Thermoelectric refrigeration and heating device based on h-bridge solid-state relay driving and method thereof

Abstract

The application discloses a thermoelectric refrigeration and heating device based on H-bridge solid-state relay driving and a method thereof, and comprises the following steps: collecting a current temperature value of a controlled object and calculating a deviation e and a deviation change rate c from a target value; switching a refrigeration, heating or stop mode according to the relationship between e and a dead zone threshold value AT; selecting a corresponding control parameter set according to the deviation interval in which |e| is located; controlling the conduction of two corresponding solid-state relays in the H-bridge in the refrigeration or heating mode to make the current flow through the TEC in a preset direction, and calculating a PWM duty cycle according to e and c by using the selected parameter set, and controlling the on-off of the solid-state relay to adjust the average power of the TEC; and performing the above steps cyclically to realize closed-loop constant temperature control. The application realizes predictive adjustment of the TEC by means of hierarchical zoning control and dynamic correction of parameters according to the deviation change rate, can effectively inhibit temperature overshoot and oscillation, improve temperature control precision, and reduce the switching loss of the solid-state relay and prolong the service life of the device.

Description

Technical Field

[0001] This invention relates to the field of thermoelectric refrigeration and heating technology, and in particular to a thermoelectric refrigeration and heating device and method based on H-bridge solid-state relay drive. Background Technology

[0002] Thermoelectric coolers operate based on the Peltier effect, switching between cooling and heating functions on the same device by changing the direction of the current flowing through it. Compared to traditional compression refrigeration or resistance heating solutions, they offer advantages such as no moving parts, no refrigerant leakage, and compact size, making them widely used in high-precision temperature control. Achieving high-precision bidirectional temperature control in thermoelectric coolers requires solving two key issues: first, the drive circuit must be able to ensure that the current flows through the device in the desired forward or reverse direction; second, the control strategy must adjust the current magnitude and direction in real time based on temperature feedback to quickly stabilize the temperature at the target value.

[0003] At the drive circuit level, existing technologies include solutions using H-bridge circuits to drive thermoelectric coolers. The H-bridge circuit achieves current commutation by changing the voltage polarity across the load through different on / off combinations of four switching elements. Combined with pulse width modulation (PWM) technology to adjust the duty cycle of the switching elements, the average operating current of the load can be controlled. At the control strategy level, a common approach is to use a microcontroller or microprocessor with a proportional-integral-derivative (PI-DE) control algorithm. This algorithm calculates the control input based on the deviation between the current temperature fed back from the temperature sensor and the target temperature to adjust the drive output.

[0004] However, the aforementioned existing technologies still have the following drawbacks in practical applications.

[0005] First, existing control strategies typically employ a single proportional-integral-derivative control parameter across the entire operating range. Because thermoelectric coolers inherently possess strong nonlinear characteristics, the relationship between their cooling capacity and operating current is not strictly linear, and the devices exhibit a certain degree of thermal inertia. A single control parameter often struggles to simultaneously meet the demands for rapid response under large deviations and precise adjustment under small deviations across the entire range, easily leading to excessively long settling times or temperature overshoot, thus affecting temperature control accuracy.

[0006] Second, existing control methods lack the ability to predict temperature change trends. Traditional closed-loop control logic is a passive response mode of "calculating output after detecting deviation." When the temperature is rapidly approaching the target value, the controller can only reduce the output after the temperature actually reaches near the target value. However, due to the thermal inertia of thermoelectric coolers, even if the output is reduced, the accumulated heat or cooling will continue to act on the controlled object, causing the temperature to exceed the target value and produce overshoot. After overshoot, reverse adjustment is required, and this repeated process forms temperature oscillations, which reduces the temperature control accuracy and increases the operating frequency of switching devices.

[0007] Third, the existing solution lacks a robust buffer mechanism for switching between cooling and heating modes. When the temperature of the controlled object fluctuates around the target value, the system tends to switch frequently between the two modes, increasing the switching losses of power devices and potentially causing unnecessary temperature fluctuations due to repeated mode switching. Summary of the Invention

[0008] Therefore, the technical problem to be solved by the present invention is to overcome the problems in the prior art where using a single control parameter makes it difficult to balance the nonlinearity and thermal inertia of TEC across the entire operating range, resulting in a contradiction between response speed and temperature control accuracy; the lack of predictive ability for temperature change trends leads to overshoot and oscillation; and the lack of a buffer mechanism for switching between cooling and heating modes leads to frequent switching. The present invention provides a thermoelectric cooling and heating device and method based on H-bridge solid-state relay drive. The PLC controller divides the deviation range according to the magnitude of the temperature deviation e and selects the corresponding set of control parameters. At the same time, the temperature deviation change rate c is introduced to dynamically correct the selected control parameters to predict the temperature change trend in advance. With the help of dead zone threshold and hysteresis interval to prevent frequent mode switching, the hierarchical and zoned control and predictive adjustment of the TEC cooling and heating execution module are realized. This can effectively suppress temperature overshoot and oscillation, shorten the adjustment time, improve temperature control accuracy, reduce the switching loss of solid-state relays, and extend the equipment life.

[0009] To address the aforementioned technical problems, this invention provides a thermoelectric cooling and heating method based on an H-bridge solid-state relay, comprising the following steps: S1. The temperature acquisition module collects the current temperature value of the controlled object in real time and sends it to the PLC controller; S2. The PLC controller calculates the temperature deviation e between the current temperature value and the preset target temperature value, and calculates the rate of change of temperature deviation c. S3, the PLC controller determines the operating mode and corresponding control parameters of the thermoelectric cooling and heating execution module based on the magnitude of the temperature deviation e: When e > ΔT, switch to cooling mode and select the corresponding cooling control parameter set from the preset set of multiple control parameters according to the deviation range of |e|. When e < -ΔT, switch to heating mode and select the corresponding heating control parameter set from the preset set of multiple control parameters according to the deviation range of |e|. When |e|≤ΔT, switch to stop mode; Wherein, ΔT is the preset dead zone threshold; S4. In cooling or heating mode, the PLC controller controls two solid-state relays in the H-bridge drive circuit composed of four solid-state relays to turn on and the other two solid-state relays to turn off through the analog output module, so that the current flows through the thermoelectric cooling and heating execution module in a preset direction; at the same time, the duty cycle of the PWM control signal is calculated using the selected control parameter set based on the temperature deviation e and the deviation change rate c. S5. The PLC controller controls the on / off duty cycle of the solid-state relays on the conduction path according to the duty cycle of the PWM control signal, so as to adjust the average working power of the thermoelectric cooling and heating execution module. S6. Repeat steps S1 to S5 to perform closed-loop constant temperature control on the controlled object.

[0010] In one embodiment of the present invention, the deviation range in step S3 includes a large deviation range, a medium deviation range, and a small deviation range; When |e|≥E1, it is determined to be a large deviation range. The selected control parameter set is the first control parameter set. The duty cycle of the PLC controller controlling the PWM control signal is 100%, and the thermoelectric cooling and heating execution module operates at maximum power. When E2≤|e|<E1, it is determined to be the medium deviation interval, and the selected control parameter set is the second control parameter set. The duty cycle of the PLC controller controlling the PWM control signal decreases linearly as |e| decreases. When ΔT < |e| < E2, it is determined to be a small deviation interval, and the selected control parameter set is the third control parameter set. The duty cycle of the PLC controller controlling the PWM control signal decreases nonlinearly as |e| decreases. Where E1 and E2 are preset temperature deviation thresholds, and E1 > E2 > ΔT.

