Step-down pure sine wave voltage transformation socket

Abstract

The utility model discloses a step-down pure sine wave voltage transformation socket, which comprises an AC input module, a main control unit, an inverter bridge module and a voltage and current feedback module, and is characterized in that the AC input module is used for receiving and introducing alternating current commercial power to a rectification filtering module, and rectifying and filtering the alternating current commercial power into direct current; the main control unit controls the on-off and duty ratio of the inverter bridge module by generating a sine wave pulse width modulation (SPWM) signal, so that the inverter bridge module converts the direct current of the rectifier filter module into a pulse voltage and outputs the pulse voltage to the energy storage filter module; the inverter bridge module comprises a plurality of switching tubes, and the energy storage filtering module is used for filtering the pulse voltage into pure sine wave alternating current voltage and outputting the pure sine wave alternating current voltage through an AC terminal; the voltage and current feedback module is connected to the output end of the energy storage filtering module and used for detecting output voltage and current and transmitting feedback signals to the main control unit, and the main control unit adjusts the SPWM signals according to the feedback voltage and current signals so as to stably output sine wave voltage.

Description

TECHNICAL FIELD

[0001] The utility model relates to socket converter technical field, especially a step-down pure sine wave voltage transformer socket. BACKGROUND

[0002] With the development of globalization and the popularity of international travel, more and more people cross the border, business trip, travel or work. However, the socket and voltage standards used in different countries are different, which brings inconvenience to the use of electronic equipment. The common voltage on the market is usually divided into 110V and 220V. When electronic equipment is used between different countries, if the plug is incompatible or the voltage is not matched, not only will cause the equipment can not be charged or run normally, but also may cause equipment damage or safety accidents.

[0003] To solve the above problems, there are AC TO AC square wave (or called modified sine wave) step-down travel socket on the market, but square wave voltage cannot be used by many devices; there are also AC TO AC pure sine wave step-down travel socket, but this kind of voltage conversion socket needs to be rectified and filtered first, then use DC TO DC step-down circuit to step down, and then use inverter bridge circuit to invert into pure sine wave voltage output, and many only have 50HZ, the circuit is complex, the cost is high, and the efficiency is low.

[0004] Therefore, the present inventors propose the following technical solutions. SUMMARY

[0005] The utility model discloses a step-down pure sine wave voltage transformer socket, which overcomes the shortcomings of the prior art. The DC TO DC step-down circuit after rectification and filtering is removed, and the inverter bridge module is directly used to step down and invert into sine wave voltage output through the adjustment of duty cycle.

[0006] In order to solve the above technical problems, the utility model adopts the following technical scheme: a step-down pure sine wave voltage transformer socket, comprising: an AC input module for receiving and introducing AC mains to a rectifier filter module, rectifying and filtering AC mains into DC; further comprising a main control unit, an inverter bridge module, a voltage and current feedback module, the main control unit generates a SPWM signal of a sine wave pulse width modulation, controls the switching and duty cycle of the inverter bridge module, and makes the inverter bridge module convert the DC of the rectifier filter module into a pulse voltage and output to an energy storage filter module; the inverter bridge module includes a plurality of switching tubes, the input end thereof is connected with the rectifier filter module, the output end thereof is connected with the energy storage filter module, the input end of the energy storage filter module is connected with the inverter bridge module, for filtering the pulse voltage into a pure sine wave AC voltage and output through an AC terminal; the voltage and current feedback module is connected to the output end of the energy storage filter module, for detecting the output voltage and current and transmitting feedback signals to the main control unit, and the main control unit adjusts the SPWM signal according to the feedback voltage and current signals to stabilize the output sine wave voltage.

[0007] Further, in the above technical solution, the switching tube includes any one of a triode, a MOS tube, an IGBT, a gallium nitride MOS and a silicon carbide MOS.

[0008] Further, in the above technical solution, the inverter bridge module includes IGBT-M1, IGBT-M2, IGBT-M3 and IGBT-M4, the G pole of each IGBT is connected to a driving chip in the main control unit through a peripheral driving unit, when the main control chip of the main control unit sends a SPWM signal of a sine wave pulse width modulation, the four IGBTs are driven to work, a sine wave pulse width modulation pulse voltage waveform is generated, and after being filtered by the connected energy storage filter module, a pure sine AC voltage is output.

[0009] Further, in the above technical solution, the energy storage filter module includes an inductor L1 and a capacitor C12, which are connected between the inverter bridge module and the AC terminal, filter the sine wave pulse width modulation pulse voltage generated by the inverter bridge module into a pure sine wave AC voltage output.

