Electric hair drier control circuit

Abstract

The utility model provides an electric hair drier control circuit, which is characterized in that alternating current is input into a live wire L and a null line N of a power supply part, is rectified by a rectifying part of the power supply part, reaches a power supply part of the power supply part, and is output from a voltage stabilizing circuit of the power supply part to supply power to a main control chip; a pin 31, a pin 32, a pin 33, a pin 34, a pin 35 and a pin 36 of the main control chip control the driving part and output duty ratios to pins 15, 10, 5, 14, 9 and 4 of the driving part, the driving part collects current of a current motor, the current passes through the detection part and forms a current signal to pins 13, 14 and 18 of the main control chip, a register in the main control chip monitors the current of the current signal, and the main control chip outputs a proper duty ratio to the driving part. The output duty ratio is automatically adjusted in a software mode, the rotating speed of the motor and the heating value of the heating wire are kept stable after adjustment, the damage probability of the air duct is reduced, the service life of the air duct is prolonged, and the replacement probability is reduced.

Description

Technical Field

[0001] The utility model relates to the field of hair dryer power supplies, in particular to a hair dryer control circuit. Background Art

[0002] With the development and progress of society, in the actual application of products, the voltage is not stable, or higher than the rated input voltage. Products with a nominal voltage of AC120V will directly burn out and damage the circuit board if the wrong voltage (220V) is plugged in. Products with a nominal voltage of AC220V will not work at all when using 120V, or will generate very little heat, or have a very low speed. Utility Model Content

[0003] (1) Technical issues to be solved

[0004] The utility model aims to provide a hair dryer control circuit, aiming to solve the problem that the input voltage used by people in the prior art is unstable, which leads to unstable internal operation and thus damages the hair dryer.

[0005] (2) Technical solution

[0006] The utility model discloses a hair dryer control circuit, which is characterized by comprising a main control chip, a power supply part, a heating part, a driving part and a detection part;

[0007] The AC power is inputted from the live wire L and the neutral wire N of the power supply part, passes through the rectifier part of the power supply part, reaches the power supply part of the power supply part after rectification, and then outputs from the voltage stabilizing circuit of the power supply part to power the main control chip. The main control chip controls the driving part and outputs the initial duty cycle to the driving part. The driving part collects the current size of the current of the motor through the detection part and forms a current signal. The current signal reaches the main control chip, and the internal register of the main control chip monitors the current signal.

[0008] The main control chip outputs the appropriate duty cycle to the drive part according to the current signal.

[0009] Furthermore, the driving part is also provided with a sampling resistor 1 for detecting whether the current in the motor reaches an overcurrent state. The sampling resistor 1 is connected to the I_V point. There are current detection point 1 and current detection point 2 on both sides of the sampling resistor 1. The current detection point 1 is connected to the positive input terminal of the operational amplifier 1, and the current detection point 2 is connected to the reverse input terminal of the operational amplifier 1.

[0010] Furthermore, the driving part is also provided with a sampling resistor 2 for detecting whether the current in the motor reaches an overcurrent state. The sampling resistor 2 is connected to the I_U point. There are current detection points 3 and 4 on both sides of the sampling resistor 2. The current detection point 3 is connected to the positive input terminal of the operational amplifier 2, and the current detection point 4 is connected to the reverse input terminal of the operational amplifier 2.

[0011] Furthermore, the driving part is also provided with a sampling resistor three for detecting whether the current in the motor reaches an overcurrent state. The sampling resistor three is connected to the I_BUS point. There are current detection points five and six on both sides of the sampling resistor three. The current detection point five is connected to the positive input terminal of the operational amplifier three, and the current detection point six is ​​connected to the reverse input terminal of the operational amplifier three.

[0012] Furthermore, a voltage range is set in the internal register of the main control chip, and the voltage range has a minimum value and a maximum value; the current signal forms a numerical value in the internal register of the main control chip, and the numerical value is the voltage detection data, and the output duty cycle of the main control chip is controlled by comparing the result with the minimum value and the maximum value.

