Electric heating clamp plate straightening iron and its precise temperature control method

Abstract

The present application relates to the technical field of temperature control of electric heating equipment, and particularly relates to an electric heating clamp plate straightening iron and a precise temperature control method thereof, which comprises a first clamp plate, a second clamp plate, a first PTC heating element, a second PTC heating element, a first temperature detection element, a second temperature detection element, a first silicon controlled rectifier power regulating circuit, a second silicon controlled rectifier power regulating circuit, an electric parameter acquisition circuit and a controller, corresponding PTC heating elements, temperature detection elements, silicon controlled rectifier power regulating circuits and electric parameter sampling branches are arranged on the first clamp plate and the second clamp plate respectively, and the first clamp plate and the second clamp plate are connected to the controller to form corresponding electric heating closed loop control branches, so that the controller can acquire the temperature state of the two clamp plates and the electric parameter state of the corresponding power supply loop, and the power supply power of the two PTC heating elements can be adjusted respectively, the pertinence of electric heating power control is improved, and the two clamp plates have better temperature consistency and temperature control stability in the working process.

Description

Technical Field

[0001] This invention relates to the field of temperature control technology for electric heating equipment, and particularly to an electric heating device for hair styling tools, automatic control of electric heating power of PTC resistance heating element, electrical parameter sampling and thyristor power control technology, specifically to an electric heating hair straightener and its precise temperature control method. Background Technology

[0002] A heated hair straightener is a common type of heated hair care device. It typically consists of two opposing plates with heating elements inside. In use, the plates clamp the hair and move along its length, transferring heat to the hair to straighten, smooth, style the ends, or perform other hair treatments.

[0003] In existing electrically heated hair straighteners, PTC heating elements are commonly used as the heating source. PTC heating elements have a certain self-limiting temperature characteristic; when their temperature rises to near a specific temperature range, their equivalent resistance changes, thus affecting the heating power. Current products typically use temperature sensors to detect the temperature of the hair straightener, and the control circuit adjusts the heating power of the heating element based on the detected temperature.

[0004] For electric heating devices using PTC resistance heating elements, their heating power is related not only to the temperature of the clamping plate, but also to the supply voltage, operating current, conduction control state in the power supply circuit of the heating element, and the change in the equivalent resistance of the PTC resistance heating element itself. Especially when using thyristor power regulation for electric heating power control, if the control circuit only performs on / off control or constant temperature control based on temperature detection results, without combining the effective value of voltage, effective value of current, power supply parameters, equivalent resistance parameters, and thyristor conduction control quantity for automatic power adjustment, it will be difficult to accurately reflect the actual electrothermal working state of the resistance heating element, and it will also be difficult to adjust the electric heating power accurately and in a timely manner.

[0005] However, in actual use, the contact between the hair and the straightener plates continuously carries away heat from them. Variations in hair thickness, moisture content, clamping force, clamping time, and movement speed all cause changes in the heat load on the plates. Especially in straighteners with two plates operating simultaneously, the heat dissipation conditions, stress states, contact area with the hair, and heating responses of the two plates are not entirely consistent. This can easily lead to asynchronous temperatures or localized temperature fluctuations between the two plates, thus affecting styling results and safety during use.

[0006] The existing technology has at least the following problems: (1) Existing electric heating straighteners mostly use a single-path temperature detection or simple constant temperature control method, which makes it difficult to reflect the actual temperature state of the first and second plates respectively, and also makes it difficult to adjust the heating power of the corresponding heating elements in the two plates respectively, which makes it easy for temperature difference to occur between the two plates, affecting the consistency of heat output on both sides.

[0007] (2) Although the existing PTC heating element has self-limiting temperature characteristics, its equivalent resistance parameters and power supply parameters will change with the temperature of the clamp and the power supply status. If the control circuit does not establish or update the corresponding data relationship based on the electrothermal characteristics of the PTC heating element, it is easy to make an inaccurate judgment on the current electrothermal status of the PTC heating element, resulting in problems such as slow heating response, large steady-state fluctuations or temperature overshoot.

[0008] (3) Existing thyristor power control usually adjusts the heating power based on the deviation between the clamp temperature and the preset temperature. It does not fully combine the voltage parameters, current parameters, equivalent resistance parameters and power parameters in the power supply circuit of the PTC heating element. This makes it difficult for the controller to identify the actual power supply status and electrothermal change status of the heating element in a timely and accurate manner. Furthermore, the existing control method usually does not associate the thyristor conduction angle, conduction duty cycle or conduction cycle with the electric heating power, the change of equivalent resistance of the PTC resistance heating element and the change of power supply, resulting in insufficient automatic power control accuracy of the electric heating device.

[0009] (4) When hair comes into contact with the clamp and causes a sudden change in heat load, the existing control method usually only increases the heating power after the clamp temperature has dropped significantly. It is difficult to make timely and targeted compensation based on the clamp temperature drop rate, which can easily lead to slow clamp temperature recovery and insufficient temperature stability when clamping multiple strands of hair continuously.

[0010] (5) Existing dual-plate temperature control methods usually lack a temperature difference linkage compensation mechanism between the two plates. When the temperature of one plate is too high and the temperature of the other plate is too low, the existing control method is difficult to simultaneously suppress the high temperature side and compensate the low temperature side, thus affecting the ability of the two plates to synchronously approach the preset temperature.

[0011] (6) The existing control method is insufficient in controlling the PTC heating element when it approaches the range of significant changes in its electrothermal characteristics. When the equivalent resistance parameter or power supply parameter of the PTC heating element changes significantly, if the conduction control quantity is still output according to the conventional temperature deviation control method, it is easy to cause the conduction control quantity to be adjusted untimely or excessively, which in turn causes temperature fluctuations or overshoot.

[0012] Therefore, it is necessary to provide an electric heating hair straightener with a clamp and a precise temperature control method thereof, so that the first clamp and the second clamp can form corresponding electric heating closed-loop control branches respectively, and control is carried out by combining clamp temperature, power supply circuit electrical parameters, PTC heating element electric heating characteristics, clamp temperature drop rate and double clamp temperature difference linkage compensation, so as to improve the electric heating control accuracy, double clamp temperature synchronization, temperature stability during continuous use and styling consistency. Summary of the Invention

[0013] To at least solve one of the above-mentioned technical problems in the prior art, the present invention aims to provide an electrically heated hair straightener.

[0014] To address at least one of the aforementioned technical problems in the prior art, the present invention aims to provide a precise temperature control method for an electrically heated hair straightener.

[0015] This invention further improves the automatic control of the electric heating power of PTC resistance heating elements. It acquires the voltage and current parameters in the power supply circuit of the PTC resistance heating element through an electrical parameter acquisition circuit, and the controller automatically adjusts the power of the first and second thyristor power adjustment circuits based on the voltage parameters, current parameters, equivalent resistance parameters, power supply parameters, clamp temperature, and thyristor conduction control quantity, thereby realizing closed-loop regulation of the electric heating power of the first and second PTC heating elements.

[0016] The first objective of this invention is achieved as follows: An electric heating hair straightener includes a first clamp plate, a second clamp plate, a first PTC heating element, a second PTC heating element, a first temperature detection element, a second temperature detection element, a first SCR power adjustment circuit, a second SCR power adjustment circuit, an electrical parameter acquisition circuit, and a controller. The first PTC heating element is disposed on the first clamp plate, the first temperature detection element is disposed on the first clamp plate or close to the first PTC heating element, and the power output terminal of the first SCR power adjustment circuit is connected to the first PTC heating element. The second PTC heating element is disposed on the second clamping plate, the second temperature detection element is disposed on the second clamping plate or near the second PTC heating element, and the power output terminal of the second thyristor power regulation circuit is connected to the second PTC heating element; The electrical parameter acquisition circuit includes a first electrical parameter sampling branch and a second electrical parameter sampling branch. The first electrical parameter sampling branch is connected to the power supply circuit of the first PTC heating element and is used to acquire the voltage and current parameters of the power supply circuit corresponding to the first PTC heating element. The second electrical parameter sampling branch is connected to the power supply circuit of the second PTC heating element and is used to acquire the voltage and current parameters of the power supply circuit corresponding to the second PTC heating element. The controller has a first temperature sampling terminal, a second temperature sampling terminal, a first power adjustment control terminal, a second power adjustment control terminal, and at least one electrical parameter sampling terminal; Wherein, the first temperature sampling terminal is connected to the first temperature detection device, the second temperature sampling terminal is connected to the second temperature detection device, the first power adjustment control terminal is connected to the control terminal of the first thyristor power adjustment circuit, the second power adjustment control terminal is connected to the control terminal of the second thyristor power adjustment circuit, and the first electrical parameter sampling branch and the second electrical parameter sampling branch are respectively connected to the corresponding electrical parameter sampling terminal. The first PTC heating element, the first temperature detection element, the first thyristor power adjustment circuit, the first electrical parameter sampling branch, and the controller form a first electrothermal closed-loop control branch, and the second PTC heating element, the second temperature detection element, the second thyristor power adjustment circuit, the second electrical parameter sampling branch, and the controller form a second electrothermal closed-loop control branch.

[0017] By installing corresponding PTC heating elements, temperature detection elements, SCR power regulation circuits, and electrical parameter sampling branches on the first and second clamping plates respectively, and forming corresponding electrothermal closed-loop control branches with the controller, the controller can obtain the temperature status of the two clamping plates and the electrical parameter status of the corresponding power supply circuits, and adjust the power supply power of the two PTC heating elements separately. This solves the problem of existing electric heating clamp hair straighteners being unable to separately detect the temperature of the two clamping plates and adjust the heating power of the two circuits, improving the targeting of electric heating power control and enabling the two clamping plates to have better temperature consistency and temperature control stability during operation.

[0018] Meanwhile, since the controller automatically controls the thyristor power regulation circuit based on the voltage parameters, current parameters, equivalent resistance parameters and power parameters of the power supply circuit, the present invention can also realize automatic adjustment of electric heating power applicable to electric heating devices.

[0019] The primary objective of this invention can also be achieved using the following technical measures: Furthermore, the first electrical parameter sampling branch includes a first voltage sampling unit and a first current sampling unit. The first voltage sampling unit is connected in parallel across the two ends of the first PTC heating element, and the first current sampling unit is connected in series in the power supply circuit of the first PTC heating element. The second electrical parameter sampling branch includes a second voltage sampling unit and a second current sampling unit. The second voltage sampling unit is connected in parallel across the two ends of the second PTC heating element, and the second current sampling unit is connected in series in the power supply circuit of the second PTC heating element.

