Peltier automatic switching cold and hot adjusting system and method

Abstract

The invention relates to a Peltier automatic switchable cold and hot adjusting system and method. The Peltier automatic switchable cold and hot adjusting system comprises an MCU, a temperature sensor, an operational amplifier and a motor driving chip, the operational amplifier is connected with the motor driving chip through the power supply circuit; the motor driving chip is connected with the temperature sensor through Peltier; the device is reasonable in design, compact in structure and convenient to use.

Description

Technical Field

[0001] The present invention relates to a Peltier automatic switching hot and cold mediation system and method, the Peltier can meet the function switching of heating and cooling, the Peltier power is adjustable, and the service life of the Peltier is effectively extended. Background Art

[0002] The existing semiconductor cooling sheet Peltier (hereinafter referred to as "Peltier") on the market can realize the functions of forward current heating and reverse current cooling.

[0003] In the use of Peltier, most users only realize one of the heating or cooling functions, and the heating or cooling power is not controllable. Some users can realize the controllable power of Peltier, but they use power electronic switches to control the power by controlling the on-off frequency of the internal MOS tube.

[0004] The use of Peltier in traditional industrial products can only achieve one of the functions of heating or cooling, and the power is not controllable, resulting in uncontrollable heating or cooling temperature. Some Peltier uses a power electronic switch to control the Peltier working power, which can only achieve one of the functions of heating or cooling; and the power is controlled by the MOS tube inside the device constantly turning on and off, and long-term use will damage both the device and the Peltier.

[0005] Explanation of the name: H-bridge: An H-bridge is an electronic circuit that can reverse the voltage / current across the connected load or output terminal. Most DC-AC converters (such as inverters and frequency converters) and some DC-DC converters (push-pull converters) in power conversion. Peltier: When the current flows from one direction to another, it realizes the heating function, and when the current reverses, it realizes the cooling function. Summary of the invention

[0006] The technical problem to be solved by the present invention is generally to provide a Peltier automatic switching hot and cold mediation system and method, which can not only meet the switching between Peltier heating and cooling modes, but also make the Peltier power controllable so that the temperature reaches the set temperature requirement, and can effectively improve the service life of components and Peltier, ensuring that the circuit design can be used stably for a long time.

[0007] To solve the above problems, the technical solution adopted by the present invention is: A Peltier automatic switching hot and cold mediation system includes an MCU and a temperature sensor, an operational amplifier and a motor drive chip electrically connected to the MCU; the operational amplifier is connected to the motor drive chip through a power circuit; The motor driver chip is connected to the temperature sensor via Peltier.

[0008] Furthermore, the power circuit includes a power chip U6, a control voltage follower circuit electrically connected to the power chip U6, and a Peltier voltage control circuit.

[0009] Further, in the power chip U6, pin 7 is connected to 24V and grounded through capacitors C20-C22, and pins 6 and 9 are grounded; The Peltier voltage control circuit includes a diode D5, capacitors C17-19, and an inductor L1; capacitor C17 is connected between pins 7 and 8 of the power chip U6, and one output of pin 8 is grounded through a diode D5, and the other output is connected to V-out after being filtered by an inductor L1 and parallel capacitors C18 and C19.

[0010] Further, the control voltage follower circuit includes an op amp U5A; pin 3 of the op amp U5A is connected to the Peltier-DA-CTR for electrical connection to the MCU, pin 3 is grounded through a capacitor, pin 2 is grounded through a resistor R17, and a resistor R18 is connected between pins 1 and 2; pin 4 is grounded, and pin 8 is connected to a voltage of +5V and grounded after passing through a capacitor C18; pin 1 is connected to pin 4 of the power chip U6 through resistors R21 and R103, and pin 1 of the op amp U5A is grounded through a parallel resistor R23 and a capacitor C13; pin 4 is grounded through a resistor R104.

[0011] Further, the DAC pin of the MCU outputs a Peltier-DA-CTR voltage signal to the non-inverting terminal of the operational amplifier U6A; the Peltier-DA-CTR voltage output signal is recorded as DA-CTR.

[0012] Further, the reference voltage of the power chip U6 includes VSENSE.

[0013] Furthermore, V-OUT output by the voltage chip U6 is connected to the pin 11 of the motor driving chip U3 as the voltage source of the chip.

