Step-down pure sine wave voltage transformation socket

Abstract

The invention 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 MOS (Metal Oxide Semiconductor) 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 (Alternating Current) 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 invention relates to the technical field of socket converters, in particular to a step-down pure sine wave voltage transformer socket. Background technology:

[0002] With the development of globalization and the popularity of international travel, more and more people are traveling across borders for business, travel or work. However, the sockets and voltage standards used in countries around the world are different, which brings inconvenience to the use of electronic devices. Currently, the common voltages on the market are usually divided into 110V and 220V. When electronic devices are used in different countries, if the plugs are incompatible or the voltages do not match, not only will the device not be able to charge or operate normally, but it may even cause device damage or safety accidents.

[0003] In order to solve the above problems, there are AC TO AC square wave (or modified sine wave) step-down travel power strips on the market, but many devices cannot use square wave voltage; there are also AC TO AC pure sine wave step-down travel power strips, but this type of voltage conversion socket needs to first rectify and filter the AC power, then use a DC TO DC step-down circuit to step down the voltage, and then use an inverter bridge circuit to invert it into a pure sine wave voltage output, and many of them are only 50HZ, the circuit is complex, the cost is high, and the efficiency is low.

[0004] In view of this, the inventor proposes the following technical solution. Summary of the invention:

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a step-down pure sine wave voltage transformer socket. The present invention removes the DC TO DC step-down circuit after rectification and filtering, and directly steps down the voltage through the inverter bridge module and inverts it into a sine wave voltage output by adjusting the duty cycle.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions: a step-down pure sine wave voltage transformer socket, comprising: an AC input module, used to receive and introduce AC mains power to a rectifier and filter module, rectify and filter the AC mains power into DC power; also comprising a main control unit, an inverter bridge module, and a voltage and current feedback module, wherein the main control unit controls the switch and duty cycle of the inverter bridge module by generating a sine wave pulse width modulated SPWM signal, so that the inverter bridge module converts the DC power of the rectifier and filter module into a pulse voltage and outputs it to an energy storage filter module; the inverter bridge module comprises a plurality of MOS tubes, the input end of which is connected to the rectifier and filter module, and the output end of which is connected to the energy storage filter module, the input end of the energy storage filter module is connected to the inverter bridge module, and is used to filter the pulse voltage into a pure sine wave AC voltage, and output it through an AC terminal; the voltage and current feedback module is connected to the output end of the energy storage filter module, and is used to detect the output voltage and current, and transmit the feedback signal to the main control unit, and the main control unit adjusts the SPWM signal according to the feedback voltage and current signals to stably output the sine wave voltage.

[0007] Furthermore, in the above technical solution, the inverter bridge module includes MOS tube M1, MOS tube M2, MOS tube M3, and MOS tube M4. The G pole of each MOS tube is connected to the driving chip in the main control unit through an external driving unit. When the main control chip of the main control unit sends a sinusoidal pulse width modulated SPWM signal, the four MOS tubes are driven to work, generating a sinusoidal pulse width modulated pulse voltage waveform, which is filtered by the energy storage filter module connected to the output to output a pure sinusoidal AC voltage output.

[0008] Furthermore, in the above technical solution, the energy storage filter module includes an inductor L1 and a capacitor C12, which are connected to the inverter bridge module and the AC terminal to filter the sinusoidal pulse width modulated pulse voltage generated by the inverter bridge module into a pure sinusoidal AC voltage output.

[0009] Furthermore, the above technical solution also includes a DC power supply circuit, which includes DC12V and DC5V, wherein DC12V is used to power the driver chip in the main control unit, and DC5V is used to power the main control chip in the main control unit.

[0010] Furthermore, the above technical solution also includes an NTC temperature detection circuit for detecting the temperature of the heating device to provide a basis for over-temperature protection of the device.

[0011] Furthermore, the above technical solution also includes a touch module, which controls the on and off of the main control unit by outputting high and low levels. When the device is in the off state, touch the touch switch, the touch IC sends a high level to the main control unit, and the main control unit generates a sinusoidal pulse width modulated SPWM signal output to drive the inverter bridge circuit to work, so that the output AC socket produces an AC voltage output; touch the touch switch again, the touch module IC sends a low level to the main control unit, the main control unit turns off the sinusoidal pulse width modulated SPWM signal, the inverter bridge circuit stops working, and the output AC socket has no output voltage.

[0012] Furthermore, the above technical solution also includes a USB charging module.

