TEC temperature control circuit based on H-bridge PWM bidirectional PID stepless regulation

Abstract

The application discloses a TEC temperature control circuit based on H-bridge PWM bidirectional PID stepless regulation, which adopts a domestic low-cost small-size direct-current brush motor driving chip (integrated H-bridge) to drive a TEC semiconductor heating and refrigeration sheet, and outputs a PWM signal by a low-cost domestic single-chip microcomputer for temperature control; the single-chip microcomputer receives temperature setting through a button and collects temperature through a negative temperature NTC sensor; a PWM signal is output by an improved bidirectional cold and hot conversion PID algorithm to drive the motor driving chip, and the motor driving chip is connected to the TEC semiconductor heating and refrigeration sheet through an LC filter circuit, so that a large-current small-size low-cost temperature control circuit is realized.

Description

Technical Field

[0001] This invention belongs to the field of integrated circuit design technology, specifically relating to a TEC temperature control circuit based on H-bridge PWM bidirectional PID stepless regulation. Background Technology

[0002] A TEC (Thermoelectric Cooler) is a device that generates cooling by utilizing the thermoelectric effect of semiconductors; it is also known as a thermoelectric cooler. Generally, two different metals are connected by a conductor. When direct current is applied, the temperature at one junction decreases, while the temperature at the other junction increases. If the power supply is reversed, the temperature at the junction changes in the opposite direction. This phenomenon is called the Peltier effect, also known as the thermoelectric effect.

[0003] TEC (Thermoelectric Cooler) features noiseless and vibration-free operation, requires no refrigerant, is small in size, and lightweight. It is reliable, easy to operate, and readily adjustable in terms of cooling capacity. However, its coefficient of performance (COP) is relatively low, and its power consumption is relatively high. Therefore, it is mainly used in applications requiring low cooling capacity and limited space, such as cooling certain components in electronic and radio communication equipment. It is also sometimes used in household refrigerators, but this is not economical. Semiconductor coolers can also be used as zero-point instruments to ensure the zero-point temperature in thermocouple measurements.

[0004] TEC (Digital Temperature Regulator) is a key component in current temperature control circuits. It's a solid-state refrigeration technology characterized by noiselessness, high efficiency, and the ability to switch between heating and cooling by controlling the current direction. Traditional PWM (Pulse Width Modulation) TEC temperature control circuits regulate voltage by setting a timer on a microcontroller to control the TEC. For example, Chinese patent application CN204128255U provides a PWM-based TEC temperature control circuit. This circuit uses a PWM control chip to control the operating voltage of the TEC module, ensuring high-precision output voltage. Simultaneously, a feedback loop is formed using a temperature acquisition unit and a signal processing unit to ensure the stability and timeliness of temperature feedback. Another example is Chinese patent application CN108628365A, which provides a TEC temperature control circuit using a microcontroller and a half-bridge driver chip. Because the voltage and current limits of the half-bridge driver chip are significantly improved, this TEC temperature control circuit is suitable for high-power TECs.

[0005] In existing technologies, H-bridge circuits in TEC temperature control systems typically employ two approaches: one uses four N-type MOSFETs, and the other uses two P-type MOSFETs as the upper transistor and two N-type MOSFETs as the lower transistor. Both methods require four PWM signals for control, meaning each MOSFET needs an independent PWM signal to control its on / off state. This increases the difficulty of C programming and, due to the use of discrete components, necessitates additional current sampling and overcurrent protection circuitry, further increasing circuit complexity. Furthermore, commercially available dedicated driver chips typically have low drive current, while high-current drive modules require larger, low-resistance, high-current MOSFETs due to the large inrush current during thermal transitions, resulting in higher costs. Summary of the Invention

[0006] In view of the above, the present invention provides a TEC temperature control circuit based on H-bridge PWM bidirectional PID stepless regulation, which is low in cost, small in size and has bidirectional PID stepless regulation function.