[0014] In the motor driver chip U3, pins 1 and 2 are connected to the pull-down circuit through the corresponding 8874-IN1 and 8874-IN2 respectively; pin 4 is externally connected to a high-level enable, and pin 4 is connected to a fault detection circuit through 8874-FAULT; pin 5 enters the external reference voltage input through 8874-VREF; pin 6 is connected to the circuit output and grounded through resistor R14, pin 7 is grounded, pins 8 and 10 are connected to 8874-out1 channel and 8874-out2 channel respectively, pins 9, 15, and 17 are grounded, pin 16 is connected to +5V through resistor R6 and grounded through resistor R11, and pin 16 is connected to the NC channel; capacitor C5 is connected between pins 13 and 14, and capacitor C6 is connected between pin 12 and pin C11 through the VCP channel; pin 11 is grounded through parallel capacitors C7 and C8; The fault detection circuit includes a resistor R15 and a lamp LED1 connected in series between the 8874-FAULT channel and 5V.

[0015] Further, the 8874-IN1 channel and the 8874-IN2 channel are connected to the IN1 control circuit and the IN2 control circuit respectively; IN1 control circuit includes optocoupler chip U1. In optocoupler chip U1, pin 1 is connected to voltage 3.3V through resistor R2, pin 3 is connected to MCU, pin 6 is connected to 5V and grounded through capacitor C1, pin 4 is grounded, pin 4 is connected to one end of diode ID1, and pin 5 is connected to resistor R5; the other end of diode ID1 is connected to 8874-IN1 channel; the output end of resistor R5 is connected to 8874-IN1 channel and 5V through resistor R1; The 8874-IN1 channel is also grounded through capacitor C3; IN2 control circuit includes optocoupler chip U2. In optocoupler chip U2, pin 1 is connected to voltage 3.3V through resistor R4, pin 3 is connected to MCU, pin 6 is connected to 5V and grounded through capacitor C2, pin 4 is grounded, pin 4 is connected to one end of diode ID2, and pin 5 is connected to resistor R6; the other end of diode ID2 is connected to 8874-IN2 channel; the output end of resistor R6 is connected to 8874-IN2 channel and 5V through resistor R3; The 8874-IN2 channel is also grounded through capacitor C4; The motor drive chip U3 is electrically connected to an enabling circuit and an external reference voltage circuit; The enabling circuit includes resistors R8 and R13 connected to the 8874-SLEEP channel respectively, and resistors R8 and R13 are connected to the power supply 5V and ground respectively; wherein, the voltage connected to pin 3 of the motor driver chip U3 is (5V*R13 / (R8*R13)); The external reference voltage circuit includes resistors R7 and R12 connected to the motor driver chip pin 4 through the 8874-VREF channel, and the resistors R7 and R12 are connected to the power supply 5V and the ground respectively; The MCU control signals MCU-ENIN1 and MCU-ENIN2 are pulled high or low to control the level state of Pin1 and Pin2 of the motor driver chip U3. The interior of the motor driver chip U3 is an H-bridge composed of four MOS tubes. The G pole of the MOS tube is controlled through the external pins Pin1 and Pin2, thereby controlling the on and off of the MOS tube to achieve forward or reverse current flow.

[0016] A Peltier automatic switching hot and cold mediation method, with the aid of the above system; performing the following steps; first, in the Peltier-DA-CTR voltage signal, the microcontroller DAC pin outputs an adjustable voltage of 0-3.3V; then, the adjustable voltage is amplified by the operational amplifier U5A and becomes an adjustable voltage of 0-6.6V, recorded as DA-CTR; secondly, in the power chip U6, based on the superposition theorem, V-OUT is given to the power supply pin of the motor driver chip U3, and the voltage value output by the motor driver chip U3 is equal to VOUT; later, the output voltage of the motor driver chip U3 is output through the two pins 8 and 10 of the driver chip U3 and is determined by pins 1 and 2.