[0013] Furthermore, a voltage stabilizing circuit is formed by a voltage stabilizing chip and a voltage stabilizing diode; pin 1 of the voltage stabilizing chip is connected to 5V, pin 2 of the voltage stabilizing chip is connected to AGND, pin 3 of the voltage stabilizing chip is connected to output point one through a current limiting resistor, the positive pole of the voltage stabilizing diode is connected to GND-15V, and the negative pole of the voltage stabilizing diode is connected to output point one.

[0014] Furthermore, the power supply part is provided with a power supply chip, a VDD pin of the power supply chip is connected to one end of the energy storage capacitor, and the other end of the energy storage capacitor is connected to output point one.

[0015] Furthermore, the heating part is also provided with a thermistor, and the thermistor is connected to pin 21 of the main control chip.

[0016] Pin 23 of the main control chip is connected to pins 1 and 2 of the SMD optocoupler 1, pin 3 of the SMD optocoupler 1 is connected to the control electrode of the bidirectional thyristor 1, pin 4 of the SMD optocoupler 1 is connected to the live wire L, the main electrode 1 of the bidirectional thyristor 1 is connected to the live wire L, and the main electrode 2 of the bidirectional thyristor 1 is connected to terminal HT1;

[0017] Pin 24 of the main control chip is connected to pins 1 and 2 of the second patch optocoupler, pin 3 of the second patch optocoupler is connected to the control electrode of the second bidirectional thyristor, pin 4 of the second patch optocoupler is connected to the live wire L, the main electrode 1 of the second bidirectional thyristor is connected to the live wire L, and the main electrode 2 of the second bidirectional thyristor is connected to terminal HT2;

[0018] A heating wire is connected between terminal HT1 and terminal HEAT, a heating wire is connected between terminal HT2 and terminal HEAT, and terminal HEAT is connected to a neutral line N.

[0019] (3) Beneficial effects

[0020] Compared with the prior art, the beneficial effects of the utility model are:

[0021] The circuit of the utility model is based on a main control chip, a power supply part, a heating part, a driving part, and a detection part. The output duty cycle is automatically adjusted by software. After the adjustment, the rotation speed of the motor and the heat generation of the heating wire remain stable, reducing the probability of damage to the hair dryer, thereby extending the service life of the hair dryer and reducing the probability of replacement. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is the main control chip of this patent.

[0023] Figure 2 This is the main control circuit schematic of this patent.

[0024] Figure 3 It is the driving part of this patent.

[0025] Figure 4 This is the detection part of this patent.

[0026] Figure 5 This is the temperature detection part of this patent.

[0027] Figure 6 This is a schematic diagram of the duty cycle change of this patent.

[0028] Figure 7 This is a schematic diagram of the process of controlling the motor of this patent.

[0029] Figure 8 This is a schematic diagram of the process of controlling the heating wire of this patent. DETAILED DESCRIPTION

[0030] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention;

[0031] refer to Figure 1-Figure 8 ;

[0032] It should be noted that Figure 6 This is a schematic diagram of the duty cycle change of this patent, t is time, T is a cycle, A1 is the PWM duty cycle (the input voltage of the motor is close to the normal voltage), A2 is the PWM duty cycle (the input voltage of the motor is higher than the normal voltage), and A3 is the PWM duty cycle (the input voltage of the motor is lower than the normal voltage).

[0033] It should be noted that the normal voltage is the rated working voltage of the hair dryer.

[0034] The circuit of the utility model includes a main control chip 1, a power supply part 2, a heating part 3, a driving part 4, and a detection part 5. Its working method is that the live wire L and the neutral wire N of the power supply part 2 input alternating current through the rectifying part 22 of the power supply part 2, and then reach the power supply part 23 of the power supply part 2 after rectification, and then output from the voltage stabilizing circuit (described in detail below) of the power supply part 23 to power the main control chip 1, the main control chip 1 starts to work, and the initial duty cycle of the output of the 31st, 32nd, 33rd, 34th, 35th, and 36th pins of the main control chip 1 reaches the 15th, 10th, 5th, 14th, 9th, and 4th pins of the driving chip 41, the driving chip 41 collects the current size of the current of the current motor and forms a current signal through the detection part 5, the current signal reaches the 13th, 14th, and 18th pins of the main control chip 1, and the internal register of the main control chip 1 monitors the current signal.