[0011] In one embodiment of the present invention, in step S3, the switching of the working mode is provided with a hysteresis interval. When the temperature deviation e changes from greater than ΔT to less than ΔT, or from less than -ΔT to greater than -ΔT, the current working mode is maintained unchanged within the hysteresis interval to prevent the thermoelectric cooling and heating execution module from frequently switching between cooling mode and heating mode.

[0012] In one embodiment of the present invention, step S4 further includes mode switching prediction control: S41. In cooling or heating mode, predict the remaining time t for the temperature deviation e to reach the dead zone boundary ΔT based on the temperature deviation change rate c. When the remaining time t is less than the preset time threshold, the duty cycle of the PWM control signal is reduced to the preset value in advance, so as to reduce the cooling or heating power of the thermoelectric cooling and heating execution module before the temperature reaches the target value.

[0013] In one embodiment of the present invention, the control parameter set is a PID control parameter set, and each set of control parameter sets includes a proportional coefficient Kp, an integral coefficient Ki, and a derivative coefficient Kd; the calculation of the duty cycle of the PWM control signal in step S4 specifically includes: When the rate of change of deviation c has the opposite sign to the temperature deviation e, it indicates that the temperature is returning to the target value. The proportional coefficient Kp in the currently selected control parameter set is reduced proportionally according to the magnitude of |c| to suppress overshoot during the temperature return process. When the deviation change rate c has the same sign as the temperature deviation e, it indicates that the temperature is moving away from the target value. The proportional coefficient Kp in the currently selected control parameter set is increased proportionally according to the magnitude of |c| to accelerate the temperature recovery. The control output is calculated based on the adjusted set of control parameters and mapped to the duty cycle of the PWM control signal.

[0014] In one embodiment of the present invention, the sampling period T of the temperature acquisition module is in the range of 0.1s to 1s, and the frequency of the PWM control signal is 1kHz to 20kHz. The sampling period T is the same as the calculation period for the temperature deviation change rate c, which is calculated according to the following formula: c = [e(k) - e(k-1)] / T; Where e(k) is the temperature deviation of the current sampling period, and e(k-1) is the temperature deviation of the previous sampling period.

[0015] In one embodiment of the present invention, the solid-state relay has a preset switching delay time τ, and the high-level duration and low-level duration of the PWM control signal in step S4 are respectively set with a minimum on-time Ton and a minimum off-time Toff. Both the minimum on-time Ton and the minimum off-time Toff are greater than the switching delay time τ; When the turn-on or turn-off time calculated by the PWM control signal is less than the corresponding minimum time threshold, the PLC controller will force the PWM cycle to be set to a fully on or fully off state to avoid the solid-state relay from operating in the nonlinear region.

[0016] To address the aforementioned technical problems, this invention also provides a thermoelectric cooling and heating device driven by an H-bridge solid-state relay, used to implement the above method, comprising an electrical control cabinet and a thermoelectric cooling and heating execution module electrically connected to the electrical control cabinet, wherein: the electrical control cabinet includes: The enclosure has an internal mounting plate. The electrical components integrated on the mounting plate include a DC switching power supply, a PLC controller, a temperature acquisition module, and an analog output module; the DC switching power supply is used for power supply; the PLC controller is connected to the temperature acquisition module and the analog output module for signal transmission. An H-bridge drive circuit consisting of four solid-state relays is connected between a DC switching power supply and the thermoelectric cooling / heating execution module. The specific connection method of the H-bridge drive circuit is as follows: the first solid-state relay is connected between the positive terminal of the DC power supply and terminal A of the thermoelectric cooling / heating execution module; the second solid-state relay is connected between terminal A of the thermoelectric cooling / heating execution module and the negative terminal of the DC power supply; the third solid-state relay is connected between the positive terminal of the DC power supply and terminal B of the thermoelectric cooling / heating execution module; and the fourth solid-state relay is connected between terminal B of the thermoelectric cooling / heating execution module and the negative terminal of the DC power supply. The control terminals of all four solid-state relays are connected to an analog output module, and their on / off combinations are controlled by a PLC controller, causing current to flow through the thermoelectric cooling / heating execution module in either the first or second direction, corresponding to either the cooling mode or the heating mode.

[0017] In one embodiment of the present invention, the mounting plate also integrates an AC contactor, a safety relay, an intermediate relay, a circuit breaker, and wiring terminals. The circuit breaker and the AC contactor are connected in series in the main power supply circuit. The circuit breaker is used for overload and short circuit protection of the main power supply, and the AC contactor is used to disconnect the main circuit by the PLC controller when the main power supply is abnormal. The safety relay is connected to the safety output terminal of the PLC controller and is used to cut off the control power supply of the H-bridge drive circuit when an over-temperature or equipment failure is detected. The intermediate relay is connected between the digital output terminal of the PLC controller and the control terminal of the solid-state relay to achieve electrical isolation and level conversion of the control signal; The DC switching power supply, PLC controller, temperature acquisition module, analog output module, AC contactor, safety relay, intermediate relay, circuit breaker, terminal block, and H-bridge drive circuit composed of four solid-state relays are all electrically connected through wires in the wire trough. The installation positions of each component are arranged on the mounting plate according to the strong current and weak current zones.

[0018] In one embodiment of the present invention, the housing is provided with an aviation plug-in, and the thermoelectric cooling and heating execution module is pluggably connected to the electrical components in the electrical control cabinet through the aviation plug-in; the thermoelectric cooling and heating execution module includes: a TEC cooling chip assembly and a DC motor, which are independently electrically connected to the H-bridge drive circuit and the DC switching power supply through different pins in the aviation plug-in.

[0019] The technical solution of the present invention has the following advantages compared with the prior art: The thermoelectric cooling and heating method based on H-bridge solid-state relay driving described in this invention achieves fine-grained power regulation of the thermoelectric cooling and heating execution module by real-time temperature acquisition and calculation of deviation and deviation change rate, combined with dynamic selection of control parameter sets based on the deviation magnitude. This method effectively addresses the nonlinear characteristics and thermal inertia of thermoelectric coolers, avoids the limitations of a single control parameter under all operating conditions, and reduces temperature overshoot and oscillation. Simultaneously, by applying dead-zone thresholds and multiple control parameter sets, the mode switching logic is optimized, reducing the risk of frequent system switching near the target temperature and improving temperature control accuracy and system stability. Attached Figure Description

[0020] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein: Figure 1 This is a schematic diagram of the main process of the thermoelectric cooling and heating method based on H-bridge solid-state relay driven by the present invention. Figure 2 This is a flowchart illustrating the segmented control strategy for the deviation interval in this invention. Figure 3 This is a flowchart illustrating the dynamic adjustment of PID parameters in this invention. Figure 4 This is a schematic diagram of the internal structure of the thermoelectric cooling and heating device driven by the H-bridge solid-state relay of the present invention. Figure 5 This is a schematic diagram of the H-bridge drive circuit of the present invention; Figure 6 This is a front structural diagram of the thermoelectric cooling and heating device based on H-bridge solid-state relay driven by the present invention. Figure 7 This is a schematic diagram of the rear structure of the thermoelectric cooling and heating device based on the H-bridge solid-state relay driven by the present invention. Instruction manual drawing reference numerals: 1. Housing; 2. Handle; 3. Human-machine interface; 4. Aviation connector; 5. Heat dissipation vent; 6. Mounting plate; 7. DC switching power supply; 8. PLC controller; 9. Temperature acquisition module; 10. Analog output module; 11. AC contactor; 12. Safety relay; 13. Intermediate relay; 14a. First solid-state relay; 14b. Second solid-state relay; 14c. Third solid-state relay; 14d. Fourth solid-state relay; 15. Circuit breaker; 16. Terminal block. Detailed Implementation

[0021] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0022] Reference Figure 1 As shown, this invention provides a thermoelectric cooling and heating method based on H-bridge solid-state relay driving. The method is characterized by the introduction of a hierarchical and zoned control approach, dividing the entire control process into different intervals according to the magnitude of the temperature deviation, configuring specific control parameters for each interval, and using the temperature deviation change rate as a parameter to predict the temperature change trend and adjust the control output in advance.