[0007] A TEC temperature control circuit based on H-bridge PWM bidirectional PID stepless regulation includes a TEC, a temperature sensor, a controller, a drive circuit, and a filter circuit, wherein:

[0008] The temperature sensor is attached to the TEC and is used to sense the temperature of the TEC and generate a temperature signal to provide to the controller.

[0009] The controller is used to acquire temperature signals and provide PWM signals to the drive circuit through voltage conversion and stepless current regulation.

[0010] The driving circuit is connected to the filtering circuit and is controlled by the PWM signal to output driving voltages in both positive and negative directions.

[0011] The filtering circuit is connected to the TEC and is used to filter the driving voltage and apply it to both ends of the TEC to realize the TEC's hot and cold conversion and temperature control.

[0012] Furthermore, the temperature sensor is an NTC negative temperature sensor.

[0013] Furthermore, the controller uses a domestically produced microcontroller, which has a programming interface, a button circuit, a buzzer, and a display circuit. The programming interface is used for programming, the button circuit is used for power on / off and temperature setting, the buzzer is used for status indication, and the display circuit is used for temperature display.

[0014] Furthermore, the TEC temperature control circuit also includes a power supply circuit for providing operating voltage to the temperature sensor, controller, and drive circuit.

[0015] Furthermore, the controller outputs two PWM signals, PWM1 and PWM2. PWM1 is used to adjust the magnitude of the drive voltage, and PWM2 is used to control the direction of the drive voltage through high and low levels. When the TEC switches between hot and cold, the two PWM signals can be used interchangeably.

[0016] Furthermore, the driving circuit uses the AT8236 driver chip with integrated H-bridge, which has a peak current of 6A, a maximum driving voltage of 36V, and a size of only 6mm×4.9mm×1.65mm.

[0017] Furthermore, the filtering circuit makes the duty cycle of the driving voltage and the PWM signal linearly proportional through filtering. It includes two inductors L4 and L5 and six capacitors C34, C37, C39, C40, C41, and C42. One end of L4 is connected to the output port OUT2 of the driving circuit, and the other end of L4 is connected to one end of C34, one end of C37, one end of C39, one end of C40, and one end of TEC. One end of L5 is connected to the output port OUT1 of the driving circuit, and the other end of L5 is connected to the other end of C34, one end of C37, one end of C41, one end of C42, and the other end of TEC. The other end of C39 is connected to the other end of C40 and grounded, and the other end of C41 is connected to the other end of C42 and grounded.

[0018] Furthermore, the stepless current regulation method of the controller is as follows: initially, signal PWM1 is used as the duty cycle control signal (for controlling the magnitude of the drive voltage), and signal PWM2 is used as the polarity control signal (for controlling the direction of the drive voltage). When the TEC heating and cooling conversion begins, signal PWM2 output by the controller to the drive circuit remains unchanged, while the duty cycle of signal PWM1 is reduced uniformly to 0. After the duty cycle is reduced to 0, both signals PWM1 and PWM2 are changed to 100% high-level signals, so that the drive circuit is in a braking state. The temperature difference of the TEC is quickly reduced by utilizing the TEC power generation effect. Then, by switching signal PWM1 as the polarity control signal and signal PWM2 as the duty cycle control signal, signal PWM1 remains unchanged, and the duty cycle of signal PWM2 is increased uniformly to the range of PID (proportional-integral-derivative) dynamic adjustment. Then, based on the temperature signal fed back by the temperature sensor, PID adjustment is performed to make the TEC reach the set temperature.

[0019] Furthermore, the controller calculates and determines the duty cycle of the duty cycle control signal using the following formula;

[0020]

[0021] Where: D n and D n-1E represents the duty cycle of the duty cycle control signal at time n and time n-1, respectively. n and E n-1 K represents the error between the measured temperature and the target temperature at time n and time n-1, respectively. p K is the scaling factor. i K is the integrating factor. d K is the differential factor. l E is a linear decreasing factor. k T represents the error between the measured temperature and the target temperature at time k. target1 and T target2 This indicates the different target temperatures set in two separate tests, T. n Let be the measured temperature at time n, and Sign() be the sign function.