[0020] By connecting the first voltage sampling unit in parallel across the first PTC heating element and the first current sampling unit in series in the power supply circuit of the first PTC heating element, and setting the same voltage and current sampling structures for the second PTC heating element, the controller can obtain the actual power supply voltage and actual operating current of the two PTC heating elements respectively. This solves the problem that existing control methods rely solely on temperature detection and cannot accurately identify the actual power supply status of the heating element, providing a more reliable data foundation for subsequently determining equivalent resistance parameters, power supply parameters, and performing electric heating power adjustment control.

[0021] Furthermore, both the first and second temperature sensing elements are NTC thermistors; the conduction control quantities output by the first and second thyristor power control circuits include at least one of the following: thyristor conduction angle, conduction duty cycle, or conduction cycle number.

[0022] By employing NTC thermistors as both the first and second temperature sensors, it is beneficial to quickly acquire information about changes in the clamping plate temperature. Simultaneously, by ensuring that the conduction control quantities of the first and second SCR power adjustment circuits include at least one of the following: conduction angle, conduction duty cycle, or number of conduction cycles, the controller can select the appropriate power adjustment mode according to different control requirements. This solves the problems of insufficient temperature detection response and inflexible heating power adjustment in existing electric heating clamping plate straighteners, improving the response speed of clamping plate temperature adjustment and the controllability of electric heating power output.

[0023] Furthermore, both the first and second PTC heating elements are resistance-type electric heating elements. The first and second thyristor power adjustment circuits adjust the electric heating power of the corresponding resistance-type electric heating elements under the control of the controller. The controller determines the equivalent resistance parameter and power supply parameter of the corresponding PTC heating element based on the voltage and current parameters of the power supply circuit of the corresponding PTC heating element. Based on the corresponding clamping plate temperature, the equivalent resistance parameter, and the power supply parameter, the controller automatically adjusts the conduction angle, conduction duty cycle, or conduction cycle of the corresponding thyristor power adjustment circuit to change the electric heating power of the corresponding PTC heating element.

[0024] Furthermore, the controller includes an electrothermal characteristic modeling module, a dual closed-loop temperature control module, a temperature difference linkage compensation module, and a power adjustment output module; The electrothermal characteristic modeling module is used to establish or update the PTC electrothermal characteristic data table based on the clamping plate temperature, the thyristor conduction control quantity, the power supply parameters and the temperature rise response of the corresponding PTC heating element. The PTC electrothermal characteristic data table includes the correspondence between clamping plate temperature, equivalent resistance parameters and power supply parameters. The dual closed-loop temperature control module is used to generate a first basic conduction control quantity and a second basic conduction control quantity based on the first clamping plate temperature, the second clamping plate temperature, the clamping plate preset temperature and the PTC electrothermal characteristic data table, respectively. The temperature difference linkage compensation module is used to generate a temperature difference linkage compensation amount based on the temperature difference between the temperature of the first clamping plate and the temperature of the second clamping plate. The power adjustment output module is used to generate a first target power adjustment quantity and a second target power adjustment quantity based on the first basic power-on control quantity, the second basic power-on control quantity, the temperature difference linkage compensation quantity, the temperature drop rate of the clamping plate, and the electrothermal characteristic correction information of the PTC heating element, and output control signals to the first thyristor power adjustment circuit and the second thyristor power adjustment circuit respectively based on the first target power adjustment quantity and the second target power adjustment quantity. The electrothermal characteristic correction information of the PTC heating element includes at least one of the changes in the equivalent resistance parameter and the changes in the power supply parameter of the corresponding PTC heating element. The power supply parameters include at least one of the effective value of the power supply voltage, the power supply frequency and the zero-crossing detection signal, and the temperature rise response includes at least one of the temperature rise per unit time, the temperature rise per unit sampling period and the temperature rise change corresponding to the unit conduction control quantity. The rate of temperature decrease of the clamping plate is determined based on the change in clamping plate temperature within adjacent sampling periods and the sampling interval. The electrothermal characteristic correction information is used to reduce, limit, or smooth the target conduction control quantity when the equivalent resistance parameter increases or the power supply parameter decreases.

[0025] By incorporating an electrothermal characteristic modeling module, a dual closed-loop temperature control module, a temperature difference linkage compensation module, and a power adjustment output module into the controller, the controller can establish or update the PTC electrothermal characteristic data table based on the clamping plate temperature, the thyristor conduction control quantity, power supply parameters, and the temperature rise response of the PTC heating element. Furthermore, it generates the target conduction control quantity by combining the temperature status, temperature difference status, temperature drop rate of the two clamping plates, and the equivalent resistance and power supply changes of the PTC heating element. This solves the problem of existing control methods not fully integrating the PTC heating element's electrothermal characteristics and power supply circuit parameters for power adjustment correction, making the thyristor power adjustment output more consistent with the current operating state of the PTC heating element, thereby reducing problems such as slow temperature rise response, large steady-state fluctuations, and temperature overshoot.

[0026] The second objective of this invention is achieved as follows: A precise temperature control method using the above-mentioned electric heating hair straightener includes: S1, the controller acquires the temperature of the first straightener and the temperature of the second straightener respectively; S2, the controller obtains the voltage and current parameters of the power supply circuits corresponding to the first PTC heating element and the second PTC heating element through the electrical parameter acquisition circuit, and determines the electrothermal operating parameters of the first PTC heating element and the second PTC heating element according to the voltage and current parameters. The electrothermal operating parameters include the equivalent resistance parameter and the power supply parameter. S3, the controller establishes a PTC electrothermal characteristic data table corresponding to the first PTC heating element and the second PTC heating element based on the temperature of the first clamping plate, the temperature of the second clamping plate, and the electrothermal working parameters; S4, the controller uses the preset temperature of the clamping plate as the control target and establishes the first clamping plate temperature closed loop and the second clamping plate temperature closed loop respectively. S5, the controller corrects the PID control parameters in the first clamping plate temperature closed loop and the second clamping plate temperature closed loop according to the PTC electrothermal characteristic data table, and generates the first basic conduction control quantity and the second basic conduction control quantity. S6, the controller calculates the temperature difference between the temperature of the first clamping plate and the temperature of the second clamping plate, and generates a temperature difference linkage compensation amount based on the temperature difference. S7, the controller generates the first target conduction control quantity and the second target conduction control quantity respectively based on the first basic conduction control quantity, the second basic conduction control quantity, the temperature difference linkage compensation quantity, the temperature drop rate of the clamping plate and the electrothermal characteristic correction information of the PTC heating element. S8, the controller controls the first thyristor power adjustment circuit according to the first target conduction control amount, and controls the second thyristor power adjustment circuit according to the second target conduction control amount, so as to adjust the power supply of the first PTC heating element and the second PTC heating element respectively, so that the first clamping plate and the second clamping plate synchronously approach the preset temperature of the clamping plate, and maintain the temperature difference between the temperature of the first clamping plate and the temperature of the second clamping plate within the preset temperature difference threshold range.

[0027] By sequentially executing steps in the precise temperature control method, including acquiring the clamping plate temperature, acquiring the power supply circuit electrical parameters, determining the electrothermal operating parameters, establishing the PTC electrothermal characteristic data table, temperature closed-loop control, PID control parameter correction, temperature difference linkage compensation, and outputting the target conduction control quantity, the first and second clamping plates can coordinate their power adjustments based on their own temperatures, electrical parameter states, and the temperature difference between the two plates. This solves the problems of existing electric heating clamping plate hair straighteners having simple control logic and difficulty in simultaneously controlling independent temperature and synchronizing the temperatures of the two clamping plates, thus improving the temperature control accuracy and temperature recovery capability of the electric heating clamping plate hair straightener during continuous operation.

[0028] The second objective of this invention can also be achieved by the following technical measures: Further, step S3 includes: during the start-up and heating stage of the electric heating hair straightener, the controller controls the first thyristor power adjustment circuit and the second thyristor power adjustment circuit to supply power to the first PTC heating element and the second PTC heating element according to multiple preset conduction control quantities, so that the first and second clamps are heated from the ambient temperature to the preset maximum temperature control temperature. Record the corresponding clamping plate temperature, equivalent resistance parameter, and power supply parameter every time the temperature of the first clamping plate and the second clamping plate increases by 3°C to 8°C. After outlier removal and mean averaging of multiple sets of data at the same temperature sampling point, the data are written into the PTC electrothermal characteristic data table.

[0029] By controlling two thyristor power adjustment circuits according to multiple preset conduction control quantities during the startup and heating phase of the electric heating hair straightener, the controller records the hair straightener temperature, equivalent resistance parameters, and power supply parameters according to temperature ranges during the heating process. After outlier removal and averaging, these data are written into the PTC electrothermal characteristic data table, enabling the controller to obtain electrothermal data that matches the actual PTC heating element and the actual assembly state. This solves the problem of insufficient adaptability of fixed control parameters due to individual differences, assembly differences, or power supply conditions of different PTC heating elements, improving the accuracy of subsequent power adjustment control and temperature correction.

[0030] Furthermore, the outlier removal includes: removing data with instantaneous temperature jumps greater than or equal to 2°C; and / or, Data whose power supply parameters deviate from the average power supply at the same temperature sampling point by more than or equal to 10% are excluded.

[0031] By removing data with excessively large instantaneous temperature fluctuations and / or excessively large deviations in power supply parameters when establishing the PTC electrothermal characteristic data table, the impact of temperature sampling jitter, current sampling interference, power supply fluctuations, and instantaneous contact changes on the data table can be reduced. This solves the problem of inaccurate power adjustment judgments caused by abnormal sampling data entering the control data table, improves the reliability of the PTC electrothermal characteristic data table, and makes the electric heating power correction made by the controller based on this data table more stable.

