signals from damaging the interface card; by setting the inverter U2 and the inverter U4, the TTL level can be automatically controlled by converting the RS485 level, and the common mode inductor can suppress common mode interference. And if the controlled end needs to connect a 120Ω matching resistor, just short-circuit the 1st and 3rd pins of the CON1 connector, so that it is more convenient to connect the 120Ω matching resistor to the controlled end.

[0022] refer to Figure 2 , the wide voltage input circuit is equipped with PW1+, PW1-, and power chip U6. The power chip U6 is a BUCK type power chip U6 LV2842XLVDDCR. PW1+ and PW1- are electrically connected to the positive and negative poles of the DC6V-30V power supply, respectively. PW1+ and PW1- are also electrically connected to the power chip U6 with a diode D6, a fuse F5, a TVS tube D7, and a common mode inductor L5. By setting a diode D6 that can prevent reverse power supply, the power supply terminal can be protected from reverse positive and negative power supply; the power supply part can use the fuse F5 and TVS tube D7 to prevent static electricity, surge, overvoltage, and short circuit, and the common mode inductor L5 can suppress common mode interference.

[0023] refer to Figure 3A power isolation chip U1 is provided inside the DC5V isolation circuit, and the power isolation chip U1 is a power isolation chip U1 B0505S-1W type.

[0024] refer to Figure 4 The RS485 level to TTL level circuit is provided with a level conversion chip IC2, a CON2 connector, an inverter U4, a resistor R14, and a resistor R15. The level conversion chip IC2 is a level conversion chip IC2 SP3485 type. The CON2 connector and the level conversion chip IC2 are electrically connected with fuses F3, fuses F4, common mode inductors L6, TVS tubes D8, TVS tubes D9, and TVS tubes D10. By setting a diode D6 that can prevent reverse power supply, the power supply terminal can be protected from reverse positive and negative power supply; the power supply part can use fuses F5 and TVS tubes D7 to prevent static electricity, surges, overvoltage, and short circuits, and the common mode inductor L5 can suppress common mode interference.

[0025] refer to Figure 5 The TTL level to RS485 level circuit is provided with a level conversion chip IC1, a CON1 connector, an inverter U2, a resistor R7, and a resistor R8. The level conversion chip IC1 is a level conversion chip IC1 SP3485 type. The CON1 connector and the level conversion chip IC1 are electrically connected with fuses F1, F2, common mode inductor L3, TVS tube D1, TVS tube D2, and TVS tube D3. External static electricity and surge are protected by TVS tubes D1, TVS tubes D2, and TVS tubes D3, and external large current is protected by fuses F1 and F2; thus, the interface card is further prevented from being damaged by static electricity, surge, and large current signals from external signals. At the same time, the common mode inductor L3 is provided to further improve the ability to suppress common mode interference.

[0026] refer to Figure 6 , the TTL level isolation chip is the TTL level isolation chip U3 π122m31 type.

[0027] refer to Figure 3 , Figure 4 , Figure 5 , LED2 is also provided inside the DC5V isolation circuit, LED3 is also provided inside the RS485 level conversion circuit, and LED1 is also provided inside the TTL level conversion circuit. LED2 and LED3 are green and blue respectively. The addition of power indicator LED2 makes it easier to troubleshoot power failures; at the same time, the addition of control end sending signal indicator LED3 and controlled end sending signal indicator LED1 makes it easier to judge the signal sending status.