[0010] Further, in the above technical solution, a DC power supply circuit is further included, the DC power supply circuit includes DC12V and DC5V, wherein the DC12V is used for power supply of the driving chip in the main control unit, and the DC5V is used for power supply of the main control chip in the main control unit.

[0011] Further, in the above technical solution, an NTC temperature detection circuit is further included, which is used for detecting the temperature on a heating device and providing a basis for device over-temperature protection.

[0012] Further, the technical scheme further comprises a touch module, which controls the opening and closing of the master control unit by outputting high and low levels, when the device is in the closed state, touching the touch switch once, the touch IC sends a high level to the master control unit, the master control unit generates a sinusoidal pulse width modulation SPWM signal output to drive the inverter bridge circuit to work, so that the output AC socket produces an alternating voltage output; touching the touch switch again, the touch IC sends a low level to the master control unit, and the master control unit closes the sinusoidal pulse width modulation SPWM signal, and the inverter bridge circuit stops working, and the output AC socket has no output voltage.

[0013] Further, the technical scheme further comprises a USB charging module.

[0014] After the technical scheme is adopted, the utility model has the following beneficial effects compared with the prior art: in the utility model, by reducing the front end DC TO DC step-down circuit, the direct step-down of DC TO AC is realized by the method of adjusting the duty cycle of the sinusoidal pulse width modulation SPWM signal of the inverter bridge module, so that the components are reduced, the cost is reduced, and the efficiency is improved. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 is the circuit diagram of the switch bridge circuit in the utility model;

[0016] Figure 2 is the circuit diagram of the master control unit in the utility model;

[0017] Figure 3 is the circuit diagram of the USB charging module in the utility model;

[0018] Figure 4 is the circuit diagram of the DC power supply circuit in the utility model;

[0019] Figure 5 is the circuit diagram of the output voltage detection module in the utility model;

[0020] Figure 6 is the circuit diagram of the output temperature detection module in the utility model. DETAILED DESCRIPTION

[0021] The utility model will be further described below in combination with specific embodiments and drawings.

[0022] See Figures 1 to 6As shown, it is a step-down pure sine wave voltage transformer socket, which comprises: AC input module 1, master unit 3, inverter bridge module 4, voltage and current feedback module 5, wherein the AC input module 1 is used to receive and introduce AC power to the rectifier filter module 2, and the AC power is rectified and filtered into DC power; the master unit 3 controls the switching and duty cycle of the inverter bridge module 4 by generating SPWM signal of sine wave pulse width modulation, so that the inverter bridge module 4 converts the DC power of the rectifier filter module 2 into pulse voltage and outputs to the energy storage filter module 6; the inverter bridge module 4 comprises a plurality of switching tubes, the input end of which is connected to the rectifier filter module 2, and the output end is connected to the energy storage filter module 6, the input end of the energy storage filter module 6 is connected to the inverter bridge module 4, which is used to filter the pulse voltage into pure sine wave AC voltage and output through the AC terminal; the voltage and current feedback module 5 is connected to the output end of the energy storage filter module 6, which is used to detect the output voltage and current and transmit the feedback signal to the master unit 3, and the master unit 3 adjusts the SPWM signal according to the feedback voltage and current signal to stabilize the output sine wave voltage. The switching tube includes but is not limited to any one of triode, MOS tube, IGBT, gallium nitride MOS and silicon carbide MOS.