[0032] Further, in step S5, the correction of the PID control parameters includes: when the difference between the current clamping temperature of any clamping plate and the lower limit of the Curie temperature range of the corresponding PTC heating element is less than or equal to 20°C, and the equivalent resistance change rate of the corresponding PTC heating element is greater than the preset resistance change rate threshold, the proportional coefficient is reduced and the derivative coefficient is increased. When the current temperature of any clamping plate is lower than the preset temperature of the clamping plate by more than the first temperature threshold, the proportional coefficient is increased and the integral coefficient is decreased. When the current temperature of any clamping plate is within the steady-state temperature range of the preset temperature of the clamping plate, the proportional coefficient, integral coefficient and derivative coefficient are adjusted to the steady-state control parameters. The steady-state temperature range is ±1℃ of the preset temperature of the clamping plate, the first temperature threshold is 3℃ to 8℃, and the preset resistance change rate threshold is 0.03kΩ / ℃ to 0.08kΩ / ℃.

[0033] By adjusting the PID control parameters in stages based on the relationship between the current temperature of the clamping plate and the lower limit of the Curie temperature range of the PTC heating element, the equivalent resistance change rate, the deviation between the clamping plate temperature and the preset temperature, and the steady-state temperature range, the controller can employ different control parameters when rapidly heating up, approaching steady state, and approaching the range where the electrothermal characteristics of the PTC heating element change significantly. This solves the problem that fixed PID parameters cannot simultaneously address heating rate, steady-state stability, and overshoot suppression, improving the temperature control adaptability of the electric heating clamp hair straightener in different operating stages.

[0034] Furthermore, the preset temperature difference threshold is 0.5℃ to 2℃; during the temperature control process, the controller acquires the temperature of the first clamping plate and the temperature of the second clamping plate at a frequency of 10 times / second to 20 times / second, and after acquiring 5 to 10 sets of temperature data, it updates at least one of the PTC electrothermal characteristic data table, PID control parameters and temperature difference linkage compensation amount. The preset temperature of the clamping plate is 150°C to 200°C, and the preset temperature of the clamping plate is lower than the lower limit of the Curie temperature range of the first PTC heating element and the second PTC heating element.

[0035] By limiting the preset temperature difference threshold, temperature sampling frequency, parameter update cycle, and preset temperature range of the clamping plates, and ensuring that the preset temperature of the clamping plates is below the lower limit of the Curie temperature range of the PTC heating element, the controller can acquire the temperature changes of the two clamping plates at a higher frequency and periodically update the PTC electrothermal characteristic data table, PID control parameters, and temperature difference linkage compensation. This solves the problems of untimely temperature control sampling, delayed parameter updates, and mismatch between the set temperature and the electrothermal characteristics of the PTC heating element in existing electric heating clamping plate hair straighteners, improving temperature stability and operational safety during continuous molding processes.

[0036] The beneficial effects of this invention are as follows: This invention, by respectively assembling a PTC heating element, a temperature detection element, a SCR power regulation circuit, and an electrical parameter sampling branch in the first and second clamping plates, enables the controller to acquire the temperature signals of the two clamping plates and the voltage and current signals of the corresponding power supply circuits, and adjust the power supply power of the corresponding PTC heating element accordingly. Therefore, the two clamping plates no longer rely on a single temperature detection path or unified heating control, improving the targeted nature of the electric heating power adjustment and making it easier for the temperatures of the two clamping plates to synchronously approach the preset temperature.

[0037] This invention collects voltage and current parameters from the power supply circuit of the PTC heating element, determines the equivalent resistance and power parameters accordingly, and then establishes or updates a PTC electrothermal characteristic data table. This allows the controller to adjust power control based on the resistance and power changes of the PTC heating element caused by temperature variations. Therefore, it reduces the problems of slow heating response, large steady-state fluctuations, or temperature overshoot caused by relying solely on the temperature deviation of the clamping plate for control, making the electric heating control process more consistent with the actual working state of the PTC heating element.

[0038] This invention establishes separate temperature control processes for the first and second hair straighteners, and generates a temperature difference compensation based on the temperature difference between the two straighteners. This allows the side with a lower temperature to appropriately increase its heating power, while the side with a higher temperature can appropriately decrease or limit its heating power. This reduces the temperature difference between the two straighteners, improves the consistency of heat output to both sides of the hair, and minimizes the problem of uneven styling results due to one side being too hot or the other too cold.

[0039] This invention further incorporates the temperature drop rate of the hair straightener and the electrothermal characteristics of the PTC heating element when generating the target conduction control value. This allows the controller to promptly increase the heating power of the corresponding hair straightener when the heat load changes due to hair contact with the straightener, and to correct the conduction control value when there are significant changes in the equivalent resistance or power supply of the PTC heating element. Therefore, it improves the temperature recovery and steady-state control capabilities of the electrically heated hair straightener during continuous hair clamping, reduces temperature fluctuations and overshoot risks, and thus improves temperature control stability and styling consistency during continuous use. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of an electrically heated hair straightener (closed state).

[0041] Figure 2 This is a schematic diagram of an electrically heated hair straightener (in the open position).

[0042] Figure 3 This is another angled view of the electrically heated hair straightener (in the open state).

[0043] Figure 4 This is a schematic diagram of the circuit connection of the electric heating hair straightener of the present invention.

[0044] Figure 5 This is a flowchart of the precise temperature control method of the present invention. Detailed Implementation

[0045] The present invention will be further described below with reference to the accompanying drawings and embodiments: This is Example 1, see... Figures 1 to 4 An electric heating hair straightener is provided, which includes a first clamping plate 1, a second clamping plate 2, a first PTC heating element 3, a second PTC heating element 4, a first temperature detection element 5, a second temperature detection element 6, a first thyristor power adjustment circuit 7, a second thyristor power adjustment circuit 8, an electrical parameter acquisition circuit 9, and a controller 10.

[0046] A first clamping plate 1 and a second clamping plate 2 are arranged opposite to each other for clamping hair. A first PTC heating element 3 is disposed on the first clamping plate 1 for electrically heating the first clamping plate 1; a second PTC heating element 4 is disposed on the second clamping plate 2 for electrically heating the second clamping plate 2. In this embodiment, both the first PTC heating element 3 and the second PTC heating element 4 are ceramic PTC heating elements with a Curie temperature range of 230°C to 280°C.

[0047] The first temperature sensor 5 is disposed on or near the first PTC heating element 3, and is used to detect the temperature of the first clamping plate. The second temperature sensor 6 is disposed on or near the second PTC heating element 4, and is used to detect the temperature of the second clamping plate. In this embodiment, both the first temperature sensor 5 and the second temperature sensor 6 are 10K type NTC thermistors.

[0048] The power output terminal of the first thyristor power adjustment circuit 7 is connected to the first PTC heating element 3, and is used to adjust the power supply of the first PTC heating element 3. The power output terminal of the second thyristor power adjustment circuit 8 is connected to the second PTC heating element 4, and is used to adjust the power supply of the second PTC heating element 4. In this embodiment, both the first thyristor power adjustment circuit 7 and the second thyristor power adjustment circuit 8 use the duty cycle as the conduction control quantity, and the value range of the conduction control quantity is 0% to 100%. In other embodiments, the conduction control quantity can also be the thyristor conduction angle or the number of conduction cycles.

[0049] The electrical parameter acquisition circuit 9 includes a first electrical parameter sampling branch 91 and a second electrical parameter sampling branch 92. The first electrical parameter sampling branch 91 includes a first voltage sampling unit 911 and a first current sampling unit 912. The first voltage sampling unit 911 is connected in parallel across the first PTC heating element 3 and is used to collect the voltage parameters across the first PTC heating element 3; the first current sampling unit 912 is connected in series in the power supply circuit of the first PTC heating element 3 and is used to collect the current parameters flowing through the first PTC heating element 3.

[0050] The second electrical parameter sampling branch 92 includes a second voltage sampling unit 921 and a second current sampling unit 922. The second voltage sampling unit 921 is connected in parallel across the two ends of the second PTC heating element 4 and is used to collect the voltage parameters across the two ends of the second PTC heating element 4; the second current sampling unit 922 is connected in series in the power supply circuit of the second PTC heating element 4 and is used to collect the current parameters flowing through the second PTC heating element 4.

[0051] Specifically, both the first voltage sampling unit 911 and the second voltage sampling unit 921 include a voltage divider resistor network and an analog-to-digital converter interface. Both the first current sampling unit 912 and the second current sampling unit 922 include a sampling resistor and a differential amplifier circuit. The controller 10 reads the voltage parameters across the corresponding PTC heating element and the current parameters flowing through the corresponding PTC heating element through the analog-to-digital converter interface, and determines the power supply parameters and equivalent resistance parameters of the corresponding PTC heating element based on the voltage and current parameters.

[0052] In this embodiment, both the first PTC heating element 3 and the second PTC heating element 4 are used as resistive electric heating elements. The first thyristor power adjustment circuit 7 and the second thyristor power adjustment circuit 8 are both automatic electric heating power control circuits, used to automatically adjust the electric heating power of the first PTC heating element 3 and the second PTC heating element 4, respectively. The controller 10 determines the equivalent resistance parameter and power supply parameter of the first PTC heating element 3 based on the voltage and current parameters of the power supply circuit of the first PTC heating element 3; and determines the equivalent resistance parameter and power supply parameter of the second PTC heating element 4 based on the voltage and current parameters of the power supply circuit of the second PTC heating element 4. The controller 10 further automatically adjusts the conduction angle, duty cycle, or number of conduction cycles of the corresponding thyristor power adjustment circuit based on the corresponding clamping plate temperature, the equivalent resistance parameter, and the power supply parameter of the corresponding PTC heating element, thereby changing the electric heating power of the corresponding PTC heating element.

[0053] The controller 10 has a first temperature sampling terminal 101, a second temperature sampling terminal 102, a first power adjustment control terminal 103, a second power adjustment control terminal 104, and at least one electrical parameter sampling terminal 105. The first temperature sampling terminal 101 is connected to the first temperature detection element 5, the second temperature sampling terminal 102 is connected to the second temperature detection element 6, the first power adjustment control terminal 103 is connected to the control terminal of the first thyristor power adjustment circuit 7, the second power adjustment control terminal 104 is connected to the control terminal of the second thyristor power adjustment circuit 8, and the first electrical parameter sampling branch 91 and the second electrical parameter sampling branch 92 are respectively connected to the corresponding electrical parameter sampling terminals 105.

[0054] Therefore, the controller 10 is able to receive the voltage sampling signal and the current sampling signal output from the first electrical parameter sampling branch 91 and the second electrical parameter sampling branch 92, respectively.

