An isolated power supply automatic switching communication device

Abstract

The present invention discloses an isolated power supply automatic switching communication device, which belongs to the field of communication technology. The scheme is as follows: the input end of the power supply interface strong current protection circuit is connected to the power supply interface, and the voltage output end of the power supply interface strong current protection circuit is sequentially connected to the device to be powered via a wide voltage power supply step-down circuit, a frequency conversion drive push-pull output boost isolation circuit, a low voltage difference output voltage stabilizing circuit, and a power supply automatic switching no-voltage loss output circuit, and the input end of the power supply automatic switching no-voltage loss output circuit is connected to a battery; the RS485 communication strong current protection circuit is connected to an optocoupler isolation communication circuit for two-way communication, and the output end of the optocoupler isolation communication circuit is connected to the device to be powered. The wide voltage power supply step-down circuit adopts a full-wave rectifier bridge, and the power supply does not distinguish polarity, which plays a good foolproof role. It cooperates with a step-down device with a wide voltage input and has a micro-ampere-level static circuit, so that the wide voltage input range is 4-50V, which effectively reduces the power consumption of the product.

Description

Technical Field

[0001] The present invention relates to the field of communication technology, and in particular to an isolated power supply automatic switching communication device. Background Art

[0002] RS485 has the characteristics of long distance, multi-node, custom protocol and low transmission cost, so it is widely used in the field of heat meters.

[0003] In the existing technical solutions, in terms of circuit protection: the power supply interface adopts a single series fuse or series diode solution, which can only meet the protection of low voltage and short circuit, and does not have the function of protecting equipment under the condition of mains power. Once the strong power (mains power 220V AC) is connected incorrectly, it is easy to cause equipment damage; and in harsh environments, there are problems of signal interference and low data transmission rate. In terms of external power supply circuit: 24V to 5V and 5V to 3.3V are used to output to the power supply switching circuit and the equipment to be powered. The existing technology does not have electrical isolation, and is easily interfered and damaged in harsh industrial environments; and some manufacturers use fixed-frequency drive transformer isolation in terms of isolation, and the single-ended output loss is large. In terms of power supply switching circuit: a single MOS tube switching and series diode solution is adopted. Because the voltage difference of the diode is 0.7V and 0.3V, it is greatly affected by temperature, so the output voltage is unstable and the voltage loss is large. Summary of the invention

[0004] The object of the present invention is to provide an isolated power supply automatic switching communication device to reduce the power consumption of an RS485 communication device.

[0005] To achieve the above purpose, the present invention adopts an isolated power supply automatic switching communication device, including: a power supply interface strong current protection circuit, a wide voltage power supply step-down circuit, a variable frequency drive push-pull output boost isolation circuit, a low voltage difference output voltage stabilization circuit, a power supply automatic switching no-voltage loss output circuit, an optical coupler isolation communication circuit, an RS485 communication strong current protection circuit and a device to be powered;

[0006] The input end of the power supply interface strong current protection circuit is connected to the power supply interface, and the voltage output end of the power supply interface strong current protection circuit is connected to the device to be powered via the wide voltage power supply step-down circuit, the frequency conversion drive push-pull output step-up isolation circuit, the low voltage difference output voltage stabilization circuit, and the power supply automatic switching no-voltage loss output circuit in sequence, and the input end of the power supply automatic switching no-voltage loss output circuit is connected to a battery;

[0007] The RS485 communication strong current protection circuit is connected to the optocoupler isolation communication circuit for two-way communication, and the output end of the optocoupler isolation communication circuit is connected to the device to be powered.

[0008] Preferably, the power supply interface strong current protection circuit includes a resettable fuse F1, a resettable fuse F2 and a TVS tube D6;

[0009] The power supply input terminal VIN1 is connected to one pin of the TVS tube D6 through the self-resetting fuse F1, and the power supply input terminal VIN2 is connected to the other pin of the TVS tube D6 through the self-resetting fuse F2.

