A control circuit for a thermostatic electric hair dryer

Abstract

The utility model discloses a control circuit of constant temperature electric blower, including power module, control unit and drive and execution unit, power module and control unit and drive and execution unit electric connection. The utility model discloses a temperature and wind speed double parameter closed loop control strategy is adopted, not only response temperature change, still real -time response wind speed change to the coupling calculation of both, when wind speed changes, control unit can immediately perceive and cooperates the adjustment heating power, greatly shorten the response time, improved dynamic performance, make the air -out temperature also can restore stability when wind speed mutation, improve constant temperature effect, make the user experience better, in addition cooperate the setting of signal conditioning circuit, can output more accurate control signal to higher precision constant temperature control is realized, effectively avoided the temperature in the set value vicinity fluctuation or the situation of appearing overshoot.

Description

Technical Field

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

[0002] Constant temperature hair dryers are widely used in homes and the beauty and hairdressing industry. Their main function is to maintain a constant air temperature while keeping the airflow speed constant, so as to prevent heat damage to the hair. Existing constant temperature hair dryers generally use microcontrollers or analog control circuits, which collect the air temperature through temperature sensors and switch or adjust the heating wire via PWM to achieve the constant temperature function. The control circuits of existing constant temperature hair dryers mainly rely on temperature feedback to adjust the heating power, ignoring the coupling relationship between airflow and heating. When the airflow speed changes, the air temperature is prone to overshoot or drop, thus failing to achieve stable constant temperature. In view of the above problems, this application proposes a control circuit for a constant temperature hair dryer. Utility Model Content

[0003] The purpose of this invention is to address the shortcomings of existing technologies by proposing a control circuit for a constant temperature electric hair dryer.

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

[0005] A control circuit for a constant temperature hair dryer includes a power module, a control unit, and a drive and execution unit. The power module, control unit, and drive and execution unit are electrically connected. The power module is electrically connected to a signal detection module, and the signal detection module is electrically connected to the control unit.

[0006] The power module includes a voltage regulator;

[0007] The signal detection module includes a temperature detection circuit, a wind speed detection circuit, and a signal conditioning circuit. The temperature detection circuit and the wind speed detection circuit are both electrically connected to the signal conditioning circuit.

[0008] Preferably, the temperature detection circuit includes a resistor R1, one end of which is electrically connected to a 5V voltage, the other end of which is electrically connected to one end of a thermistor NTC, the other end of which is electrically connected to one end of a resistor R2, the other end of which is electrically connected to one end of a capacitor C1, the other end of which is electrically connected to the other end of a resistor R1, and the other ends of the thermistor NTC and resistor R2 are both grounded.

[0009] Preferably, the wind speed detection circuit includes a Hall effect sensor chip U1, pin 2 of the Hall effect sensor chip U1 is electrically connected to pin 1 of the operational amplifier U2, pin 3 of the Hall effect sensor chip U1 is grounded, pin 2 of the operational amplifier U2 is electrically connected to one end of a capacitor C3, the other end of the capacitor C3 is electrically connected to one end of a capacitor C2, the other end of the capacitor C2 is electrically connected to one end of a resistor R3, and the other end of the resistor R3 is electrically connected to pin 3 of the operational amplifier U2.

[0010] Preferably, the signal conditioning circuit includes an operational amplifier U3. Pin 1 of the operational amplifier U3 is electrically connected to one end of resistor R7 and one end of resistor R8. The other end of resistor R7 is electrically connected to a 5V voltage. Pin 2 of the operational amplifier U3 is electrically connected to one end of resistor R5, one end of resistor R6, and one end of resistor R9. The other end of resistor R5 is electrically connected to one end of resistor R4 and one end of capacitor C4. The other end of capacitor C4 is electrically connected to the other end of resistor R6. The other ends of capacitor C4, resistor R6, and resistor R9 are all grounded. The other end of resistor R8 is electrically connected to one end of capacitor C5. The other end of capacitor C5 is electrically connected to pin 3 of the operational amplifier U3. The other end of resistor R4 is electrically connected to pin 3 of the operational amplifier U2 and the other end of resistor R1.

[0011] Preferably, the control unit includes a microcontroller (MCU), which has a sampling pin ADC and a pin IO. Pin 3 of the operational amplifier U3 is electrically connected to the sampling pin ADC, and the pin IO is used to read the pulse frequency representing the wind speed and calculate the actual rotational speed through an internal counter.