[0055] In this embodiment, Figure 4 The solid lines in the diagram represent the main power circuit connection relationship, while the dashed lines represent the control signal and sampling signal connection relationship. This control signal and sampling signal connection relationship does not belong to the main power supply circuit.

[0056] Specifically, the AC power input 11 has an L terminal and an N terminal. A first thyristor power regulation circuit 7, a first current sampling unit 912, and a first PTC heating element 3 are connected in series between the L and N terminals of the AC power input 11 to form a first heating branch; a first voltage sampling unit 911 is connected in parallel across the first PTC heating element 3 to collect voltage parameters across the first PTC heating element 3. A second thyristor power regulation circuit 8, a second current sampling unit 922, and a second PTC heating element 4 are connected in series between the L and N terminals of the AC power input 11 to form a second heating branch; a second voltage sampling unit 921 is connected in parallel across the second PTC heating element 4 to collect voltage parameters across the second PTC heating element 4.

[0057] The first temperature sensor 5 is connected to the first temperature sampling terminal 101 of the controller 10 and is used to output the first clamping plate temperature sampling signal to the controller 10; the second temperature sensor 6 is connected to the second temperature sampling terminal 102 of the controller 10 and is used to output the second clamping plate temperature sampling signal to the controller 10.

[0058] Figure 4 To facilitate the representation of the main power circuit, the first voltage sampling unit 911 and the first current sampling unit 912 are respectively shown at their corresponding sampling positions, and together they constitute the first electrical parameter sampling branch 91; the second voltage sampling unit 921 and the second current sampling unit 922 are respectively shown at their corresponding sampling positions, and together they constitute the second electrical parameter sampling branch 92.

[0059] The sampling signals from the first voltage sampling unit 911 and the first current sampling unit 912 are fed into the first electrical parameter sampling branch 91, which is connected to the electrical parameter sampling terminal 105 of the controller 10. The sampling signals from the second voltage sampling unit 921 and the second current sampling unit 922 are fed into the second electrical parameter sampling branch 92, which is connected to the electrical parameter sampling terminal 105 of the controller 10.

[0060] The first power adjustment control terminal 103 of the controller 10 is connected to the control terminal of the first thyristor power adjustment circuit 7 and is used to output a first power adjustment control signal to the first thyristor power adjustment circuit 7; the second power adjustment control terminal 104 of the controller 10 is connected to the control terminal of the second thyristor power adjustment circuit 8 and is used to output a second power adjustment control signal to the second thyristor power adjustment circuit 8.

[0061] Through the aforementioned connection, the controller 10 can acquire the temperature sampling signals of the first clamping plate 1 and the second clamping plate 2, and can acquire the voltage and current parameters of the power supply circuits corresponding to the first PTC heating element 3 and the second PTC heating element 4, respectively. Simultaneously, the controller 10 can control the conduction control of the first thyristor power adjustment circuit 7 and the second thyristor power adjustment circuit 8, respectively, to adjust the power supply of the first PTC heating element 3 and the second PTC heating element 4, thereby achieving independent power adjustment and coordinated temperature control of the two clamping plates.

[0062] Thus, the first PTC heating element 3, the first temperature detection element 5, the first thyristor power adjustment circuit 7, the first electrical parameter sampling branch 91 and the controller 10 form the first electrothermal closed-loop control branch; the second PTC heating element 4, the second temperature detection element 6, the second thyristor power adjustment circuit 8, the second electrical parameter sampling branch 92 and the controller 10 form the second electrothermal closed-loop control branch.

[0063] The controller 10 includes an electrothermal characteristic modeling module 106, a dual closed-loop temperature control module 107, a temperature difference linkage compensation module 108, and a power adjustment output module 109.

[0064] In this embodiment, the electrothermal operating parameters are the current operating parameters determined by sampling from the electrical parameter acquisition circuit 9, and the electrothermal characteristic correction information is the control correction basis generated based on the changes in the equivalent resistance parameters and / or the changes in the power supply parameters.

[0065] The electrothermal characteristic modeling module 106 is used to establish or update the PTC electrothermal characteristic data table based on the clamping plate temperature, the thyristor conduction control quantity, power supply parameters, and the temperature rise response of the corresponding PTC heating element. The PTC electrothermal characteristic data table includes the correspondence between clamping plate temperature, equivalent resistance parameters, and power supply parameters.

[0066] In this embodiment, the power supply parameters include at least one of the following: effective value of power supply voltage, power supply frequency, and zero-crossing detection signal. The temperature rise response includes at least one of the following: temperature rise per unit time, temperature rise per unit sampling period, and temperature rise change corresponding to a unit conduction control quantity.

[0067] The dual closed-loop temperature control module 107 is used to generate a first basic conduction control quantity and a second basic conduction control quantity based on the temperature of the first clamping plate, the temperature of the second clamping plate, the preset temperature of the clamping plate, and the PTC electrothermal characteristic data table.

[0068] The temperature difference linkage compensation module 108 is used to generate a temperature difference linkage compensation amount based on the temperature difference between the temperature of the first clamping plate and the temperature of the second clamping plate.

[0069] The power adjustment output module 109 is used to generate a first target power adjustment quantity and a second target power adjustment quantity based on the first basic power adjustment quantity, the second basic power adjustment quantity, the temperature difference linkage compensation quantity, the temperature drop rate of the clamping plate, and the electrothermal characteristic correction information of the PTC heating element, and output control signals to the first thyristor power adjustment circuit 7 and the second thyristor power adjustment circuit 8 respectively based on the first target power adjustment quantity and the second target power adjustment quantity.

[0070] The electrothermal characteristic correction information of the PTC heating element includes at least one of the changes in the equivalent resistance parameter and the changes in the power supply parameter of the corresponding PTC heating element.

[0071] The preset temperature of the clamping plate is the target temperature set by the user, and the preset maximum temperature control temperature is the upper limit temperature for temperature rise when establishing the PTC electrothermal characteristic data table.

[0072] Example 2, combined with Figure 5 This embodiment 2 provides a precise temperature control method using the electric heating hair straightener described in embodiment 1, including the following steps.

[0073] S1, after the device is started, the controller 10 obtains the temperature of the first clamping plate and the temperature of the second clamping plate through the first temperature detection element 5 and the second temperature detection element 6, respectively. In this embodiment, the controller 10 obtains the temperature of the first clamping plate and the temperature of the second clamping plate at a sampling frequency of 15 times / second.

[0074] The controller 10 can filter the temperatures of the first and second clamping plates to reduce the impact of NTC thermistor sampling noise, analog-to-digital conversion errors, or transient interference on the temperature control results. The filtering process can be at least one of moving average filtering, median filtering, or amplitude limiting filtering.

[0075] S2, the controller 10 obtains the voltage and current parameters of the power supply circuits corresponding to the first PTC heating element 3 and the second PTC heating element 4 through the electrical parameter acquisition circuit 9, and determines the electrothermal operating parameters of the first PTC heating element 3 and the second PTC heating element 4 based on the voltage and current parameters.

[0076] The electrothermal operating parameters include equivalent resistance parameters and power supply parameters. Specifically, the controller 10 synchronously samples the voltage parameters across the corresponding PTC heating element and the current parameters flowing through the corresponding PTC heating element, and performs effective value calculation, mean processing, or filtering on the sampled voltage and current parameters.

[0077] When the corresponding PTC heating element is in an effective conducting power supply state, the controller 10 determines the power supply parameters based on the voltage parameters across the corresponding PTC heating element and the current parameters flowing through the corresponding PTC heating element, and determines the equivalent resistance parameters based on the correspondence between the voltage parameters across the corresponding PTC heating element and the current parameters flowing through the corresponding PTC heating element.

[0078] In one embodiment, the controller 10 determines the power supply parameter P and the equivalent resistance parameter R based on the effective voltage value U and the effective current value I, where P = U × I and R = U / I; or, in AC chopper power regulation state, the controller 10 determines the power supply parameter based on the average value of the product of instantaneous voltage u(t) and instantaneous current i(t) within one or more AC cycles, and determines the equivalent resistance parameter based on the ratio of the effective voltage value to the effective current value.

[0079] When the first thyristor power regulation circuit 7 and the second thyristor power regulation circuit 8 adopt AC chopper power regulation or zero-crossing power regulation mode, the controller 10 acquires the effective voltage value across the corresponding PTC heating element and the effective current value flowing through the corresponding PTC heating element within one or more AC power cycles, and determines the power supply parameters and equivalent resistance parameters based on the effective voltage value and the effective current value; or, the controller 10 samples the instantaneous voltage parameters and instantaneous current parameters within one or more conduction cycles, and determines the power supply parameters based on the average result of the product of the instantaneous voltage parameters and the instantaneous current parameters within the sampling period.

[0080] When the current parameter collected is less than the preset effective current threshold, or when the corresponding PTC heating element is not in an effective conducting power supply state, the controller 10 determines that the sampling data is invalid and does not use the sampling data to update the equivalent resistance parameter and power supply parameter.

[0081] In this embodiment, the voltage parameter corresponding to the first PTC heating element 3 is collected by the first voltage sampling unit 911, and the current parameter corresponding to the first PTC heating element 3 is collected by the first current sampling unit 912. The voltage parameter corresponding to the second PTC heating element 4 is collected by the second voltage sampling unit 921, and the current parameter corresponding to the second PTC heating element 4 is collected by the second current sampling unit 922.

[0082] S3, the controller 10 establishes a PTC electrothermal characteristic data table corresponding to the first PTC heating element 3 and the second PTC heating element 4 based on the temperature of the first clamping plate, the temperature of the second clamping plate, and the electrothermal working parameters.

[0083] Specifically, during the start-up and heating phase of the electric heating hair straightener, the controller 10 controls the first thyristor power adjustment circuit 7 and the second thyristor power adjustment circuit 8 to supply power to the first PTC heating element 3 and the second PTC heating element 4 according to multiple preset conduction control values, so that the first clamping plate 1 and the second clamping plate 2 are heated from the ambient temperature to the preset maximum temperature control temperature.

[0084] In this embodiment, the preset conduction control values ​​may include 30%, 45%, 60%, 75%, 90%, and 100%. The preset maximum temperature control temperature is 200°C. In other embodiments, the preset conduction control values ​​may also be set according to the PTC heating element power, the heat capacity of the clamping plate, the target temperature level, and safety control requirements.