[0010] Preferably, the wide voltage power supply buck circuit includes a full-wave rectifier bridge, a voltage regulator tube D2, rectifier filter capacitors C2 and C3, and a buck U1;

[0011] The node where the resettable fuse F1 is connected to one pin of the TVS tube D6, and the node where the resettable fuse F2 is connected to another pin of the TVS tube D6 are respectively connected to the AC input end of the full-wave rectifier bridge;

[0012] The positive output terminal of the full-wave rectifier bridge is connected to the rectifier filter capacitor C2, the voltage regulator tube D2, the capacitor C3 to the input VIN terminal and the EN enable terminal of the buck U1, and the other ends of the rectifier filter capacitors C2, C3 and the voltage regulator tube D2 are connected to the reference ground GND1 respectively;

[0013] The RT terminal of the buck U1 is connected to the resistor R4 to the reference ground GND1, the LX terminal of the buck U1 is connected to one end of the capacitor C1 and one end of the resistor R2 through the inductor L1, the other end of the capacitor C1 is connected to the GND terminal of the buck U1, the other end of the resistor R2 is connected to the capacitor C1 through the capacitor C4 and then to the reference ground GND1, the output terminal voltage of the buck U1 is connected to the FB terminal of the buck U1 and the resistor R5 through the resistor R3, and the other end of the resistor R5 is connected to the reference ground GND1.

[0014] Preferably, the variable frequency drive push-pull output boost isolation circuit comprises a high frequency push-pull drive circuit and a high frequency push-pull input and output transformer circuit;

[0015] The voltage output end of the power supply interface strong current protection circuit is connected to the voltage interface of the high-frequency push-pull driving circuit, and the voltage output end of the high-frequency push-pull driving circuit is connected to the high-frequency push-pull input-output transformer circuit.

[0016] Preferably, the high-frequency push-pull drive circuit includes a frequency conversion driver U3 and a bypass capacitor C7, the GND terminal of the frequency conversion driver U3 is connected to the reference ground GND1, the driving end of the frequency conversion driver U3 is connected to the voltage output end of the high-current protection circuit and then connected to one end of the bypass capacitor C7, and the other end of the bypass capacitor C7 is connected to the reference ground GND1; the driving end of the frequency conversion driver U3 is also connected to the primary coil of the high-frequency push-pull input-output transformer circuit.

[0017] Preferably, the high-frequency push-pull input-output transformer circuit includes a high-frequency transformer T1, a diode D9, a diode D3, a diode D12, a voltage regulator tube D11, a voltage regulator tube D1 and filter capacitors C10, C11 and C6;

[0018] The primary coil of the high-frequency transformer T1 is connected to the driving end of the variable frequency driver U3, the power supply line of the high-frequency transformer T1 is connected to the power interface of the variable frequency driver U3, the two ends of the secondary coil of the high-frequency transformer T1 are respectively connected to the positive electrode of the diode D9 and the positive electrode of the diode D3, the negative electrode of the diode D9 is connected to the negative electrode of the diode D3, and then connected to one end of the filter capacitor C10, one end of the filter capacitor C11, and the negative electrode of the voltage regulator D11 in sequence, the negative electrode of the voltage regulator D11 is connected to the 4.3V power supply as the power supply end, the other end of the filter capacitor C10 is connected, the other end of the filter capacitor C11 is connected, and the positive electrode of the voltage regulator D11 is connected and then connected to the reference ground GND2;

[0019] The anode of the diode D3 is connected to the filter capacitor C6 and the resistor R10 through the diode D12. The resistor R10 is connected to the cathode of the voltage regulator tube D1 and then connected to the 3.6V power supply. The filter capacitor C6 is connected to the anode of the voltage regulator tube D1 and then connected to the reference ground GND2.

[0020] Preferably, the low voltage difference output voltage stabilizing circuit comprises a low voltage linear regulator U2, a filter capacitor C8, a bypass capacitor C9 and a field effect transistor Q1, the input terminal VIN of the low voltage linear regulator U2 is connected to the 4.3V power supply, the voltage output terminal Vout of the low voltage linear regulator U2 is sequentially connected to one end of the filter capacitor C8 and one end of the bypass capacitor C9, and then connected to the device to be powered as a power supply terminal, the other end of the filter capacitor C8 is connected to the other end of the bypass capacitor C9 and then connected to the reference ground GND2;

[0021] The drain of the field effect transistor Q1 is connected to the power supply end, and the gate of the field effect transistor Q1 is connected to the 3.6V power supply.

[0022] Preferably, the power supply automatic switching lossless output circuit includes a field effect transistor Q2 and a lithium battery P3, the source of the field effect transistor Q2 is connected to the source of the field effect transistor Q1, the drain of the field effect transistor Q2 is connected to the positive electrode of the lithium battery P3, the gate of the field effect transistor Q2 is connected to the 3.6V power supply, and the negative electrode of the lithium battery P3 is connected to the reference ground GND2.