[0017] Furthermore, the output of the driver chip U3 is divided into three situations: Case A, OUT1 and OUT2 are both equal to 0; In case B, OUT1 outputs positive voltage and OUT2 outputs GND; In case C, OUT2 outputs positive voltage and OUT1 outputs GND; Among them, MCU controls the high and low levels of the GPIO pins, controls the high and low levels of pins 1 and 2 of the motor driver chip U3, and then controls the three output modes of the motor driver chip U3; The ambient temperature is then measured by a temperature sensor and the temperature value is transmitted to the MCU. The MCU determines the size of the output DAC based on the set temperature value and the measured temperature value. The ambient temperature obtained by the temperature sensor is Tget, and the set ambient temperature is Tflag. According to the superposition theorem, a voltage output linearly adjustable circuit is built, which can not only control the power of Peltier heating or cooling, but also extend the service life of Peltier and circuit components. A complete design solution with automatic switching of Peltier heating and cooling and automatic power adjustment.

[0018] First, the MCU obtains the ambient temperature Tget through the temperature sensor; then, the MCU compares the obtained ambient temperature Tget with the set ambient temperature Tflag; If the obtained ambient temperature Tget is greater than the set ambient temperature Tflag, the output cooling control is performed, ENIN1 is low level and ENIN2 is high level, and at the same time, according to the difference between Tget and Tflag, PID adjusts the DAC output of the MCU, that is, the Peltier-DA-CTR signal; If the obtained ambient temperature Tget is less than the set ambient temperature Tflag, output heating control is performed, and the motor driver chip U6 heats the DAC output PID to adjust the Peltier.

[0019] According to the superposition theorem, the present invention constructs a voltage output linearly adjustable circuit, which can not only control the power of Peltier heating or cooling, but also extend the service life of Peltier and circuit components.

[0020] The present invention discloses a complete design scheme in which Peltier heating and cooling can be automatically switched and power can be automatically adjusted.

[0021] The invention has reasonable design, low cost, durability, safety and reliability, simple operation, time and labor saving, money saving, compact structure and convenient use. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of a voltage linearly adjustable circuit of the present invention.

[0023] Figure 2 It is a schematic diagram of the IN1 control circuit of the present invention.

[0024] Figure 3 It is a schematic diagram of the IN2 control circuit of the present invention.

[0025] Figure 4 It is a peripheral circuit schematic diagram of the present invention.

[0026] Figure 5 It is a schematic diagram of the H1 bridge control circuit of the present invention.

[0027] Figure 6 It is a schematic diagram of the logic control circuit of the present invention.

[0028] Figure 7 It is a circuit block diagram of the present invention.

[0029] Figure 8 It is the internal logic processing diagram of the MCU of the present invention.

[0030] Fig. 9 It is a schematic diagram of the forward drive of the present invention.

[0031] Fig.10 It is a reverse schematic diagram of the present invention. DETAILED DESCRIPTION

[0032] like Figure 1-10 , such as Figure 8 , the system of this embodiment includes an MCU; the MCU is electrically connected to a temperature sensor, an operational amplifier and a motor driver chip, and the operational amplifier is connected to the motor driver chip through a power circuit; The motor driver chip is connected to the temperature sensor via Peltier; like Figure 8 The serial numbers in the figure mark the signal flow. (1) The MCU outputs a controllable analog voltage to the op amp. (2) The op amp follows the controllable analog voltage value and increases the signal strength before sending it to the power chip.

[0033] (3) The power chip outputs a linearly variable power voltage value to the motor driver chip.

[0034] (4) The MCU outputs high and low levels to control the suspension, heating, and cooling states of the Peltier through the motor driver chip.

[0035] (5) The motor driver chip outputs a voltage to the Peltier diode that can control power and change the direction of current.

[0036] (6) The operation of Peltier diode causes the ambient temperature to change, and the ambient temperature information is captured by the temperature sensor.

[0037] (7) The temperature sensor transmits temperature information to the MCU.