[0085] During the heating process, the controller 10 records the corresponding clamping plate temperature, equivalent resistance parameter, and power supply parameter every time the temperature of the first clamping plate 1 and the second clamping plate 2 increases by 3°C to 8°C. In this embodiment, the controller 10 records the corresponding data every time the temperature of the first clamping plate 1 and the second clamping plate 2 increases by 5°C.

[0086] For the same temperature sampling point, the controller 10 can continuously collect multiple sets of data, and after removing outliers and averaging the multiple sets of data at the same temperature sampling point, write them into the PTC electrothermal characteristic data table.

[0087] The outlier removal includes removing data with instantaneous temperature jumps greater than or equal to 2°C, and / or removing data with power supply parameters deviating from the average power supply at the same temperature sampling point by more than or equal to 10%.

[0088] By removing outliers and averaging, the impact of temperature sampling jitter, instantaneous power supply voltage fluctuations, instantaneous thermal disturbances caused by hair contacting the hair straightener, and electrical parameter sampling noise on the PTC electrothermal characteristic data sheet can be reduced.

[0089] In this embodiment, the PTC electrothermal characteristic data table includes at least the correspondence between the clamping plate temperature, equivalent resistance parameter, and power supply parameter. Furthermore, the PTC electrothermal characteristic data table may also include at least one of the following: thyristor conduction control quantity, power supply parameters, and temperature rise response.

[0090] The power supply parameters may include at least one of the following: the effective value of the power supply voltage, the power supply frequency, and the zero-crossing detection signal; the temperature rise response may include at least one of the following: the temperature rise per unit time, the temperature rise per unit sampling period, or the temperature rise change corresponding to a unit conduction control quantity.

[0091] For example, in the PTC electrothermal characteristic data table corresponding to the first PTC heating element 3, the equivalent resistance parameters and power supply parameters corresponding to temperature points such as 150℃, 180℃, and 200℃ can be recorded. The second PTC heating element 4 has its corresponding PTC electrothermal characteristic data table established in the same way. Since the two PTC heating elements may have individual differences and assembly differences, the first PTC heating element 3 and the second PTC heating element 4 can each have their own corresponding PTC electrothermal characteristic data tables established.

[0092] S4, the controller 10 establishes a first clamping plate temperature closed loop and a second clamping plate temperature closed loop, with the preset temperature of the clamping plate as the control target. In this embodiment, the preset temperature of the clamping plate is 180°C, which is lower than the lower limit of the Curie temperature range of the first PTC heating element 3 and the second PTC heating element 4.

[0093] The dual closed-loop temperature control module 107 generates a first basic conduction control quantity based on the deviation between the temperature of the first clamping plate and the preset temperature of the clamping plate, and generates a second basic conduction control quantity based on the deviation between the temperature of the second clamping plate and the preset temperature of the clamping plate.

[0094] In this embodiment, the first basic conduction control quantity and the second basic conduction control quantity can be generated according to the classic PID control algorithm in the field of automatic control. Specifically, the controller 10 determines the basic conduction control quantities of the first thyristor power adjustment circuit 7 and the second thyristor power adjustment circuit 8 based on the deviation between the preset temperature of the clamping plate and the actual temperature of the clamping plate, the cumulative deviation, and the deviation change trend.

[0095] The basic conduction control quantity can be at least one of the following: conduction angle, conduction duty cycle, or number of conduction cycles. In this embodiment, the basic conduction control quantity is the conduction duty cycle.

[0096] By establishing separate temperature closed loops for the first and second clamping plates, the controller 10 enables the first clamping plate 1 and the second clamping plate 2 to independently adjust their power according to their respective real-time temperature states, instead of using a single-path temperature detection or a unified heating control method. This improves the specificity and synchronization of the temperature control for the two clamping plates.

[0097] S5, the controller 10 corrects the PID control parameters in the first clamping plate temperature closed loop and the second clamping plate temperature closed loop according to the PTC electrothermal characteristic data table, and generates the first basic conduction control quantity and the second basic conduction control quantity.

[0098] Specifically, when the difference between the current temperature of any clamping plate and the lower limit of the Curie temperature range of the corresponding PTC heating element is less than or equal to 20°C, and the equivalent resistance change rate of the corresponding PTC heating element is greater than the preset resistance change rate threshold, the controller 10 reduces the proportional coefficient and increases the differential coefficient in the corresponding temperature closed loop to suppress the temperature overshoot that may occur during the rapid resistance change phase of the PTC heating element.

[0099] When the current temperature of any clamping plate is lower than the preset temperature of the clamping plate by more than a first temperature threshold, the controller 10 increases the proportional coefficient and decreases the integral coefficient in the corresponding temperature closed loop to improve the heating response speed and reduce the risk of temperature overshoot caused by integral accumulation. The first temperature threshold is 3°C to 8°C; in this embodiment, the first temperature threshold is 5°C.

[0100] In this embodiment, the preset resistance change rate threshold can be determined based on the specifications of the first PTC heating element 3 and the second PTC heating element 4, the heat capacity of the clamping plate, the preset temperature of the clamping plate, and the PTC electrothermal characteristic data table established during the start-up heating phase. Specifically, the controller 10 can determine the equivalent resistance change rate of the corresponding PTC heating element in different temperature ranges based on the changes in the equivalent resistance parameters corresponding to adjacent temperature sampling points in the PTC electrothermal characteristic data table, and use the equivalent resistance change rate that is significantly higher than that in the normal temperature heating range when approaching the lower limit of the Curie temperature range as the preset resistance change rate threshold. As a specific example, the preset resistance change rate threshold can be from 0.03kΩ / ℃ to 0.08kΩ / ℃, preferably 0.05kΩ / ℃; in other embodiments, the preset resistance change rate threshold can also be determined by experimental calibration.

[0101] Furthermore, when the controller 10 corrects the PID control parameters, it can use a proportional correction method or a preset parameter table switching method. When using the proportional correction method, if the difference between the current clamping temperature of any clamping plate and the lower limit of the Curie temperature range of the corresponding PTC heating element is less than or equal to 20°C, and the equivalent resistance change rate of the corresponding PTC heating element is greater than the preset resistance change rate threshold, the controller 10 reduces the proportional coefficient in the corresponding temperature closed loop to 60% to 90% of the current proportional coefficient and increases the derivative coefficient to 110% to 150% of the current derivative coefficient to reduce temperature overshoot when the temperature approaches the rapid resistance change range of the PTC heating element; if the current clamping temperature of any clamping plate is lower than the clamping plate preset temperature by more than the first temperature threshold, the controller 10 increases the proportional coefficient in the corresponding temperature closed loop to 110% to 160% of the current proportional coefficient and reduces the integral coefficient to 40% to 80% of the current integral coefficient to improve the heating response speed and reduce overshoot caused by integral accumulation; if the current clamping temperature of any clamping plate is within the steady-state temperature range of the clamping plate preset temperature, the controller 10 adjusts the proportional coefficient, integral coefficient, and derivative coefficient to the steady-state control parameters to reduce steady-state temperature fluctuations.

[0102] In another embodiment, the controller 10 can also use a preset parameter table switching method to correct the PID control parameters. The preset parameter table includes a low-temperature rapid heating parameter group, a steady-state temperature control parameter group, and a parameter group close to the Curie temperature range. When the current temperature of any clamping plate is lower than the preset clamping plate temperature by more than a first temperature threshold, the controller 10 calls the low-temperature rapid heating parameter group; when the current temperature of any clamping plate is within the steady-state temperature range of the preset clamping plate temperature, the controller 10 calls the steady-state temperature control parameter group; when the difference between the current temperature of any clamping plate and the lower limit of the Curie temperature range of the corresponding PTC heating element is less than or equal to 20°C, and the equivalent resistance change rate of the corresponding PTC heating element is greater than the preset resistance change rate threshold, the controller 10 calls the parameter group close to the Curie temperature range. Therefore, the controller 10 can select matching PID control parameters according to different electrothermal operating stages, improving the response speed during the heating stage, the temperature stability during the steady-state stage, and the overshoot suppression capability when approaching the range of significant changes in PTC electrothermal characteristics.

[0103] When the current temperature of any clamping plate is within the steady-state temperature range of the preset clamping plate temperature, the controller 10 adjusts the proportional coefficient, integral coefficient, and derivative coefficient to the steady-state control parameters to reduce steady-state temperature fluctuations. In this embodiment, the steady-state temperature range is the preset clamping plate temperature ±1℃.

[0104] In one specific embodiment, when the current temperature of any clamping plate is more than 5°C lower than the preset temperature of the clamping plate, the controller 10 adopts a heating control parameter to improve the response speed during the heating phase. When the current temperature of any clamping plate is within ±1°C of the preset temperature of the clamping plate, the controller 10 adopts a steady-state control parameter to reduce temperature fluctuations. When the current temperature of any clamping plate is close to the lower limit of the Curie temperature range of the corresponding PTC heating element, and the equivalent resistance parameter of the corresponding PTC heating element changes significantly, the controller 10 adopts an overshoot suppression control parameter to reduce the risk of temperature overshoot. S6, the controller 10 calculates the temperature difference between the first clamping plate temperature and the second clamping plate temperature, and generates a temperature difference linkage compensation amount based on the temperature difference. In this embodiment, the preset temperature difference threshold is 1℃.

[0105] When the temperature of the first clamping plate is higher than that of the second clamping plate, and the temperature difference between the two exceeds the preset temperature difference threshold, the temperature difference linkage compensation module 108 generates a temperature difference linkage compensation amount to reduce the conduction control amount of the first thyristor power adjustment circuit 7 and increase the conduction control amount of the second thyristor power adjustment circuit 8.

[0106] When the temperature of the second clamping plate is higher than that of the first clamping plate, and the temperature difference between the two exceeds the preset temperature difference threshold, the temperature difference linkage compensation module 108 generates a temperature difference linkage compensation amount to reduce the conduction control amount of the second thyristor power adjustment circuit 8 and increase the conduction control amount of the first thyristor power adjustment circuit 7.

[0107] When the temperature difference between the first clamping plate and the second clamping plate does not exceed the preset temperature difference threshold, the controller 10 may not perform temperature difference linkage compensation, or may set the temperature difference linkage compensation amount to zero.