[0023] Preferably, the optical coupling isolation communication circuit includes a logic gate U7, a logic gate U8, an optical coupler U5, an optical coupler U7, an optical coupler U8, an optical coupler U9, an optical coupler U10, an optical coupler U11 and an optical coupler U12;

[0024] The digital output terminal DO of the RS485 communication strong current protection circuit is connected to the input terminal of the optocoupler U11 and the input terminal of the optocoupler U5. The output terminal of the optocoupler U11 is connected to the output terminal of the optocoupler U5 and then connected to the input terminal of the logic gate U8. The output terminal of the logic gate U8 is connected to the RX terminal of the signal receiving terminal MCU of the device to be powered. The optocoupler U5 and the logic gate U8 are both connected to a power supply. The input terminal of the optocoupler U5, the input terminal of the optocoupler U11 and the input terminal of the logic gate U8 are all grounded.

[0025] The DE end of the RS485 communication strong current protection circuit is connected to the input end of the optical coupler U9, and the output end of the optical coupler U9 is connected to the R / D end of the signal receiving end MCU;

[0026] The DI end of the RS485 communication high-current protection circuit is connected to the input end of the logic gate U7, the output end of the logic gate U7 is connected to the input end of the optocoupler U10, the output end of the optocoupler U10 is respectively connected to the output end of the optocoupler U12 and the TX end of the signal receiving end MCU, the input end of the optocoupler U10 is connected to the input end of the optocoupler U12, the logic gate U7 and the optocoupler U12 are both connected to the power supply, and the output end of the logic gate U7, the output end of the optocoupler U10 and the output end of the optocoupler U12 are all grounded.

[0027] Compared with the prior art, the present invention has the following technical effects: the high-current protection circuit of the power supply interface in the present invention has the function of high-current protection and overcurrent protection for the wide-voltage power supply step-down circuit. The wide-voltage power supply step-down circuit adopts a full-wave rectifier bridge to make the power supply regardless of polarity, which plays a good anti-mistake effect. At the same time, it cooperates with the step-down device with wide voltage input and has a micro-ampere-level static circuit, so that the wide voltage input range is 4-50V, which effectively reduces the power consumption of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings:

[0029] Figure 1 It is a principle block diagram of an isolated power supply automatic switching communication device;

[0030] Figure 2 It is the topological structure diagram of the strong current protection circuit of the power supply interface;

[0031] Figure 3 It is a topological diagram of a wide voltage power supply buck circuit;

[0032] Figure 4 It is the topological structure diagram of the variable frequency drive push-pull output boost isolation circuit;

[0033] Figure 5 It is a topological connection structure diagram of a low voltage difference output voltage stabilization circuit and a power supply automatic switching voltage loss-free output circuit;

[0034] Figure 6 It is a topological diagram of the optocoupler isolation communication circuit. DETAILED DESCRIPTION

[0035] In order to further illustrate the features of the present invention, please refer to the following detailed description and drawings of the present invention. The drawings are for reference and illustration only and are not intended to limit the scope of protection of the present invention.

[0036] See also Figure 1 As shown, this embodiment discloses an isolated power supply automatic switching communication device, including a power supply interface strong current protection circuit, a wide voltage power supply step-down circuit, a variable frequency drive push-pull output boost isolation circuit, a low voltage difference output voltage stabilization circuit, a power supply automatic switching no-voltage loss output circuit, an optocoupler isolation communication circuit, an RS485 communication strong current protection circuit, and a device to be powered;

[0037] The input end of the power supply interface strong current protection circuit is connected to the power supply interface, and the voltage output end of the power supply interface strong current protection circuit is connected to the device to be powered via the wide voltage power supply step-down circuit, the frequency conversion drive push-pull output step-up isolation circuit, the low voltage difference output voltage stabilization circuit, and the power supply automatic switching no-voltage loss output circuit in sequence, and the input end of the power supply automatic switching no-voltage loss output circuit is connected to a battery;

[0038] The RS485 communication strong current protection circuit is connected to the optocoupler isolation communication circuit for two-way communication, and the output end of the optocoupler isolation communication circuit is connected to the device to be powered.