[0023] The AC input is converted to DC by the rectifier filter module 2 and sent to the inverter bridge module 4. The DC is converted to AC output by the inverter bridge module 4 composed of IGBT-M1, IGBT-M2, IGBT-M3 and IGBT-M4. A group of switches is composed of IGBT-M2, IGBT-M3 and IGBT-M4. When IGBT-M2 and IGBT-M3 are working, IGBT-M1 is not working. The SPWM 20KHz driving signal sent to IGBT-M2 switch tube by the main control unit 3 drives IGBT-M2 switch to work. IGBT-M4 is turned on when IGBT-M2 is turned off to provide a freewheeling path for inductor L1. IGBT-M3 switch tube is continuously turned on. The SPWM switching waveform duty cycle increases from small to large in turn, and then decreases from large to small after increasing to the top of the sine wave. The HV DC high voltage is delivered from IGBT-M2 switch tube to the energy storage filter network composed of inductor L1 and capacitor C12. The filter network composed of inductor L1 and capacitor C12 changes the switching pulse sent by IGBT-M2 into a positive half cycle sine wave. At the same time, the negative half cycle of the sine wave is composed of IGBT-M1, IGBT-M4 and IGBT-M2 switch tubes. The SPWM 20KHz driving waveform sent by the main control unit 3 drives IGBT-M4 switch tube to work. IGBT-M3 is not working. IGBT-M2 is turned on when IGBT-M4 is turned off to provide a freewheeling path for inductor L1. IGBT-M1 switch tube is continuously turned on. The SPWM switching waveform duty cycle increases from small to large in turn, and then decreases from large to small after increasing to the top of the sine wave. The HV DC high voltage is delivered from IGBT-M1 switch tube to the energy storage filter network composed of inductor L1 and capacitor C12. The filter network composed of inductor L1 and capacitor C12 changes the switching pulse sent by IGBT-M1 into a negative half cycle sine wave. In this process, the SPWM pulse sent by the switch tube is filtered into a sine wave by the filter network composed of inductor L1 and capacitor C12.

[0024] In an embodiment, the voltage transformer socket of the step-down pure sine wave voltage includes the IGBT-M1, IGBT-M2, IGBT-M3, and IGBT-M4. The G pole of each IGBT is connected to the driving chip in the main control unit 3 through the peripheral driving unit. When the main control chip in the main control unit 3 sends the SPWM signal of the sine wave pulse width modulation, the four IGBTs are driven to work, to generate the SPWM pulse voltage waveform. After being filtered by the energy storage filter module 6 connected to the output, the pure sine wave AC voltage is output. The driving unit includes the first driving module 43 connected to the IGBT-M1 and the switching bridge control circuit 5, the second driving module 44 connected to the IGBT-M2 and the switching bridge control circuit 5, the third driving module 45 connected to the IGBT-M3 and the switching bridge control circuit 5, and the fourth driving module 46 connected to the IGBT-M4 and the switching bridge control circuit 5.

[0025] The first driving module 43 includes the resistance R3, diode D1, and resistance R9 connected in parallel to the G pole of the IGBT-M1. The resistance R3 and the other end of the diode D1 are connected to the H0-1 pin in the main control unit 3. The resistance R9 and the S pole of the IGBT-M1 are connected to the N-OUT pin of the energy storage filter module 6 and the D pole of the IGBT-M3. The D pole of the IGBT-M1 is connected to the rectifier filter module 2. The third driving module 45 has the same structure as the first driving module 43, and is connected to the L0-1 pin in the main control unit 3. The second driving module 44 includes the resistance R7 and resistance R8 connected in series between the G pole of the IGBT-M1 and the H0-2 pin in the main control unit 3, the diode D4 connected in parallel to the resistance R8, and the resistance R12 connected between the G pole of the IGBT-M1 and the VS2 pin in the main control unit 3. The D pole of the IGBT-M2 is connected to the rectifier filter module 2. The S pole of the IGBT-M2 is connected to the VS2 pin in the main control unit 3, the inductor L1 in the energy storage filter module 6, and the D pole of the IGBT-M4. The fourth driving module 46 has the same structure as the second driving module 44, and is connected to the L0-1 pin in the main control unit 3.

[0026] In an embodiment, the energy storage filter module 6 includes the inductor L1 and the capacitor C12 connected between the inverter bridge module 4 and the AC terminal, to filter the SPWM pulse voltage generated by the inverter bridge module 4 into the pure sine wave AC voltage output. The AC terminal includes the N-OUT pin connected to the IGBT-M1 and the IGBT-M3, and the L-OUT pin connected to the IGBT-M2 and the IGBT-M4. The inductor L1 of the energy storage filter module 6 is arranged between the L-OUT pin and the IGBT-M2 and the IGBT-M4. The capacitor C12 of the energy storage filter module 6 is connected between the L-OUT pin and the N-OUT pin.