[0022] The TEC temperature control circuit of this invention uses a domestically produced, low-cost, small-size DC brushed motor driver chip (integrated H-bridge) to drive the TEC semiconductor heating and cooling chip. The low-cost domestic microcontroller outputs a PWM signal for temperature control. The microcontroller receives the temperature setting via a button, collects the temperature via a negative temperature NTC sensor, and outputs a PWM signal to drive the motor driver chip using an improved bidirectional hot and cold conversion PID algorithm. The signal is then filtered by an LC filter circuit and connected to the TEC semiconductor heating and cooling chip, thus realizing a high-current, small-size, low-cost temperature control circuit. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the TEC temperature control circuit of the present invention.

[0024] Figure 2 This is a schematic diagram illustrating the specific circuit structure and principle of the driver chip in an embodiment of the present invention.

[0025] Figure 3 This is a schematic diagram illustrating the fine-tuning timing of the PWM signal output by the microcontroller during the cooling / heating transition. Detailed Implementation

[0026] To describe the present invention in more detail, the technical solution of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0027] This invention relates to a TEC temperature control circuit based on H-bridge PWM bidirectional PID stepless adjustment. The circuit comprises a TEC, a domestically produced microcontroller, a domestically produced low-cost DC brushed motor driver (integrated H-bridge) chip, a dual LC (inductor-capacitor) filter circuit, a power supply circuit, and a negative temperature NTC sensor. The microcontroller performs voltage conversion and stepless current adjustment. The H-bridge drive power supply of the motor driver chip is connected to the power supply required by the TEC. The H-bridge output of the motor driver chip is connected to the LC filter circuit. The input control of the motor driver chip is connected to the PWM signal of the microcontroller. The LC filter circuit is connected to the TEC semiconductor heating and cooling element. The negative temperature NTC sensor is attached to the TEC and connected to the ADC pin of the microcontroller. The microcontroller dynamically adjusts the temperature to the set temperature using proportional-integral-derivative (PID) based on the temperature returned by the negative temperature NTC sensor. The microcontroller has a programming interface, a button circuit, a buzzer, and a display circuit. The programming interface is used for programming the microcontroller program, the button circuit is used for power on / off and function settings, the buzzer is used for status indication, the display circuit is used for temperature display, and the power supply circuit supplies power to the microcontroller and the TEC drive circuit.

[0028] To address the issue of high inrush current during thermal transitions, the microcontroller employs fine-grained stepless adjustment of the PWM signal. The specific adjustment method is as follows:

[0029] 1. When the hot-cold conversion begins, the polarity control signal output by the microcontroller to the motor drive chip (H-bridge) remains unchanged, and the duty cycle of the currently effective positive or reverse PWM signal is reduced to 0 at a constant speed.

[0030] 2. At this point, all PWM signals of the microcontroller are changed to 100% high level signals, so that the motor drive chip (H bridge) is in braking state, and the temperature difference of the TEC is quickly reduced by utilizing the TEC power generation effect.

[0031] 3. The polarity control signal output by the microcontroller to the motor drive chip (H-bridge) is changed, and the duty cycle of the currently effective positive or reverse PWM signal is increased at a constant speed. The microcontroller then dynamically adjusts the signal to the set temperature using proportional-integral-derivative (PID) based on the temperature collected by the NTC negative temperature sensor.

[0032] Example

[0033] like Figure 1 As shown, in this embodiment, the microcontroller 1 receives the input from the button 2 to turn the machine on and off and set the temperature. The microcontroller 1 is connected to the motor driver chip 5 through a PWM signal. One PWM signal is used to adjust the duty cycle of the TEC drive voltage, and the other PWM signal is used to control the direction of the drive by high and low levels. When the hot and cold switching alternates, the two PWM signals can be used interchangeably.

[0034] The LC filter circuit 6 filters the PWM power output of the motor drive chip 5 into a voltage that is linearly proportional to the duty cycle, and applies it to both ends of the TEC semiconductor heating and cooling chip 7 so that its effective working surface can be heated or cooled.