[0039] See also Figures 2 to 3 As shown, the power supply interface strong current protection circuit includes a resettable fuse F1, a resettable fuse F2 and a TVS tube D6;

[0040] The power input terminal VIN1 is connected to the pin 1 of the TVS tube D6, the pin 3 of the diode D4, and the pin 1 of the diode D5 through the self-recovery fuse F1. The power input terminal VIN2 is connected to the pin 2 of the TVS tube D6, the pin 3 of the diode D8, and the pin 1 of the diode D10 through the self-recovery fuse F2; the pin 1 of the diode D4 and the pin 1 of D8 are both connected to GND1

[0041] like Figure 3As shown, the wide voltage power supply step-down circuit includes a full-wave rectifier bridge, a voltage regulator tube D2, rectifier filter capacitors C2 and C3, and a voltage regulator U1; the node N1 is respectively connected to the pin 3 of the diode D4 and the pin 1 of the diode D5, the node N2 is respectively connected to the pin 3 of the diode D8 and the pin 1 of D10, the pin 1 of the diode D4 and the pin 1 of the diode D8 are both connected to GND1, the pin 3 of the diode D5 and the pin 3 of the diode D10 are connected and then connected to one end of the capacitor C2, the negative electrode of the voltage regulator tube D2, and one end of the capacitor C3 to the input VIN end of the voltage regulator U1, the other end of the rectifier filter capacitor C2, the other end of the rectifier filter capacitor C3, and the other end of the voltage regulator tube D9 are respectively connected to the reference ground GND1, and a resistor R1 is connected between one section of the capacitor C2 and the negative electrode of the voltage regulator tube D2. The EN enable terminal of the buck U1 is connected to its input VIN terminal, the RT terminal of the buck U1 is connected to the resistor R4 to the reference ground GND1, the 10th pin of the buck U1 is connected to the capacitor C1 and the resistor R2 through the inductor L1, the other end of the capacitor C1 and the other end of the resistor R2 are respectively connected to the reference ground GND1, the capacitor C4 is connected between the other end of the capacitor C1 and the other end of the resistor R2, the output voltage VCC_3.3V of the buck U1 is connected to the 5th pin FB terminal of U1 and the resistor R5 through the resistor R3, and the other end of R5 is connected to the reference ground GND1.

[0042] It should be noted that the power supply interface high-current protection circuit combines the overcurrent protection characteristics of F2 and F1 with the transient suppression characteristics of D4 to enable it to have the functions of high-current AC220 protection and overcurrent protection; the full-wave rectifier bridge composed of diodes D4, D5, D8, and D10 makes the power supply regardless of polarity and plays a good anti-mistake effect. The wide-voltage input step-down device U1 has a quiescent current of microamperes and an efficient conversion circuit, which effectively reduces power consumption and has a wide voltage input range of 4-50V.

[0043] Compared with the existing technology, this solution uses a high-efficiency wide voltage input DC-DC converter, with an efficiency of 92% and a quiescent current power consumption of less than 1uA. The existing technology uses a power input of 24v, an efficiency of 80%, and a quiescent current power consumption greater than 1mA. In addition, the energy consumption of the DC conversion part in this solution is saved by more than 12%, and the wide voltage input range reaches 4~50V, which is much larger than the power input range of the existing technology, greatly improving the power supply capacity of the product.

[0044] In addition, the existing technical protection can only meet the requirements of voltage transient current protection and short-circuit overcurrent protection; the strong current protection in this solution adopts the matching design of fuse response time and TVS response time to enable it to have the functions of AC power protection, overvoltage protection, short-circuit protection, etc., and the circuit design is simple.

[0045] See also Figure 4As shown, the variable frequency drive push-pull output boost isolation circuit includes a high-frequency push-pull drive circuit and a high-frequency push-pull input-output transformer circuit; the voltage output end of the power supply interface strong current protection circuit is connected to the voltage interface of the high-frequency push-pull drive circuit, and the voltage output end of the high-frequency push-pull drive circuit is connected to the high-frequency push-pull input-output transformer circuit.

[0046] The high-frequency push-pull drive circuit includes a variable frequency driver U3 and a bypass capacitor C7, and the high-frequency push-pull input and output transformer circuit includes a high-frequency transformer T1, a diode D9, a diode D3, a diode D12, a voltage regulator tube D11, a voltage regulator tube D1 and filter capacitors C10, C11 and C6. The specific connections are:

[0047] Pin 3 of the variable frequency driver U3 is connected to pin 1 of the high frequency transformer T1, pin 1 of the variable frequency driver U3 is connected to pin 3 of the high frequency transformer T1, pin 2 of the variable frequency driver U3 is connected to voltage VCC_3.3V and bypass capacitor C7, and the other end of capacitor C7 is connected to reference ground GND1. Pin 6 of the high frequency transformer T1 is connected to the positive electrode of diode D9, pin 4 of the high frequency transformer T1 is connected to the positive electrode of diode D3, the negative electrode of diode D9 is connected to the negative electrode of diode D3, and then connected to one end of filter capacitor C10, one end of capacitor C11, and the negative electrode of voltage regulator D11 in sequence, and the negative electrode of voltage regulator D11 serves as the VCC_4.3V voltage output terminal; the other end of capacitor C10, the other end of capacitor C11, and the other end of voltage regulator D11 are respectively connected to reference ground GND2.