[0035] It should be noted that the internal register of the main control chip 1 makes a judgment by detecting the voltage of the motor. The internal register of the main control chip 1 converts the current signal into a voltage signal for detection.

[0036] In the present technical solution, a voltage range is set in the internal register of the main control chip 1, and there is a minimum value in the voltage range. The voltage signal forms a numerical value in the internal register of the main control chip 1, and the numerical value is the voltage detection data. When the voltage detection data is less than the minimum value, the main control chip 1 determines that the voltage is too low, and the 31, 32, 33, 34, 35, and 36 pins of the main control chip 1 output a new duty cycle to the 15, 10, 5, 14, 9, and 4 pins of the driver chip 41, and the lower the voltage detection data, the higher the output duty cycle of the 31, 32, 33, 34, 35, and 36 pins of the main control chip 1.

[0037] Similarly, there is a maximum value in the voltage range. When the voltage detection data is greater than the maximum value, the main control chip 1 determines that the voltage is too high, and the 31, 32, 33, 34, 35, and 36 pins of the main control chip 1 output a new duty cycle. The higher the voltage detection data, the lower the output duty cycle of the 31, 32, 33, 34, 35, and 36 pins of the main control chip 1.

[0038] After the driver chip 41 receives the new duty cycle, the duty cycle and the input voltage of the motor reach a balance. At this time, the speed of the motor is maintained within a certain range, fully protecting customer safety and usage experience.

[0039] The duty cycle is output using PWM (Pulse Width Modulation).

[0040] It should be noted that the duty cycle is defined by the motor speed. The higher the motor speed, the higher the duty cycle, and the lower the motor voltage, the lower the duty cycle.

[0041] Among them, the model of the main control chip 1 is CMS32M5710L048, and the model of the driver chip 41 is CS5755.

[0042] like Figure 2 As shown, the power supply part 2 includes an input part 21 and a rectifying part 22, which are used to activate the MOS tube inside the power chip 231 and provide an initial voltage for the power chip 231;

[0043] Pin 1 of the autotransformer 221 is connected to the live wire L, pin 2 of the autotransformer 221 is connected to one end of the rectifier bridge 222, pin 3 of the autotransformer 221 is connected to the other end of the rectifier bridge 222, pin 4 of the autotransformer 221 is connected to the neutral wire N, and another end of the rectifier bridge 222 is connected to pins 5, 6, 7, and 8 of the power chip 231.

[0044] When the wind tube starts to supply power, the voltage is filtered by the autotransformer 221 and rectified by the rectifier bridge 222. After rectification, it enters the 5th, 6th, 7th and 8th pins of the power chip 231;

[0045] When the power chip 231 detects voltage and the VDD pin of the power chip 231 starts to supply power, the power chip 231 starts to work normally, and the CS pin output voltage of the power chip 231 reaches the output point 1 235, thereby providing input voltage for the voltage regulator chip 232 (the negative voltage is the GND pin of the voltage regulator chip).

[0046] The VDD pin of the power chip 231 is connected to pins 5, 6, 7, and 8 in the internal circuit of the power chip 231. The VDD pin of the power chip 231 charges the energy storage capacitor 233 through the voltage of pins 5, 6, 7, and 8 of the power chip 231. The energy storage capacitor 233 reaches the voltage required for the power chip 231 to work. The energy storage capacitor 233 outputs power to the VDD pin of the power chip 231, and the power chip 231 starts to work normally. One end of the energy storage capacitor 233 is connected to the VDD pin of the power chip 231, and one end of the energy storage capacitor 233 is connected to the output point 235.

[0047] The model of the power chip 231 is KP3210SG.

[0048] The power supply part 2 is also provided with a voltage stabilizing circuit to ensure that the input voltage of the main control chip 1 is 5V. The voltage stabilizing circuit includes a voltage stabilizing chip 232 and a voltage stabilizing diode 236. Pin 1 of the voltage stabilizing chip 232 is connected to output point 2 238, pin 2 of the voltage stabilizing chip 232 is connected to AGND, pin 3 of the voltage stabilizing chip 232 is connected to output point 1 235 through a current limiting resistor, the positive pole of the voltage stabilizing diode 236 is connected to GND-15V, and the negative pole of the voltage stabilizing diode 236 is connected to output point 1 235. The voltage stabilizing diode 236 is provided to protect the circuit.