[0108] Furthermore, the temperature difference linkage compensation amount is determined based on the temperature difference between the first clamping plate and the second clamping plate, as well as a preset temperature difference threshold. Specifically, when the temperature difference between the first clamping plate and the second clamping plate exceeds the preset temperature difference threshold, the controller 10 determines a compensation reference amount based on the portion of the temperature difference exceeding the preset temperature difference threshold, and generates a temperature difference linkage compensation amount based on the compensation reference amount.

[0109] When the temperature of the first clamping plate is higher than that of the second clamping plate, the controller 10 deducts the temperature difference linkage compensation amount from the first basic conduction control amount and adds the temperature difference linkage compensation amount to the second basic conduction control amount, so as to reduce the power supply of the first PTC heating element 3 and increase the power supply of the second PTC heating element 4.

[0110] When the temperature of the second clamping plate is higher than that of the first clamping plate, the controller 10 adds the temperature difference linkage compensation amount to the first basic conduction control amount and deducts the temperature difference linkage compensation amount from the second basic conduction control amount, so as to increase the power supply of the first PTC heating element 3 and reduce the power supply of the second PTC heating element 4.

[0111] In one specific embodiment, the controller 10 can determine the temperature difference linkage compensation amount according to a preset compensation ratio. The preset compensation ratio is used to characterize the correspondence between the portion of the temperature difference exceeding a preset temperature difference threshold and the adjustment range of the conduction control amount. The controller 10 can also limit the temperature difference linkage compensation amount to ensure that the temperature difference linkage compensation amount does not exceed a preset maximum compensation amount, thereby avoiding temperature oscillations between the two clamping plates due to overcompensation.

[0112] Through temperature difference linkage compensation, the heating power of the clamping plate on the side with a higher temperature can be reduced or limited, while the heating power of the clamping plate on the side with a lower temperature can be increased, so that the first clamping plate 1 and the second clamping plate 2 approach the preset temperature of the clamping plate simultaneously, and the temperature difference between the two clamping plates is maintained within the preset temperature difference threshold range.

[0113] S7, the controller 10 generates the first target conduction control quantity and the second target conduction control quantity respectively based on the first basic conduction control quantity, the second basic conduction control quantity, the temperature difference linkage compensation quantity, the temperature drop rate of the clamping plate, and the electrothermal characteristic correction information of the PTC heating element.

[0114] Specifically, the controller 10 uses the first basic conduction control quantity as the reference control quantity for the first target conduction control quantity, and uses the second basic conduction control quantity as the reference control quantity for the second target conduction control quantity.

[0115] Based on this, the controller 10 performs temperature difference linkage compensation on the first target conduction control quantity and the second target conduction control quantity according to the temperature difference between the first clamping plate temperature and the second clamping plate temperature. When the temperature of the first clamping plate is higher than the temperature of the second clamping plate and the temperature difference exceeds a preset temperature difference threshold, the controller 10 decreases the first target conduction control quantity and increases the second target conduction control quantity. When the temperature of the second clamping plate is higher than the temperature of the first clamping plate and the temperature difference exceeds a preset temperature difference threshold, the controller 10 increases the first target conduction control quantity and decreases the second target conduction control quantity.

[0116] Simultaneously, the controller 10 determines the clamping plate temperature decrease rate based on the changes in clamping plate temperature within adjacent sampling periods. Specifically, the controller 10 can determine the clamping plate temperature decrease rate based on the difference between the clamping plate temperature in the current sampling period and the clamping plate temperature in the previous sampling period, as well as the time interval between two adjacent sampling periods; or, the controller 10 can determine the average clamping plate temperature decrease rate based on the clamping plate temperature changes within multiple consecutive sampling periods and the corresponding sampling time length.

[0117] When the temperature drop rate of any hair straightener exceeds the preset temperature drop rate threshold, the controller 10 determines that the hair straightener is subjected to external heat load disturbances such as hair contact, thick hair strands, high hair moisture content, or long clamping time, and increases the target conduction control quantity corresponding to the hair straightener to compensate for the heat carried away by the hair from the hair straightener.

[0118] In one specific embodiment, when the controller 10 detects a continuous decrease in the temperature of the clamping plate within two or more consecutive sampling cycles, and the rate of temperature decrease exceeds a preset temperature drop rate threshold, it generates a heat load compensation amount and adds the heat load compensation amount to the target conduction control amount of the corresponding clamping plate. In this embodiment, the preset temperature drop rate threshold is 0.5℃ / s.

[0119] Furthermore, the controller 10 corrects the target conduction control quantity based on the electrothermal characteristic correction information of the PTC heating element. The electrothermal characteristic correction information of the PTC heating element includes at least one of the changes in the equivalent resistance parameter of the corresponding PTC heating element and the changes in the power supply parameter.

[0120] When controller 10 detects a significant increase in the equivalent resistance parameter of the corresponding PTC heating element with changes in clamping plate temperature, it indicates that the PTC heating element may be approaching a range of rapid resistance changes. When controller 10 detects a significant decrease in the power supply parameter of the corresponding PTC heating element with changes in clamping plate temperature, it indicates that the self-limiting effect of the PTC heating element is enhanced. At this time, controller 10 reduces, limits, or smooths the target conduction control quantity to reduce temperature overshoot and control oscillation.

[0121] In this embodiment, the power output module 109 further limits the first target conduction control quantity and the second target conduction control quantity to ensure that they do not exceed the conduction control quantity range allowed by the corresponding thyristor power control circuit. When the conduction control quantity is the conduction duty cycle, the limiting range is 0% to 100%.

[0122] Through the above processing, the first target conduction control quantity and the second target conduction control quantity simultaneously consider the temperature deviation of a single clamping plate, the temperature difference between the two clamping plates, the temperature drop state of the clamping plate when subjected to heat load disturbance, and the change of the electrothermal characteristics of the PTC heating element itself, thereby improving the temperature control accuracy and temperature synchronization of the dual clamping plates.

[0123] S8, the controller 10 controls the first thyristor power adjustment circuit 7 according to the first target conduction control amount, and controls the second thyristor power adjustment circuit 8 according to the second target conduction control amount, so as to adjust the power supply of the first PTC heating element 3 and the second PTC heating element 4 respectively, so that the first clamping plate 1 and the second clamping plate 2 synchronously approach the preset temperature of the clamping plate, and maintain the temperature difference between the temperature of the first clamping plate and the temperature of the second clamping plate within the preset temperature difference threshold range.

[0124] During temperature control, the controller 10 acquires the temperatures of the first and second clamping plates at a frequency of 10 to 20 times per second. After acquiring 5 to 10 sets of temperature data, it updates at least one of the following: the PTC electrothermal characteristic data table, the PID control parameters, and the temperature difference linkage compensation amount. In this embodiment, the controller 10 acquires the temperatures of the first and second clamping plates at a frequency of 15 times per second, and after acquiring 8 sets of temperature data, it updates at least one of the following: the PTC electrothermal characteristic data table, the PID control parameters, and the temperature difference linkage compensation amount.

[0125] Through the above steps, this embodiment enables the first clamp 1 and the second clamp 2 to perform independent closed-loop temperature control based on their respective temperature states, and can perform linkage compensation based on the temperature difference between the two clamps. When hair comes into contact with either clamp, causing the temperature of that clamp to drop, the controller 10 can increase the target conduction control quantity of the corresponding clamp according to the rate of temperature drop, thereby compensating for heat loss caused by external heat load. When the equivalent resistance parameter and power supply parameter of the PTC heating element change significantly with temperature, the controller 10 can correct the target conduction control quantity through the electrothermal characteristic correction information of the PTC heating element, thereby reducing temperature overshoot and steady-state fluctuations.

[0126] In the above control process, the controller 10's control of the first thyristor power adjustment circuit 7 and the second thyristor power adjustment circuit 8 is an automatic control of the electric heating power of the resistive electric heating element. The controller 10 does not only control the on / off state based on the temperature deviation of the clamping plate, but also combines the voltage parameters, current parameters, equivalent resistance parameters, and power supply parameters in the corresponding PTC heating element power supply circuit to automatically adjust the thyristor conduction angle, conduction duty cycle, or conduction cycle number, thereby realizing closed-loop regulation of the electric heating power of the first PTC heating element 3 and the second PTC heating element 4.

[0127] In other embodiments, the above-described automatic electric heating power control method based on PTC resistance heating element power supply circuit parameter sampling, equivalent resistance parameter determination, power supply parameter determination, thyristor conduction control quantity adjustment, and temperature closed-loop feedback is not limited to electric heating hair straighteners. Any electric heating device that uses a PTC resistance heating element, resistance heating sheet, heating film, heating plate, heating tube, or other resistive electric heating element as a heat source and requires automatic adjustment of electric heating power based on temperature, voltage, current, equivalent resistance, and power supply parameters can employ the electrical parameter acquisition circuit, thyristor power adjustment circuit, controller, and electric heating characteristic correction control method described in this embodiment. For example, the electric heating device can be an electric heating comb, curling iron, hair straightener, electric heating care appliance, electric heating clamp, constant temperature heating plate, local heating device, or other equipment requiring closed-loop control of electric heating power. At this time, the first clamping plate and the second clamping plate can be replaced by the first heating part and the second heating part, and the first PTC heating element and the second PTC heating element can be replaced by the first resistive electric heating element and the second resistive electric heating element. The controller can still determine the equivalent resistance parameters and power supply parameters according to the temperature signal of the corresponding heating part, the voltage parameters and current parameters of the power supply circuit of the corresponding electric heating element, and realize automatic control of the electric heating power of the corresponding electric heating equipment by adjusting the thyristor conduction angle, conduction duty cycle or conduction cycle.

[0128] Therefore, the control method described in this embodiment is essentially a power supply detection, automatic power adjustment and temperature closed-loop control scheme for resistive electric heating elements, and can be used as a general power control structure for electric heating devices.

[0129] Working principle In this embodiment, the first clamping plate 1 and the second clamping plate 2 are electrically heated by independent PTC heating elements, and their temperatures are collected by independent temperature detection elements. The first thyristor power adjustment circuit 7 and the second thyristor power adjustment circuit 8 adjust the power supply of the corresponding PTC heating elements, thereby forming two independent electrothermal closed-loop control branches.

