A hair dryer thermostat control method and system

Abstract

This invention discloses a method and system for constant temperature control of a hair dryer. By controlling the on / off state of the heating wire inside the hair dryer, the invention controls the heating power of the heating wire. Through hybrid switching control, the temperature of the heating wire (feedback temperature) is rapidly brought close to the target temperature (preset temperature). Constant temperature control is achieved through PI control. This invention maintains a constant air outlet temperature during hair dryer operation, protecting hair and improving the user experience.

Description

Technical Field

[0001] This invention relates to the field of hair dryer control technology, and in particular to a method and system for constant temperature control of a hair dryer. Background Technology

[0002] Most existing hair dryers use mechanical temperature control. During use, the air outlet temperature of the hair dryer is affected by ambient temperature, motor speed, and fluctuations in mains power, resulting in an unstable air outlet temperature. Excessive temperature can damage hair, while insufficient temperature leads to longer drying times and a poor user experience. Summary of the Invention

[0003] The purpose of this invention is to propose a method and system for constant temperature control of a hair dryer, so as to maintain a constant temperature at the air outlet during the operation of the hair dryer, protect the hair, and improve the user experience.

[0004] To achieve the above objectives, the present invention provides the following solution:

[0005] This invention provides a method for constant temperature control of a hair dryer, the method comprising the following steps:

[0006] Obtain the feedback temperature; the feedback temperature is the detected temperature of the heating wire inside the hair dryer.

[0007] Determine whether the absolute value of the difference between the feedback temperature and the set temperature is greater than a preset threshold to obtain the first judgment result;

[0008] If the first judgment result indicates yes, then a first control signal is generated based on the difference between the feedback temperature and the set temperature using a hybrid switch control method.

[0009] Based on the first control signal, the power on / off state of the heating wire in the blower is controlled, and after a preset time period, the process returns to the "obtain feedback temperature" step.

[0010] If the first judgment result indicates no, then based on the difference between the feedback temperature and the set temperature, a second control signal is generated using PI control, and the power on / off state of the heating wire in the blower is controlled based on the second control signal.

[0011] Optionally, a hybrid switching control method is used to generate the first control signal, specifically including:

[0012] Determine if the difference between the feedback temperature and the set temperature is greater than 0 to obtain a second judgment result;

[0013] If the second judgment result indicates no, then a first control signal is generated based on one or more control arrays in the preset control table where the number of Byte1 is greater than the current number of Byte1; the preset control table stores multiple control arrays, each control array includes 50 bytes, 1 bit of control duration represents 1 AC cycle, Byte1 indicates that the heating wire in the hair dryer is powered on, Byte0 indicates that the heating wire in the hair dryer is powered off, and the current number of Byte1 is the number of Byte1 in the control array that generates the current first control signal;

[0014] If the second judgment result indicates yes, then a first control signal is generated based on one or more control arrays in the preset control table where the number of Byte1 is less than the current number of Byte1.

[0015] Optionally, obtaining feedback temperature, previously also included:

[0016] Determine whether AC power is supplied to the AC input terminal of the hair dryer to obtain the third determination result;

[0017] If the third judgment result indicates yes, then the step of "obtaining feedback temperature" is executed;

[0018] If the third judgment result is negative, then the step of "judging whether AC power is supplied to the AC input terminal of the hair dryer and obtaining the third judgment result" is executed.

[0019] Optionally, the on / off state of the heating wire inside the hair dryer is controlled based on the first control signal, specifically including:

[0020] Using the zero-crossing point of the AC power input to the AC input terminal of the hair dryer as the control interrupt signal, the on / off state of the heating wire inside the hair dryer is controlled according to the on / off state represented by the first control signal.

[0021] Optionally, the on / off state of the heating wire inside the hair dryer is controlled based on the second control signal, specifically including:

[0022] Using the zero-crossing point of the AC power input to the AC input terminal of the hair dryer as the control interrupt signal, the on / off state of the heating wire inside the hair dryer is controlled according to the on / off state represented by the second control signal.