[0049] Its working principle is that when the power chip 231 outputs DC power, the voltage of the DC power is greater than or equal to 15V, and the power reaches the output point 238 through the current limiting resistor and the voltage regulator chip 232 to form a path. The voltage regulator chip 232 functions to output a stable 5V voltage (the receiving point of the negative voltage is connected to pin 2 of the voltage regulator chip 232).

[0050] The model of the voltage regulator diode 236 is BZT52C18V, and the model of the voltage regulator chip 232 is 78L05SOT89.

[0051] like Figure 1 and Figure 3-4 As shown, when the driving part 4 starts to work, the pins 20 and 21 of the driving chip 41 are connected in the internal circuit of the driving chip 41, and the terminal V provides current to the I_V point of the detection part 5 through the pins 20 and 21 of the driving chip 41. The I_V point is connected to the sampling resistor 512. Due to the on-resistance of the sampling resistor 512, different currents will be generated at both ends thereof. The current is detected and amplified by the operational amplifier 514, and the amplification result forms a current signal 1.

[0052] More specifically, current detection point 1 511 is connected to the positive input terminal of operational amplifier 1 514, current detection point 2 513 is connected to the reverse input terminal of operational amplifier 1 514, and the output terminal of operational amplifier 1 514 is connected to pin 14 of main control chip 1. Main control chip 1 decides whether to change the output duty cycle of main control chip 1 based on the voltage detection data formed by current signal 1 (refer to the above for the principle).

[0053] Similarly, pins 18 and 19 of the driver chip 41 are connected in the internal circuit of the driver chip 41, and the terminal U provides current to the I_U point of the detection part 5 through the pins 18 and 19 of the driver chip 41. The I_U point is connected to the sampling resistor 2 522. Due to the on-resistance of the sampling resistor 2 522, different currents will be generated at both ends thereof. The current is detected and amplified by the operational amplifier 2 524, and the amplification result forms the current signal 2.

[0054] Similarly, current detection point three 521 is connected to the positive input terminal of operational amplifier two 524, current detection point four 523 is connected to the reverse input terminal of operational amplifier two 524, and the output terminal of operational amplifier two 524 is connected to pin 18 of main control chip 1. Main control chip 1 decides whether to change the output duty cycle of main control chip 1 based on the voltage detection data formed by current signal two.

[0055] Similarly, pins 22 and 23 of the driver chip 41 are connected in the internal circuit of the driver chip 41, and the terminal W provides current to the I_BUS point of the detection part 5 through the pins 22 and 23 of the driver chip 41. The I_BUS point is connected to the sampling resistor three 532. Due to the on-resistance of the sampling resistor three 532, different currents will be generated at both ends of the sampling resistor three 532. The current is detected and amplified by the operational amplifier three 534, and the amplification result forms the current signal three.

[0056] Current detection point five 531 is connected to the positive input terminal of operational amplifier three 534, current detection point six 533 is connected to the reverse input terminal of operational amplifier three 534, and the output terminal of operational amplifier three 534 is connected to pin 13 of main control chip 1. Main control chip 1 decides whether to change the output duty cycle of main control chip 1 based on the voltage detection data formed by current signal three to ensure that the duty cycle and voltage are balanced.

[0057] Among them, terminal U, terminal V and terminal W are connected to a three-phase asynchronous motor.

[0058] It should be noted that, since the utility model uses a three-phase asynchronous motor, current signal one is approximately equal to current signal two and approximately equal to current signal three, so the above current signal one, current signal two and current signal three are collectively referred to as current signals (as described above).

[0059] It should be noted that when the voltage detection data exceeds the limit value set by the main control chip 1, the main control chip 1 quickly triggers the overcurrent protection, the main control chip 1 will stop working, and then suspend the work of the driving part 4 to achieve the effect of short circuit protection.

[0060] like Figure 2 and Figure 5 As shown, in order to ensure that the utility model has a stable heating effect, the heating part 3 is also provided with a temperature control circuit 1 and a temperature control circuit 2 for controlling the working state of the heating part 3, and the circuit is specifically configured as follows: the temperature control circuit 1 includes a patch optocoupler 1 31 and a bidirectional thyristor 1 32, and the temperature control circuit 2 includes a patch optocoupler 2 33 and a bidirectional thyristor 2 34.

