Multi-channel program control fixed voltage circuit

Abstract

The utility model provides a multichannel program-controlled fixed voltage circuit, which relates to the field of aging test and comprises a chip machine, a charging control drive circuit, a charging interface circuit, a signal acquisition circuit, an acquisition channel switching circuit, an ADC (analog to digital converter) acquisition circuit, an address selection circuit and a communication circuit. A control circuit and a charging interface of a product are all integrated on one PCB (Printed Circuit Board), so that the space is greatly reduced, the cost is also saved, a charging protection function of a DC (Direct Current) power supply is realized, data can be quickly read and parameters can be quickly set through a specific communication mode with software of an upper computer, and a 485 remote transmission interface is designed, so that the cost is reduced. A fixed power supply is adopted for power supply, one power supply can supply power to multiple channels at the same time, then reasonable distribution is achieved through the charging aging device, and the charging aging device is safer, more reliable and low in cost.

Description

Technical Field

[0001] The utility model relates to the technical field of aging testing, in particular to a multi-channel program-controlled fixed voltage circuit. Background Art

[0002] With the rapid development of science and technology, charging aging devices play a vital role in the production of electronic products. At present, the aging treatment of fixed voltage charging products in the market mainly relies on DC power supply instruments. For the aging of a single product, this method is undoubtedly efficient and suitable. However, when faced with the aging needs of batch products, the cost problem of this method becomes prominent. Since multiple identical DC power supply instruments need to be prepared, not only does the overall aging equipment become bulky, but it also brings many inconveniences in management.

[0003] In addition, DC power instruments need to be pre-set before use, which increases the complexity of operation. What is more worthy of attention is that DC power has certain safety hazards. During the aging process, if the DC power supply is damaged, it is easy to burn the aging product and cause losses to production. At the same time, some DC power instruments are not designed with a charging interface for the product, which means that an additional transfer PCB board that meets the product interface needs to be designed and produced, which undoubtedly further increases the overall aging cost.

[0004] In summary, the charging aging devices currently on the market have many problems and challenges when using DC power instruments for product aging, which need to be solved urgently. Utility Model Content

[0005] In order to overcome the deficiencies in the prior art, the utility model provides a multi-channel programmable fixed voltage circuit, which greatly improves the convenience of the aging device, while improving the aging efficiency and reducing the aging cost.

[0006] The utility model solves the technical problem by adopting a technical solution: a multi-channel program-controlled fixed voltage circuit, which is improved in that it comprises: a single-chip microcomputer, a charging control driving circuit, a charging interface circuit, a signal acquisition circuit, an acquisition channel switching circuit, an ADC acquisition circuit, an address selection circuit and a communication circuit, wherein the input end of the charging control driving circuit is connected to the single-chip microcomputer for controlling the charging output, and the output end of the charging control driving circuit is connected to the input end of the charging interface circuit; the output end of the signal acquisition circuit is connected to the input end of the acquisition channel switching circuit for acquiring the voltage and current in the aging device; the input end of the acquisition channel switching circuit is also connected to the single-chip microcomputer, and the output end of the acquisition channel switching circuit is connected to the input end of the ADC acquisition circuit for switching the signal acquisition channel; the ADC acquisition circuit is connected to the single-chip microcomputer for the single-chip microcomputer to read the converted aging data; the address selection circuit is connected to the single-chip microcomputer for the single-chip microcomputer to identify the current address; the communication circuit is connected to the single-chip microcomputer for the single-chip microcomputer to communicate with the host computer.