[0048] Pin 5 of the high-frequency transformer T1 is connected to the reference ground GND2, and pin 4 of the high-frequency transformer T1 is connected to the resistor R10 through the diode D12. One end of the resistor R10 connected to the diode D12 is connected to one end of the filter capacitor C6, and the other end of the resistor R10 is connected to the negative electrode of the Zener diode D1. The positive electrode of the Zener diode D1 is connected to the other end of the capacitor C6 and then connected to the reference ground GND2. The negative electrode of the Zener diode D1 serves as the VCC_3.6V voltage output end.

[0049] The frequency conversion drive push-pull output boost isolation circuit adopts a high-frequency push-pull input and output transformer circuit and a high-frequency push-pull drive circuit. The push-pull circuit has the advantages of complementarity, low loss, and high transformer core utilization, which can improve the transformer conversion efficiency and load capacity. Therefore, the isolation circuit has the functions of low loss, electrical isolation and high conversion rate, which greatly reduces the power consumption of the product.

[0050] It should be noted that in this embodiment, a frequency conversion driver push-pull topology is used to output a frequency in the range of 220KHZ-550KHZ to drive a high-frequency step-up transformer, and the driving frequency is automatically adjusted according to the load size. The drive output frequency amplitude is equal, and the phase difference is 180°, so that the pulse amplitude of the driving transformer is 2×VCC_3.6V. It is coupled to the secondary coil of the transformer through the transformer core, and has high impedance, so it has electrical isolation characteristics. The transformer turns ratio N1=18 (primary): N2=23 (secondary), Uo=VCC×N2 / N1 makes it have a boosting effect; the 6th and 4th feet of the transformer secondary coil provide two alternating complementary outputs with pulses of equal amplitude and 180° phase difference, and the low-voltage difference Schottky diodes D9, D3, capacitors C10, C11 are used for full-wave rectification and filtering, so that the output current has continuity and improves the load capacity.

[0051] See also Figure 5 As shown, the low voltage difference output voltage stabilization circuit includes a low voltage linear voltage regulator U2, a filter capacitor C8, a bypass capacitor C9 and a field effect transistor Q1; the power supply automatic switching lossless output circuit includes a field effect transistor Q2 and a lithium battery P3. The 4.3V voltage output end of the voltage regulator D11, i.e., the node VDD_4.3V (referring to the transformer output voltage 4.3V after isolation), is connected to pin 1 (input end VIN) of the low voltage difference linear regulator U2, pin 2 (ground end GND) of U2 is connected to the reference ground GND2, pin 5 of U2 (voltage output end Vout) is connected to one end of the filter capacitor C8 and one end of the bypass capacitor C9, and the output voltage 3.6V is provided to the device to be powered, the node 3.6V is connected to the drain of Q1, the source of Q1 is connected to the source of Q2, the 3.6V voltage output end of the voltage regulator D1, i.e., the node VDD_3.6V (referring to the transformer output voltage 3.6V after isolation), is respectively connected to the gate of Q1 and the gate of Q2, the drain of Q2 is connected to pin 1 of P3, and pin 2 of P3 is connected to the reference ground GND2 (P3 is a lithium battery 3.6V, pin 1 of P3 is the positive electrode of the lithium battery, and pin 2 is the negative electrode of the lithium battery).

[0052] The circuit principle is as follows: when the external power supply is used, the isolation transformer outputs 4.3V and 3.6V voltages, and the 4.3V voltage is stepped down by the low voltage difference linear regulator U2 to output 3.6V to power the device to be powered. When Q1 and Q2 are both turned off, the output voltage of battery P3 is turned off to prevent the current from flowing back into battery P3 and causing damage to the battery. When the external power supply is not used, the output voltage of the isolation transformer is 0V, and Q1 and Q2 are turned on to make the output voltage of battery P3 3.6V to power the device to be powered.