[0061] The heating part 3 is also provided with a thermistor 35 for detecting the current temperature of the heating wire and sending the temperature information to the main control chip 1 .

[0062] Pin 1 and pin 2 of the patch optocoupler 31 are connected to pin 23 of the main control chip 1, pin 3 of the patch optocoupler 31 is connected to the control electrode of the bidirectional thyristor 32, pin 4 of the patch optocoupler 31 is connected to the live wire L, the main electrode 1 of the bidirectional thyristor 32 is connected to the live wire L, the main electrode 2 of the bidirectional thyristor 32 is connected to the terminal HT1, and the neutral line N is connected to the terminal HEAT;

[0063] Its working principle is that when the main control chip 1 outputs a control signal and the SMD optocoupler 31 works normally, the SMD optocoupler 31 outputs a control signal that reaches the control electrode of the bidirectional thyristor 32, and the main electrode 1 and the main electrode 2 of the bidirectional thyristor 32 are connected to form a path, and the live wire L passes through the bidirectional thyristor 32, the terminal HT1, and the heating wire to reach the neutral wire N to form a path, and the heating wire starts to heat up, thereby achieving the purpose of the hair dryer blowing out hot air stably.

[0064] Pin 1 and pin 2 of the patch optocoupler 233 are connected to pin 24 of the main control chip 1, pin 3 of the patch optocoupler 233 is connected to the control electrode of the bidirectional thyristor 234, pin 4 of the patch optocoupler 233 is connected to the live wire L, the main electrode 1 of the bidirectional thyristor 234 is connected to the live wire L, the main electrode 2 of the bidirectional thyristor 234 is connected to the terminal HT2, and the neutral line N is connected to the terminal HEAT;

[0065] Its working principle is that when the main control chip 1 outputs a control signal and the SMD optocoupler 2 33 works normally, the SMD optocoupler 2 33 outputs a control signal that reaches the control electrode of the bidirectional thyristor 2 34, and the main electrode 1 of the bidirectional thyristor 2 34 is connected with the main electrode 2 to form a path, and the live wire L passes through the bidirectional thyristor 2 34, the terminal HT2, and the heating wire to reach the neutral wire N to form a path, and the heating wire starts to heat.

[0066] Among them, the models of the chip optocoupler 1 31 and the chip optocoupler 2 33 are ORM3053 / KTLP160J.

[0067] It should be noted that a heating wire (not shown) is connected between the terminal HT1 and the terminal HT2 and the terminal HEAT respectively.

[0068] It should be noted that when thermistor 35 detects that the temperature is too high and the main control chip 1 is working normally, the thermistor 35 outputs a temperature signal to the 21st pin of the main control chip 1. The main control chip 1 controls the 23rd and 24th pins of the main control chip 1 to output a suitable duty cycle through the temperature signal. At this time, the power of the heating wire begins to decrease, achieving the purpose of controlling the normal operation of the heating part 3. (For the specific process, refer to Figure 8 )

[0069] It should be noted that the above connections are all referred to as electrical connections.

[0070] It is obvious to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be regarded as exemplary and non-restrictive from any point of view, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention. Any reference numeral in a claim should not be regarded as limiting the claim to which it relates.

[0071] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementations that can be understood by those skilled in the art.

Claims

1. A hair dryer control circuit, characterized in that: It comprises a main control chip (1), a power supply part (2), a heating part (3), a driving part (4) and a detection part (5); The live wire L and the neutral wire N of the power supply part (2) input alternating current through the rectifying part (22) of the power supply part (2), and after rectification, it reaches the power supply part (23) of the power supply part (2), and then the voltage stabilizing circuit output of the power supply part (23) can supply power to the main control chip (1), the main control chip (1) outputs the initial duty cycle to the driving part (4), the driving part (4) collects the current of the current motor through the detecting part (5) and forms a current signal, the current signal reaches the main control chip (1), and the internal register of the main control chip (1) monitors the current signal; The main control chip (1) outputs a suitable duty cycle according to the current signal to the driving part (4).