[0038] like Figure 1 , the power supply circuit includes a power supply chip U6 and a control voltage follower circuit and a Peltier voltage control circuit electrically connected to the power supply chip U6; In the power chip U6, pin 7 is connected to 24V and grounded through capacitors C20-C22, and pins 6 and 9 are grounded; The Peltier voltage control circuit includes a diode D5, capacitors C17-19, and an inductor L1; capacitor C17 is connected between pins 7 and 8 of the power chip U6, one output of pin 8 is grounded through a diode D5, and the other output is connected to V-out after being filtered by an inductor L1 and parallel capacitors C18 and C19; The control voltage follower circuit includes an operational amplifier U5A; Pin 3 of the operational amplifier U5A is connected to the Peltier-DA-CTR for electrically connecting to the MCU, Pin 3 is grounded through a capacitor, Pin 2 is grounded through a resistor R17, and a resistor R18 is connected between Pins 1 and 2; Pin 4 is grounded, and Pin 8 is connected to a voltage of +5V and grounded after passing through a capacitor C18; Pin 1 is connected to Pin 4 of the power chip U6 through resistors R21 and R103, and Pin 1 of the operational amplifier U5A is grounded through a parallel resistor R23 and a capacitor C13; Pin 4 is grounded through a resistor R104; The DAC pin of the MCU outputs the "Peltier-DA-CTR" voltage signal to the non-inverting terminal of the operational amplifier U6A. According to the matching of the peripheral circuit resistors of the operational amplifier (R17=10K R18=10K), the Peltier-DA-CTR voltage signal is amplified by 1 times and then output, which is recorded as DA-CTR.

[0039] MCU outputs Peltier-DA-CTR analog voltage value. In order to prevent the analog signal from being interfered, an external op amp (MCP6002) is connected to output DA-CTR to enhance the stability of the signal. The voltage amplification is based on the characteristics of the op amp, and the amplification factor is based on the matching of the peripheral circuit resistance value; the output voltage of the DAC pin is within a continuously adjustable range. When the output voltage of the DAC pin is different, the value of V-OUT mentioned below also changes linearly within a certain range.

[0040] By building the above voltage linear adjustment, the heating or cooling power can be adjusted, and the current direction can be switched to achieve the switching of heating or cooling. Through the controllable voltage source, the temperature can reach the desired temperature requirement, such as Figure 7 , feedback regulation is formed by a sensor specially used to measure temperature and Peltier. Since the output of the voltage source is ripple-processed, the output voltage value changes smoothly. The ripple processing is achieved through inductance and capacitance, but the role of ripple processing is secondary; the main reason is that the continuous on-off regulation of PWM is different from the continuous on-off process of duty cycle, which can effectively extend the service life of Peltier and circuit components.

[0041] VSENSE is a reference voltage of the power chip U6. The reference voltage has good stability and small temperature drift, and serves as a constant voltage source. The DA-CRT signal is another voltage source controlled by the MCU. According to the design of the power chip, the output V-OUT of the power chip is related to the voltage source VSENSE, the voltage source DC-CTR, the resistor R101 (voltage fine-tuning function), the resistor R102, the resistor R103, and the resistor R104.

[0042] Since the circuit components of the output part of the power chip are all composed of resistors, this part is a linear circuit; and because the reference voltage VSNSE of the power chip is a constant voltage source, DA-CTR is a controlled linearly changing voltage source, from the superposition theorem (when one independent source is constant and an independent source changes linearly, the response also changes linearly), it can be seen that the output voltage V-OUT of the power chip also changes linearly within a certain controlled range.

[0043] According to the superposition theorem, V-OUT * (R103 / / R104) / [(R101+R102) / / (R103 / / R104)] + DC-CRT * [(R101+R102) / / R104] / {[(R101+R102) / / R104]+R103} = VSENSE = 1.221 (constant value); like Figure 2-Figure 6, V-OUT output by the voltage chip U6 is connected to pin 11 of the motor driver chip U3 as the voltage source of the chip.