[0023] Specifically, the technical solution of this application first acquires the current temperature value of the controlled object in real time through a temperature acquisition module and sends it to the PLC controller. The PLC controller calculates the temperature deviation e between the current temperature value and the preset target temperature value, and simultaneously calculates the rate of change of the temperature deviation c. The temperature deviation e reflects the degree to which the current temperature deviates from the target value, while the rate of change of the temperature deviation c reflects the speed and direction of change of the temperature deviation. These two parameters constitute the input basis for subsequent hierarchical control.

[0024] After determining the magnitude of the temperature deviation *e*, the PLC controller determines the appropriate operating mode based on the relationship between *e* and the preset dead-zone threshold *ΔT*. When *e* is greater than *ΔT*, it indicates that the actual temperature is higher than the target temperature and exceeds the allowable fluctuation range. The system switches to cooling mode, allowing current to flow through the thermoelectric cooler in the first direction, and the TEC begins cooling. When *e* is less than a negative *ΔT*, it indicates that the actual temperature is lower than the target temperature and exceeds the allowable fluctuation range. The system switches to heating mode, allowing current to flow through the thermoelectric cooler in the second direction, and the TEC begins heating. When the absolute value of *e* is not greater than *ΔT*, it indicates that the actual temperature is within the allowable fluctuation range near the target value. The system switches to stop mode, all four solid-state relays disconnect, and the TEC stops working. The dead-zone threshold *ΔT* provides a buffer zone near the target value, allowing for small temperature fluctuations. This prevents the system from continuously outputting power when the temperature requirement is met, saving energy and avoiding unnecessary power switching. From a control principle perspective, the selection of the dead zone threshold ΔT directly relates to the balance between control accuracy and system stability: if ΔT is too small, temperature fluctuations will frequently trigger the controller, leading to excessively high switching frequency of the solid-state relay and shortening the device's lifespan; if ΔT is too large, the allowable temperature fluctuation range near the target value will be too wide, sacrificing control accuracy. In engineering practice, the value of ΔT is usually determined based on the temperature accuracy requirements of the controlled object, generally set as the boundary value of the allowable temperature fluctuation range. For example, when a temperature control accuracy of ±0.1℃ is required, ΔT can be initially set to 0.05℃ to 0.1℃, and then fine-tuned according to the actual temperature fluctuation amplitude and solid-state relay operating frequency during operation.

[0025] After determining the operating mode, this application further selects a set of control parameters corresponding to the deviation range from a preset set of multiple control parameters based on the absolute value of the temperature deviation *e*. The logic behind this technique is as follows: when the temperature deviation is large, the system needs to drive the temperature back to its normal state quickly with maximum power; in this case, the control objective is response speed rather than adjustment accuracy. When the temperature deviation shrinks to a moderate range, the system needs to balance response speed and overshoot suppression; in this case, control parameters capable of producing moderate output should be used. When the temperature deviation has shrunk to a small deviation range close to the dead zone boundary, the system needs to focus on fine adjustment, using high proportional and low integral control parameters to prevent overshoot caused by integral saturation. By configuring different sets of control parameters for different deviation ranges, this application overcomes the contradiction that a single control parameter cannot simultaneously balance response speed and control accuracy across the entire range.

[0026] In cooling or heating mode, the PLC controller sends a conduction signal to the two corresponding solid-state relays in the H-bridge drive circuit through the analog output module, causing the current to flow through the thermoelectric cooler in a preset direction. Simultaneously, the PLC controller calculates the duty cycle of the pulse width modulation signal using the selected set of control parameters based on the current temperature deviation *e* and the deviation change rate *c*. The introduction of the deviation change rate *c* is a key element in the method of this application. When the system is in a callback process, the absolute value of the temperature deviation is gradually decreasing, and the sign of *c* is opposite to that of *e*. In this case, the proportional coefficient in the control parameters is reduced proportionally according to the magnitude of *c*, moderately weakening the control output. This allows the thermoelectric cooler (TEC) to reduce power output in advance when the temperature approaches the target value, utilizing the TEC's thermal inertia to glide precisely to near the target value. Conversely, when the system is deviating from the target, the sign of *c* is the same as that of *e*, indicating that the temperature is rapidly moving away from the target value. In this case, the proportional coefficient is increased proportionally according to the magnitude of *c* to strengthen the control effect and quickly suppress the deviation trend. This strategy of dynamically correcting control parameters by utilizing the sign and magnitude of the rate of change of deviation enables the controller to have predictive capabilities, allowing it to adjust the control output in advance before the actual temperature reaches the target value, thereby effectively suppressing temperature overshoot and subsequent oscillations caused by TEC thermal inertia.

[0027] Finally, the PLC controller controls the switching action of the two solid-state relays on the conduction path based on the calculated duty cycle of the pulse width modulation signal, thereby precisely adjusting the average operating power of the TEC. These steps are executed cyclically, forming a continuous closed-loop control.

[0028] Through the above technical solution, this application has achieved the following beneficial effects: First, the hierarchical and zoned control strategy combined with deviation change rate correction enables the system to respond quickly when the temperature deviation is large, and to decelerate in advance and smoothly enter steady state when the temperature approaches the target value. This effectively shortens the adjustment time and reduces the overshoot, significantly improving the temperature control accuracy.

[0029] Secondly, the combination of dead zone threshold and hysteresis control logic effectively avoids frequent mode switching of the system near the target value, reduces the switching losses of solid-state relays, and extends the equipment life.

[0030] Third, the above control method, together with the H-bridge drive circuit composed of solid-state relays and the PLC industrial control system, forms a complete thermoelectric cooling and heating control scheme, which can meet the requirements of high-end industrial scenarios such as semiconductor manufacturing and laser temperature control for temperature control accuracy and reliability.

[0031] Reference Figure 2 As shown, based on the above method, this application refines the judgment of temperature deviation e and the selection of control parameters. Specifically, the deviation range is divided into a large deviation range, a medium deviation range, and a small deviation range. When the absolute value of the temperature deviation |e| is greater than or equal to the preset threshold E1, the system determines that it is in the large deviation range. In this case, in order to achieve rapid temperature adjustment, the PLC controller selects the first set of control parameters and directly controls the duty cycle of the PWM control signal to 100%, so that the thermoelectric cooling and heating execution module operates at maximum power, thereby quickly reducing the large temperature deviation. When the absolute value of the temperature deviation |e| is between E2 and E1 (i.e., E2≤|e|<E1), the system determines that it is in the medium deviation range. At this time, the PLC controller selects the second set of control parameters and controls the duty cycle of the PWM control signal to decrease linearly as |e| decreases. This linear adjustment method helps to smoothly reduce the output power when the temperature approaches the target value, avoiding over-cooling or over-heating. When the absolute value of the temperature deviation, |e|, is between ΔT and E2 (i.e., ΔT < |e| < E2), the system determines that it is in the small deviation range. Within this range, the PLC controller selects the third set of control parameters and controls the duty cycle of the PWM control signal to decrease non-linearly as |e| decreases. This non-linear reduction strategy allows for more precise and sensitive control when the temperature is very close to the target value, effectively suppressing oscillations caused by small deviations and ensuring that the system stably enters the dead zone. Here, E1 and E2 are preset temperature deviation thresholds, and E1 > E2 > ΔT. These threshold settings ensure the effective division of different deviation ranges and the smooth transition of the control strategy.

