Patent ID: 6208541
Filing Date: 2001-03-27
Classification: H02M,Y02B

Abstract:
A PWM inverter apparatus including a first and second current control type semiconductor switching elements connected in series and connected in parallel with a DC power supply, diodes being respectively connected in parallel with respective ones of said first and second semiconductor switching elements with polarity opposite to that of said DC power supply, a line connecting said first and second semiconductor switching elements being connected to an output circuit, an output being generated by alternately switching said first and second semiconductor switching elements, said PWM inverter apparatus comprising:resistive semiconductor switching elements having a higher switching speed than said first and second semiconductor switching elements and a resistance-to-current characteristics producing voltage drop, said resistive semiconductor switching elements being respectively connected in parallel to respective ones of said first and second semiconductor switching elementswherein in a half cycle of an alternating output current, while said output current is higher than a predetermined rate with respect to a peak current, a switching timing is controlled to produce a switching control signal to said resistive semiconductor switching elements in advance of a switching control signal to said first and second semiconductor switching elements, said switching control signal to said resistive semiconductor switching elements being terminated at a time when a predetermined period passes after said switching control signal to said first and second semiconductor switching elements has been terminated, andin the half cycle of the alternating output current, while said output current is lower than the predetermined rate with respect to the peak current, said switching timing is controlled to generate the output by the switching operation only of said resistive semiconductor switching elements.