[0044] In the motor driver chip U3, pins 1 and 2 are connected to the pull-down circuit through the corresponding 8874-IN1 and 8874-IN2 respectively; pin 4 is externally connected to a high-level enable, and pin 4 is connected to a fault detection circuit through 8874-FAULT; pin 5 enters the external reference voltage input through 8874-VREF; pin 6 is connected to the circuit output and grounded through resistor R14, pin 7 is grounded, pins 8 and 10 are connected to 8874-out1 channel and 8874-out2 channel respectively, pins 9, 15, and 17 are grounded, pin 16 is connected to +5V through resistor R6 and grounded through resistor R11, and pin 16 is connected to the NC channel; capacitor C5 is connected between pins 13 and 14, and capacitor C6 is connected between pin 12 and pin C11 through the VCP channel; pin 11 is grounded through parallel capacitors C7 and C8; The 8874-IN1 channel and the 8874-IN2 channel are connected to the IN1 control circuit and the IN2 control circuit respectively; IN1 control circuit includes optocoupler chip U1. In optocoupler chip U1, pin 1 is connected to voltage 3.3V through resistor R2, pin 3 is connected to MCU, pin 6 is connected to 5V and grounded through capacitor C1, pin 4 is grounded, pin 4 is connected to one end of diode ID1, and pin 5 is connected to resistor R5; the other end of diode ID1 is connected to 8874-IN1 channel; the output end of resistor R5 is connected to 8874-IN1 channel and 5V through resistor R1; The 8874-IN1 channel is also grounded through capacitor C3; IN2 control circuit includes optocoupler chip U2. In optocoupler chip U2, pin 1 is connected to voltage 3.3V through resistor R4, pin 3 is connected to MCU, pin 6 is connected to 5V and grounded through capacitor C2, pin 4 is grounded, pin 4 is connected to one end of diode ID2, and pin 5 is connected to resistor R6; the other end of diode ID2 is connected to 8874-IN2 channel; the output end of resistor R6 is connected to 8874-IN2 channel and 5V through resistor R3; The 8874-IN2 channel is also grounded through capacitor C4; like Figure 1 First, in the Peltier-DA-CTR voltage signal, the DAC pin of the microcontroller outputs an adjustable voltage of 0-3.3V; then, the voltage is amplified by 1 times through the op amp U5A and becomes 0-6.6V adjustable, recorded as DA-CTR; secondly, because DA-CTR is adjustable within a certain range, in the power chip U6, the superposition theorem shows that: V-OUT is adjustable within a certain range. Again, if Figure 5, V-OUT is given to the power supply pin of the motor driver chip U3, and the voltage output by the chip is equal to VOUT. Later, the output voltage of the motor driver chip U3 is obtained by Figure 5 There are three situations for the outputs of the two pins 8 and 10: (1) OUT1 and OUT2 are both equal to 0; (2) OUT1 outputs a positive voltage (equal to the V-OUT value connected to pin 11), and OUT2 outputs GND. (3) OUT2 outputs a positive voltage (equal to the V-OUT value connected to pin 11), and OUT1 outputs GND; then combined Figure 6 The three output conditions of the motor driver chip U3 are determined by pin 1 and pin 2. Specifically, Figure 2 , 3 , MCU controls the high and low levels of these two GPIO pins, controls the high and low levels of pins 1 and 2 of the motor driver chip U3, and then controls the three output modes of the motor driver chip U3; then the ambient temperature is measured by the temperature sensor, and the temperature value is transmitted to the MCU. The MCU determines the size of the output DAC according to the set temperature value and the measured temperature value.

[0045] like Figure 4 The enabling circuit includes resistors R8 and R13 connected to the 8874-SLEEP channel respectively, and the resistors R8 and R13 are connected to the power supply 5V and the ground respectively; the resistor R8 and R13 are used to set the resistor division voltage: among which, the voltage connected to the pin 3 of the motor drive chip is (5V*R13 / (R8*R13)).

[0046] like Figure 4 , the external reference voltage circuit includes resistors R7 and R12 connected to the motor driver chip pin 4 through the 8874-VREF channel, and the resistors R7 and R12 are connected to the power supply 5V and the ground respectively; The fault detection circuit includes a resistor R15 and a lamp LED1 connected in series between the 8874-FAULT channel and 5V; In general, the MCU control signals MCU-ENIN1 and MCU-ENIN2 are pulled high or low to control the level state of Pin1 and Pin2 of the motor driver chip U3. The interior of the motor driver chip U3 is an H-bridge composed of four MOS tubes. The G pole of the MOS tube is controlled by the external pins Pin1 and Pin2, thereby controlling the on and off of the MOS tube to realize the forward or reverse flow of current, that is, the heating function or cooling function of the Peltier.

[0047] According to the output logic control of the motor driver chip DRV8874 (U3) in the attached figure, the MCU only needs to simply pull it high or low to switch the heating or cooling function.

[0048] In process Figure 8In: Tget is the ambient temperature obtained by the temperature sensor, and Tflag is the set ambient temperature. According to the superposition theorem, a circuit with linearly adjustable voltage output can be built, which can not only control the power of Peltier heating or cooling, but also extend the service life of Peltier and circuit components. A complete design solution with automatic switching of Peltier heating and cooling and automatic power adjustment.