[0053] Therefore, the low voltage difference output voltage stabilizing circuit and the power supply automatic switching lossless output circuit have the characteristics of automatic power supply switching, lossless voltage output and protection against current backflow, which solves the voltage loss phenomenon caused by the series connection of diodes, and at the same time prevents the loss and device damage caused by the backflow of current, thereby improving the battery utilization rate and effectively reducing the loss.

[0054] See also Figure 6 As shown, the optocoupler isolation communication circuit includes a logic gate U7, a logic gate U8, an optocoupler U5, an optocoupler U7, an optocoupler U8, an optocoupler U9, an optocoupler U10, an optocoupler U11 and an optocoupler U12;

[0055] The digital output terminal DO of the RS485 communication high-current protection circuit is connected to pin 1 of the optocoupler U11 and pin 2 of U5 through capacitor C27. Pin 2 of U11 and pin 1 of U5 are respectively connected to the reference ground GND1. Pin 4 of the optocoupler U11 is connected to pin 3 of the optocoupler U5 and then connected to one end of the resistor R15 and one end of the capacitor C17 in sequence, and then connected to pin 2 of the logic gate U8. The other end of the resistor R15 and the other end of the capacitor C17 are both connected to the reference ground GND2. Pin 3 of the optocoupler U11 is connected to resistor R16 and then to the reference ground GND2. Pin 4 of the optocoupler U5 is connected to resistor R34 and then to a 3.6V power supply. Pin 3 of the logic gate U8 is connected to the reference ground GND2. Pin 5 of U8 is connected to a 3.6V power supply. Pin 4 of U8 is connected to the RX end of the signal receiving end MCU of the device to be powered (microcontrol unit (MCU)).

[0056] The DE end of the RS485 communication high-current protection circuit is connected to pin 3 of the optocoupler U9 and one end of the resistor R9, the other end of the resistor R9 is connected to the reference ground GND1, pin 2 of the optocoupler U9 is connected to the reference ground GND2, pin 1 of the optocoupler U9 is connected to the R / D node of the MCU, and pin 4 of the optocoupler U9 is connected to the output voltage VCC_3.3V of the buck U1.

[0057] The DI pin of the RS485 communication high-current protection circuit is connected to pin 4 of the logic gate U7, pin 5 of U7 is connected to the output voltage VCC_3.3V of the voltage reducer U1, pin 2 of U7 is connected to one end of the resistor R17, one end of the capacitor C16, pin 4 of the optocoupler U10, and pin 3 of the optocoupler U12. The other end of the resistor R17 and the other end of the capacitor C16 are both connected to the reference ground GND1. The VCC_3.3V node is connected to pin 4 of the optocoupler U12 through the resistor R18, and the pin 3 of the optocoupler U10 is connected to the reference ground GND1 through the resistor R7. The pin 2 of the optocoupler U10 and the pin 1 of the optocoupler U12 are both connected to the reference ground GND2. The pin 1 of U10 is connected to the pin 2 of U12 and then connected to the TX node of the MCU through the capacitor C15 and the resistor R28.

[0058] In this embodiment, the receiving and sending signals of the RS485 communication strong current protection circuit respectively adopt a dual optical communication isolation coupling circuit. The advantage of this circuit is that it adopts a capacitor isolation DC solution when processing pulse timing, reduces the power consumption during optical coupling communication, and the rising edge and falling edge during optical coupling communication are converted by different optical couplings without affecting each other, which solves the communication failure caused by discrete types at different temperatures and different batches, and is compatible with the use of multiple models of optical coupling devices. It provides favorable convenience in purchasing, selection, and material substitution. It solves the communication abnormality caused by the single optical coupling circuit being affected by temperature, improves the product's use environment, and is compatible with the use of multiple models of optical coupling devices, making the product selection range wider.

[0059] It should be noted that the working principle of the isolated power supply automatic switching communication device in this embodiment is:

[0060] When the external power supply is 4-50V, the protection input of the strong current protection circuit is used to convert the wide voltage power supply step-down circuit to VCC_3.3V output. The VCC_3.3V voltage is input to the frequency conversion drive push-pull output boost isolation circuit to isolate and boost the voltage to VDD_4.3V. VDD_4.3V outputs a voltage of 3.6V through a low voltage difference output voltage regulator circuit. The voltage of 3.6V is provided to the device to be powered through the power supply automatic switching no-voltage loss output circuit to cut off the battery power supply. When the battery is powered and there is no external power supply, the power supply is switched to the battery power supply through the power supply automatic switching circuit to provide the device to be powered.