[0023] A constant temperature control system for a hair dryer, the control system comprising:

[0024] Heating wire temperature detection circuit, heating wire control circuit, and heating wire controller;

[0025] The heating wire temperature detection circuit is connected to the heating wire inside the hair dryer and the heating wire controller, respectively; the heating wire temperature detection circuit is used to detect the temperature of the heating wire inside the hair dryer as the feedback temperature.

[0026] The heating wire controller is connected to the heating wire control circuit, and the heating wire control circuit is connected to the heating wire inside the hair dryer. The heating wire controller is used to generate a control signal using the above-mentioned control method, and controls the switching state of the heating wire control circuit based on the control signal, thereby controlling the on / off state of the heating wire inside the hair dryer. The control signal is a first control signal or a second control signal.

[0027] Optionally, the heating wire temperature detection circuit specifically includes: heating wire terminals, pull-up resistor R15, current-limiting resistor R24, and filter capacitor C11;

[0028] The first port of the heating wire terminal is connected to one end of the pull-up resistor R15 and one end of the current limiting resistor R24 ​​respectively. The other end of the pull-up resistor R15 is connected to the system power supply. The other end of the current limiting resistor R24 ​​is connected to one end of the filter capacitor C11. The common terminal of the connection between the other end of the current limiting resistor R24 ​​and one end of the filter capacitor C11 is connected to the heating wire controller.

[0029] The other end of the filter capacitor C11 and the second port of the heating wire terminal are both grounded;

[0030] The heating wire terminal is used to connect to the heating wire inside the hair dryer.

[0031] Optionally, the heating wire control circuit includes: a current-limiting resistor R21, a silicon controlled rectifier optocoupler, a voltage divider resistor R22, a voltage divider resistor R23, and a bidirectional silicon controlled rectifier;

[0032] One end of the current-limiting resistor R21 is connected to the heating wire controller;

[0033] The other end of the current-limiting resistor R21 is connected to the cathode of the light-emitting diode inside the thyristor optocoupler, and the anode of the light-emitting diode inside the thyristor optocoupler is connected to the system power supply.

[0034] One end of the bidirectional diode inside the thyristor optocoupler is connected to the second end of the bidirectional thyristor, the other end of the bidirectional diode inside the thyristor optocoupler is connected to one end of the voltage divider resistor R22, the other end of the voltage divider resistor R22 is connected to the third end of the bidirectional thyristor and one end of the voltage divider resistor R23 respectively, and the other end of the resistor R23 is connected to the first end of the bidirectional thyristor.

[0035] The second end of the bidirectional thyristor is also connected to one end of the heating wire inside the blower, and the other end of the heating wire inside the blower is connected to the AC live wire input terminal; the first end of the bidirectional thyristor is connected to the AC neutral wire input terminal.

[0036] Optionally, the control system further includes: a zero-crossing detection circuit;

[0037] The zero-crossing detection circuit is connected to the AC input terminal and the heating wire controller respectively. The zero-crossing detection circuit is used to detect whether AC power is applied to the AC input terminal and the zero-crossing point of the AC power input to the AC input terminal.

[0038] Optionally, the zero-crossing detection circuit includes: a pull-up resistor R6, a current-limiting resistor R7, a filter capacitor C5, a voltage divider resistor R47, a voltage divider resistor R5, and an AC input optocoupler;

[0039] One end of the voltage divider resistor R47 is connected to the AC neutral input terminal, and one end of the voltage divider resistor R5 is connected to the AC live input terminal.

[0040] The other ends of the voltage divider resistor R47 and the other ends of the voltage divider resistor R5 are respectively connected to the two ends of the bidirectional light-emitting diode in the AC input optocoupler. The collector of the transistor in the AC input optocoupler is connected to one end of the pull-up resistor R6 and one end of the current limiting resistor R7. The emitter of the transistor in the AC input optocoupler is grounded.

[0041] The other end of the pull-up resistor R6 is connected to the system power supply, the other end of the current-limiting resistor R7 is connected to the heating wire controller, and the other end of the current-limiting resistor R7 is also connected to one end of the filter capacitor C5; the other end of the filter capacitor C5 is grounded.