[0130] Compared with the ordinary single closed-loop temperature control method, this embodiment not only performs closed-loop temperature control based on the deviation between the temperature of each clamping plate and the preset temperature of the clamping plate, but also further collects the voltage and current parameters of the power supply circuit of the corresponding PTC heating element, determines the equivalent resistance parameters and power supply parameters, and establishes a PTC electrothermal characteristic data table accordingly.

[0131] Because the PTC heating element has a self-limiting temperature characteristic that the resistance increases and the power supply changes when the temperature rises, the controller 10 can determine the current electrothermal state of the PTC heating element based on the PTC electrothermal characteristic data table, and correct the PID control parameters and the target conduction control quantity.

[0132] Simultaneously, the controller 10 compares the temperatures of the first clamping plate and the second clamping plate in real time. When a temperature difference occurs between the two clamping plates, the temperature difference linkage compensation module 108 reduces the target conduction control quantity on the side with the higher temperature and increases the target conduction control quantity on the side with the lower temperature, thereby causing the temperatures of the two clamping plates to synchronously approach the preset temperature of the clamping plates.

[0133] When hair comes into contact with any hair straightener, causing the temperature of that straightener to drop rapidly, the controller 10 generates heat load compensation control based on the rate of temperature drop of that straightener, thereby increasing the target conduction control quantity of the corresponding straightener, thereby increasing the power supply of the corresponding PTC heating element, and causing the straightener to heat up quickly.

[0134] Through the above method, this embodiment can achieve independent closed-loop temperature control, temperature difference linkage compensation, heat load compensation and PTC electrothermal characteristic correction of the first clamping plate 1 and the second clamping plate 2, so that the temperature difference between the two clamping plates is kept within the preset temperature difference threshold range, and temperature overshoot and temperature fluctuation are reduced.

[0135] Example 1: Double-ply plate temperature difference compensation At a certain temperature control moment, the preset temperature of the clamping plates is 180℃, the temperature of the first clamping plate is 182.0℃, the temperature of the second clamping plate is 180.5℃, and the preset temperature difference threshold is 1℃. At this time, the temperature of the first clamping plate is higher than that of the second clamping plate, and the temperature difference between the two clamping plates exceeds the preset temperature difference threshold.

[0136] The controller 10 determines that the first clamping plate 1 is the side with a higher temperature and the second clamping plate 2 is the side with a lower temperature. The power output module 109 reduces the target conduction control quantity of the first thyristor power control circuit 7 and increases the target conduction control quantity of the second thyristor power control circuit 8. As a result, the heating power of the first clamping plate 1, which has a higher temperature, is reduced, and the heating power of the second clamping plate 2, which has a lower temperature, is increased, thereby reducing the temperature difference between the two clamping plates.

[0137] Example 2: Heat load disturbance compensation At another temperature-controlled moment, after the hair comes into contact with the first clamp 1, the temperature of the first clamp drops from near the preset temperature to 177.8℃, while the temperature of the second clamp is 180.2℃. At this time, the rate of temperature drop of the first clamp 1 exceeds the preset temperature drop rate threshold, and the temperature of the second clamp is higher than that of the first clamp.

[0138] The controller 10 determines the thermal load disturbance caused by hair contact with the first clamp plate 1 and increases the target conduction control value of the first thyristor power control circuit 7, causing the first PTC heating element 3 to increase its power supply to compensate for the heat carried away by the hair from the first clamp plate 1. Simultaneously, the controller 10 decreases or limits the target conduction control value of the second thyristor power control circuit 8 to prevent the temperature of the second clamp plate 2 from continuing to be too high. Thus, the temperature of the first clamp plate 1 and the second clamp plate 2 is synchronously restored.

[0139] Test Result Example Under the conditions of ambient temperature of 25℃, power supply voltage of 220V, preset temperature of clamping plate of 180℃, temperature sampling frequency of 15 times / second, and preset temperature difference threshold of 1℃, after the electric heating clamping plate hair straightener is started and enters steady-state temperature control, the first clamping plate 1 and the second clamping plate 2 maintain stable temperature control for 3 minutes.

[0140] Test results show that the temperature difference between the first clamping plate 1 and the second clamping plate 2 is maintained between 0.3℃ and 0.9℃, and the temperature fluctuation of a single clamping plate is maintained within ±0.5℃.

[0141] When simulated hair comes into contact with the first clamp plate 1, causing the temperature of the first clamp plate to drop briefly, the controller 10 increases the target conduction control quantity of the first thyristor power adjustment circuit 7 according to the rate of temperature drop, so that the temperature of the first clamp plate rises back to near the preset temperature of the clamp plate in a short time, and at the same time, the temperature difference between the first clamp plate 1 and the second clamp plate 2 returns to the preset temperature difference threshold range.

[0142] Application scenarios, usage methods and technical effects The electric heating straightener of this embodiment is suitable for everyday hair straightening, smoothing, inward curling of hair ends, outward curling of hair ends, partial bangs styling, and continuous styling of multiple strands of hair. It is especially suitable for use scenarios that require high stability of plate temperature, consistency of temperature between the two plates, and continuity of styling.

[0143] When using the electric heating hair straightener, first connect it to the power supply, and then select the target temperature setting using the buttons, knobs, or touch panel. The target temperature setting can be selected according to hair type; for example, fine hair can be set to 150℃ to 160℃, normal hair to 170℃ to 180℃, and coarse hair to 190℃ to 200℃.

[0144] The controller 10 determines the preset temperature of the clamping plate according to the target temperature setting selected by the user, and controls the first thyristor power adjustment circuit 7 and the second thyristor power adjustment circuit 8 respectively to raise the temperature of the first PTC heating element 3 and the second PTC heating element 4. When the temperatures of the first clamping plate and the second clamping plate both reach near the preset temperature of the clamping plate, the electric heating clamping plate hair straightener can prompt the user to start using it through indicator lights, buzzers, or displays.

[0145] In actual use, when the user places a strand of hair between the first and second plates and moves it along the length of the hair strand, the controller can adjust the power supply of the first and second PTC heating elements in real time based on the temperatures of the first and second plates, the temperature difference between the two plates, and the rate of temperature drop of the plates. Therefore, even if the thickness, moisture content, clamping force, or moving speed of the hair strand changes, the first and second plates can quickly return to near their preset temperatures and maintain the temperature difference between the two plates within the preset temperature difference threshold range. This ensures stable heat output from the plates, even heating on both sides, and smooth hair straightening when multiple strands of hair are continuously clamped, while minimizing the risk of localized overheating or underheating. This improves the precise temperature control and styling consistency of the electric heating hair straightener.

[0146] When a user clamps their hair and moves the heated hair straightener along the length of the hair, the hair carries away some of the heat from the first and second plates 1, causing the plate temperature to drop. Due to differences in hair strand thickness, hair moisture content, clamping force, and moving speed, the degree of temperature drop of the first and second plates 1 may vary.

[0147] In this embodiment, the controller 10 collects the temperatures of the first and second clamping plates in real time through the first temperature detection element 5 and the second temperature detection element 6, and obtains the electrothermal operating parameters of the corresponding PTC heating element through the electrical parameter acquisition circuit 9. When a clamping plate temperature drops rapidly, the controller 10 increases the target conduction control quantity of the corresponding thyristor power regulation circuit according to the temperature drop rate of the clamping plate, thereby increasing the power supply of the corresponding PTC heating element and enabling the clamping plate to quickly recover its temperature.

[0148] Simultaneously, the controller 10 calculates the temperature difference between the first clamping plate and the second clamping plate in real time. When the temperature difference exceeds the preset temperature difference threshold, the controller 10 generates a temperature difference linkage compensation amount, which increases the conduction control amount of the thyristor power adjustment circuit corresponding to the clamping plate with the lower temperature, and decreases or maintains the conduction control amount of the thyristor power adjustment circuit corresponding to the clamping plate with the higher temperature, so that the first clamping plate 1 and the second clamping plate 2 synchronously approach the preset clamping plate temperature, and the temperature difference between the two clamping plates is maintained within the preset temperature difference threshold range.

[0149] Furthermore, the controller 10 also modifies the PID control parameters according to the PTC electrothermal characteristic data table, so that the control process adapts to the self-limiting temperature characteristics of the PTC heating element when the temperature rises, the resistance increases and the power supply changes, thereby reducing temperature overshoot, response lag and steady-state fluctuations.

[0150] Through the above control method, this embodiment can achieve precise temperature control of the electrically heated hair straightener. Specifically, the precise temperature control includes at least the following: First, ensuring that the temperatures of the first and second straighteners are stably close to the user-set preset temperatures; Second, maintaining the temperature difference between the first straightener 1 and the second straightener 2 within a preset temperature difference threshold range; Third, when hair contacts the straightener causing a sudden change in heat load, rapidly increasing the heating power of the corresponding straightener according to the rate of temperature drop; Fourth, when the PTC heating element approaches its Curie temperature range or its resistance changes significantly, suppressing temperature overshoot by correcting the PID control parameters and the target conduction control quantity.

[0151] The precise temperature control in this embodiment has the following beneficial effects: On the one hand, the two plates can apply more uniform heat to both sides of the hair, reducing the risk of localized overheating, dryness, frizz, or burns caused by one plate being too hot; on the other hand, it can reduce the problem of insufficient styling and the need for repeated clamping and pulling caused by one plate being too cold, thereby improving styling efficiency and styling uniformity. For scenarios where multiple strands of hair are clamped continuously, this embodiment can maintain a stable plate temperature during changes in heat load, reducing the impact of fluctuating temperatures on the styling effect.

[0152] In this invention, the terms "first" and "second" are used only to distinguish different technical features and do not indicate any limitation on order, quantity, or importance. The terms "an" and "a type" are used in this invention and do not indicate a quantity limitation, but rather indicate that at least one of the described objects exists. The terms "top," "bottom," "side," "longitudinal," "transverse," "middle," "center," "outer," "inner," "horizontal," "vertical," "left," "right," "above," and "below" are used in this invention to describe relative positional relationships and do not indicate absolute positional limitations.

[0153] The above embodiments are merely preferred embodiments of the present invention, used to illustrate the technical concept of the present invention, and should not be construed as limiting the scope of protection of the present invention. For those skilled in the art, various modifications and improvements can be made without departing from the technical concept of the present invention, and all such modifications and improvements should fall within the scope of protection of the present invention.