[0027] In an embodiment, the step-down pure sine wave voltage transformer socket further comprises a DC power supply circuit 7, the DC power supply circuit 7 comprising a MOS tube M5 and a chip U1 connected in series between the USB charging module 10 and the main control unit 3, a capacitor C9 connected between the IN pin and the GND pin of the chip U1, a capacitor C17 connected between the OUT pin and the GND pin of the chip U1, a capacitor C19 connected between the D pole and the G pole of the MOS tube M5, a capacitor C20 and a capacitor C16 connected in parallel to the S pole and the G pole of the MOS tube M5, wherein the S pole of the MOS tube M5 is connected to the IN pin of the chip U1 and connected to a +12V voltage, the D pole of the MOS tube M5 is connected to the VCC pin of the USB charging module 10, the G pole of the MOS tube M5 is connected to the HGND pin, the GND pin of the chip U1 is connected to the HGND pin, and the OUT pin of the chip U1 is connected to AC-5V, wherein DC12V is used for power supply of the driving chip in the main control unit 3, and DC5V is used for power supply of the main control chip in the main control unit 3.

[0028] In an embodiment, the step-down pure sine wave voltage transformer socket further comprises an NTC temperature detection circuit 8 for detecting the temperature of a heating device to provide a basis for device over-temperature protection. The NTC temperature detection circuit 8 comprises a capacitor C14, a capacitor C15, a resistor R15, a resistor R17 and a resistor R18, wherein the resistor R17 is an NTC temperature detection resistor and is connected to the AC-5V pin, the resistor R15, the capacitor 14 and the resistor R18 are connected in parallel to one end of the resistor R17, the capacitor C15 is connected between the capacitor C14 and the resistor 15 and the resistor R18, and one end is connected to the TFB pin of the main control chip and the other end is connected to the HGND pin.

[0029] In an embodiment, the step-down pure sine wave voltage transformer socket further comprises a touch module 9 for controlling the opening and closing of the main control unit 3 by outputting high and low levels. When the device is in the closed state, touch the touch switch once, the touch IC sends a high level to the main control unit 3, the main control unit 3 generates a SPWM signal output of sine wave pulse width modulation to drive the inverter bridge circuit to work, so that the output AC socket produces an alternating voltage output; touch the touch switch again, the touch IC sends a low level to the main control unit 3, the main control unit 3 closes the SPWM signal of sine wave pulse width modulation, and the inverter bridge circuit stops working, so that the output AC socket has no output voltage.

[0030] In an embodiment, the voltage step-down pure sine wave voltage transformer socket further comprises a USB charging module 10. The USB charging module 10 comprises a fuse F3, a power supply master control chip U2, a transformer TI, a power supply controller U6, a synchronous step-down converter U9, a first USB unit 101, a second USB unit 102, a third USB unit 103 and a fourth USB unit 104, wherein the fuse F3 is connected to the rectification and filtering module 2, the DC power supply circuit 7 is connected to the VCC pin of the power supply master control chip U2, and the first USB unit 101 and the second USB unit 102 are both TYPE-C output interfaces.

[0031] In an embodiment, the voltage and current feedback module 5 comprises an output voltage detection module 51 connected to the energy storage and filtering module 6 and an output current detection module 52 connected to the inverter bridge module 4. The output voltage detection module 51 comprises resistors R38, R39 and R40 connected in series to the L-OUT pin and resistors R41 and a capacitor C25 connected in parallel to the resistor R40, wherein the other ends of the resistors R40, R41 and the capacitor C25 are connected to the master control unit 3. The output current detection module 52 comprises resistors R30, R31 and R32 connected in parallel to the S pole of the IGBT-M3 and the S pole of the IGBT-M4, a resistor R27, and a capacitor C24 and a resistor R25 connected in parallel to the resistor R27.

[0032] The master control unit 3 further comprises a fan control module 30, which comprises resistors R29, R35, R66, R67, an optocoupler P2, a MOS tube M6 and a fan F2, wherein the resistor R44 and the resistor R46 are connected in series to the FANCTR pin of the master control chip, one end of the resistor R46 is connected to the HGND pin, the optocoupler P2B is connected in parallel to the resistor R35; the D pole of the MOS tube M6 and the optocoupler P2A are respectively connected to two ends of the fan F2, the resistor R66 is connected between the G pole of the MOS tube M6 and the optocoupler P2A, the resistor R67 is connected to the G pole of the MOS tube M6 and grounded, and the S pole of the MOS tube M6 is grounded.