[0007] In the above circuit, the charging control drive circuit includes resistor R66, resistor R67, resistor R68, resistor R69, resistor R70, resistor R71, resistor R72, resistor R73, resistor R82, resistor R83, resistor R84, resistor R85, resistor R86, resistor R87, resistor R88, resistor R89, resistor R90, field effect transistor Q1, field effect transistor Q2, field effect transistor Q3, field effect transistor Q4, field effect transistor Q5, field effect transistor Q6, field effect transistor Q7, field effect transistor Q8, Transistor Q9, transistor Q10, transistor Q11, transistor Q12, transistor Q13, transistor Q14, transistor Q15 and transistor Q16, wherein the control signal of the single chip microcomputer controls the transistor Q9-Q16 to be turned on or off through resistor R82-resistor R90, resistor R74-resistor R81 pulls up the collector signal of the transistor, the collector of the transistor is connected to the gate of the field effect transistor Q1-Q8 through resistor R66-resistor R73, and the emitter of the transistor Q9-Q16 is connected to a low level.

[0008] In the above circuit, the charging interface circuit includes eight parallel thermistors PT1, PT2, PT3, PT4, PT5, PT6, PT7 and PT8, one end of the thermistors PPT1, PT2, PT3, PT4, PT5, PT6, PT7 and PT8 is connected to a DC power supply, and the other end of the PT1, PT2, PT3 and PT4 is connected to the charging control drive circuit.

[0009] In the above circuit, the address selection circuit includes a 6-bit dip switch S1 and resistors R1, R4, R8, R9, R10 and R12, wherein one end of the resistors R1, R4, R8, R9, R10 and R12 is connected to a high level, and the other ends of the resistors R1, R4, R8, R9, R10 and R12 are connected to the 6-bit dip switch S1. By changing the state of the 6-bit dip switch S1, the signals of the six wires connected to the resistors are changed, and the six signal lines are connected to the single-chip microcomputer to provide address information for the circuit.

[0010] In the above circuit, the signal acquisition circuit includes a voltage acquisition circuit and a current acquisition circuit, wherein the voltage acquisition circuit includes eight groups of parallel voltage divider circuits, each group of voltage divider circuits includes two resistors and one capacitor; the current acquisition circuit includes eight groups of parallel current acquisition units, each group of current acquisition units includes three capacitors and two resistors.

[0011] In the above circuit, the acquisition channel switching circuit includes a voltage acquisition channel switching circuit and a current acquisition channel switching circuit.

[0012] In the above circuit, the ADC acquisition circuit includes resistor R20, resistor R26, capacitor C21, capacitor C28, capacitor C33 and AD conversion chip U2, wherein one end of the resistor R20 and resistor R26 is connected to the single-chip microcomputer, the other end of the resistor R14 is connected to one end of the capacitor C21, capacitor C28 and the AD conversion chip U2, and the other end of the capacitor C21 is connected to a low level; the other end of the resistor R26 is connected to the other end of the capacitor C28, one end of the capacitor C33 and the AD conversion chip U2, and the other end of the capacitor C33 is connected to a low level.

[0013] In the above circuit, the communication circuit includes two optocoupler chips U7 and U9 and a communication chip U8. The optocoupler chips U7 and U9 are used to increase the anti-interference ability of the circuit. The communication chip U8 is used to convert the TTL serial port signal of the microcontroller into a 485 communication signal to communicate with the host computer.

[0014] In the above circuit, the communication circuit also includes resistors R96, R97, R98 and transistors Q17 and Q18, wherein the third pin of the optocoupler chip U9 is connected to the collector of the transistor Q18, the base of the transistor Q18 is connected to the single-chip microcomputer through resistor R99, the seventh and eighth pins of the optocoupler chip U9 are connected to the second and third pins of the communication chip U7 and the collector of the transistor Q17 through resistor R94, the resistor R97 is connected between the seventh and eighth pins and the sixth pin of the optocoupler chip U9, the base of the transistor Q17 is connected to the sixth pin of the optocoupler chip U8, and the emitter of the transistor Q17 is connected to a low level.