[0013] After adopting the above technical scheme, the present invention has the following beneficial effects compared with the prior art: in the present invention, by reducing the front-end DC TO DC buck circuit, the inverter bridge module controls the duty cycle by adjusting the SPWM signal of the sinusoidal pulse width modulation to achieve direct DC TO AC buck, thereby reducing components, reducing costs and improving efficiency. Description of the drawings:

[0014] Figure 1 is a circuit diagram of a switch bridge circuit in the present invention;

[0015] Figure 2 is a circuit diagram of the main control unit in the present invention;

[0016] Figure 3 is a circuit diagram of the USB charging module in the present invention;

[0017] Figure 4 is a circuit diagram of a DC power supply circuit in the present invention;

[0018] Figure 5 is a circuit diagram of an output voltage detection module in the present invention;

[0019] Figure 6 It is a circuit diagram of the output temperature detection module in the present invention. Specific implementation method:

[0020] The present invention is further described below in conjunction with specific embodiments and drawings.

[0021] See Figures 1 to 6As shown, a step-down pure sine wave voltage transformer socket includes: an AC input module 1, a main control unit 3, an inverter bridge module 4, and a voltage and current feedback module 5, wherein the AC input module 1 is used to receive and introduce AC mains power to the rectifier and filter module 2, and rectify and filter the AC mains power into DC power; the main control unit 3 controls the switch and duty cycle of the inverter bridge module 4 by generating a sine wave pulse width modulated SPWM signal, so that the inverter bridge module 4 converts the DC power of the rectifier and filter module 2 into a pulse voltage and outputs it to the energy storage filter module 6; the inverter The bridge module 4 includes a plurality of MOS tubes, an input end of which is connected to the rectifier filter module 2, and an output end of which 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, and is used to filter the pulse voltage into a pure sinusoidal 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, and is used 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 signals to stabilize the output sinusoidal voltage.

[0022] The rectifier filter module 2 is used to convert the AC input into DC and send it to the inverter bridge module 4. The inverter bridge module 4 composed of MOS tubes M1, MOS tubes M2, MOS tubes M3, and MOS tubes M4 converts DC into AC output. The MOS tubes M2, M3, and M4 form a group of switches. When the MOS tubes M2 and M3 are working, the MOS tube M1 is not working. The SPWM 20KHz drive signal adjusted by the main control unit 3 is sent to the MOS tube M2 switch tube to drive the MOS tube M2 switch to work. When the MOS tube M2 is closed, the MOS tube M4 is turned on as an inductor. L1 provides a freewheeling channel, and the MOS tube M3 switch tube is continuously turned on. The duty cycle of the SPWM switch waveform increases from small to large, and after increasing to the top of the sine wave, it decreases from large to small. The HV DC high voltage is transmitted by the MOS tube M2 switch tube to the energy storage filter network composed of the inductor L1 and the capacitor C12. The filter network composed of the inductor L1 and the capacitor C12 converts the switch pulse sent by the MOS tube M2 into a sine wave waveform of the positive half cycle; at the same time, the negative half cycle of the sine wave is composed of the MOS tube M1, the MOS tube M4 and the MOS tube M2 switch tubes, and the SPWM widened by the main control unit 3 The 20KHz driving waveform drives the MOS tube M4 switch tube to work, and the MOS tube M3 does not work. The MOS tube M2 is turned on when the MOS tube M4 is turned off to provide a freewheeling channel for the inductor L1. The MOS tube M1 switch tube is continuously turned on. The duty cycle of the SPWM switch waveform increases from small to large, and after increasing to the top of the sine wave, it decreases from large to small. The HV DC high voltage is transmitted by the MOS tube M1 switch tube to the energy storage filter network composed of the inductor L1 and the capacitor C12. The filter network composed of the inductor L1 and the capacitor C12 converts the switch pulse sent by the MOS tube M1 into a negative half-cycle sine wave waveform. In this process, the filter network composed of the inductor L1 and the capacitor C12 is used to filter the SPWM pulse sent by the switch tube into a sine wave.

[0023] In one embodiment, the inverter bridge module 4 of the step-down pure sine wave voltage transformer socket includes MOS tube M1, MOS tube M2, MOS tube M3, and MOS tube M4. The G pole of each MOS tube is connected to the driving chip in the main control unit 3 through an external driving unit. When the main control chip of the main control unit 3 sends a sine wave pulse width modulated SPWM signal, it drives the four MOS tubes to work, generates a sine wave pulse width modulated pulse voltage waveform, and is filtered by the energy storage filter module 6 connected to the output to become a pure sine AC voltage output. The driving unit includes a first driving module 43 connecting the MOS tube M1 and the switch bridge control circuit 5, a second driving module 44 connecting the MOS tube M2 and the switch bridge control circuit 5, a third driving module 45 connecting the MOS tube M3 and the switch bridge control circuit 5, and a fourth driving module 46 connecting the MOS tube M4 and the switch bridge control circuit 5.