[0012] Preferably, the drive and execution unit includes a TRIAC drive circuit and a motor drive circuit. The TRIAC drive circuit is electrically connected to a heating wire, and the motor drive circuit is electrically connected to a fan motor. The heating wire is used to generate heat, and the fan motor is used to generate airflow.

[0013] The voltage regulator is a linear voltage regulator chip, which is used to process unstable low-voltage DC power into stable and clean DC voltage.

[0014] Preferably, the thermistor NTC and resistor R2 form a voltage divider circuit. The thermistor NTC is used to detect the temperature change at the outlet of the hair dryer, and resistor R1 is a current-limiting resistor used to limit the current flowing from the 5V power supply to the voltage divider circuit, thus providing a certain degree of protection.

[0015] Preferably, a small magnet is installed on the rotor of the fan motor, and the magnet will pass over the Hall detection chip U1 once for each rotation of the rotor.

[0016] Compared with existing technologies, the beneficial effects of this utility model are:

[0017] This invention employs a dual-parameter closed-loop control strategy based on temperature and wind speed. It not only responds to temperature changes but also to wind speed changes in real time, and performs coupled calculations on both. When the wind speed changes, the control unit can immediately sense and coordinately adjust the heating power, greatly shortening the response time and improving dynamic performance. This allows the outlet air temperature to quickly recover and stabilize even when the wind speed changes abruptly, improving the constant temperature effect and providing a better user experience. In addition, with the addition of a signal conditioning circuit, it can output more precise control signals, thereby achieving higher precision constant temperature control and effectively avoiding temperature fluctuations around the set value or overshoot. Attached Figure Description

[0018] Figure 1 This is a connection block diagram of the control circuit of a constant temperature electric hair dryer proposed in this utility model;

[0019] Figure 2 The circuit diagram of the temperature detection circuit in the control circuit of the constant temperature electric hair dryer proposed in this utility model;

[0020] Figure 3 The circuit diagram of the wind speed detection circuit in the control circuit of the constant temperature electric hair dryer proposed in this utility model;

[0021] Figure 4 The circuit diagram of the signal conditioning circuit in the control circuit of the constant temperature electric hair dryer proposed in this utility model. Detailed Implementation

[0022] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present utility model. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments.

[0023] Reference Figure 1-4 A control circuit for a constant temperature hair dryer includes a power module, a control unit, and a drive and execution unit. The power module, control unit, and drive and execution unit are electrically connected. The drive and execution unit includes a TRIAC drive circuit and a motor drive circuit. The TRIAC drive circuit is electrically connected to a heating wire, and the motor drive circuit is electrically connected to a fan motor. The heating wire is used to generate heat, and the fan motor is used to generate airflow.

[0024] The power module is electrically connected to a signal detection module, which is electrically connected to the control unit.

[0025] The power module includes a voltage regulator, which is a linear voltage regulator chip used to process unstable low-voltage DC power into a stable and clean DC voltage.

[0026] The signal detection module includes a temperature detection circuit, a wind speed detection circuit, and a signal conditioning circuit. Both the temperature detection circuit and the wind speed detection circuit are electrically connected to the signal conditioning circuit.

[0027] The temperature detection circuit includes a resistor R1, one end of which is electrically connected to a 5V voltage, the other end of which is electrically connected to one end of a thermistor NTC, the other end of which is electrically connected to one end of a resistor R2, the other end of which is electrically connected to one end of a capacitor C1, the other end of which is electrically connected to the other end of a resistor R1, and the other ends of the thermistor NTC and the other end of a resistor R2 are both grounded.

[0028] The thermistor NTC and resistor R2 form a voltage divider circuit. The thermistor NTC is used to detect the temperature change at the outlet of the hair dryer, and resistor R1 is a current-limiting resistor used to limit the current flowing from the 5V power supply to the voltage divider circuit, thus playing a certain protective role.

[0029] The wind speed detection circuit includes a Hall effect sensor chip U1. A small magnet is installed on the rotor of the fan motor. Every time the rotor rotates once, the magnet will pass by the Hall effect sensor chip U1 once. According to the Hall effect, whenever the magnet approaches, the Hall effect sensor chip U1 will output a low-level pulse; when the magnet moves away, it will output a high-level pulse.