[0061] The power supply interface strong current protection circuit in this solution has the purpose of preventing the equipment from being damaged due to improper operation of personnel when strong current is connected to the equipment so that the equipment can work normally. The wide voltage power supply step-down circuit has the function of widening the input power supply range and improving the customer's power supply application environment. The frequency conversion drive push-pull output boost isolation circuit improves the conversion efficiency of the isolation circuit through push-pull drive, and the transformer isolation reduces the mutual interference between circuits, and suppresses the common mode interference of the ground to effectively improve the anti-interference ability of the product. The optocoupler isolation communication circuit has the function of signal isolation and power consumption reduction. The RS485 communication strong current protection circuit has the function of protecting the RS485 chip from being damaged when it is connected to the mains. When the device sends and receives TTL data, it is isolated by the optocoupler isolation communication circuit and then a differential signal is generated by the RS485 chip AB and sent to the host computer.

[0062] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An isolated power supply automatic switching communication device, characterized in that: include: Power supply interface strong current protection circuit, wide voltage power supply step-down circuit, variable frequency drive push-pull output boost isolation circuit, low voltage difference output voltage stabilization circuit, power supply automatic switching no-voltage loss output circuit, optocoupler isolation communication circuit, RS485 communication strong current protection circuit and equipment to be powered; The input end of the power supply interface strong current protection circuit is connected to the power supply interface, and the voltage output end of the power supply interface strong current protection circuit is connected to the device to be powered via the wide voltage power supply step-down circuit, the frequency conversion drive push-pull output step-up isolation circuit, the low voltage difference output voltage stabilization circuit, and the power supply automatic switching no-voltage loss output circuit in sequence, and the input end of the power supply automatic switching no-voltage loss output circuit is connected to a battery; The RS485 communication strong current protection circuit is connected to the optocoupler isolation communication circuit for two-way communication, and the output end of the optocoupler isolation communication circuit is connected to the device to be powered; The variable frequency drive push-pull output boost isolation circuit includes a high-frequency push-pull drive circuit and a high-frequency push-pull input-output transformer circuit. The high-frequency push-pull input-output transformer circuit includes a high-frequency transformer T1, a diode D9, a diode D3, a diode D12, a voltage regulator D11, a voltage regulator D1 and filter capacitors C10, C11 and C6; the primary coil of the high-frequency transformer T1 is connected to the driving end of the variable frequency driver U3 in the high-frequency push-pull drive circuit, the power supply line of the high-frequency transformer T1 is connected to the power supply interface of the variable frequency driver U3, and the two ends of the secondary coil of the high-frequency transformer T1 are respectively connected to the positive electrode of the diode D9 and the positive electrode of the diode D3. The cathode of the tube D9 is connected to the cathode of the diode D3 and then connected to one end of the filter capacitor C10, one end of the filter capacitor C11, and the cathode of the voltage regulator tube D11 in sequence. The cathode of the voltage regulator tube D11 is used as a 4.3V voltage output terminal. The other end of the filter capacitor C10, the other end of the filter capacitor C11, and the anode of the voltage regulator tube D11 are connected and then connected to the reference ground GND2. The anode of the diode D3 is connected to the filter capacitor C6 and the resistor R10 through the diode D12. The resistor R10 is connected to the cathode of the voltage regulator tube D1. The cathode of the voltage regulator tube D1 is used as a 3.6V voltage output terminal. The filter capacitor C6 is connected to the anode of the voltage regulator tube D1 and then connected to the reference ground GND2. The low voltage difference output voltage stabilizing circuit includes a low voltage linear regulator U2, a filter capacitor C8, a bypass capacitor C9 and a field effect tube Q1, the input end VIN of the low voltage linear regulator U2 is connected to the 4.3V voltage output end of the voltage regulator tube D11, the voltage output end Vout of the low voltage linear regulator U2 is sequentially connected to one end of the filter capacitor C8 and one end of the bypass capacitor C9, and then connected to the device to be powered as a power supply end, the other end of the filter capacitor C8 is connected to the other end of the bypass capacitor C9, and then connected to the reference ground GND2; the drain of the field effect tube Q1 is connected to the power supply end, and the gate of the field effect tube Q1 is connected to the 3.6V voltage output end of the voltage regulator tube D1; The power supply automatic switching lossless output circuit includes a field effect tube Q2 and a lithium battery P3, the source of the field effect tube Q2 is connected to the source of the field effect tube Q1, the drain of the field effect tube Q2 is connected to the positive electrode of the lithium battery P3, the gate of the field effect tube Q2 is connected to the 3.6V voltage output terminal, and the negative electrode of the lithium battery P3 is connected to the reference ground GND2.