[0049] First, the MCU obtains the ambient temperature Tget through the temperature sensor; then, the MCU compares the obtained ambient temperature Tget with the set ambient temperature Tflag; If the obtained ambient temperature Tget is greater than the set ambient temperature Tflag, the output cooling control is performed, ENIN1 is low level and ENIN2 is high level, and at the same time, according to the difference between Tget and Tflag, PID adjusts the DAC output of the MCU, that is, the Peltier-DA-CTR signal; If the obtained ambient temperature Tget is less than the set ambient temperature Tflag, output heating control is performed, and the motor driver chip U6 heats the DAC output PID to adjust the Peltier.

[0050] The present invention is fully described for a clearer disclosure, and the prior art is not listed one by one.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some of the technical features therein with equivalents; it is obvious for those skilled in the art to combine multiple technical solutions of the present invention. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention. The technical contents not described in detail in the present invention are all known technologies.

Claims

1. A Peltier automatic switching hot and cold mediation system, characterized in that: It includes an MCU and a temperature sensor, an operational amplifier and a motor driver chip which are electrically connected to the MCU respectively; the operational amplifier is connected to the motor driver chip through a power circuit; The motor driver chip is connected to the temperature sensor via Peltier.

2. The Peltier automatic switching hot and cold mediation system according to claim 1, characterized in that: The power circuit includes a power chip U6, a control voltage follower circuit electrically connected to the power chip U6, and a Peltier voltage control circuit.

3. The Peltier automatic switching hot and cold mediation system according to claim 2, characterized in that: In the power chip U6, pin 7 is connected to 24V and grounded through capacitors C20-C22, and pins 6 and 9 are grounded; The Peltier voltage control circuit includes a diode D5, capacitors C17-19, and an inductor L1; capacitor C17 is connected between pins 7 and 8 of the power chip U6, and one output of pin 8 is grounded through a diode D5, and the other output is connected to V-out after being filtered by an inductor L1 and parallel capacitors C18 and C19.

4. The Peltier automatic switching hot and cold regulating system according to claim 2, characterized in that: The control voltage follower circuit includes an operational amplifier U5A; pin 3 of the operational amplifier U5A is connected to the Peltier-DA-CTR for electrical connection to the MCU, pin 3 is grounded through a capacitor, pin 2 is grounded through a resistor R17, and a resistor R18 is connected between pins 1 and 2; pin 4 is grounded, and pin 8 is connected to a voltage of +5V and grounded after passing through a capacitor C18; pin 1 is connected to pin 4 of the power chip U6 through resistors R21 and R103, and pin 1 of the operational amplifier U5A is grounded through a parallel resistor R23 and a capacitor C13; pin 4 is grounded through a resistor R104.

5. The Peltier automatic switching hot and cold mediation system according to claim 1, characterized in that: The DAC pin of the MCU outputs a Peltier-DA-CTR voltage signal to the non-inverting terminal of the operational amplifier U6A; the Peltier-DA-CTR voltage output signal is recorded as DA-CTR.

6. The Peltier automatic switching hot and cold regulating system according to claim 2, characterized in that: The reference voltage of the power chip U6 includes VSENSE.

7. The Peltier automatic switching hot and cold regulating system according to claim 1, characterized in that: The V-OUT output of the voltage chip U6 is connected to the pin 11 of the motor driver chip U3 as the voltage source of the chip; In the motor driver chip U3, pins 1 and 2 are connected to the pull-down circuit through the corresponding 8874-IN1 and 8874-IN2 respectively; pin 4 is externally connected to a high-level enable, and pin 4 is connected to a fault detection circuit through 8874-FAULT; pin 5 enters the external reference voltage input through 8874-VREF; pin 6 is connected to the circuit output and grounded through resistor R14, pin 7 is grounded, pins 8 and 10 are connected to 8874-out1 channel and 8874-out2 channel respectively, pins 9, 15, and 17 are grounded, pin 16 is connected to +5V through resistor R6 and grounded through resistor R11, and pin 16 is connected to the NC channel; capacitor C5 is connected between pins 13 and 14, and capacitor C6 is connected between pin 12 and pin C11 through the VCP channel; pin 11 is grounded through parallel capacitors C7 and C8; The fault detection circuit includes a resistor R15 and a lamp LED1 connected in series between the 8874-FAULT channel and 5V.