[0030] Pin 2 of Hall effect sensor chip U1 is electrically connected to pin 1 of operational amplifier U2. Pin 3 of Hall effect sensor chip U1 is grounded. Pin 2 of operational amplifier U2 is electrically connected to one end of capacitor C3. The other end of capacitor C3 is electrically connected to one end of capacitor C2. The other end of capacitor C2 is electrically connected to one end of resistor R3. The other end of resistor R3 is electrically connected to pin 3 of operational amplifier U2.

[0031] Capacitors C2 and C3 together form a low-pass filter network, providing a stable, filtered reference voltage for the inverting input. This voltage value is approximately the average value of the original signal voltage.

[0032] The signal conditioning circuit includes operational amplifier U3. Pin 1 of operational amplifier U3 is electrically connected to one end of resistor R7 and one end of resistor R8. The other end of resistor R7 is electrically connected to a 5V voltage. Pin 2 of operational amplifier U3 is electrically connected to one end of resistor R5, one end of resistor R6, and one end of resistor R9. The other end of resistor R5 is electrically connected to one end of resistor R4 and one end of capacitor C4. The other end of capacitor C4 is electrically connected to the other end of resistor R6. The other ends of capacitor C4, resistor R6, and resistor R9 are all grounded. The other end of resistor R8 is electrically connected to one end of capacitor C5. The other end of capacitor C5 is electrically connected to pin 3 of operational amplifier U3. The other end of resistor R4 is electrically connected to pin 3 of operational amplifier U2 and the other end of resistor R1.

[0033] The control unit includes a microcontroller MCU, which has a sampling pin ADC and an I / O pin. Pin 3 of the operational amplifier U3 is electrically connected to the sampling pin ADC. The I / O pin is used to read the pulse frequency representing the wind speed and calculate the actual rotation speed through an internal counter.

[0034] The microcontroller (MCU) adjusts the heating power based on the difference between the user-set temperature and the feedback temperature using an internal control algorithm. The formula used is as follows: ,in For the controller's output signal, Real-time error is defined as the difference between the set value and the measured value. and These are the proportional, integral, and differential coefficients, respectively. The target temperature set by the user, It is the actual temperature measured at time t;

[0035] This invention employs a dual-parameter closed-loop control strategy based on temperature and wind speed. It not only responds to temperature changes but also to wind speed changes in real time, and performs coupled calculations on both. When the wind speed changes, the control unit can immediately sense and coordinately adjust the heating power, greatly shortening the response time and improving dynamic performance. This allows the outlet air temperature to quickly recover and stabilize even when the wind speed changes abruptly, improving the constant temperature effect and providing a better user experience. In addition, with the addition of a signal conditioning circuit, it can output more precise control signals, thereby achieving higher precision constant temperature control and effectively avoiding temperature fluctuations around the set value or overshoot.

[0036] Working Principle: During operation, the power module converts mains power into stable low-voltage DC power through a voltage regulator, supplying power to the control unit, signal detection module, and drive and execution unit. The thermistor NTC in the temperature detection circuit senses changes in the air outlet temperature and converts it into a voltage signal. The Hall effect sensor chip U1 in the wind speed detection circuit senses the magnet on the fan motor rotor, converting the motor speed into a pulse frequency signal. Both the voltage and pulse frequency signals are sent to the signal conditioning circuit. The signal conditioning circuit filters and amplifies the temperature analog signal, suppressing high-frequency noise, improving the signal-to-noise ratio, and amplifying the weak voltage changes to a range suitable for sampling by the ADC pin on the microcontroller MCU, thereby significantly improving temperature measurement accuracy. The signal conditioning circuit also shapes and compares the wind speed pulse signal, transforming the potentially glitch-prone or irregular waveform generated by the Hall effect sensor chip U1 into a clean, steep waveform. A square wave signal ensures that the microcontroller (MCU) can accurately capture and count the signals. After conditioning, the high-precision temperature signal and accurate wind speed frequency signal are sent to the control unit. The MCU adjusts the heating power based on the difference between the user-set temperature and the feedback temperature using its internal control algorithm. It also dynamically compensates for the heating control based on real-time wind speed (for example, when an increase in wind speed is detected, the MCU increases the heating power while anticipating the dilution effect of cold air on hot air and providing control input in advance to prevent a sudden temperature drop). Finally, the MCU outputs two control signals: one continuously adjusts the heating power of the heating wire through the TRIAC drive circuit, and the other adjusts the fan motor speed through the motor drive circuit. Under the coordinated control of the MCU, both signals quickly respond to external changes, jointly maintaining a constant outlet air temperature, achieving effective coupling of airflow and heating, and improving the constant temperature effect.

