Voltage converter without electrolytic capacitor

A voltage converter, comprising:

• a high-frequency modulation unit comprising a first switching tube and a second switching tube, the drain of the first switching tube connected to a DC voltage, the source of the first switching tube connected to the drain of the second switching tube, and the source of the second switching tube earthed, the grids of the first and second switching tubes respectively connected to two-path anti-phased PWM pulse signals;
• an inductance filtering unit comprising a filtering inductor, the front end of the filtering inductor connected to the source of the first switching tube, wherein when the first switching tube is on-switched and the second switching tube is off-switched, a DC voltage from the drain of the first switching tube is transmitted to the back end of the filter inductor;
• when the first switching tube is off-switched and the second switching tube is on-switched, an electromotive force generated from the back end of the filtering inductor is released from the second switch tube to the front end of the filter inductor, and the voltage of the back end of the filter inductor is reduced to a preset value by adjusting a duty ratio of the two-path PWM pulse signals respectively loaded on the grids of the first and second switching tubes;
• and wherein
• an inverting paraphrase unit, with its input terminal connected to the back end of the filtering inductor, is configured for invertedly converting a half-wave pulse voltage outputted from the back end of the filtering inductor to a sine AC voltage;
• an AC input unit used to connect to a mains voltage;
• a rectifying and filtering unit, with the input terminal of the rectifying and filtering unit connected to the output terminal of the AC input unit and the output terminal of the rectifying and filtering unit connected to the drain of the first switching tube, configured for rectifying and filtering the mains voltage and then forming the DC voltage to load into the drain of the first switching tube;
• an MCU controlling unit connected to all the grid of the first switching tube, the grid of the second switching tube and a control terminal of the inverting paraphrase unit, and configured for outputting the two-path anti-phased PWM pulse signals and controlling a conversion frequency of the inverting paraphrase unit;
• an AC sampling unit, with the input terminal of the AC sampling unit connected to the AC input unit and the output terminal of the AC sampling unit connected to the MCU controlling unit, configured for collecting a voltage value and a phase of the mains voltage and then transmitting to the MCU controlling unit;
• and wherein the MCU controlling unit is configured for:
• determining whether the mains voltage exceeding a preset value according to the voltage value collected by the AC sampling unit;
• if the preset value is exceeded, the two-path anti-phased PWM pulse signals are respectively loaded to the grid of the first switching tube and the grid of the second switching tube;
• if the preset value isn't exceeded, the first switching tube is maintained to on-switched situation;
• and
• controlling the conversion frequency of the inverting paraphrase unit according to the phase of the mains voltage collected by the AC sampling unit in order to the inverting paraphrase unit output the same sine AC voltage as the phase of the mains voltage.