2. A hair dryer control circuit according to claim 1, characterized in that: The detection part (5) is provided with a sampling resistor 1 (512), the sampling resistor 1 (512) is connected to the I_V point, and there are a current detection point 1 (511) and a current detection point 2 (513) on both sides of the sampling resistor 1 (512), the current detection point 1 (511) is connected to the positive input end of the operational amplifier 1 (514), the current detection point 2 (513) is connected to the negative input end of the operational amplifier 1 (514), and the output end of the operational amplifier 1 (514) is connected to the 14th pin of the main control chip (1).

3. A hair dryer control circuit according to claim 2, characterized in that: The detection part (5) is further provided with a second sampling resistor (522), the second sampling resistor (522) being connected to the I_U point, a third current detection point (521) and a fourth current detection point (523) being present on both sides of the second sampling resistor (522), the third current detection point (521) being connected to the positive input end of the second operational amplifier (524), the fourth current detection point (523) being connected to the negative input end of the second operational amplifier (524), and the output end of the second operational amplifier (524) being connected to the 18th pin of the main control chip (1).

4. A hair dryer control circuit according to claim 3, characterized in that: The detection part (5) is further provided with a sampling resistor three (532), the sampling resistor three (532) is connected to the I_BUS point, and there are a current detection point five (531) and a current detection point six (533) on both sides of the sampling resistor three (532), the current detection point five (531) is connected to the positive input end of the operational amplifier three (534), the current detection point six (533) is connected to the negative input end of the operational amplifier three (534), and the output end of the operational amplifier three (534) is connected to the 13th pin of the main control chip (1).

5. A hair dryer control circuit according to claim 4, characterized in that: The internal register of the main control chip (1) sets a voltage range, and the voltage range has a minimum value and a maximum value; the current signal is converted into a voltage signal in the internal register of the main control chip (1), and the voltage signal forms a numerical value in the internal register of the main control chip (1), and the numerical value is voltage detection data, and the output duty cycle of the main control chip (1) is controlled by comparing the result with the minimum value and the maximum value.

6. A hair dryer control circuit according to claim 1, characterized in that: The voltage stabilizing circuit comprises a voltage stabilizing chip (232) and a voltage stabilizing diode (236), wherein pin 1 of the voltage stabilizing chip (232) is connected to 5V, pin 2 of the voltage stabilizing chip (232) is connected to AGND, pin 3 of the voltage stabilizing chip (232) is connected to output point one (235) via a current limiting resistor, the positive electrode of the voltage stabilizing diode (236) is connected to GND-15V, and the negative electrode of the voltage stabilizing diode (236) is connected to output point one (235).

7. A hair dryer control circuit according to claim 6, characterized in that: The power supply part (23) is provided with a power chip (231), a VDD pin of the power chip (231) is connected to an energy storage capacitor (233), and the other end of the energy storage capacitor (233) is connected to the output point one (235).

8. The hair dryer control circuit according to claim 1, characterized in that: The heating part (3) is also provided with a thermistor (35), and the thermistor (35) is connected to pin 21 of the main control chip (1).

9. A hair dryer control circuit according to claim 8, characterized in that: Pin 23 of the main control chip (1) is connected to pins 1 and 2 of a patch optocoupler (31), pin 3 of the patch optocoupler (31) is connected to the control electrode of a bidirectional thyristor (32), pin 4 of the patch optocoupler (31) is connected to a live wire L, a main electrode 1 of the bidirectional thyristor (32) is connected to the live wire L, and a main electrode 2 of the bidirectional thyristor (32) is connected to terminal HT1; Pin 24 of the main control chip (1) is connected to pins 1 and 2 of the patch optocoupler (33), pin 3 of the patch optocoupler (33) is connected to the control electrode of the bidirectional thyristor (34), pin 4 of the patch optocoupler (33) is connected to the live wire L, the main electrode 1 of the bidirectional thyristor (34) is connected to the live wire L, and the main electrode 2 of the bidirectional thyristor (34) is connected to the terminal HT2; A heating wire is connected between the terminal HT1 and the terminal HEAT, a heating wire is connected between the terminal HT2 and the terminal HEAT, and the terminal HEAT is connected to a neutral line N.

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