[0015] The beneficial effects of the utility model are as follows: through the multi-channel programmable fixed voltage circuit, the control circuit and the charging interface of the product are all integrated on one PCB board, which greatly reduces the space and saves costs, and has a charging protection function of a DC power supply. Through the unique communication method with the upper computer software, it can quickly read data and set parameters, and a 485 long-distance transmission interface is designed. It adopts a fixed power supply, and one power supply can supply power to multiple channels at the same time, and then the charging aging device is used to reasonably distribute it, which is safer, more reliable and low-cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A block diagram of a multi-channel programmable fixed voltage circuit;

[0017] Figure 2 The present invention is a circuit diagram of a charging control driving circuit in a multi-channel programmable fixed voltage circuit;

[0018] Figure 3 It is a circuit diagram of a charging interface circuit in a multi-channel programmable fixed voltage circuit;

[0019] Figure 4 The present invention is a circuit diagram of a signal acquisition circuit in a multi-channel programmable fixed voltage circuit;

[0020] Figure 5 The present invention is a circuit diagram of a collection channel switching circuit in a multi-channel programmable fixed voltage circuit;

[0021] Figure 6 It is a circuit diagram of an ADC acquisition circuit in a multi-channel programmable fixed voltage circuit;

[0022] Figure 7 The present invention is a circuit diagram of an address selection circuit in a multi-channel programmable fixed voltage circuit;

[0023] Figure 8 The present invention is a circuit diagram of a communication circuit in a multi-channel programmable fixed voltage circuit. DETAILED DESCRIPTION

[0024] The utility model is further described below in conjunction with the accompanying drawings and embodiments.

[0025] The following will clearly and completely describe the concept, specific structure and technical effects of the utility model in combination with the embodiments and drawings, so as to fully understand the purpose, characteristics and effects of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of them. Based on the embodiments of the utility model, other embodiments obtained by technicians in this field without creative work are all within the scope of protection of the utility model. In addition, all the connection / connection relationships involved in the patent do not refer to the direct connection of components, but refer to the formation of a better connection structure by adding or reducing connection accessories according to the specific implementation situation. The various technical features in the creation of the utility model can be combined interchangeably without conflicting with each other.

[0026] The utility model provides a multi-channel program-controlled fixed voltage circuit, such as Figure 1 As shown, it includes a single chip microcomputer 10, a charging control driving circuit 20, a charging interface circuit 30, a signal acquisition circuit 40, an acquisition channel switching circuit 50, an ADC acquisition circuit 60, an address selection circuit 70 and a communication circuit 80, wherein:

[0027] The input end of the charging control driving circuit 20 is connected to the P2.4-P2.7 pins and the P0.0-P0.3 pins of the single-chip microcomputer 10 for controlling the charging output, and the output end of the charging control driving circuit 20 is connected to the input end of the charging interface circuit 30; the output end of the signal acquisition circuit 40 is connected to the input end of the acquisition channel switching circuit 50 for acquiring the voltage and current in the aging device; the input end of the acquisition channel switching circuit 50 is also connected to the P2.0-P2.3 and P3.4-P3.7 pins of the single-chip microcomputer 10, and the acquisition channel switching circuit The output end of the circuit 50 is connected to the input end of the ADC acquisition circuit 60 for switching the signal acquisition channel; the ADC acquisition circuit 60 is connected to the P3.2-P3.3 pins and P5.5, P1.6-P1.7 pins of the single-chip microcomputer 10, and is used for the single-chip microcomputer 10 to read the converted charging data; the address selection circuit 70 is connected to the P1.0-P1.5 pins of the single-chip microcomputer 10, and is used for the single-chip microcomputer 10 to identify the current address; the communication circuit 80 is connected to the P3.0 and P3.1 pins of the single-chip microcomputer 10, and is used for the single-chip microcomputer 10 to communicate with the host computer.