[0042] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0043] This invention provides a method and system for constant temperature control of a hair dryer. The control method includes the following steps: acquiring a feedback temperature; the feedback temperature is the detected temperature of the heating wire inside the hair dryer; determining whether the absolute value of the difference between the feedback temperature and the set temperature is greater than a preset threshold to obtain a first judgment result; if the first judgment result indicates yes, then generating a first control signal using a hybrid switch control method based on the difference between the feedback temperature and the set temperature; if the first judgment result indicates no, then generating a second control signal using a PI control method based on the difference between the feedback temperature and the set temperature, and controlling the on / off state of the heating wire inside the hair dryer based on the second control signal. This invention controls the heating power of the heating wire inside the hair dryer by controlling the on / off state of the heating wire, rapidly bringing the heating wire temperature (feedback temperature) close to the target temperature (preset temperature) through hybrid switch control, and achieving constant temperature control through PI control. This invention maintains a constant outlet temperature during hair dryer operation, protecting hair and improving user experience. Attached Figure Description

[0044] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0045] Figure 1 A flowchart of a constant temperature control method for a hair dryer provided in an embodiment of the present invention;

[0046] Figure 2 The circuit schematic diagram of the zero-crossing detection circuit provided in the embodiment of the present invention;

[0047] Figure 3 A circuit diagram of the heating wire temperature detection circuit provided in an embodiment of the present invention;

[0048] Figure 4 This is the original circuit diagram of the heating wire control circuit provided in an embodiment of the present invention;

[0049] Figure 5 The control principle diagram of the constant temperature control module provided in the embodiment of the present invention is shown. Detailed Implementation

[0050] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0051] The purpose of this invention is to provide a method and system for constant temperature control of a hair dryer, so as to maintain a constant temperature at the air outlet during the operation of the hair dryer, protect the hair, and improve the user experience.

[0052] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0053] This invention provides a method for constant temperature control of a hair dryer, such as... Figure 1 As shown, the control method includes the following steps:

[0054] Obtain the feedback temperature; the feedback temperature is the temperature of the heating wire inside the hair dryer that has been detected.

[0055] Determine whether the absolute value of the difference between the feedback temperature and the set temperature is greater than a preset threshold to obtain the first judgment result.

[0056] If the first judgment result indicates yes, then a first control signal is generated based on the difference between the feedback temperature and the set temperature using a hybrid switch control method.

[0057] Based on the first control signal, the power on / off state of the heating wire inside the blower is controlled, and after a preset time period, the process returns to the "obtain feedback temperature" step.

[0058] If the first judgment result indicates no, then based on the difference between the feedback temperature and the set temperature, a second control signal is generated using PI control, and the power on / off state of the heating wire in the blower is controlled based on the second control signal.

[0059] For example, the present invention employs a hybrid switching control method to avoid temperature fluctuations caused by prolonged on / off switching during power regulation. The generation of the first control signal using the hybrid switching control method in this embodiment specifically includes:

[0060] Determine whether the difference between the feedback temperature and the set temperature is greater than 0 to obtain a second judgment result.

[0061] If the second judgment result indicates no, then a first control signal is generated based on one or more control arrays in the preset control table where the number of Byte1 is greater than the current number of Byte1. The preset control table stores multiple control arrays, each of which includes 50 bytes. One bit of control duration represents one AC cycle. Byte1 indicates that the heating wire in the blower is powered on, and Byte0 indicates that the heating wire in the blower is powered off. The current number of Byte1 is the number of Byte1 in the control array that generates the current first control signal.

[0062] If the second judgment result indicates yes, then a first control signal is generated based on one or more control arrays in the preset control table where the number of Byte1 is less than the current number of Byte1.

[0063] In a preferred embodiment, obtaining the feedback temperature further includes: determining whether AC power is supplied to the AC input terminal of the hair dryer and obtaining a third determination result; if the third determination result indicates yes, then the step of "obtaining the feedback temperature" is executed; if the third determination result indicates no, then the step of "determining whether AC power is supplied to the AC input terminal of the hair dryer and obtaining a third determination result" is executed.