[0032] It needs further explanation that the physical meaning of the second threshold E2 is to define the boundary between the medium deviation range and the small deviation range. When the temperature deviation is less than E2 but greater than ΔT, the system is in the small deviation range close to the target value. Within this range, a fine-tuning strategy is required, typically employing a control parameter set with a high proportional coefficient and a low integral coefficient to suppress overshoot caused by integral saturation and ensure the temperature smoothly approaches the target value. The value of E2 is closely related to the thermal inertia time constant of the TEC (Temperature Control Unit). Its determination principle is: when the system enters the small deviation range, the control output should be able to allow the temperature to slide precisely to the target value without overshoot under the influence of the TEC's thermal inertia. The specific calibration method is as follows: when the system is close to steady state (temperature deviation approximately 1℃~2℃), apply a step excitation (such as a short-term shutdown of the PWM output), record the temperature response curve, and determine the reasonable range of E2 based on the response characteristics of the temperature naturally falling back to the dead zone boundary from this deviation value.

[0033] The physical meaning of the first threshold E1 is to define the boundary between the large deviation range and the medium deviation range. When the temperature deviation is greater than or equal to E1, the system is in a large deviation state. At this time, the system should output maximum power to quickly bring the temperature back to the target value, and the PWM duty cycle should be set to 100%. The value of E1 determines the response threshold for the system to enter the saturation region. If the value of E1 is too small, the system will enter full power output when the deviation is medium, which may lead to overshoot due to excessively rapid temperature recovery; if the value of E1 is too large, the response will be lagging, and the adjustment time will be prolonged. The calibration of E1 needs to be determined in combination with the maximum cooling / heating capacity of the TEC and the heat capacity of the system.

[0034] In some of the above embodiments, the PLC controller directly switches the operating mode of the thermoelectric cooling / heating execution module based on the comparison between the temperature deviation e and the preset dead zone threshold ΔT. However, when the temperature deviation e fluctuates near the dead zone boundary ΔT, for example, in cooling mode, if the temperature deviation e changes from slightly greater than ΔT to slightly less than ΔT and then quickly returns to slightly greater than ΔT, the system may frequently switch between cooling mode and stop mode, or frequently switch between heating mode and stop mode. This frequent mode switching may not only lead to instability in system control but also accelerate the wear of key components such as solid-state relays in the thermoelectric cooling / heating execution module, reducing their service life.

[0035] In response, this application further proposes that in step S3, the switching of the working mode is set with a hysteresis interval. When the temperature deviation e changes from greater than ΔT to less than ΔT, or from less than -ΔT to greater than -ΔT, the current working mode is maintained unchanged within the hysteresis interval to prevent the thermoelectric cooling and heating execution module from frequently switching between cooling mode and heating mode.

[0036] Specifically, the hysteresis interval refers to an insensitive region with a certain width introduced in the control system to avoid frequent switching caused by tiny signal fluctuations near the switching point. Within this region, the output state of the system, such as the working mode of the thermoelectric cooling and heating execution module, will not change immediately with the change of the input signal, such as the temperature deviation e, but will maintain the original state until the input signal exceeds the other boundary of this region. For example, a threshold ΔTlower slightly smaller than ΔT and a threshold -ΔTupper slightly larger than -ΔT can be set to define the hysteresis interval. When the system is in the cooling mode and the temperature deviation e decreases from the direction greater than ΔT and enters the interval of ΔTlower<e ≤ ΔT, the PLC controller will maintain the current cooling mode unchanged. Only when e further decreases to e ≤ ΔTlower will the system switch to the stop mode. Similarly, when the system is in the heating mode and the temperature deviation e increases from the direction smaller than -ΔT and enters the interval of -ΔT ≤ e<-ΔTupper, the PLC controller will maintain the current heating mode unchanged. Only when e further increases to e ≥ -ΔTupper will the system switch to the stop mode. This strategy of "maintaining the current working mode unchanged" is the core of hysteresis control, which suppresses the mode oscillation caused by tiny fluctuations of the temperature deviation e near the dead zone boundary by introducing a memory effect.

[0037] In some of the above embodiments, the PLC controller determines the working mode of the thermoelectric cooling and heating execution module according to the magnitude of the temperature deviation e, and switches to the stop mode when the temperature deviation e enters the preset dead zone threshold ΔT. However, due to the certain thermal inertia of the thermoelectric cooling and heating execution module, if the work is stopped directly when the temperature approaches the target value and is about to enter the dead zone, overshoot or undershoot of the temperature near the target value may occur, thus affecting the temperature control accuracy and stability. In addition, frequent switching between full-power operation and stop may also cause energy waste and system impact.

[0038] In this regard, the present application further proposes a mode switching predictive control. This control method aims to optimize the behavior of the thermoelectric cooling and heating execution module when approaching the target temperature, so as to improve control accuracy and system stability.

[0039] Specifically, in cooling or heating mode, the PLC controller predicts the remaining time t for the temperature deviation e to reach the dead zone boundary ΔT based on the temperature deviation change rate c. The temperature deviation change rate c characterizes the rate and direction of temperature change. For example, it can be calculated by dividing the difference between the temperature deviation e(k) of the current sampling period and the temperature deviation e(k-1) of the previous sampling period by the sampling period T, i.e., c = [e(k) - e(k-1)] / T. Based on this change rate, the PLC controller can use linear extrapolation or more complex prediction models to estimate when the temperature will enter the dead zone. For example, if the temperature approaches the dead zone boundary ΔT at a constant rate c, the remaining time t can be approximated as (|e| - ΔT) / |c|.

[0040] When the predicted remaining time t is less than a preset time threshold, the PLC controller will take measures in advance to reduce the duty cycle of the PWM control signal to a preset value. This preset value can be a fixed, small duty cycle, or a dynamic value calculated based on the remaining time t or temperature deviation e, to achieve finer power regulation. In this way, the cooling or heating power of the thermoelectric cooling / heating actuator can be gradually reduced before the temperature reaches the target value. For example, when it is predicted that the temperature will enter the dead zone in the next few seconds, the duty cycle will no longer be maintained at 100%, but will be reduced to 50% or lower, or even a smoother transition curve can be used.

[0041] In this embodiment, the control parameter set is a PID control parameter set, and each set of control parameter sets includes a proportional coefficient Kp, an integral coefficient Ki, and a derivative coefficient Kd; (Refer to...) Figure 3 As shown, the calculation of the duty cycle of the PWM control signal in step S4 specifically includes: when the deviation change rate c and the temperature deviation e have opposite signs, it indicates that the temperature is returning to the target value. The proportional coefficient Kp in the currently selected control parameter set is reduced proportionally according to the magnitude of |c| to suppress overshoot during the temperature return process; when the deviation change rate c and the temperature deviation e have the same sign, it indicates that the temperature is moving away from the target value. The proportional coefficient Kp in the currently selected control parameter set is increased proportionally according to the magnitude of |c| to accelerate the temperature return; the control output is calculated based on the adjusted control parameter set and mapped to the duty cycle of the PWM control signal.

