Patent ID: 6798676
Filing Date: 2004-09-28
Classification: H02M

Abstract:
An inverter for changing direct current to alternating current, comprising:a switch circuit, providing a direct power source end to connect with a direct current power source directly, four metal oxide semiconductor-field effect transistors (MOS-FETs) and two alternating current ends; an energy storage inductor, having an end thereof being connected to one of the alternating current ends in series; a transformer, having an input end thereof being connected to another end of the energy storage inductor and having another input end thereof being connected to the other one of the alternating current ends; two diodes, corresponding to and being connected to the two alternating current ends respectively; an integrated circuit with an input end and an output ends, being composed of a plurality of resistors and capacitors and the input end thereof being connected to the diodes; a pulse width modulator with a reference potential end, a feedback end and an output end, the feedback end being connected to the output end of the integrated circuit; a wave generator, connecting with the reference potential end of the pulse width modulator and outputting a half-periodical pure sine wave, which is guided to the pulse width modulator as a reference voltage via the reference potential end, and two low frequency square waves; and a control-drive circuit, being connected to the output end of the pulse width modulator and to the wave generator and further being connected to the four transistors of the switch circuit; wherein, an output pulse width from the integrated circuit can be regulated with the pulse width modulator by way of a result obtained by way of the half-periodical pure sine wave being compared to a wave from the integrated circuit; the output pulse is synthesized with the low frequency square waves and produces two wave signals, which are a high frequency pulse width and a low frequency square wave respectively, to be sent to the four transistors in the switch circuit from the control-drive circuit with one of the signals controlling two of the transistors being in a state of close circuit in case of the half periodical sine wave being positive and the other one of the signals controlling the other two of the transistors being in a state of close circuit in case of the half periodical sine wave being negative; whereby, the direct current can be changed to alternating current via the inverter without need of any additional components for filtering high frequency current.