[0064] In this embodiment of the invention, controlling the on / off state of the heating wire inside the hair dryer based on the first control signal specifically includes: using the zero-crossing point of the AC power input at the AC input terminal of the hair dryer as the control interrupt signal, and controlling the on / off state of the heating wire inside the hair dryer according to the on / off state represented by the first control signal.

[0065] The power-on / off state of the heating wire inside the hair dryer is controlled based on the second control signal. Specifically, the power-on / off state of the heating wire inside the hair dryer is controlled according to the power-on / off state represented by the second control signal, using the zero-crossing point of the AC power input at the AC input terminal of the hair dryer as the control interrupt signal.

[0066] In this embodiment of the invention, the zero-crossing point is used as the control interruption signal, that is, the on / off control is performed at the zero-crossing point, which can avoid the fluctuation of AC power caused by the on / off switching.

[0067] This invention also provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the control method described above.

[0068] This invention also provides a computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed, implements the control method described above.

[0069] This invention also provides a constant temperature control system for a hair dryer, comprising: a heating wire temperature detection circuit, a heating wire control circuit, and a heating wire controller; the heating wire temperature detection circuit is connected to the heating wire inside the hair dryer and the heating wire controller, respectively, and is used to detect the temperature of the heating wire inside the hair dryer as a feedback temperature; the heating wire controller is connected to the heating wire control circuit, and the heating wire control circuit is connected to the heating wire inside the hair dryer, and the heating wire controller is used to generate a control signal based on the feedback temperature using a hybrid switching control method and / or a PI control method, and to control the power output of the heating wire control circuit to the heating wire inside the hair dryer based on the control signal, thereby maintaining a constant temperature for the air outlet temperature of the hair dryer. As a preferred embodiment, the control system in Embodiment 1 of the present invention further includes a zero-crossing detection circuit, which is connected to the AC input terminal and the heating wire controller respectively. The zero-crossing detection circuit is used to detect whether AC power is supplied to the AC input terminal and the zero-crossing point of the AC power input to the AC input terminal. The heating wire controller is also used to generate a control signal according to the feedback temperature after detecting that AC power is supplied, using a hybrid switching control method and / or a PI control method. The present invention switches the load power supply at the zero-crossing point, which can reduce the fluctuation of power supply switching.

[0070] For example, the specific circuit structures of the zero-crossing detection circuit, the heating wire temperature detection circuit, and the heating wire control circuit provided in this invention are as follows: Figures 2-4 As shown.

[0071] like Figure 2As shown, the zero-crossing detection circuit includes a pull-up resistor R6, a current-limiting resistor R7, a filter capacitor C5, a voltage divider resistor R47, a voltage divider resistor R5, and an AC input optocoupler U1. In this embodiment, one end of voltage divider resistor R47 and one end of voltage divider resistor R5 are respectively connected to the AC neutral input terminal ACN and the AC live input terminal; the other ends of voltage divider resistor R47 and the other ends of voltage divider resistor R5 are respectively connected to the two ends of the bidirectional light-emitting diode in AC input optocoupler U1; the collector of the transistor in AC input optocoupler U1 is respectively connected to one end of pull-up resistor R6 and one end of current-limiting resistor R7; the emitter of the transistor in AC input optocoupler is grounded; the other end of pull-up resistor R6 is connected to the system power supply +5VB; the other end of current-limiting resistor R7 is connected to the heating wire controller (in this exemplary embodiment, the other end of current-limiting resistor R7 is first connected to the ZERO terminal, which is connected to the detection pin of the heating wire controller); the other end of current-limiting resistor R7 is also connected to one end of filter capacitor C5; the other end of filter capacitor C5 is grounded.

[0072] See Figure 2 The working principle of the zero-crossing detection circuit is as follows:

[0073] When the voltage of ACN is higher than that of ACL, the voltage flows from ACN through the voltage divider R47, enters the LED of U1, and then through the voltage divider R5 back to ACL.

[0074] When ACL is higher than ACN, the voltage flows from ACL through R5 (voltage divider), into the LED of U1, and then through R47 (voltage divider) back to ACN.