[0024] The first driving module 43 includes a resistor R3, a diode D1 and a resistor R9 connected in parallel to the G pole of the MOS tube M1, wherein the other ends of the resistor R3 and the diode D1 are connected to the H0-1 pin of the main control unit 3, the resistor R9 and the S pole of the MOS tube M1 are connected to the N-OUT pin of the energy storage filter module 6 and the D pole of the MOS tube M3, and the D pole of the MOS tube 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 the third driving module 45 is connected to the L0-1 pin of the main control unit 3; the second driving module 44 includes a resistor R3 connected in series to the G pole of the MOS tube M1, wherein the other ends of the resistor R3 and the diode D1 are connected to the H0-1 pin of the main control unit 3, the resistor R9 and the S pole of the MOS tube M1 are connected to the N-OUT pin of the energy storage filter module 6 and the D pole of the MOS tube M3, and the D pole of the MOS tube 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 the third driving module 45 is connected to the L0-1 pin of the main control unit 3; Resistors R7 and R8 between the G pole in the MOS tube M1 and the H0-2 pin in the main control unit 3, a diode D4 connected in parallel to the resistor R8, and a resistor R12 connected between the G pole in the MOS tube M1 and the VS2 pin in the main control unit 3, wherein the D pole of the MOS tube M2 is connected to the rectifier filter module 2, the S pole of the MOS tube M2 is connected to the VS2 pin in the main control unit 3 and the inductor L1 in the energy storage filter module 6 and the D pole of the MOS tube M4, the fourth driving module 46 has the same structure as the second driving module 44, and the fourth driving module 46 is connected to the L0-1 pin in the main control unit 3.

[0025] In one embodiment, 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, and filter the sinusoidal pulse width modulated pulse voltage generated by the inverter bridge module 4 into a pure sinusoidal AC voltage output. The AC terminal includes an N-OUT pin connected to the MOS tube M1 and the MOS tube M3 and an L-OUT pin connected to the MOS tube M2 and the MOS tube M4, wherein the inductor L1 of the energy storage filter module 6 is arranged between the L-OUT pin and the MOS tube M2 and the MOS tube M4, and the capacitor C12 of the energy storage filter module 6 is connected between the L-OUT pin and the N-OUT pin.

[0026] In one embodiment, the step-down pure sine wave voltage transformer socket further includes a DC power supply circuit 7, which includes a MOS tube M5 and a chip U1 connected in series with the USB charging module 10 and the main control unit 3, a capacitor C9 connected between the IN pin and the GND pin in the chip U1, a capacitor C17 connected between the OUT pin and the GND pin in the chip U1, a capacitor C19 connected between the D pole and the G pole in the MOS tube M5, and a capacitor C20 and a capacitor C16 connected in parallel on the S pole and the G pole in 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 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.

[0027] In one embodiment, the step-down pure sine wave voltage transformer socket also includes an NTC temperature detection circuit 8, which is used to detect the temperature of the heating device and provide a basis for the over-temperature protection of the device. The NTC temperature detection circuit 8 includes 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.

[0028] In one embodiment, the step-down pure sine wave voltage transformer socket also includes a touch module 9, which controls the on and off of the main control unit 3 by outputting high and low levels. When the device is in the off state, touch the touch switch, the touch IC sends a high level to the main control unit 3, and the main control unit 3 generates a sine wave pulse width modulated SPWM signal output to drive the inverter bridge circuit to work, so that the output AC socket produces an AC 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 turns off the sine wave pulse width modulated SPWM signal, the inverter bridge circuit stops working, and the output AC socket has no output voltage.

[0029] In one embodiment, the step-down pure sine wave voltage transformer socket further includes a USB charging module 10. The USB charging module 10 includes a fuse F3, a power main control chip U2, a transformer TI, a power 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 rectifier filter module 2, the DC power supply circuit 7 is connected to the VCC pin of the power main control chip U2, and the first USB unit 101 and the second USB unit 102 are both TYPE-C output interfaces.