8. The Peltier automatic switching hot and cold regulating system according to claim 1, characterized in that: The 8874-IN1 channel and the 8874-IN2 channel are connected to the IN1 control circuit and the IN2 control circuit respectively; IN1 control circuit includes optocoupler chip U1. In optocoupler chip U1, pin 1 is connected to voltage 3.3V through resistor R2, pin 3 is connected to MCU, pin 6 is connected to 5V and grounded through capacitor C1, pin 4 is grounded, pin 4 is connected to one end of diode ID1, and pin 5 is connected to resistor R5; the other end of diode ID1 is connected to 8874-IN1 channel; the output end of resistor R5 is connected to 8874-IN1 channel and 5V through resistor R1; The 8874-IN1 channel is also grounded through capacitor C3; IN2 control circuit includes optocoupler chip U2. In optocoupler chip U2, pin 1 is connected to voltage 3.3V through resistor R4, pin 3 is connected to MCU, pin 6 is connected to 5V and grounded through capacitor C2, pin 4 is grounded, pin 4 is connected to one end of diode ID2, and pin 5 is connected to resistor R6; the other end of diode ID2 is connected to 8874-IN2 channel; the output end of resistor R6 is connected to 8874-IN2 channel and 5V through resistor R3; The 8874-IN2 channel is also grounded through capacitor C4; The motor drive chip U3 is electrically connected to an enabling circuit and an external reference voltage circuit; The enabling circuit includes resistors R8 and R13 connected to the 8874-SLEEP channel respectively, and resistors R8 and R13 are connected to the power supply 5V and ground respectively; wherein, the voltage connected to pin 3 of the motor driver chip U3 is (5V*R13 / (R8*R13)); The external reference voltage circuit includes resistors R7 and R12 connected to the motor driver chip pin 4 through the 8874-VREF channel, and the resistors R7 and R12 are connected to the power supply 5V and the ground respectively; The MCU control signals MCU-ENIN1 and MCU-ENIN2 are pulled high or low to control the level state of Pin1 and Pin2 of the motor driver chip U3. The interior of the motor driver chip U3 is an H-bridge composed of four MOS tubes. The G pole of the MOS tube is controlled through the external pins Pin1 and Pin2, thereby controlling the on and off of the MOS tube to achieve forward or reverse current flow.

9. A Peltier automatic switching hot and cold mediation method, characterized in that: With the help of the system described in claim 1; perform the following steps; first, in the Peltier-DA-CTR voltage signal, the microcontroller DAC pin outputs an adjustable voltage of 0-3.3V; then, the adjustable voltage is amplified by the operational amplifier U5A and becomes an adjustable voltage of 0-6.6V, recorded as DA-CTR; secondly, in the power chip U6, based on the superposition theorem, V-OUT is given to the power supply pin of the motor driver chip U3, and the voltage value output by the motor driver chip U3 is equal to VOUT; later, the output voltage of the motor driver chip U3 is output through the two pins 8 and 10 of the driver chip U3 and is determined by pins 1 and 2.

10. The Peltier automatic switching hot and cold mediation method according to claim 9, characterized in that: The output of driver chip U3 is divided into three situations: Case A, OUT1 and OUT2 are both equal to 0; In case B, OUT1 outputs positive voltage and OUT2 outputs GND; In case C, OUT2 outputs positive voltage and OUT1 outputs GND; Among them, MCU controls the high and low levels of the GPIO pins, controls the high and low levels of pins 1 and 2 of the motor driver chip U3, and then controls the three output modes of the motor driver chip U3; The ambient temperature is then measured by a temperature sensor and the temperature value is transmitted to the MCU. The MCU determines the size of the output DAC based on the set temperature value and the measured temperature value. The ambient temperature obtained by the temperature sensor is Tget, and the set ambient temperature is Tflag; when adjusting the temperature, perform the following steps: First, the MCU obtains the ambient temperature Tget through the temperature sensor; then, the MCU compares the obtained ambient temperature Tget with the set ambient temperature Tflag; If the obtained ambient temperature Tget is greater than the set ambient temperature Tflag, the output cooling control is performed, ENIN1 is low level and ENIN2 is high level, and at the same time, according to the difference between Tget and Tflag, PID adjusts the DAC output of the MCU, that is, the Peltier-DA-CTR signal; If the obtained ambient temperature Tget is less than the set ambient temperature Tflag, output heating control is performed, and the motor driver chip U6 heats the DAC output PID to adjust the Peltier.

Images