Claims

1. An electrically heated hair straightener, comprising a first clamping plate, a second clamping plate, a first PTC heating element, a second PTC heating element, a first temperature detection element, a second temperature detection element, a first thyristor power adjustment circuit, a second thyristor power adjustment circuit, an electrical parameter acquisition circuit, and a controller, characterized in that: The first PTC heating element is disposed on the first clamping plate, the first temperature detection element is disposed on the first clamping plate or near the first PTC heating element, and the power output terminal of the first thyristor power regulation circuit is connected to the first PTC heating element. The second PTC heating element is disposed on the second clamping plate, the second temperature detection element is disposed on the second clamping plate or near the second PTC heating element, and the power output terminal of the second thyristor power regulation circuit is connected to the second PTC heating element; The electrical parameter acquisition circuit includes a first electrical parameter sampling branch and a second electrical parameter sampling branch. The first electrical parameter sampling branch is connected to the power supply circuit of the first PTC heating element and is used to acquire the voltage and current parameters of the power supply circuit corresponding to the first PTC heating element. The second electrical parameter sampling branch is connected to the power supply circuit of the second PTC heating element and is used to acquire the voltage and current parameters of the power supply circuit corresponding to the second PTC heating element. The controller has a first temperature sampling terminal, a second temperature sampling terminal, a first power adjustment control terminal, a second power adjustment control terminal, and at least one electrical parameter sampling terminal; Wherein, the first temperature sampling terminal is connected to the first temperature detection device, the second temperature sampling terminal is connected to the second temperature detection device, the first power adjustment control terminal is connected to the control terminal of the first thyristor power adjustment circuit, the second power adjustment control terminal is connected to the control terminal of the second thyristor power adjustment circuit, and the first electrical parameter sampling branch and the second electrical parameter sampling branch are respectively connected to the corresponding electrical parameter sampling terminal. The first PTC heating element, the first temperature detection element, the first thyristor power adjustment circuit, the first electrical parameter sampling branch, and the controller form a first electrothermal closed-loop control branch, and the second PTC heating element, the second temperature detection element, the second thyristor power adjustment circuit, the second electrical parameter sampling branch, and the controller form a second electrothermal closed-loop control branch.

2. The electric heating hair straightener according to claim 1, characterized in that: The first electrical parameter sampling branch includes a first voltage sampling unit and a first current sampling unit. The first voltage sampling unit is connected in parallel across the two ends of the first PTC heating element, and the first current sampling unit is connected in series in the power supply circuit of the first PTC heating element. The second electrical parameter sampling branch includes a second voltage sampling unit and a second current sampling unit. The second voltage sampling unit is connected in parallel across the two ends of the second PTC heating element, and the second current sampling unit is connected in series in the power supply circuit of the second PTC heating element.

3. The electric heating hair straightener according to claim 1, characterized in that: Both the first and second temperature sensing elements are NTC thermistors; The conduction control quantities output by the first and second thyristor power control circuits include at least one of the following: thyristor conduction angle, conduction duty cycle, or conduction cycle number.

4. The electric heating hair straightener according to claim 1, characterized in that, The controller includes an electrothermal characteristic modeling module, a dual closed-loop temperature control module, a temperature difference linkage compensation module, and a power adjustment output module. The electrothermal characteristic modeling module is used to establish or update the PTC electrothermal characteristic data table based on the clamping plate temperature, the thyristor conduction control quantity, the power supply parameters and the temperature rise response of the corresponding PTC heating element. The PTC electrothermal characteristic data table includes the correspondence between clamping plate temperature, equivalent resistance parameters and power supply parameters. The dual closed-loop temperature control module is used to generate a first basic conduction control quantity and a second basic conduction control quantity based on the first clamping plate temperature, the second clamping plate temperature, the clamping plate preset temperature and the PTC electrothermal characteristic data table, respectively. The temperature difference linkage compensation module is used to generate a temperature difference linkage compensation amount based on the temperature difference between the temperature of the first clamping plate and the temperature of the second clamping plate. The power adjustment output module is used to generate a first target power adjustment quantity and a second target power adjustment quantity based on the first basic power-on control quantity, the second basic power-on control quantity, the temperature difference linkage compensation quantity, the temperature drop rate of the clamping plate, and the electrothermal characteristic correction information of the PTC heating element, and output control signals to the first thyristor power adjustment circuit and the second thyristor power adjustment circuit respectively based on the first target power adjustment quantity and the second target power adjustment quantity. The electrothermal characteristic correction information of the PTC heating element includes at least one of the changes in the equivalent resistance parameter and the changes in the power supply parameter of the corresponding PTC heating element. The power supply parameters include at least one of the effective value of the power supply voltage, the power supply frequency and the zero-crossing detection signal, and the temperature rise response includes at least one of the temperature rise per unit time, the temperature rise per unit sampling period and the temperature rise change corresponding to the unit conduction control quantity. The rate of temperature decrease of the clamping plate is determined based on the change in clamping plate temperature within adjacent sampling periods and the sampling interval. The electrothermal characteristic correction information is used to reduce, limit, or smooth the target conduction control quantity when the equivalent resistance parameter increases or the power supply parameter decreases.

5. The electric heating hair straightener according to claim 1, characterized in that: Both the first and second PTC heating elements are resistance-type electric heating elements. The first and second thyristor power adjustment circuits adjust the electric heating power of the corresponding resistance-type electric heating elements under the control of the controller. The controller determines the equivalent resistance parameter and power supply parameter of the corresponding PTC heating element based on the voltage and current parameters of the power supply circuit of the corresponding PTC heating element. Based on the corresponding clamping plate temperature, the equivalent resistance parameter, and the power supply parameter, the controller automatically adjusts the conduction angle, conduction duty cycle, or conduction cycle of the corresponding thyristor power adjustment circuit to change the electric heating power of the corresponding PTC heating element.

6. A method for precise temperature control using an electric heating hair straightener as described in any one of claims 1 to 5, characterized in that, include: S1, the controller obtains the temperature of the first clamping plate and the temperature of the second clamping plate respectively; S2, the controller obtains the voltage and current parameters of the power supply circuits corresponding to the first PTC heating element and the second PTC heating element through the electrical parameter acquisition circuit, and determines the electrothermal operating parameters of the first PTC heating element and the second PTC heating element according to the voltage and current parameters. The electrothermal operating parameters include the equivalent resistance parameter and the power supply parameter. S3, the controller establishes a PTC electrothermal characteristic data table corresponding to the first PTC heating element and the second PTC heating element based on the temperature of the first clamping plate, the temperature of the second clamping plate, and the electrothermal working parameters; S4, the controller uses the preset temperature of the clamping plate as the control target and establishes the first clamping plate temperature closed loop and the second clamping plate temperature closed loop respectively. S5, the controller corrects the PID control parameters in the first clamping plate temperature closed loop and the second clamping plate temperature closed loop according to the PTC electrothermal characteristic data table, and generates the first basic conduction control quantity and the second basic conduction control quantity. S6, the controller calculates the temperature difference between the temperature of the first clamping plate and the temperature of the second clamping plate, and generates a temperature difference linkage compensation amount based on the temperature difference. S7, the controller generates the first target conduction control quantity and the second target conduction control quantity respectively based on the first basic conduction control quantity, the second basic conduction control quantity, the temperature difference linkage compensation quantity, the temperature drop rate of the clamping plate and the electrothermal characteristic correction information of the PTC heating element. S8, the controller controls the first thyristor power adjustment circuit according to the first target conduction control amount, and controls the second thyristor power adjustment circuit according to the second target conduction control amount, so as to adjust the power supply of the first PTC heating element and the second PTC heating element respectively, so that the first clamping plate and the second clamping plate synchronously approach the preset temperature of the clamping plate, and maintain the temperature difference between the temperature of the first clamping plate and the temperature of the second clamping plate within the preset temperature difference threshold range.

7. The precise temperature control method according to claim 6, characterized in that, Step S3 includes: during the start-up and heating stage of the electric heating hair straightener, the controller controls the first thyristor power adjustment circuit and the second thyristor power adjustment circuit to supply power to the first PTC heating element and the second PTC heating element according to multiple preset conduction control quantities, so that the first and second clamps are heated from the ambient temperature to the preset maximum temperature control temperature. Record the corresponding clamping plate temperature, equivalent resistance parameter, and power supply parameter every time the temperature of the first clamping plate and the second clamping plate increases by 3°C to 8°C. After outlier removal and mean averaging of multiple sets of data at the same temperature sampling point, the data are written into the PTC electrothermal characteristic data table.

8. The precise temperature control method according to claim 7, characterized in that, The outlier removal includes: Data with instantaneous temperature jumps greater than or equal to 2°C were excluded; and / or, Data whose power supply parameters deviate from the average power supply at the same temperature sampling point by more than or equal to 10% are excluded.

9. The precise temperature control method according to claim 6, characterized in that, Step S5, correcting the PID control parameters includes: When the difference between the current temperature of any clamping plate and the lower limit of the Curie temperature range of the corresponding PTC heating element is less than or equal to 20℃, and the equivalent resistance change rate of the corresponding PTC heating element is greater than the preset resistance change rate threshold, the proportional coefficient is reduced and the differential coefficient is increased. When the current temperature of any clamping plate is lower than the preset temperature of the clamping plate by more than the first temperature threshold, the proportional coefficient is increased and the integral coefficient is decreased. When the current temperature of any clamping plate is within the steady-state temperature range of the preset temperature of the clamping plate, the proportional coefficient, integral coefficient and derivative coefficient are adjusted to the steady-state control parameters. The steady-state temperature range is ±1℃ of the preset temperature of the clamping plate, the first temperature threshold is 3℃ to 8℃, and the preset resistance change rate threshold is 0.03kΩ / ℃ to 0.08kΩ / ℃.

10. The precise temperature control method according to claim 6, characterized in that: The preset temperature difference threshold is 0.5℃ to 2℃; During the temperature control process, the controller acquires the temperature of the first clamping plate and the temperature of the second clamping plate at a frequency of 10 times / second to 20 times / second, and updates at least one of the PTC electrothermal characteristic data table, PID control parameters and temperature difference linkage compensation amount after acquiring 5 to 10 sets of temperature data. The preset temperature of the clamping plate is 150°C to 200°C, and the preset temperature of the clamping plate is lower than the lower limit of the Curie temperature range of the first PTC heating element and the second PTC heating element.

Images