[0042] Specifically, the PID control parameter set is a feedback control algorithm widely used in industrial control. Its core lies in processing the deviation of the controlled object through three components: proportional, integral, and derivative, to generate a control output. The proportional coefficient Kp reflects the instantaneous response strength to the current deviation; a larger Kp results in a faster response, but excessive Kp may lead to overshoot and oscillation. The integral coefficient Ki is used to eliminate steady-state error by adjusting the output through accumulating historical deviations; a larger Ki eliminates steady-state error faster, but excessive Ki may lead to integral saturation. The derivative coefficient Kd reflects the predictive ability of the deviation's changing trend; a larger Kd strengthens the suppression of deviation changes, helping to reduce overshoot and improve system stability, but excessive Kd may increase sensitivity to noise. By properly configuring these three parameters (Kp, Ki, and Kd), the system can achieve the desired dynamic response and steady-state performance.

[0043] When the rate of change of deviation *c* and the temperature deviation *e* have opposite signs, it means that the temperature of the controlled object is changing towards the target temperature, i.e., the system is in a "reverse" state. For example, in cooling mode, if the temperature is higher than the target value (*e*>0) and the temperature is decreasing (*c*<0), then *c* and *e* have opposite signs. In this case, to prevent the temperature from overshooting due to inertia as it approaches the target value, this application reduces the proportional coefficient *Kp* in the currently selected control parameter set proportionally based on the absolute value of the rate of change of deviation *c*. Specifically, the larger |*c*| is, the faster the temperature reverses, and the greater the reduction in *Kp*, thereby reducing the controller's output strength and making the system more stable as it approaches the target value, effectively suppressing overshoot.

[0044] When the rate of change of deviation *c* and the temperature deviation *e* have the same sign, it means that the temperature of the controlled object is changing away from the target temperature, i.e., the system is in a "deviation" state. For example, in cooling mode, if the temperature is higher than the target value (*e*>0) and the temperature is still rising (*c*>0), then *c* and *e* have the same sign. In this case, to quickly bring the temperature back to the target value, this application increases the proportional coefficient *Kp* in the currently selected control parameter set according to the absolute value of the rate of change of deviation *c*. Specifically, the larger |*c*| is, the faster the temperature deviates, and the greater the increase in *Kp*, thereby enhancing the controller's output strength, enabling the system to respond more quickly to temperature deviations, accelerating the temperature recovery process to the target value, and improving the system's response speed.

[0045] After dynamically adjusting the proportional coefficient Kp, the PLC controller uses the updated PID control parameter set (including the adjusted Kp and the original Ki and Kd) to calculate the current control output. This control output is a continuous value calculated by the PID algorithm based on the current temperature deviation e, the rate of change of deviation c, and the historical cumulative deviation. Subsequently, this continuous control output is mapped or converted into the duty cycle of the PWM control signal. The duty cycle is the ratio of the high-level duration in the PWM signal to the entire cycle, and it directly determines the average operating power of the thermoelectric cooling / heating actuator. By mapping the PID control output to the duty cycle, the PLC controller can precisely regulate the current flowing through the thermoelectric cooling / heating actuator, thereby achieving fine control of the cooling or heating power.

[0046] This application further proposes optimized settings for key parameters in the aforementioned control method. Specifically, the sampling period T of the temperature acquisition module is limited to a range of 0.1s to 1s, and the frequency of the PWM control signal is set to 1kHz to 20kHz. Simultaneously, the sampling period T is kept identical to the calculation period of the temperature deviation change rate c, and c is calculated according to the formula c=[e(k)-e(k-1)] / T, where e(k) represents the temperature deviation of the current sampling period, and e(k-1) represents the temperature deviation of the previous sampling period.

[0047] The sampling period T of the temperature acquisition module refers to how often the module acquires the current temperature value of the controlled object. This parameter directly affects the system's real-time performance and control accuracy. Setting the sampling period T within the range of 0.1s to 1s aims to balance the system's response speed, control accuracy, computational resource consumption, and noise immunity. For example, a shorter sampling period of 0.1s allows the system to respond to temperature changes more quickly, providing more refined control data, suitable for scenarios sensitive to temperature changes and requiring rapid adjustments; while a longer sampling period of 1s reduces the amount of data and the computational burden on the PLC controller, suitable for scenarios where temperature changes are relatively slow and real-time requirements are less stringent. Within this optimized range, the system can effectively capture temperature dynamics and provide sufficiently timely and stable data for subsequent control algorithms.

[0048] The frequency of a PWM control signal refers to the number of times the PWM signal repeats within one cycle. A high-frequency PWM signal can make the average power regulation of the thermoelectric cooling / heating actuator smoother, reduce ripple, and avoid generating audible noise. Setting the frequency of the PWM control signal within the range of 1kHz to 20kHz is determined after comprehensively considering efficiency, noise, switching losses, and the response characteristics of the solid-state relay. For example, a frequency of 1kHz can meet basic power regulation requirements, while a frequency of 20kHz can significantly reduce current ripple, making the operation of the thermoelectric cooling / heating actuator more stable and efficient, while pushing switching noise beyond the range of human hearing. Within this range, the system can achieve efficient, smooth, and noiseless power regulation.

[0049] Furthermore, the sampling period T is the same as the calculation period of the temperature deviation change rate c. This means that the calculation of the temperature deviation change rate c is performed immediately after each temperature sampling, or in other words, the data points e(k) and e(k-1) used to calculate c are data obtained from two consecutive sampling periods T. This synchronization ensures that the calculation of the temperature deviation change rate c is consistent with the real-time temperature acquisition, avoiding the impact on the timeliness and effectiveness of c-based control decisions due to calculation lag or inaccuracy. The formula for calculating the temperature deviation change rate c, c=[e(k)-e(k-1)] / T, is a simple and intuitive differential calculation method, easy to implement in PLC controllers, and can accurately reflect the trend and speed of temperature changes, providing crucial dynamic information for subsequent control algorithms (such as the derivative term in PID control or mode switching predictive control).

[0050] This application further proposes to fully consider the physical characteristics of solid-state relays during PWM control. Specifically, the solid-state relay has a preset switching delay time τ, which refers to the time required for the solid-state relay to fully turn on or off its internal semiconductor device from receiving a control signal. This delay time is an inherent property of the device, typically in the millisecond or microsecond range. To ensure the stable and reliable operation of the solid-state relay, the high-level duration (i.e., on-time) and low-level duration (i.e., off-time) of the PWM control signal are respectively set with a minimum on-time Ton and a minimum off-time Toff. The minimum on-time Ton is the minimum duration required to ensure the solid-state relay can fully turn on and operate stably, while the minimum off-time Toff is the minimum duration required to ensure the solid-state relay can fully turn off and stably recover. Furthermore, both the minimum on-time Ton and the minimum off-time Toff are set to be greater than the switching delay time τ of the solid-state relay. This setting is crucial; it ensures that even when the PWM control signal requires the shortest on or off cycle, the solid-state relay has sufficient time to complete its state transition, avoiding intermediate states due to insufficient time. When the turn-on or turn-off time of the PWM control signal calculated by the PLC controller based on the temperature deviation e and the rate of change of deviation c is less than the corresponding minimum time threshold (i.e., Ton or Toff), the PLC controller will take mandatory measures to force the current PWM cycle to a fully on or fully off state. For example, if the calculated turn-on time is less than Ton, the solid-state relay remains fully on throughout the entire PWM cycle; if the calculated turn-off time is less than Toff, the solid-state relay remains fully off throughout the entire PWM cycle. These measures aim to prevent the solid-state relay from operating in the nonlinear region. When the solid-state relay operates in the nonlinear region, its internal losses increase sharply, leading to device heating, reduced efficiency, and potentially shortened lifespan. By ensuring that the solid-state relay always operates in a stable state of full on or full off, these problems can be effectively avoided.