[0033] In summary, the working principle of the utility model is as follows:

[0034] In operation, the municipal alternating current is input after being prevented from surge by the fuse NTC of the AC input module 1, rectified by the DB1 bridge stack, filtered by the capacitors C5, C6 and C30, and becomes a smooth direct current voltage HV which is sent to the full-bridge DC-AC inverter circuit composed of the IGBT-M1, IGBT-M2, IGBT-M3, IGBT-M4, inductor L1 and capacitor C12;

[0035] Further, the SPMW 20KHz width modulation waveform generated by the main control unit 3 drives the four IGBTs IGBT-M1, IGBT-M2, IGBT-M3, and IGBT-M4 to work alternately;

[0036] Further, a group of switches is formed by IGBT-M2, IGBT-M3, and IGBT-M4, and the SPMW 20KHz drive signal from the main control unit 3 is sent to the IGBT-M2 switch tube to drive IGBT-M2 to work as a switch, IGBT-M3 is continuously turned on, IGBT-M1 is not turned on, and IGBT-M4 is turned on when IGBT-M2 is turned off to provide a freewheeling path for inductor L1. The duty cycle of the SPMW switch waveform increases from small to large, and then decreases from large to small after reaching the top of the sine wave. The HV DC high voltage is delivered from the IGBT-M2 switch tube to the energy storage filter network composed of inductor L1 and capacitor C12. The filter network composed of inductor L1 and capacitor C12 converts the switch pulse sent by IGBT-M2 into a positive half-cycle sine wave;

[0037] Further, the negative half-cycle of the sine wave is formed by IGBT-M1, IGBT-M4, and IGBT-M2 switch tubes, and the SPMW 20KHz drive waveform from the main control unit 3 drives IGBT-M4 switch tube to work, IGBT-M3 does not work, IGBT-M2 is turned on when IGBT-M4 is turned off to provide a freewheeling path for inductor L1, and IGBT-M1 switch tube is continuously turned on. The duty cycle of the SPMW switch waveform increases from small to large, and then decreases from large to small after reaching the top of the sine wave. The HV DC high voltage is delivered from the IGBT-M1 switch tube to the energy storage filter network composed of inductor L1 and capacitor C12. The filter network composed of inductor L1 and capacitor C12 converts the switch pulse sent by IGBT-M1 into a negative half-cycle sine wave;

[0038] Further, the filter network composed of inductor L1 and capacitor C12 smoothes the SPMW pulse sent by the switch tube into a sine wave, which is output from the L-OUT pin and the N-OUT pin;

[0039] Further, the output voltage feedback loop composed of resistors R38, R39, R40, R41, and capacitor C25 detects the size of the output voltage and sends it to the main control chip in time. The main control chip adjusts the duty cycle to adjust the output voltage according to the voltage size, so that the output voltage remains stable;

[0040] Further, the output current detection circuit composed of resistors R30, R31, R32, R27, and capacitor C24 detects the size of the output current and output short circuit, and turns off the output in time if the output current is too large or short-circuited to protect the circuit;

[0041] Further, the touch switch circuit is composed of the chip U8 and its attached circuits, and the working state of the master control chip, such as the opening output and the closing output;

[0042] Further, the fan control circuit is composed of the resistance R29, the resistance R35, the photo-coupler P2 and the MOS tube M6, when the temperature is high, the master control chip outputs a high level to drive the photo-coupler P2 to control the fan F2 to work;

[0043] Further, the temperature detection circuit is composed of the resistance R17, the resistance R18, the resistance R15 and the capacitor C14, the resistance R17 is an NTC temperature detection resistance, the resistance value decreases with the change of the temperature, when the master control chip detects that the temperature is high, a high level is outputted to drive the fan F2 to work to dissipate heat, and when the temperature exceeds the rated limit value, the circuit output is closed, and the over-temperature protection is formed;

[0044] Further, the power supply circuit of the IC1 is composed of the MOS tube M5 and the chip U1, the power supply is taken from the VCC end of the power master control chip U2 in the USB charging module 10, is stepped down into DC 12V and DC 5V, and respectively supplies power for the control circuit and the driving circuit of the master control chip;

[0045] In the above scheme, the utility model adopts the input AC voltage (110-250V) directly rectifies and filters, and is changed into 100-130V AC voltage output by the circuit composed of IGBT-M1, IGBT-M2, IGBT-M3, IGBT-M4, inductance L1 and capacitor C12 by the way of adjusting duty ratio, without needing to change the input 200-250V voltage into 100-130V AC voltage output by the circuit composed of IGBT-M1, IGBT-M2, IGBT-M3, IGBT-M4, inductance L1 and capacitor C12 after step-down, saves the step-down circuit, makes the circuit more simple, and is lower in loss.