[0035] The NTC negative temperature sensor 8 is in close contact with the effective working surface of the TEC semiconductor heating and cooling chip 7, and its temperature is collected in real time and sent to the ADC pin of the microcontroller 1. The microcontroller 1 then performs proportional-integral-derivative (PID) calculations to obtain a dynamically adjusted PWM signal and polarity control, thereby forming a temperature control closed loop for precise temperature control.

[0036] Figure 2 The circuit diagram shows the driving principle of the motor driver chip driving TEC. The motor driver chip U5 uses the AT8236 chip from Hangzhou Zhongke Microelectronics, which has a peak current of 6A, a maximum driving voltage of 36V, and a size of only 6mm×4.9mm×1.65mm. The control input pin of U5 is connected to the TEC1_PWM1 and TEC1_PWM2 signals of the microcontroller. The two outputs of U5 are connected to inductors L4 and L5 respectively, and then filtered by capacitors C34, C37, C39, C40, C41, and C42, and finally connected to TEC1.

[0037] Figure 3 The diagram shows the timing sequence for fine-tuning the PWM signal during the microcontroller's hot / cold switching process. Timing 9 illustrates the duty cycle at the start of the hot / cold switching, with PWM1 as the duty cycle control signal and PWM2 as the polarity control signal. Timing 10 illustrates the gradual decrease of the duty cycle, where the PWM1 duty cycle decreases while the PWM2 polarity control signal remains unchanged. Timing 11 illustrates the decrease of the duty cycle to 0, where the PWM1 duty cycle is 0 and the PWM2 polarity control signal remains unchanged. Timing 12 illustrates the gradual increase of the duty cycle, where the PWM1 signal becomes a polarity control signal to change the direction of the TEC drive voltage, and PWM2 becomes a duty cycle control signal. Timing 13 illustrates the gradual increase of the duty cycle, where the PWM1 signal remains a polarity control signal, and the PWM2 duty cycle gradually increases to the range of PID dynamic adjustment.

[0038] The expression for calculating the duty cycle of the PWM signal is as follows:

[0039]

[0040] Where: D n and D n-1 E represents the duty cycle of the duty cycle control signal at time n and time n-1, respectively. n and E n-1 K represents the error between the measured temperature and the target temperature at time n and time n-1, respectively. p K is the scaling factor.i K is the integrating factor. d K is the differential factor. l E is a linear decreasing factor. k T represents the error between the measured temperature and the target temperature at time k. target1 and T target2 This indicates the different target temperatures set in two separate tests, T. n Let be the measured temperature at time n, and Sign() be the sign function.

[0041] When the temperature is being regulated normally, the duty cycle of the PWM is approximated by the proportional-integral-differential algorithm.

[0042] When the target temperature is changed and its polarity is opposite to the previous target temperature, the duty cycle of the PWM decreases linearly until it reaches 0.

[0043] When the duty cycle of the PWM is as small as 0, both PWM channels go high at the same time, that is, the duty cycle is 100%, and the braking function of the H bridge is activated.

[0044] Then it enters the next normal PID temperature adjustment cycle.

[0045] Using the above technical solution, this embodiment realizes a low-cost, small-volume H-bridge PWM bidirectional PID stepless adjustment TEC temperature control circuit. The microcontroller receives the temperature setting through the button, collects the temperature through the negative temperature NTC sensor, and outputs a PWM signal from the improved bidirectional hot and cold conversion PID algorithm to drive the motor drive chip (H-bridge). The signal is then connected to the TEC semiconductor heating and cooling chip through an LC filter circuit, thus realizing a high-current, small-volume, low-cost temperature control circuit.

[0046] The above description of the embodiments is provided to enable those skilled in the art to understand and apply the present invention. Those skilled in the art can readily make various modifications to the above embodiments and apply the general principles described herein to other embodiments without creative effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made to the present invention by those skilled in the art based on the disclosure thereof should be within the scope of protection of the present invention.