[0075] When the LED of U1 is not conducting, the transistor of U1 is cut off, and 5V flows to the ZERO terminal through the pull-up resistor R6 and the current-limiting resistor R7. At this time, the MCU detects a high level.

[0076] After AC power is connected, the voltage difference between ACN and ACL changes sinusoidally. The greater the voltage difference between ACN and ACL, the greater the voltage difference across the LED. When the LED's turn-on voltage is met, the LED of U1 turns on, and the transistor of U1 also turns on. 5V flows into the collector of the transistor through the pull-up resistor R6 and flows out from the emitter of the transistor. Therefore, there is no voltage through R7, and there is no voltage at the ZERO terminal. At this time, the MCU detects the falling edge, which means that the zero-crossing point of the AC power has been detected.

[0077] like Figure 3As shown, the heating wire temperature detection circuit specifically includes: heating wire terminal CN4, pull-up resistor R15, current-limiting resistor R24, and filter capacitor C11; the first port of heating wire terminal CN4 is connected to one end of the pull-up resistor R15 and one end of the current-limiting resistor R24 ​​respectively, the other end of the pull-up resistor R15 is connected to the system power supply +5VB, the other end of the current-limiting resistor R24 ​​is connected to one end of the filter capacitor C11, and the common terminal HEAT_TEMP connected to the other end of the current-limiting resistor R24 ​​and one end of the filter capacitor C11 is connected to the heating wire controller (the common terminal HEAT_TEMP is connected to the ADC sampling pin of the heating wire controller); the other end of the filter capacitor C11 and the second port of heating wire terminal CN4 are both grounded to GND; the heating wire terminal is used to connect to the heating wire inside the blower.

[0078] See Figure 3 The working principle of the heating wire temperature detection circuit is as follows:

[0079] When the NTC (heating wire) is not connected, 5V passes through R15 and R24 to HEAT_TEMP. The MCU detects that the AD value is full, which indicates that the NTC is open-circuited.

[0080] When the CN4 pin is soldered, 5V passes through R15 to GND, and the HEAT_TEMP voltage is close to 0. The MCU detects that the AD value is close to 0, which indicates that there is an NTC short circuit fault.

[0081] When the NTC is connected and there is no solder joint on the CN4 pin, the 5V is divided by R15 and the NTC. The divided voltage enters HEAT_TEMP through R24. When the NTC temperature changes, the NTC resistance changes, the divided voltage changes, and the MCU samples the AD value. At this time, the AD value sampled by the MCU can represent the NTC temperature.

[0082] like Figure 4As shown, the heating wire control circuit includes: a current-limiting resistor R21, a silicon controlled rectifier (SCR) optocoupler U3, a voltage divider resistor R22, a voltage divider resistor R23, and a bidirectional SCR BT1; one end of the current-limiting resistor R21 is connected to the heating wire controller (in this embodiment, one end of the current-limiting resistor R21 is connected to the control pin of the heating wire controller via the HEAT_EN terminal); the other end of the current-limiting resistor R21 is connected to the cathode of the light-emitting diode (LED) inside the SCR optocoupler U3, and the anode of the LED inside the SCR optocoupler U3 is connected to the system power supply +5VB; one end of the bidirectional diode inside the SCR optocoupler U3 is connected to the second end of the bidirectional SCR BT1, and the bidirectional diode inside the SCR optocoupler U3... The other end of the diode is connected to one end of the voltage divider resistor R22. The other end of the voltage divider resistor R22 is connected to the third end of the bidirectional thyristor BT1 and one end of the voltage divider resistor R23. The other end of the resistor R23 is connected to the first end of the bidirectional thyristor BT1. The second end of the bidirectional thyristor BT1 is also connected to one end of the heating wire inside the blower (for example, the second end of the bidirectional thyristor BT1 is connected to the HN1 terminal, and the HN1 terminal is connected to one end of the heating wire inside the blower). The other end of the heating wire inside the blower is connected to the AC live wire input terminal. The first end of the bidirectional thyristor BT1 is connected to the AC neutral wire input terminal ACN.