[0030] In one embodiment, the voltage and current feedback module 5 includes an output voltage detection module 51 connected to the energy storage filter module 6 and an output current detection module 52 connected to the inverter bridge module 4. The output voltage detection module 51 includes a resistor R38, a resistor R39, and a resistor R40 connected in series to the L-OUT pin, and a resistor R41 and a capacitor C25 connected in parallel to the resistor R40, wherein the other ends of the resistor R40, the resistor R41 and the capacitor C25 are connected to the main control unit 3. The output current detection module 52 includes a resistor R30, a resistor R31, a resistor R32, a resistor R27 connected in parallel to the S pole of the MOS tube M3 and the S pole of the MOS tube M4, and a capacitor 24 and a resistor R25 connected in parallel to the resistor R27.

[0031] The main control unit 3 also includes a fan control module 30, which includes a resistor R29, a resistor R35, a resistor R66, a resistor R67, an optical coupler 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 main control chip, one end of the resistor R46 is connected to the HGND pin, and the optical coupler P2B is connected in parallel to the resistor R35; the D pole of the MOS tube and the optical coupler P2A are respectively connected to the two ends of the fan F2, the resistor R66 is connected between the G pole of the MOS tube M6 and the optical coupler 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.

[0032] In summary, the working principle of the present invention is as follows:

[0033] When working, the municipal AC power is input after the surge protection of the fuse NTC of the AC input module 1, rectified by the DB1 bridge stack, filtered by capacitors C5, C6 and C30, and then becomes a smooth DC voltage HV and sent to the full-bridge DC-AC inverter circuit composed of MOS tubes M1, M2, M3, M4, inductor L1 and capacitor C12;

[0034] Further, the main control unit 3 generates a 20KHz SPMW width modulation waveform to drive the four MOS tubes M1, M2, M3 and M4 to work alternately;

[0035] Further, a group of switches is formed by the MOS tube M2, the MOS tube M3 and the MOS tube M4. The SPWM 20KHz drive signal adjusted by the main control unit 3 is sent to the MOS tube M2 switch tube to drive the MOS tube M2 to perform switching operation. The MOS tube M3 switch tube is continuously turned on, and the MOS tube M1 is not turned on. When the MOS tube M2 is turned off, the MOS tube M4 is turned on to provide a freewheeling channel for the inductor L1. The duty cycle of the SPWM switch waveform increases from small to large, and after increasing to the top of the sine wave, it decreases from large to small. The HV DC high voltage is transmitted by the MOS tube M2 switch tube to the energy storage filter network composed of the inductor L1 and the capacitor C12. The filter network composed of the inductor L1 and the capacitor C12 converts the switch pulse sent by the MOS tube M2 into a sine wave waveform of a positive half cycle.

[0036] Furthermore, the negative half cycle of the sine wave formed by the MOS tube M1, the MOS tube M4 and the MOS tube M2 switch tubes is driven by the SPWM 20KHz driving waveform adjusted by the main control unit 3 to work, and the MOS tube M3 is not working. When the MOS tube M4 is turned off, the MOS tube M2 is turned on to provide a freewheeling channel for the inductor L1, and the MOS tube M1 switch tube is continuously turned on. The duty cycle of the SPWM switch waveform increases from small to large, and after increasing to the top of the sine wave, it decreases from large to small, and the HV DC high voltage is transmitted by the MOS tube M1 switch tube to the energy storage filter network composed of the inductor L1 and the capacitor C12. The filter network composed of the inductor L1 and the capacitor C12 converts the switch pulse sent by the MOS tube M1 into a sine wave waveform of the negative half cycle;

[0037] Furthermore, the inductor L1 and the capacitor C12 form a filter network to smooth the SPWM pulse sent by the switch tube into a sine wave, which is output from the L-OUT pin and the N-OUT pin;

[0038] Furthermore, the output voltage feedback loop composed of resistor R38, resistor R39, resistor R40, resistor R41, and capacitor C25 detects the magnitude of the output voltage and sends it to the main control chip in time, and the main control chip adjusts the output voltage by adjusting the duty cycle according to the voltage magnitude to keep the output voltage stable;

[0039] Furthermore, the output current detection circuit is composed of resistor R30, resistor R31, resistor R32, resistor R27, and capacitor C24 to detect the output current and output short circuit. If the output current is too large or short circuited, the output is shut down in time to protect the circuit safety.

[0040] Furthermore, the touch switch circuit is composed of chip U8 and its auxiliary circuits, which controls the working state of the main chip, such as turning on and off the output;

[0041] Furthermore, a fan control circuit is formed by resistor R29, resistor R35, optocoupler P2, and MOS tube M6. When the temperature is high, the main control chip outputs a high level to drive the optocoupler P2 to control the fan F2 to work;

[0042] Furthermore, a temperature detection circuit is formed by resistors R17, R18, R15, and C14. Resistor R17 is an NTC temperature detection resistor, and its resistance value decreases with the change of temperature. When the main control chip detects that the temperature is high, it outputs a high level to drive the fan F2 to work and dissipate heat. When the temperature exceeds the rated limit, the circuit output is turned off to form an over-temperature protection.