Claims

1. A TEC temperature control circuit based on H-bridge PWM bidirectional PID stepless regulation, comprising a TEC, a temperature sensor, a controller, a drive circuit, and a filter circuit, characterized in that: The temperature sensor is attached to the TEC and is used to sense the temperature of the TEC and generate a temperature signal to provide to the controller. The controller is used to acquire temperature signals and provide PWM signals to the drive circuit through voltage conversion and stepless current regulation. The driving circuit is connected to the filtering circuit and is controlled by the PWM signal to output driving voltages in both positive and negative directions. The filtering circuit is connected to the TEC and is used to filter the driving voltage and apply it to both ends of the TEC to realize the TEC's heating and cooling conversion and temperature control. The controller's stepless current regulation method is as follows: Initially, signal PWM1 is used as the duty cycle control signal and signal PWM2 is used as the polarity control signal. When the TEC heating and cooling conversion begins, the signal PWM2 output by the controller to the drive circuit remains unchanged, while the duty cycle of signal PWM1 is reduced uniformly to 0. When the duty cycle is reduced to 0, both signals PWM1 and PWM2 are changed to 100% high-level signals, putting the drive circuit in a braking state. The temperature difference of the TEC is quickly reduced by utilizing the TEC power generation effect. Then, by switching signal PWM1 as the polarity control signal and signal PWM2 as the duty cycle control signal, signal PWM1 remains unchanged, while the duty cycle of signal PWM2 is increased uniformly to the range of PID dynamic adjustment. Then, based on the temperature signal fed back by the temperature sensor, PID adjustment is performed to make the TEC reach the set temperature. The controller calculates and determines the duty cycle of the duty cycle control signal using the following formula; Where: D n and D n-1 E represents the duty cycle of the duty cycle control signal at time n and time n-1, respectively. n and E n-1 K represents the error between the measured temperature and the target temperature at time n and time n-1, respectively. p K is the scaling factor. i K is the integrating factor. d K is the differential factor. l E is a linear decreasing factor. k T represents the error between the measured temperature and the target temperature at time k. target1 and T target2 This indicates the different target temperatures set in two separate tests, T. n Let be the measured temperature at time n, and Sign() be the sign function.

2. The TEC temperature control circuit according to claim 1, characterized in that: The temperature sensor is an NTC negative temperature sensor.

3. The TEC temperature control circuit according to claim 1, characterized in that: The controller uses a domestically produced microcontroller and has a programming interface, button circuit, buzzer, and display circuit. The programming interface is used for programming, the button circuit is used for power on / off and temperature setting, the buzzer is used for status indication, and the display circuit is used for temperature display.

4. The TEC temperature control circuit according to claim 1, characterized in that: The TEC temperature control circuit also includes a power supply circuit to provide operating voltage for the temperature sensor, controller, and drive circuit.

5. The TEC temperature control circuit according to claim 1, characterized in that: The controller outputs two PWM signals, PWM1 and PWM2. PWM1 is used to adjust the magnitude of the drive voltage, and PWM2 is used to control the direction of the drive voltage through high and low levels. When the TEC switches between hot and cold, the two PWM signals can be switched.

6. The TEC temperature control circuit according to claim 1, characterized in that: The driving circuit uses the AT8236 driver chip with integrated H-bridge, which has a peak current of 6A and a maximum driving voltage of 36V, while its size is only 6mm×4.9mm×1.65mm.

7. The TEC temperature control circuit according to claim 1, characterized in that: The filtering circuit makes the duty cycle of the driving voltage and the PWM signal linearly proportional by filtering. It includes two inductors L4 and L5 and six capacitors C34, C37, C39, C40, C41, and C42. One end of L4 is connected to the output port OUT2 of the driving circuit, and the other end of L4 is connected to one end of C34, one end of C37, one end of C39, one end of C40, and one end of TEC. One end of L5 is connected to the output port OUT1 of the driving circuit, and the other end of L5 is connected to the other end of C34, one end of C37, one end of C41, one end of C42, and one end of TEC. The other end of C39 is connected to the other end of C40 and grounded, and the other end of C41 is connected to the other end of C42 and grounded.

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