[0051] Reference Figures 4-7 As shown in the illustration, this application also discloses a thermoelectric cooling and heating device driven by an H-bridge solid-state relay to implement the above method. The device includes an electrical control cabinet and a thermoelectric cooling and heating execution module electrically connected to the electrical control cabinet. The electrical control cabinet includes: The housing 1 has an installation plate 6 inside; The electrical components integrated on the mounting plate 6 include a DC switching power supply 7, a PLC controller 8, a temperature acquisition module 9, and an analog output module 10; the DC switching power supply 7 is used for power supply; the PLC controller 8 is connected to the temperature acquisition module 9 and the analog output module 10 for signal connection. An H-bridge drive circuit consisting of four solid-state relays is connected between the DC switching power supply 7 and the thermoelectric cooling / heating execution module. The specific connection method of the H-bridge drive circuit is as follows: the first solid-state relay 14a is connected between the positive terminal of the DC power supply and the A terminal of the thermoelectric cooling / heating execution module; the second solid-state relay 14b is connected between the A terminal of the thermoelectric cooling / heating execution module and the negative terminal of the DC power supply; the third solid-state relay is connected between the positive terminal of the DC power supply and the B terminal of the thermoelectric cooling / heating execution module; and the fourth solid-state relay is connected between the B terminal of the thermoelectric cooling / heating execution module and the negative terminal of the DC power supply. The control terminals of the four solid-state relays are all connected to the analog output module 10, and their on / off combinations are programmed and controlled by the PLC controller 8 to make the current flow through the thermoelectric cooling / heating execution module in the first direction or the second direction, thereby realizing the cooling mode or the heating mode.

[0052] The core innovation of this embodiment lies in combining the H-bridge drive circuit with solid-state relays in a specific topology, and cooperating with the PLC controller 8 for precise programming control of the on / off combinations. This solves the problems of insufficient temperature control accuracy, temperature overshoot oscillation, and frequent mode switching caused by the nonlinear characteristics of thermoelectric coolers in high-precision temperature control, thus achieving the effect of improving temperature control stability and reducing power device losses. Specifically, the device uses four solid-state relays to form the H-bridge drive circuit. Their connection relationship is strictly limited to the first solid-state relay 14a being located between the positive terminal of the DC power supply and the A terminal of the thermoelectric cooling / heating execution module, the second solid-state relay 14b being located between the A terminal of the thermoelectric cooling / heating execution module and the negative terminal of the DC power supply, the third solid-state relay 14c being located between the positive terminal of the DC power supply and the B terminal of the thermoelectric cooling / heating execution module, and the fourth solid-state relay 14d being located between the B terminal of the thermoelectric cooling / heating execution module and the negative terminal of the DC power supply. This structural design enables the PLC controller 8 to independently control the on / off state of each solid-state relay through the analog output module 10. When cooling mode is required, it controls the first solid-state relay 14a and the fourth solid-state relay 14d to be turned on, and the second solid-state relay 14b and the third solid-state relay 14c to be turned off, so that the current flows through the thermoelectric cooling and heating execution module in the first direction. When heating mode is required, it controls the second solid-state relay 14b and the third solid-state relay 14c to be turned on, and the first solid-state relay 14a and the fourth solid-state relay 14d to be turned off, so that the current flows through the thermoelectric cooling and heating execution module in the second direction.

[0053] The mounting plate 6 of the electrical control cabinet integrates a DC switching power supply 7, a PLC controller 8, a temperature acquisition module 9, and an analog output module 10. The DC switching power supply 7 provides a stable operating voltage for the entire system, and the PLC controller 8, as the core control unit, receives real-time data from the temperature acquisition module 9 and outputs control commands.

[0054] In actual operation, the PLC controller 8 dynamically adjusts the on / off combination of solid-state relays and the PWM duty cycle in the H-bridge drive circuit according to the temperature deviation. Because solid-state relays are contactless, their switching action is free from arc interference and has a fast response speed. Combined with the settings of minimum on-time Ton and minimum off-time Toff, the nonlinear operating range problem caused by the switching delay time τ is effectively avoided. When the temperature deviation enters the dead zone threshold range, the system automatically switches to stop mode. Combined with the hysteresis interval setting, the frequent switching between cooling and heating modes is significantly reduced, thereby reducing the switching losses of power devices and suppressing temperature fluctuations. Through the above structural design, this device provides a highly reliable hardware execution platform for thermoelectric cooling and heating control methods, ensuring the accuracy of current direction switching and the smoothness of power regulation during temperature control.

[0055] In this embodiment, the mounting plate 6 of the aforementioned thermoelectric cooling and heating control equipment driven by the H-bridge solid-state relay further integrates an AC contactor 11, a safety relay 12, an intermediate relay 13, a circuit breaker 15, and a terminal block 16. The circuit breaker 15 and the AC contactor 11 are connected in series in the main power supply circuit. The circuit breaker 15 is used for overload and short-circuit protection of the main power supply, while the AC contactor 11 is used by the PLC controller 8 to disconnect the main circuit when the main power supply is abnormal. The safety relay 12 is connected to the safety output terminal of the PLC controller 8 and is used to cut off the control power supply to the H-bridge drive circuit when an over-temperature or equipment malfunction is detected. The intermediate relay 13 is connected between the digital output terminal of the PLC controller 8 and the control terminal of the solid-state relay, used to achieve electrical isolation and level conversion of the control signal. The DC switching power supply 7, PLC controller 8, temperature acquisition module 9, analog output module 10, AC contactor 11, safety relay 12, intermediate relay 13, circuit breaker 15, terminal block 16, and H-bridge drive circuit composed of four solid-state relays are all electrically connected through wires in the wire trough. The installation positions of each component are arranged on the mounting plate 6 according to the strong current and weak current zones.

[0056] Specifically, the circuit breaker 15 is an automatically operating electrical switch whose core function is to protect the circuit from damage caused by overload or short-circuit current. In this embodiment, the circuit breaker 15 is connected in series at the entrance of the main power circuit as the first line of defense. When an overload occurs in the main power circuit where the current exceeds a preset safety threshold, or when a short-circuit fault occurs, the circuit breaker 15 can quickly and automatically trip to cut off the power supply, thereby effectively preventing dangers such as electrical fires, equipment damage, and electric shock.

[0057] The AC contactor 11 is an electrical switch operated by an electromagnet, mainly used for frequently connecting or disconnecting AC circuits. In this device, the AC contactor 11 is also connected in series in the main power supply circuit, and its on / off state is controlled by the PLC controller 8. When the system detects an abnormality in the main power supply (such as excessively high or low voltage or unstable frequency) or when a planned shutdown is required, the PLC controller 8 can issue a command to disconnect the AC contactor 11 from the main circuit, thereby achieving remote and safe control of the main power supply of the entire device.