[0028] Through the above-mentioned multi-channel programmable fixed voltage circuit, the control circuit and the charging interface of the product are all integrated on one PCB board, which greatly reduces the space and saves costs. It also has the charging protection function of the DC power supply. Through the unique communication method with the upper computer software, it can quickly read data and set parameters. In addition, a 485 long-distance transmission interface is designed. It adopts a fixed power supply. One power supply can supply power to multiple channels at the same time, and then the charging aging device is used to reasonably distribute it, which is safer, more reliable and low-cost.

[0029] In an exemplary embodiment, if Figure 2 As shown, the charging control driving circuit 20 includes a resistor R66, a resistor R67, a resistor R68, a resistor R69, a resistor R70, a resistor R71, a resistor R72, a resistor R73, a resistor R82, a resistor R83, a resistor R84, a resistor R85, a resistor R86, a resistor R87, a resistor R88, a resistor R89, a resistor R90, a field effect transistor Q1, a field effect transistor Q2, a field effect transistor Q3, a field effect transistor Q4, a field effect transistor Q5, a field effect transistor Q6, a field effect transistor Q7, a field effect transistor Q8, a transistor Q9, a transistor Q10, a transistor Q11, a transistor Q12, a transistor Q13, a transistor Q14, a transistor Q15 and a transistor Q16, wherein:

[0030] The control signal of the single-chip microcomputer 10 controls the transistors Q9-Q16 to be turned on or off through resistors R82-R90, and resistors R74-R81 pull up the collector signal of the transistor, and the collector of the transistor is connected to the gate of the field effect transistor Q1-Q8 through resistors R66-R73, and the emitter of the transistor Q9-Q16 is connected to a low level. The field effect transistors Q1-Q8 can be indirectly driven by the single-chip microcomputer control signal after being driven by the front stage of Q9-Q16, and the single-chip microcomputer 10 can indirectly control the conduction and cutoff of Q1-Q8 through the internal program to control the charging circuit.

[0031] In an exemplary embodiment, if Figure 3 As shown, the charging interface circuit 30 includes eight parallel thermistors PT1, PT2, PT3, PT4, PT5, PT6, PT7 and PT8, one end of the thermistors PPT1, PT2, PT3, PT4, PT5, PT6, PT7 and PT8 is connected to a DC power supply, and the other end of the PT1, PT2, PT3 and PT4 is connected to the charging control drive circuit.

[0032] After the overcurrent protection PTC circuit PT1-PT8, it is connected to the main field effect transistor drive circuit of the field effect transistor Q1-Q8 of the charging control drive circuit 20, and to the USB1-USB20 and DC1-DC4 and DC7, 8, 11, 12 charging output interfaces. The other end of the charging output interface is connected to the current sampling resistors R40, R42, R49, R50, R56, R57, R62, R63, and the connection between the sampling resistor and the charging output interface is connected to the signal acquisition circuit 40 for signal acquisition. D1-D12 is a charging indication circuit that is connected in parallel to the charging output interface through current limiting resistors R41, R47, R48, R51, R52, R55, R58, R61 to indicate the charging output status.

[0033] In an exemplary embodiment, if Figure 4 As shown, the signal acquisition circuit 40 includes a voltage acquisition circuit and a current acquisition circuit.

[0034] The voltage acquisition circuit includes eight groups of parallel voltage divider circuits composed of resistors R27-R46, each group of voltage divider circuits includes two resistors and one capacitor, and is used to collect the voltage at the output interface of each channel. For example, the connection between the resistor R29 and the resistor R30 is the voltage after voltage division, that is, the proportionally reduced voltage is connected to the acquisition channel switching circuit 50;

[0035] The current acquisition circuit includes eight groups of current acquisition units connected in parallel, each group of current acquisition units includes three capacitors and two resistors. The current acquisition circuit acquires the signal output from the sampling resistor in the charging circuit through resistors R2-R25. The signal is filtered by capacitors C3-C30 and then sent to the acquisition channel switching circuit 50 for the single-chip microcomputer 10 to select the switching channel.

[0036] In an exemplary embodiment, if Figure 5 As shown, the acquisition channel switching circuit 50 includes a voltage acquisition channel switching circuit and a current acquisition channel switching circuit.