2. The isolated power supply automatic switching communication device according to claim 1, characterized in that: The power supply interface strong current protection circuit includes a resettable fuse F1, a resettable fuse F2 and a TVS tube D6; The power supply input terminal VIN1 is connected to one pin of the TVS tube D6 through the self-resetting fuse F1, and the power supply input terminal VIN2 is connected to the other pin of the TVS tube D6 through the self-resetting fuse F2.

3. The isolated power supply automatic switching communication device according to claim 2, characterized in that: The wide voltage power supply step-down circuit includes a full-wave rectifier bridge, a voltage regulator tube D2, rectifier filter capacitors C2 and C3, and a voltage reducer U1; The node where the resettable fuse F1 is connected to one pin of the TVS tube D6, and the node where the resettable fuse F2 is connected to another pin of the TVS tube D6 are respectively connected to the AC input end of the full-wave rectifier bridge; The positive output terminal of the full-wave rectifier bridge is connected to the rectifier filter capacitor C2, the voltage regulator tube D2, the capacitor C3 to the input VIN terminal and the EN enable terminal of the buck U1, and the other ends of the rectifier filter capacitors C2, C3 and the voltage regulator tube D2 are connected to the reference ground GND1 respectively; The RT terminal of the buck U1 is connected to the resistor R4 to the reference ground GND1, the LX terminal of the buck U1 is connected to one end of the capacitor C1 and one end of the resistor R2 through the inductor L1, the other end of the capacitor C1 is connected to the GND terminal of the buck U1, the other end of the resistor R2 is connected to the capacitor C1 through the capacitor C4 and then to the reference ground GND1, the output terminal voltage of the buck U1 is connected to the FB terminal of the buck U1 and the resistor R5 through the resistor R3, and the other end of the resistor R5 is connected to the reference ground GND1.

4. The isolated power supply automatic switching communication device according to claim 1, characterized in that: The voltage output end of the power supply interface strong current protection circuit is connected to the voltage interface of the high-frequency push-pull driving circuit, and the voltage output end of the high-frequency push-pull driving circuit is connected to the high-frequency push-pull input-output transformer circuit.

5. The isolated power supply automatic switching communication device according to claim 4, characterized in that: The high-frequency push-pull drive circuit includes a frequency conversion driver U3 and a bypass capacitor C7. The GND terminal of the frequency conversion driver U3 is connected to the reference ground GND1. The driving end of the frequency conversion driver U3 is connected to the voltage output end of the high-voltage protection circuit and then connected to one end of the bypass capacitor C7. The other end of the bypass capacitor C7 is connected to the reference ground GND1. The driving end of the frequency conversion driver U3 is also connected to the primary coil of the high-frequency push-pull input-output transformer circuit.

6. The isolated power supply automatic switching communication device according to any one of claims 1 to 5, characterized in that: The optical coupling isolation communication circuit includes a logic gate U7, a logic gate U8, an optical coupler U5, an optical coupler U7, an optical coupler U8, an optical coupler U9, an optical coupler U10, an optical coupler U11 and an optical coupler U12; The digital output terminal DO of the RS485 communication strong current protection circuit is connected to the input terminal of the optocoupler U11 and the input terminal of the optocoupler U5. The output terminal of the optocoupler U11 is connected to the output terminal of the optocoupler U5 and then connected to the input terminal of the logic gate U8. The output terminal of the logic gate U8 is connected to the RX terminal of the signal receiving terminal MCU of the device to be powered. The optocoupler U5 and the logic gate U8 are both connected to a power supply. The input terminal of the optocoupler U5, the input terminal of the optocoupler U11 and the input terminal of the logic gate U8 are all grounded. The DE end of the RS485 communication strong current protection circuit is connected to the input end of the optical coupler U9, and the output end of the optical coupler U9 is connected to the R / D end of the signal receiving end MCU; The DI end of the RS485 communication high-current protection circuit is connected to the input end of the logic gate U7, the output end of the logic gate U7 is connected to the input end of the optocoupler U10, the output end of the optocoupler U10 is respectively connected to the output end of the optocoupler U12 and the TX end of the signal receiving end MCU, the input end of the optocoupler U10 is connected to the input end of the optocoupler U12, the logic gate U7 and the optocoupler U12 are both connected to the power supply, and the output end of the logic gate U7, the output end of the optocoupler U10 and the output end of the optocoupler U12 are all grounded.

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