[0083] See Figure 4 The working principle of the heating wire control circuit is as follows:

[0084] When HEAT_EN is high, there is no voltage difference across the LED of the optocoupler, the LED is off, the bidirectional diode of the optocoupler is cut off, the bidirectional thyristor is turned off, HN1 is disconnected from ACN, and the heating wire does not work at this time.

[0085] When HEAT_EN is low, 5V passes through the LED of the optocoupler and R21, enters HEAT_EN, the LED lights up, and the bidirectional diode of the optocoupler is turned on.

[0086] When the voltage of HN1 is higher than that of ACN, the voltage flows from HN1 through the bidirectional diode, is divided by R22 and R23, and enters ACN, causing a voltage difference between pin 3 and pin 1 of the thyristor, turning on the thyristor. At this time, HN1 and ACN are connected, and the heating wire works.

[0087] When the voltage of ACN is higher than that of HN1, the voltage flows from ACN through R23, R22, and the bidirectional diode into HN1. The voltage is divided by R23 and R22, which creates a voltage difference between pins 3 and 2 of the thyristor, turning on the thyristor. At this time, ACN and HN1 are connected, and the heating wire works.

[0088] In this embodiment of the invention, the heating wire controller is the MCU of the entire control system. In order to keep the temperature of the air outlet constant, the software part of the heating wire controller of this invention is equipped with a heating wire control module, a temperature detection module and a constant temperature control module.

[0089] First, the on / off state of the heating wire needs to be controlled. The heating wire control module detects the zero-crossing point of the AC power through the zero-crossing detection circuit. Once the zero-crossing point is detected, it means that the heating wire control circuit can be used to turn on the heating wire.

[0090] Secondly, the temperature of the heating wire needs to be detected. The temperature detection module detects the temperature near the heating wire through the heating wire temperature detection circuit and uses the AD value of the NTC as the input of the constant temperature control module.

[0091] Finally, the constant temperature control module continuously compares the AD value of the NTC with the AD value of the set temperature, and adjusts the output of the heating wire control module to make the AD value of the NTC approach the AD value of the set temperature, so that the temperature of the air outlet remains constant.

[0092] 1. Heating wire control module

[0093] The module's concept is to use one cycle of alternating current as a reference, detecting 50 references as one control cycle. Assuming the heating wire's rated power is 1200W, the controllable power of the heating wire under each reference is subdivided into 24W. (1200W / 50 = 24W)

[0094] This module executes in a 22kHz timer interrupt to detect zero crossings and switch the heating element in a timely manner.

[0095] To facilitate software control, the software uses a lookup table to determine whether the heating wire is on. A 2500-byte table is created in the software, with 50 bytes per group (1 byte represents 1 AC cycle), for a total of 50 groups (1 group represents 1 heating level). 0 represents heating wire off, and 1 represents heating wire on. The first group has 0 bytes of Byte1, the second group has 1 byte of Byte1, the third group has 2 bytes of Byte1, and so on, with the 49th group having 48 bytes of Byte1, and the last group having 50 bytes of Byte1.

[0096]

[0097]

[0098] When controlling the heating wire, if the heating wire is turned on and off for a period of time, it will cause temperature fluctuations. Therefore, the switching time can be mixed in the array to reduce temperature fluctuations.

[0099] 2. Temperature detection module

[0100] This module calls the MCU's 12-bit ADC peripheral, triggers one NTC AD value sampling in a 22kHz timer interrupt, performs AD value low-pass filtering once every 1ms, and then outputs the filtered AD value to the constant temperature control module.

[0101] 3. Temperature control module

[0102] like Figure 5 As shown, the control principle of the constant temperature control module is as follows:

[0103] After the hair dryer is turned on, it outputs a fixed heating level for a period of time (open-loop control), and then judges whether the feedback temperature is close to the set temperature. If it is not close, it continues to control the heating wire in open loop; if it is close, it converts the heating level into the integral value of PI and then switches to closed-loop control.