[0046] In addition, the scheme for realizing the purpose is not limited to the single polarity adjusting circuit in the above circuit, and also includes a double polarity adjusting circuit, for example: the double polarity adjusting is that two pairs of tubes are simultaneously driven by SPWM waveforms, for example, when IGBT-M2 and IGBT-M3 work, IGBT-M2 and IGBT-M3 are driven to work by the complementary 20KHz SPWM switching waveforms, and not IGBT-M2 is driven by the 20KHz waveform, and IGBT-M3 is straight through; the inductance L1 is two inductances or is an inductance composed of two mutual inductance coils wound on the same magnetic core; and the voltage detection circuit is also two-way.

[0047] Of course, the above only the specific embodiments of the present application, not to limit the scope of the present application, all equivalent changes or modifications made in accordance with the principles of the present application described in the scope of the present application, should be included in the scope of the present application.

Claims

1. A step-down pure sine wave voltage transformer socket, comprising an AC input module (1) for receiving and introducing AC mains power to a rectifier and filter module (2) to rectify and filter the AC mains power into DC power; characterized in that: It also includes a main control unit (3), an inverter bridge module (4), and a voltage and current feedback module (5). The main control unit (3) generates a sinusoidal pulse width modulation (SPWM) signal to control the switching and duty cycle of the inverter bridge module (4), so that the inverter bridge module (4) converts the DC power of the rectifier filter module (2) into a pulse voltage and outputs it to the energy storage filter module (6). The inverter bridge module (4) includes multiple switching transistors. Its input terminal is connected to the rectifier filter module (2), and its output terminal is connected to the energy storage filter module (6). The input terminal of the energy storage filter module (6) is connected to the inverter bridge module (4) to filter the pulse voltage into a pure sine wave AC voltage and output it through the AC terminal. The voltage and current feedback module (5) is connected to the output end of the energy storage filter module (6) to detect the output voltage and current and transmit the feedback signal to the main control unit (3). The main control unit (3) adjusts the SPWM signal according to the feedback voltage and current signal to stabilize the output sinusoidal voltage.

2. The step-down pure sine wave voltage transformer socket according to claim 1, characterized in that: The switching transistor includes any one of the following: transistor, MOSFET, IGBT, gallium nitride MOSFET, and silicon carbide MOSFET.

3. The step-down pure sine wave voltage transformer socket according to claim 1, characterized in that: The inverter bridge module (4) includes IGBT-M1, IGBT-M2, IGBT-M3, and IGBT-M4. The gate of each IGBT is connected to the drive chip in the main control unit (3) through the peripheral drive unit. When the main control chip of the main control unit (3) sends out a sinusoidal pulse width modulation (SPWM) signal, it drives the four IGBTs to work and generates a sinusoidal pulse width modulation pulse voltage waveform. After being filtered by the energy storage filter module (6) connected to the output, it becomes a pure sinusoidal AC voltage output.

4. A step-down pure sine wave voltage transformer socket according to claim 3, characterized in that: The energy storage filter module (6) includes an inductor L1 and a capacitor C12, which are connected to the inverter bridge module (4) and the AC terminal to filter the sinusoidal pulse width modulation pulse voltage generated by the inverter bridge module (4) into a pure sinusoidal AC voltage output.

5. A step-down pure sine wave voltage transformer socket according to any one of claims 1-4, characterized in that: It also includes a DC power supply circuit (7), which includes DC12V and DC5V. DC12V is used to power the driver chip in the main control unit (3), and DC5V is used to power the main control chip in the main control unit (3).

6. A step-down pure sine wave voltage transformer socket according to any one of claims 1-4, characterized in that: It also includes an NTC temperature detection circuit (8) for detecting the temperature on the heating device and providing a basis for over-temperature protection of the device.

7. A step-down pure sine wave voltage transformer socket according to any one of claims 1-4, characterized in that: It also includes a touch module (9), which controls the opening and closing of the main control unit (3) by outputting high and low levels. When the device is in the off state, touching the touch switch once will cause the touch IC to send a high level to the main control unit (3), and the main control unit (3) will generate a sinusoidal pulse width modulation (SPWM) signal to drive the inverter bridge circuit to work, so that the output AC socket produces AC voltage output; touching the touch switch again will cause the touch IC to send a low level to the main control unit (3), and the main control unit (3) will turn off the sinusoidal pulse width modulation (SPWM) signal, the inverter bridge circuit will stop working, and the output AC socket will have no output voltage.

8. A step-down pure sine wave voltage transformer socket according to any one of claims 1-4, characterized in that: It also includes a USB charging module (10).

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