[0037] The above description is only a preferred embodiment of the present utility model, but the protection scope of the present utility model is not limited thereto. Any equivalent substitutions or changes made by those skilled in the art within the technical scope disclosed in the present utility model, based on the technical solution and the inventive concept of the present utility model, should be included within the protection scope of the present utility model.

Claims

1. A control circuit for a constant temperature hair dryer, comprising a power module, a control unit, and a drive and execution unit, wherein the power module, control unit, and drive and execution unit are electrically connected, characterized in that, The power module is electrically connected to a signal detection module, and the signal detection module is electrically connected to the control unit; The power module includes a voltage regulator; The signal detection module includes a temperature detection circuit, a wind speed detection circuit, and a signal conditioning circuit. The temperature detection circuit and the wind speed detection circuit are both electrically connected to the signal conditioning circuit.

2. The control circuit for a constant temperature hair dryer according to claim 1, characterized in that, The temperature detection circuit includes a resistor R1, one end of which is electrically connected to a 5V voltage, and the other end of which is electrically connected to one end of a thermistor NTC. The other end of the thermistor NTC is electrically connected to one end of a resistor R2, and the other end of the resistor R2 is electrically connected to one end of a capacitor C1. The other end of the capacitor C1 and the other end of the resistor R1 are electrically connected. The other ends of the thermistor NTC and one end of the resistor R2 are both grounded.

3. The control circuit for a constant temperature hair dryer according to claim 1, characterized in that, The wind speed detection circuit includes a Hall effect sensor chip U1. Pin 2 of the Hall effect sensor chip U1 is electrically connected to pin 1 of the operational amplifier U2. Pin 3 of the Hall effect sensor chip U1 is grounded. Pin 2 of the operational amplifier U2 is electrically connected to one end of a capacitor C3. The other end of the capacitor C3 is electrically connected to one end of a capacitor C2. The other end of the capacitor C2 is electrically connected to one end of a resistor R3. The other end of the resistor R3 is electrically connected to pin 3 of the operational amplifier U2.

4. The control circuit for a constant temperature hair dryer according to claim 3, characterized in that, The signal conditioning circuit includes an operational amplifier U3. Pin 1 of the operational amplifier U3 is electrically connected to one end of resistor R7 and one end of resistor R8. The other end of resistor R7 is electrically connected to a 5V voltage. Pin 2 of the operational amplifier U3 is electrically connected to one end of resistor R5, one end of resistor R6, and one end of resistor R9. The other end of resistor R5 is electrically connected to one end of resistor R4 and one end of capacitor C4. The other end of capacitor C4 is electrically connected to the other end of resistor R6. The other ends of capacitor C4, resistor R6, and resistor R9 are all grounded. The other end of resistor R8 is electrically connected to one end of capacitor C5. The other end of capacitor C5 is electrically connected to pin 3 of the operational amplifier U3. The other end of resistor R4 is electrically connected to pin 3 of the operational amplifier U2 and the other end of resistor R1.

5. The control circuit for a constant temperature hair dryer according to claim 1, characterized in that, The control unit includes a microcontroller (MCU), which has a sampling pin (ADC) and an I / O pin. Pin 3 of the operational amplifier U3 is electrically connected to the sampling pin (ADC), and the I / O pin is used to read the pulse frequency representing the wind speed and calculate the actual rotational speed through an internal counter.

6. The control circuit for a constant temperature electric hair dryer according to claim 1, characterized in that, The drive and execution unit includes a TRIAC drive circuit and a motor drive circuit. The TRIAC drive circuit is electrically connected to a heating wire, and the motor drive circuit is electrically connected to a fan motor. The heating wire is used to generate heat, and the fan motor is used to generate airflow. The voltage regulator is a linear voltage regulator chip, which is used to process unstable low-voltage DC power into stable and clean DC voltage.

7. The control circuit for a constant temperature hair dryer according to claim 2, characterized in that, The thermistor NTC and resistor R2 form a voltage divider circuit. The thermistor NTC is used to detect the temperature change at the outlet of the hair dryer, and resistor R1 is a current-limiting resistor used to limit the current flowing from the 5V power supply to the voltage divider circuit, thus providing a certain degree of protection.

8. The control circuit for a constant temperature hair dryer according to claim 6, characterized in that, The fan motor has a small magnet installed on its rotor. Each time the rotor rotates once, the magnet will pass over the Hall effect detection chip U1.

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