[0037] Among them, U5 is a voltage acquisition channel switching circuit, and its 9th-11th pins are connected to the single-chip computer 10. The single-chip computer 10 controls U5 to switch and select the channel leading to the ADC acquisition circuit 60 by controlling these pins. The 3rd pin of U5 is connected to the ADC acquisition circuit 60, and the selected channel signal is output from this pin. The 16th pin of U5 is connected to the positive pole of the power supply to power the chip IC. The 7th and 8th pins of U5 are connected to the negative pole of the power supply to provide negative power to the chip IC. The 6th pin of U5 is connected to the single-chip computer 10 to control the U5 chip to enable the selection. The other pins of U5 are connected to the voltage acquisition circuit to receive the voltage acquisition signal.

[0038] U1 and U4 are current acquisition channel switching circuits, whose pins 9-11 are connected to the microcontroller 10 to switch the acquisition channels, whose pin 6 is the selection pin and the microcontroller 10 controls the IC selection, the pin 16 is connected to the positive pole of the power supply, the pins 8 and 7 are connected to the negative pole of the power supply to power the IC, the pins 3 and 13 are connected to the ADC acquisition circuit 60 to collect the selected current data, and the other pins of U1 and U4 are connected to the current acquisition circuit to receive the current signal.

[0039] In an exemplary embodiment, if Figure 6 As shown, the ADC acquisition circuit 60 includes a resistor R20, a resistor R26, a resistor R31, a capacitor C21, a capacitor C28, a capacitor C33, a capacitor C36 and an AD conversion chip U2.

[0040] One end of the resistor R20 and the resistor R26 are connected to the single-chip microcomputer 10 to receive the current data after the strobe, and then the capacitor C21 is connected to the capacitor C33 and the capacitor C28 for filtering, wherein the other end of the resistor R26 is connected to the other end of the capacitor C28, one end of the capacitor C33 and the AD conversion chip U2 for AD conversion, and the other end of the capacitor C33 is connected to a low level. The other end of the resistor R14 is connected to the capacitor C21, one end of the capacitor C28 and the AD conversion chip U2, and the other end of the capacitor C21 is connected to a low level.

[0041] The resistor R31 is connected to the acquisition channel switching circuit 50, receives the selected voltage data, and then filters it through the capacitor C36, and connects to the 6th pin of the AD conversion chip U2 to perform AD conversion. The 1st pin, the 5th pin, and the 12th to 14th pins of the AD conversion chip U2 are connected to the single-chip microcomputer 10, and the single-chip microcomputer 10 reads the converted voltage and current data through these pins.

[0042] In an exemplary embodiment, if Figure 7 As shown, the address selection circuit 70 includes a 6-bit DIP switch S1 and resistors R1, R4, R8, R9, R10 and R12.

[0043] Among them, one end of the resistor R1, the resistor R4, the resistor R8, the resistor R9, the resistor R10 and the resistor R12 is connected to a high level, and the other ends of the resistor R1, the resistor R4, the resistor R8, the resistor R9, the resistor R10 and the resistor R12 are connected to the 6-bit dip switch S1. By changing the state of the 6-bit dip switch S1, the signals of the six wires connected to the resistors are changed, and the six signal lines are connected to the single-chip microcomputer to provide address information for the circuit.

[0044] In an exemplary embodiment, if Figure 8As shown, the communication circuit 80 includes two optocoupler chips U7 and U9 and a communication chip U8. The optocoupler chips U7 and U9 are used to increase the anti-interference ability of the circuit. The communication chip U8 is used to convert the TTL serial port signal of the microcontroller into a 485 communication signal to communicate with the host computer.

[0045] In a possible implementation, the communication circuit 80 further includes a resistor R96, a resistor R97, a resistor R98 and a transistor Q17 and a transistor Q18.