[0104] Due to the response delay of NTC, starting the heating wire control with a closed loop will cause temperature overshoot, and the temperature will only stabilize after multiple oscillations. At this point, outputting a fixed heating level for a period of time will cause the NTC temperature to stabilize at a certain temperature point. By using debugging software, the heating level corresponding to the target temperature point can be found.

[0105] Closed-loop control is achieved using a PI loop. In the open-loop phase, when the NTC approaches the target temperature, the fixed heating level is converted into the integral value of the PI loop, and then the PI loop is switched on. This avoids temperature fluctuations caused by the PI loop starting from 0 when switching to the closed loop. After switching to the closed loop, the PI loop continuously adjusts the heating level to make the feedback temperature close to the target temperature, thus achieving a constant temperature function.

[0106] In summary, implementing the embodiments of the present invention has the following beneficial effects:

[0107] The technical solution provided by this invention achieves a constant air outlet temperature for a hair dryer under different operating conditions. The technical solution provided by this invention includes heating wire control and temperature detection functions. This invention proposes a system, method, and controller that can maintain a constant air outlet temperature under different operating conditions, thus protecting hair and improving user experience while the hair dryer is working.

[0108] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the systems disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple; relevant parts can be referred to the method section.

[0109] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for constant temperature control of a hair dryer, characterized in that, The control method includes the following steps: Obtain the feedback temperature; the feedback temperature is the detected temperature of the heating wire inside the hair dryer. Determine whether the absolute value of the difference between the feedback temperature and the set temperature is greater than a preset threshold to obtain the first judgment result; If the first judgment result indicates yes, then a first control signal is generated based on the difference between the feedback temperature and the set temperature using a hybrid switch control method. Based on the first control signal, the power on / off state of the heating wire in the blower is controlled, and after a preset time period, the process returns to the "obtain feedback temperature" step. If the first judgment result indicates no, then based on the difference between the feedback temperature and the set temperature, a second control signal is generated using PI control, and the on / off state of the heating wire in the blower is controlled based on the second control signal. The first control signal is generated using a hybrid switching control method, specifically including: Determine if the difference between the feedback temperature and the set temperature is greater than 0 to obtain a second judgment result; If the second judgment result indicates no, then a first control signal is generated based on one or more control arrays in the preset control table where the number of Byte1 is greater than the current number of Byte1. The preset control table stores multiple control arrays, each of which includes 50 bytes. One bit of control duration represents one AC cycle. Byte1 indicates that the heating wire in the hair dryer is energized, and Byte0 indicates that the heating wire in the hair dryer is de-energized. The current number of Byte1 is the number of Byte1 in the control array that generates the current first control signal. Different numbers of Byte1 represent different heating levels. If the second judgment result indicates yes, then a first control signal is generated based on one or more control arrays in the preset control table where the number of Byte1 is less than the current number of Byte1; The power supply to the heating element inside the hair dryer is controlled based on the first control signal, specifically including: Using the zero-crossing point of the AC power input to the AC input terminal of the hair dryer as the control interrupt signal, the on / off state of the heating wire inside the hair dryer is controlled according to the on / off state represented by the first control signal. The process of switching from hybrid switching control mode to PI control mode is as follows: first, the heating level is converted into the integral value of PI, and then the control mode is switched to PI control mode.

2. The constant temperature control method for a hair dryer according to claim 1, characterized in that, Previously, obtaining feedback temperature also included: Determine whether AC power is supplied to the AC input terminal of the hair dryer to obtain the third determination result; If the third judgment result indicates yes, then the "obtain feedback temperature" step is executed; If the third judgment result indicates no, then the step of "judging whether AC power is supplied to the AC input terminal of the hair dryer and obtaining the third judgment result" is executed.

3. The constant temperature control method for a hair dryer according to claim 1, characterized in that, The power supply to the heating element inside the blower is controlled based on the second control signal, specifically including: Using the zero-crossing point of the AC power input to the AC input terminal of the hair dryer as the control interrupt signal, the on / off state of the heating wire inside the hair dryer is controlled according to the on / off state represented by the second control signal.