[0058] The safety relay 12 is a special relay with high reliability and self-monitoring function, designed to ensure the implementation of safety functions. In this embodiment, the safety relay 12 is connected to the safety output terminal of the PLC controller 8. When the temperature acquisition module 9 detects that the temperature of the controlled object exceeds the preset safety range (e.g., severe overheating or underheating), or when the PLC controller 8 diagnoses a serious internal fault in the equipment, the safety output terminal of the PLC controller 8 will trigger the safety relay 12. The safety relay 12 then cuts off the control power supply to the H-bridge drive circuit, causing the thermoelectric cooling and heating execution module to immediately stop working, thereby avoiding further danger or damage caused by uncontrolled operation.

[0059] Intermediate relay 13 is a general-purpose relay commonly used for signal amplification, electrical isolation, or level conversion. In this device, intermediate relay 13 is connected between the digital output terminal of PLC controller 8 and the control terminal of solid-state relay. The digital output of PLC controller 8 is typically a low-voltage, low-current signal, while the control terminal of solid-state relay may require different voltage or current drives, and solid-state relay may generate back electromotive force or electromagnetic interference during switching. Intermediate relay 13, through its internal coil and contacts, achieves electrical isolation between PLC controller 8 and solid-state relay, effectively protecting the sensitive output circuit of PLC from high voltage or current surges, while ensuring level matching and stable transmission of control signals, and reducing the impact of electromagnetic interference on control accuracy.

[0060] Furthermore, to optimize the electrical layout and improve system stability, all electrical components, including the DC switching power supply 7, PLC controller 8, temperature acquisition module 9, analog output module 10, AC contactor 11, safety relay 12, intermediate relay 13, circuit breaker 15, terminal blocks 16, and the H-bridge drive circuit composed of four solid-state relays, are all electrically connected via wires in the wiring troughs. Simultaneously, the installation positions of each component on the mounting plate 6 are arranged according to high-voltage and low-voltage zones. The high-voltage zone mainly houses components carrying high current and high voltage, such as circuit breaker 15, AC contactor 11, and the power supply section of the H-bridge drive circuit; the low-voltage zone houses control and signal processing components sensitive to electromagnetic interference, such as PLC controller 8, temperature acquisition module 9, and analog output module 10. This zoned arrangement effectively isolates electromagnetic interference generated by the high-voltage circuit, preventing it from affecting the low-voltage control signals, thereby ensuring the stability and accuracy of the control system. The terminal blocks 16 provide a standardized and modular interface for all wire connections, greatly facilitating equipment installation, commissioning, maintenance, and troubleshooting.

[0061] In this embodiment, an aviation plug-in 4 is provided on the enclosure 1 of the electrical control cabinet. The thermoelectric cooling and heating execution module is pluggably connected to the electrical components inside the electrical control cabinet through the aviation plug-in 4. The thermoelectric cooling and heating execution module includes a TEC cooling chip assembly and a DC motor, which are independently electrically connected to the H-bridge drive circuit and the DC switching power supply 7 through different pins in the aviation plug-in 4.

[0062] Specifically, the aviation connector 4, also known as a circular connector or heavy-duty connector, is an electrical connection device widely used in industrial control, aerospace, and other fields. It is characterized by its robust structure, reliable connection, high protection level, and quick-connect / remove capability. The aviation connector 4 is installed on the enclosure 1 of the electrical control cabinet to provide a standardized and convenient electrical interface for connecting external devices to internal electrical components. This connector typically consists of a plug and a socket; the socket is fixed to the enclosure 1, and the plug connects to the external device. Internally, it contains multiple conductive pins, which can carry different types and numbers of signal or power lines as needed.

[0063] Plug-in connections refer to electrical connections that can be established or disconnected through mechanical insertion and removal. Compared to traditional screw wiring or soldering, plug-in connections significantly simplify the installation, commissioning, and maintenance of equipment. When thermoelectric cooling / heating actuators need to be installed, replaced, or repaired, operators do not need to perform complex wiring operations; they only need to insert or remove the aviation-grade plug-in 4. This greatly reduces operation time, lowers the skill requirements for operators, and effectively reduces the risk of malfunctions due to wiring errors.

[0064] The thermoelectric cooling / heating actuator module is the core component for temperature control, typically comprising a TEC (Thermoelectric Cooler) assembly and a DC motor. The TEC assembly is a semiconductor device that achieves cooling or heating based on the Peltier effect; its operating direction and power are determined by the direction and magnitude of the current flowing through it. The DC motor is often used to drive a fan to enhance heat exchange efficiency, for example, transferring the cold / heat generated by the TEC assembly to the controlled object or dissipating waste heat generated by the TEC assembly. These two components are the main energy consumers and functional execution units in the thermoelectric cooling / heating actuator module.

[0065] Independent electrical connections refer to the TEC cooling chip assembly and the DC motor establishing their own independent electrical paths with the H-bridge drive circuit and DC switching power supply 7 within the electrical control cabinet, respectively, via different pins inside the aviation plug-in 4. The TEC cooling chip assembly requires a variable direction and magnitude of current from the H-bridge drive circuit to achieve cooling or heating functions; while the DC motor typically requires a stable DC power supply to drive the fan. Independent connections via different pins in the aviation plug-in 4 ensure that each component receives its required operating power and control signals, avoids mutual interference, and allows for optimized design and control based on its individual electrical characteristics. For example, the H-bridge drive circuit provides bidirectional adjustable current to the TEC cooling chip assembly, while the DC switching power supply 7 provides a unidirectional stable voltage to the DC motor.

[0066] The enclosure 1 is also equipped with a human-machine interface 3, preferably a touch screen, which is connected to the PLC controller 8 inside the enclosure 1. Operators can use this touch screen to set target temperature values, adjust control parameters, and view current temperature data and system operating status in real time.

[0067] Ventilation holes 5 are provided on both the left and right sides of the enclosure 1. The ventilation holes 5 can adopt a louvered structure, which can effectively prevent dust from falling directly into the enclosure 1 while ensuring air circulation through the inclined blades. Alternatively, the ventilation holes 5 can adopt a mesh structure, that is, a matrix of ventilation holes is directly opened on the wall of the enclosure 1 and covered with a dustproof mesh on the inside.

[0068] The enclosure 1 is also equipped with handles 2, which can be U-shaped or bow-shaped and are fixedly installed on the top or sides of the enclosure 1. The handles 2 facilitate the operation of operators to move and adjust the position of the electrical control cabinet during equipment installation, on-site deployment, or maintenance.

[0069] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A thermoelectric cooling and heating method based on H-bridge solid-state relay driving, characterized in that, Includes the following steps: S1. The temperature acquisition module collects the current temperature value of the controlled object in real time and sends it to the PLC controller; S2. The PLC controller calculates the temperature deviation e between the current temperature value and the preset target temperature value, and calculates the rate of change of temperature deviation c. S3, the PLC controller determines the operating mode and corresponding control parameters of the thermoelectric cooling and heating execution module based on the magnitude of the temperature deviation e: When e > ΔT, switch to cooling mode and select the corresponding cooling control parameter set from the preset set of multiple control parameters according to the deviation range of |e|. When e < -ΔT, switch to heating mode and select the corresponding heating control parameter set from the preset set of multiple control parameters according to the deviation range of |e|. When |e|≤ΔT, switch to stop mode; Wherein, ΔT is the preset dead zone threshold; S4. In cooling or heating mode, the PLC controller controls two solid-state relays in the H-bridge drive circuit composed of four solid-state relays to turn on and the other two solid-state relays to turn off through the analog output module, so that the current flows through the thermoelectric cooling and heating execution module in a preset direction; at the same time, the duty cycle of the PWM control signal is calculated using the selected control parameter set based on the temperature deviation e and the deviation change rate c. S5. The PLC controller controls the on / off duty cycle of the solid-state relays on the conduction path according to the duty cycle of the PWM control signal, so as to adjust the average working power of the thermoelectric cooling and heating execution module. S6. Repeat steps S1 to S5 to perform closed-loop constant temperature control on the controlled object.