[0046] Among them, the third pin of the optocoupler chip U9 is connected to the collector of the transistor Q18, the base of the transistor Q18 is connected to the single-chip microcomputer through the resistor R99, the 7th and 8th pins of the optocoupler chip U9 are connected to the 2nd and 3rd pins of the communication chip U7 and the collector of the transistor Q17 through the resistor R94, the resistor R97 is connected between the 7th and 8th pins and the 6th pin of the optocoupler chip U9, the base of the transistor Q17 is connected to the 6th pin of the optocoupler chip U8, and the emitter of the transistor Q17 is connected to a low level.

[0047] Through the above embodiments, the present application integrates the control circuit and the charging interface of the product on one PCB board through the above multi-channel programmable fixed voltage circuit, which greatly reduces the space and saves costs, and has the charging protection function of the DC power supply. Through the unique communication method with the host computer software, it can quickly read data and set parameters, and a 485 long-distance transmission interface is designed. It adopts a fixed power supply. One power supply can supply power to multiple channels at the same time, and then the charging aging device is used to reasonably distribute it, which is safer, more reliable and low-cost. At the same time, the PTC hardware protection function is designed to prevent short circuits when the product is aged and to stop charging in emergency in other special circumstances. The data can be uploaded to the host computer software, and the software will automatically generate different intuitive curves and data reports according to different channels. The software can control the charging aging device at a single point, and the aging is more intuitive and flexible. It is worth mentioning that in the embodiment of the present application, only an 8-channel programmable fixed voltage circuit is used for explanation, but it is not limited to this. Among them, the number of channels of the programmable fixed voltage circuit can be increased as needed.

[0048] The above is a specific description of the preferred implementation of the utility model, but the invention of the utility model is not limited to the described embodiments. Technical personnel familiar with the field can also make various equivalent deformations or substitutions without violating the spirit of the utility model. These equivalent deformations or substitutions are all included in the scope defined by the claims of this application.

Claims

1. A multi-channel programmable fixed voltage circuit for a charging aging device, characterized in that: include: A single chip microcomputer, a charging control drive circuit, a charging interface circuit, a signal acquisition circuit, an acquisition channel switching circuit, an ADC acquisition circuit, an address selection circuit and a communication circuit, wherein: The input end of the charging control driving circuit is connected to the single chip microcomputer for controlling the charging output, and the output end of the charging control driving circuit is connected to the input end of the charging interface circuit; The output end of the signal acquisition circuit is connected to the input end of the acquisition channel switching circuit, and is used to acquire the voltage and current in the aging device; The input end of the acquisition channel switching circuit is also connected to the single chip microcomputer, and the output end of the acquisition channel switching circuit is connected to the input end of the ADC acquisition circuit, for switching the signal acquisition channel; The ADC acquisition circuit is connected to the single chip microcomputer, and is used for the single chip microcomputer to read the converted aging data; The address selection circuit is connected to the single chip microcomputer and is used for the single chip microcomputer to identify the current address; The communication circuit is connected to the single chip microcomputer and is used for the single chip microcomputer to communicate with a host computer.

2. The multi-channel programmable fixed voltage circuit according to claim 1, characterized in that: The charging control driving circuit includes a resistor R66, a resistor R67, a resistor R68, a resistor R69, a resistor R70, a resistor R71, a resistor R72, a resistor R73, a resistor R82, a resistor R83, a resistor R84, a resistor R85, a resistor R86, a resistor R87, a resistor R88, a resistor R89, a resistor R90, a field effect transistor Q1, a field effect transistor Q2, a field effect transistor Q3, a field effect transistor Q4, a field effect transistor Q5, a field effect transistor Q6, a field effect transistor Q7, a field effect transistor Q8, a transistor Q9, a transistor Q10, a transistor Q11, a transistor Q12, a transistor Q13, a transistor Q14, a transistor Q15 and a transistor Q16, wherein: The control signal of the single chip microcomputer controls the transistors Q9-Q16 to be turned on or off through resistors R82-R90, and resistors R74-R81 pull up the collector signal of the transistor. The collector of the transistor is connected to the gate of the field effect transistor Q1-Q8 through resistors R66-R73, and the emitter of the transistor Q9-Q16 is connected to a low level.