[0028] Brief description of the use process: Power supply part: In the wide voltage input circuit (DC6V-30V), PW1+ is connected to the positive pole of the DC6V-30V power supply, and PW1- is connected to the negative pole of the DC6V-30V power supply. The DC power supply passes through the power supply anti-reverse connection diode D6, the 0.5A self-recovery fuse for overcurrent protection, the unidirectional TVS tube D7 for anti-static surge, and then the common mode inductor L5 for filtering common mode interference, and then enters the BUCK type power chip U6 LV2842XLVDDCR. After passing through the power chip U6, the input voltage will be converted into a stable DC5V, and start to supply power to the control side of the power isolation chip U1, inverter U4, level conversion chip IC2 and level isolation chip U3; at this time, DC5V is isolated by the power isolation chip U1 B0505S-1W to generate DC5VO, which is responsible for supplying power to the controlled end of the level conversion chip IC1, inverter U2 and level isolation chip U3 on the control side; Principle of signal transmission: When sending data, the control end sends data to the controlled end. The control end sends data through the CON2 connector. The data passes through fuse F3, fuse F4, and common mode inductor L6 to reach the level conversion chip IC2 SP3485. At this time, the level conversion chip IC2 is in the data receiving state. The data is converted to TTL level through the level conversion chip IC2. The TTL level passes through the level isolation chip U3π122m31 to achieve 3000V signal isolation. After the TTL level passes through the TTL level isolation chip U3 π122m31, there will be two situations: First, if the signal sent at this time is 0, the TX signal of the TTL level isolation chip U3 becomes a high level after passing through the inverter U2 and is connected to the level conversion chip IC1 The R / T pin of SP3485 and the R / T pin of the level conversion chip IC1 are high level and enter the sending mode. The TX data reaches the controlled end connector CON1 connector through the level conversion chip IC1, the common mode inductor L3, the fuse F1 and the fuse F2. Secondly, if the data to be sent is 1 at this time, the TX signal of the TTL level isolation chip U3 chip is 1, which becomes a low level after passing through the inverter U2 and is connected to the R / T pin of the SP3485 of the level conversion chip IC1. The R / T pin of the level conversion chip IC1 is low level and enters the receiving mode. At this time, the A\B of the level conversion chip IC1 enters the high impedance mode. Since the resistor R7 pulls the A signal high and the resistor R8 pulls the B signal low, the A\B signal transmission is 1. The data reaches the controlled end connector CON1 connector through the common mode inductor L3, the fuse F1 and the fuse F2. When receiving data, the controlled end sends data to the controlling end. The data passes through fuse F1, fuse F2, and common mode inductor L3 before reaching the level conversion chip IC1. At this time, the level conversion chip IC1 is in the data receiving mode. The data passes through the level conversion chip IC1 SP3485 and is converted to TTL level. The TTL level passes through the level isolation chip U3π122m31 to achieve 3000V signal isolation. After the TTL level passes through the TTL level isolation chip U3π122m31, there will be two situations: First, if 0 is sent at this time, the TX1 signal of the TTL level isolation chip U3 becomes a high level after passing through the inverter U4 and is connected to the level conversion chip IC2 The R / T1 pin of SP3485 and the R / T1 pin of the level conversion chip IC2 are high level and enter the sending mode. The TX1 data reaches the controlled end connector CON2 connector through the level conversion chip IC2, common mode inductor L6, fuse F3, and fuse F4; secondly, if the data sent at this time is 1, the TX1 signal of the TTL level isolation chip U3 chip is 1, which becomes a low level after passing through the inverter U4 and is connected to the R / T1 pin of the level conversion chip IC2 SP3485. The R / T1 pin of the level conversion chip IC2 is low level and enters the receiving mode. At this time, A\B of the level conversion chip IC2 SP3485 enters the high impedance mode. Since the resistor R14 pulls the A1 signal high and the resistor R15 pulls the B1 signal low, the A1\B1 signal transmission is 1, and the data reaches the controlled end connector CON2 connector through the common mode inductor L6, fuse F3, and fuse F4.

[0029] This specific embodiment is merely an explanation of the present invention and is not a limitation of the present invention. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed. However, as long as they are within the scope of the claims of the present invention, they are protected by the patent law.

Claims

1. A low-cost wide-voltage powered RS485 signal isolator, comprising a wide-voltage input circuit, a DC5V isolation circuit, an RS485 level conversion circuit to a TTL level circuit, a TTL level conversion circuit to an RS485 level circuit, and a TTL level isolation chip, characterized in that: The TTL level isolation chip is arranged between the RS485 level conversion TTL level circuit and the TTL level conversion RS485 level circuit, the input end of the wide voltage input circuit is electrically connected to a DC6V-30V power supply, the wide voltage input circuit is electrically connected to the DC5V isolation circuit and the RS485 level conversion TTL level circuit respectively, and the DC5V isolation circuit is electrically connected to the TTL level isolation chip and the TTL level conversion RS485 level circuit respectively.

2. A low-cost wide-voltage powered RS485 signal isolator according to claim 1, characterized in that: The wide voltage input circuit is internally provided with PW1+, PW1-, and a power chip U6, wherein the power chip U6 is a BUCK type power chip U6LV2842XLVDDCR, and the PW1+ and PW1- are electrically connected to the positive and negative electrodes of a DC6V-30V power supply, respectively. A diode D6, a fuse F5, a TVS tube D7, and a common mode inductor L5 are also electrically connected between the PW1+ and PW1- and the power chip U6, respectively.

3. A low-cost wide-voltage powered RS485 signal isolator according to claim 1, characterized in that: A power isolation chip U1 is provided inside the DC5V isolation circuit, and the power isolation chip U1 is a power isolation chip U1B0505S-1W.

4. A low-cost wide-voltage powered RS485 signal isolator according to claim 1, characterized in that: The RS485 level to TTL level circuit is internally provided with a level conversion chip IC2, a CON2 connector, an inverter U4, a resistor R14, and a resistor R15. The level conversion chip IC2 is a level conversion chip IC2 SP3485 type. A fuse F3, a fuse F4, a common mode inductor L6, a TVS tube D8, a TVS tube D9, and a TVS tube D10 are electrically connected between the CON2 connector and the level conversion chip IC2, respectively.

5. The low-cost wide-voltage powered RS485 signal isolator according to claim 1, characterized in that: The TTL level to RS485 level circuit is internally provided with a level conversion chip IC1, a CON1 connector, an inverter U2, a resistor R7, and a resistor R8. The level conversion chip IC1 is a level conversion chip IC1 SP3485 type. A fuse F1, a fuse F2, a common mode inductor L3, a TVS tube D1, a TVS tube D2, and a TVS tube D3 are electrically connected between the CON1 connector and the level conversion chip IC1, respectively.

6. The low-cost wide-voltage powered RS485 signal isolator according to claim 1, characterized in that: The TTL level isolation chip is a TTL level isolation chip U3π122m31 type.

7. The low-cost wide-voltage powered RS485 signal isolator according to claim 1, characterized in that: The DC5V isolation circuit is further provided with an LED2, the RS485 level conversion circuit is further provided with an LED3, and the TTL level conversion circuit is further provided with an LED1. The LED2 and LED3 are green and blue respectively.

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