2. The thermoelectric cooling and heating method based on H-bridge solid-state relay driving according to claim 1, characterized in that: In step S3, the deviation range includes a large deviation range, a medium deviation range, and a small deviation range; When |e|≥E1, it is determined to be a large deviation range. The selected control parameter set is the first control parameter set. The duty cycle of the PLC controller controlling the PWM control signal is 100%, and the thermoelectric cooling and heating execution module operates at maximum power. When E2≤|e|<E1, it is determined to be the medium deviation interval, and the selected control parameter set is the second control parameter set. The duty cycle of the PLC controller controlling the PWM control signal decreases linearly as |e| decreases. When ΔT < |e| < E2, it is determined to be a small deviation interval, and the selected control parameter set is the third control parameter set. The duty cycle of the PLC controller controlling the PWM control signal decreases nonlinearly as |e| decreases. Where E1 and E2 are preset temperature deviation thresholds, and E1 > E2 > ΔT.

3. The thermoelectric cooling and heating method based on H-bridge solid-state relay driving according to claim 1, characterized in that: In step S3, the switching of the working mode is set with a hysteresis interval. When the temperature deviation e changes from greater than ΔT to less than ΔT, or from less than -ΔT to greater than -ΔT, the current working mode is maintained within the hysteresis interval to prevent the thermoelectric cooling and heating execution module from frequently switching between cooling mode and heating mode.

4. The thermoelectric cooling and heating method based on H-bridge solid-state relay driving according to claim 1, characterized in that: Step S4 also includes mode switching predictive control: S41. In cooling or heating mode, predict the remaining time t for the temperature deviation e to reach the dead zone boundary ΔT based on the temperature deviation change rate c. When the remaining time t is less than the preset time threshold, the duty cycle of the PWM control signal is reduced to the preset value in advance, so as to reduce the cooling or heating power of the thermoelectric cooling and heating execution module before the temperature reaches the target value.

5. The thermoelectric cooling and heating method based on H-bridge solid-state relay driving according to claim 1, characterized in that: The control parameter set is a PID control parameter set, and each set of control parameter sets includes the proportional coefficient Kp, integral coefficient Ki, and derivative coefficient Kd; the calculation of the duty cycle of the PWM control signal in step S4 specifically includes: When the rate of change of deviation c has the opposite sign to the temperature deviation e, it indicates that the temperature is returning to the target value. The proportional coefficient Kp in the currently selected control parameter set is reduced proportionally according to the magnitude of |c| to suppress overshoot during the temperature return process. When the deviation change rate c has the same sign as the temperature deviation e, it indicates that the temperature is moving away from the target value. The proportional coefficient Kp in the currently selected control parameter set is increased proportionally according to the magnitude of |c| to accelerate the temperature recovery. The control output is calculated based on the adjusted set of control parameters and mapped to the duty cycle of the PWM control signal.

6. The thermoelectric cooling and heating method based on H-bridge solid-state relay driving according to claim 1, characterized in that: The sampling period T of the temperature acquisition module ranges from 0.1s to 1s, and the frequency of the PWM control signal is from 1kHz to 20kHz. The sampling period T is the same as the calculation period for the temperature deviation change rate c, which is calculated according to the following formula: c = [e(k) - e(k-1)] / T; Where e(k) is the temperature deviation of the current sampling period, and e(k-1) is the temperature deviation of the previous sampling period.

7. The thermoelectric cooling and heating method based on H-bridge solid-state relay driving according to claim 1, characterized in that: The solid-state relay has a preset switching delay time τ, and the high-level duration and low-level duration of the PWM control signal in step S4 are respectively set with minimum on-time Ton and minimum off-time Toff; Both the minimum on-time Ton and the minimum off-time Toff are greater than the switching delay time τ; When the turn-on or turn-off time calculated by the PWM control signal is less than the corresponding minimum time threshold, the PLC controller will force the PWM cycle to be set to a fully on or fully off state to avoid the solid-state relay from operating in the nonlinear region.

8. A thermoelectric cooling and heating device driven by an H-bridge solid-state relay, used to implement the method described in any one of claims 1 to 7, characterized in that: It includes an electrical control cabinet and a thermoelectric cooling / heating actuator module electrically connected to the electrical control cabinet, wherein: the electrical control cabinet includes: The enclosure has an internal mounting plate. The electrical components integrated on the mounting plate include a DC switching power supply, a PLC controller, a temperature acquisition module, and an analog output module; the DC switching power supply is used for power supply; the PLC controller is connected to the temperature acquisition module and the analog output module for signal transmission. An H-bridge drive circuit consisting of four solid-state relays is connected between a DC switching power supply and the thermoelectric cooling / heating execution module. The specific connection method of the H-bridge drive circuit is as follows: the first solid-state relay is connected between the positive terminal of the DC power supply and terminal A of the thermoelectric cooling / heating execution module; the second solid-state relay is connected between terminal A of the thermoelectric cooling / heating execution module and the negative terminal of the DC power supply; the third solid-state relay is connected between the positive terminal of the DC power supply and terminal B of the thermoelectric cooling / heating execution module; and the fourth solid-state relay is connected between terminal B of the thermoelectric cooling / heating execution module and the negative terminal of the DC power supply. The control terminals of all four solid-state relays are connected to an analog output module, and their on / off combinations are controlled by a PLC controller, causing current to flow through the thermoelectric cooling / heating execution module in either the first or second direction, corresponding to either the cooling mode or the heating mode.

9. The thermoelectric cooling and heating device based on H-bridge solid-state relay drive according to claim 8, characterized in that: The mounting plate also integrates AC contactors, safety relays, intermediate relays, circuit breakers, and terminal blocks. The circuit breaker and the AC contactor are connected in series in the main power supply circuit. The circuit breaker is used for overload and short circuit protection of the main power supply, and the AC contactor is used to disconnect the main circuit by the PLC controller when the main power supply is abnormal. The safety relay is connected to the safety output terminal of the PLC controller and is used to cut off the control power supply of the H-bridge drive circuit when an over-temperature or equipment failure is detected. The intermediate relay is connected between the digital output terminal of the PLC controller and the control terminal of the solid-state relay to achieve electrical isolation and level conversion of the control signal; The DC switching power supply, PLC controller, temperature acquisition module, analog output module, AC contactor, safety relay, intermediate relay, circuit breaker, terminal block, and H-bridge drive circuit composed of four solid-state relays are all electrically connected through wires in the wire trough. The installation positions of each component are arranged on the mounting plate according to the strong current and weak current zones.

10. The thermoelectric cooling and heating device based on H-bridge solid-state relay drive according to claim 8, characterized in that: The enclosure is equipped with aviation plug-in modules, through which the thermoelectric cooling and heating execution module can be plugged into and connected to the electrical components in the electrical control cabinet. The thermoelectric cooling and heating execution module includes a TEC cooling chip assembly and a DC motor, which are independently electrically connected to the H-bridge drive circuit and the DC switching power supply through different pins in the aviation plug-in.

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