3. The multi-channel programmable fixed voltage circuit according to claim 1, characterized in that: The charging interface circuit includes eight parallel thermistors PT1, PT2, PT3, PT4, PT5, PT6, PT7 and PT8, one end of the thermistors PPT1, PT2, PT3, PT4, PT5, PT6, PT7 and PT8 is connected to a DC power supply, and the other end of the PT1, PT2, PT3 and PT4 is connected to the charging control drive circuit.

4. The multi-channel programmable fixed voltage circuit according to claim 1, characterized in that: The address selection circuit includes a 6-bit DIP switch S1 and resistors R1, R4, R8, R9, R10 and R12, wherein: One end of the resistor R1, the resistor R4, the resistor R8, the resistor R9, the resistor R10 and the resistor R12 is connected to a high level, and the other ends of the resistor R1, the resistor R4, the resistor R8, the resistor R9, the resistor R10 and the resistor R12 are connected to the 6-bit dip switch S1. By changing the state of the 6-bit dip switch S1, the signals of the six wires connected to the resistors are changed, and the six signal lines are connected to the single-chip microcomputer to provide address information for the circuit.

5. The multi-channel programmable fixed voltage circuit according to claim 1, characterized in that: The signal acquisition circuit includes a voltage acquisition circuit and a current acquisition circuit, wherein: The voltage acquisition circuit includes eight groups of voltage divider circuits connected in parallel, and each group of voltage divider circuits includes two resistors and one capacitor; The current collection circuit includes eight groups of current collection units connected in parallel, and each group of current collection units includes three capacitors and two resistors.

6. The multi-channel programmable fixed voltage circuit according to claim 1, characterized in that: The acquisition channel switching circuit includes a voltage acquisition channel switching circuit and a current acquisition channel switching circuit.

7. The multi-channel programmable fixed voltage circuit according to claim 1, characterized in that: The ADC acquisition circuit includes a resistor R20, a resistor R26, a capacitor C21, a capacitor C28, a capacitor C33 and an AD conversion chip U2, wherein: One end of the resistor R20 and the resistor R26 are connected to the single chip microcomputer, the other end of the resistor R14 is connected to one end of the capacitor C21, the capacitor C28 and the AD conversion chip U2, and the other end of the capacitor C21 is connected to a low level; The other end of the resistor R26 is connected to the other end of the capacitor C28, one end of the capacitor C33 and the AD conversion chip U2, and the other end of the capacitor C33 is connected to a low level.

8. The multi-channel programmable fixed voltage circuit according to claim 1, characterized in that: The communication circuit includes two optocoupler chips U7 and U9 and a communication chip U8. The optocoupler chips U7 and U9 are used to increase the anti-interference ability of the circuit. The communication chip U8 is used to convert the TTL serial port signal of the single-chip microcomputer into a 485 communication signal to communicate with the host computer.

9. The multi-channel programmable fixed voltage circuit according to claim 8, characterized in that: The communication circuit also includes resistors R96, R97, R98 and transistors Q17 and Q18, wherein: The third pin of the optocoupler chip U9 is connected to the collector of the transistor Q18, the base of the transistor Q18 is connected to the single-chip microcomputer through the resistor R99, the seventh and eighth pins of the optocoupler chip U9 are connected to the second and third pins of the communication chip U7 and the collector of the transistor Q17 through the resistor R94, the resistor R97 is connected between the seventh and eighth pins and the sixth pin of the optocoupler chip U9, the base of the transistor Q17 is connected to the sixth pin of the optocoupler chip U8, and the emitter of the transistor Q17 is connected to a low level.

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