[0043] Furthermore, the power supply circuit of IC1 is composed of MOS tube M5 and chip U1. The power supply is taken from the VCC terminal of the power main control chip U2 in the USB charging module 10, and the voltage is stepped down to DC12V and DC5V, which are used to supply power to the control circuit and the drive circuit of the main control chip respectively.

[0044] In the above scheme, the present invention directly rectifies and filters the input AC voltage (110-250V), and then converts it into an AC voltage output of 100-130V by adjusting the duty cycle through a circuit composed of MOS tube M1, MOS tube M2, MOS tube M3, MOS tube M4, inductor L1, and capacitor C12, without first reducing the input voltage of 200-250V and then converting it into an AC voltage output of 100-130V by a circuit composed of MOS tube M1, MOS tube M2, MOS tube M3, MOS tube M4, inductor L1, and capacitor C12, thereby eliminating the step-down circuit, making the circuit simpler and reducing the loss.

[0045] In addition, the solution to achieve this purpose is not limited to the unipolar regulation circuit in the above circuit, but also includes a bipolar regulation circuit. For example, the bipolar regulation is that two pairs of tubes are driven by the SPWM waveform at the same time. For example, when the MOS tube M2 and the MOS tube M3 are working, the MOS tube M2 and the MOS tube M3 are driven by the complementary 20KHz SPWM switch waveform, and the MOS tube M2 is not driven by the 20KHz waveform and the MOS tube M3 is directly passed; the inductor L1 is two inductors or an inductor composed of two coils with mutual inductance wound on the same magnetic core; the voltage detection circuit is also two-way.

[0046] Of course, the above description is only a specific embodiment of the present invention and is not intended to limit the scope of implementation of the present invention. All equivalent changes or modifications made according to the structure, characteristics and principles described in the patent application scope of the present invention should be included in the patent application scope of the present invention.

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) for rectifying and filtering 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 sine wave pulse width modulated SPWM signal to control the switch and duty cycle of the inverter bridge module (4), so that the inverter bridge module (4) converts the direct current 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) comprises a plurality of MOS tubes, an input end of which is connected to the rectifier filter module (2), and an output end of which 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) and is used for filtering the pulse voltage into a pure sinusoidal AC voltage and outputting it through an AC terminal; The voltage and current feedback module (5) is connected to the output end of the energy storage filter module (6) and is used 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 signals to stabilize the output sinusoidal wave voltage.

2. A step-down pure sine wave voltage transformer socket according to claim 1, characterized in that: The inverter bridge module (4) comprises a MOS tube M1, a MOS tube M2, a MOS tube M3 and a MOS tube M4. The G pole of each MOS tube is connected to a drive chip in the main control unit (3) through an external drive unit. When the main control chip of the main control unit (3) sends a sinusoidal pulse width modulated SPWM signal, the four MOS tubes are driven to work, thereby generating a sinusoidal pulse width modulated pulse voltage waveform, which is filtered by an energy storage filter module (6) connected to the output to be output as a pure sinusoidal AC voltage.

3. The step-down pure sine wave voltage transformer socket according to claim 1, characterized in that: The energy storage filter module (6) comprises an inductor L1 and a capacitor C12, which is connected to the inverter bridge module (4) and the AC terminal, and filters the sinusoidal pulse width modulated pulse voltage generated by the inverter bridge module (4) into a pure sinusoidal AC voltage output.

4. The step-down pure sine wave voltage transformer socket according to claim 2, characterized in that: It also includes a DC power supply circuit (7), which includes DC12V and DC5V, wherein 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).

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

6. The step-down pure sine wave voltage transformer socket according to claim 1, characterized in that: The device also includes a touch module (9), which controls the on and off of the main control unit (3) by outputting high and low levels. When the device is in the off state, the touch switch is touched, and the touch IC sends a high level to the main control unit (3). The main control unit (3) generates a sine wave pulse width modulated SPWM signal output to drive the inverter bridge circuit to work, so that the output AC socket produces an AC voltage output; When the touch switch is touched again, the touch IC sends a low level to the main control unit (3), and the main control unit (3) turns off the SPWM signal of the sine wave pulse width modulation, the inverter bridge circuit stops working, and the output AC socket has no output voltage.

7. The step-down pure sine wave voltage transformer socket according to claim 1, characterized in that: Also included is a USB charging module (10).

Images