4. A constant temperature control system for a hair dryer, characterized in that, The control system includes: Heating wire temperature detection circuit, heating wire control circuit, and heating wire controller; The heating wire temperature detection circuit is connected to the heating wire inside the hair dryer and the heating wire controller, respectively; the heating wire temperature detection circuit is used to detect the temperature of the heating wire inside the hair dryer as the feedback temperature. The heating wire controller is connected to the heating wire control circuit, and the heating wire control circuit is connected to the heating wire inside the hair dryer. The heating wire controller is used to generate a control signal using the control method described in any one of claims 1-3, and control the switching state of the heating wire control circuit based on the control signal, thereby controlling the on / off state of the heating wire inside the hair dryer. The control signal is a first control signal or a second control signal.

5. The constant temperature control system for the hair dryer according to claim 4, characterized in that, The heating wire temperature detection circuit specifically includes: heating wire terminals, pull-up resistor R15, current-limiting resistor R24, and filter capacitor C11; The first port of the heating wire terminal is connected to one end of the pull-up resistor R15 and one end of the current limiting resistor R24 ​​respectively. The other end of the pull-up resistor R15 is connected to the system power supply. The other end of the current limiting resistor R24 ​​is connected to one end of the filter capacitor C11. The common terminal of the connection between the other end of the current limiting resistor R24 ​​and one end of the filter capacitor C11 is connected to the heating wire controller. The other end of the filter capacitor C11 and the second port of the heating wire terminal are both grounded; The heating wire terminal is used to connect to the heating wire inside the hair dryer.

6. The constant temperature control system for a hair dryer according to claim 4, characterized in that, The heating wire control circuit includes: a current-limiting resistor R21, a silicon controlled rectifier optocoupler, a voltage divider resistor R22, a voltage divider resistor R23, and a bidirectional silicon controlled rectifier; One end of the current-limiting resistor R21 is connected to the heating wire controller; The other end of the current-limiting resistor R21 is connected to the cathode of the light-emitting diode inside the thyristor optocoupler, and the anode of the light-emitting diode inside the thyristor optocoupler is connected to the system power supply. One end of the bidirectional diode inside the thyristor optocoupler is connected to the second end of the bidirectional thyristor, the other end of the bidirectional diode inside the thyristor optocoupler is connected to one end of the voltage divider resistor R22, the other end of the voltage divider resistor R22 is connected to the third end of the bidirectional thyristor and one end of the voltage divider resistor R23 respectively, and the other end of the resistor R23 is connected to the first end of the bidirectional thyristor. The second end of the bidirectional thyristor is also connected to one end of the heating wire inside the blower, and the other end of the heating wire inside the blower is connected to the AC live wire input terminal; the first end of the bidirectional thyristor is connected to the AC neutral wire input terminal.

7. The constant temperature control system for a hair dryer according to claim 4, characterized in that, The control system further includes: a zero-crossing detection circuit; The zero-crossing detection circuit is connected to the AC input terminal and the heating wire controller respectively. The zero-crossing detection circuit is used to detect whether AC power is applied to the AC input terminal and the zero-crossing point of the AC power input to the AC input terminal.

8. The constant temperature control system for a hair dryer according to claim 7, characterized in that, The zero-crossing detection circuit includes: a pull-up resistor R6, a current-limiting resistor R7, a filter capacitor C5, a voltage divider resistor R47, a voltage divider resistor R5, and an AC input optocoupler; One end of the voltage divider resistor R47 is connected to the AC neutral input terminal, and one end of the voltage divider resistor R5 is connected to the AC live input terminal. The other ends of the voltage divider resistor R47 and the other ends of the voltage divider resistor R5 are respectively connected to the two ends of the bidirectional light-emitting diode in the AC input optocoupler. The collector of the transistor in the AC input optocoupler is connected to one end of the pull-up resistor R6 and one end of the current limiting resistor R7. The emitter of the transistor in the AC input optocoupler is grounded. The other end of the pull-up resistor R6 is connected to the system power supply, the other end of the current-limiting resistor R7 is connected to the heating wire controller, and the other end of the current-limiting resistor R7 is also connected to one end of the filter capacitor C5; the other end of the filter capacitor C5 is grounded.

Images