Abstract: A switching power supply apparatus which effectively utilizes energy accumulated in a leak inductance of a circuit to enhance the efficiency. The switching power supply apparatus having a switch element on/off controlled by a driving signal generated from a driver circuit, wherein a first capacitor and a first diode are inserted in series between both terminals of the switch , and a second capacitor and a second diode are further connected in series between a connecting point of the first capacitor and the first diode and a grounding terminal of the switch element to use charges accumulated on the second capacitor as a voltage source.

Abstract: An inverter for DC/AC conversion includes an inverter bridge controlled by a PWM controller. The inverter has a first control loop for performing PWM control in accordance with the difference between the instantaneous AC value of an inverter output and an amplitude of waveform data read out from an AC waveform memory. The inverter also has a second control loop for multiplying the amplitude value of the waveform data by a coefficient adjusted on the basis of the error between the means AC current or voltage value of the inverter outputs and a target control value, and performing PWM control in accordance with waveform data having the adjusted amplitude. By using a delta scheme of finely increasing/decreasing at a time the coefficient by which waveform data is multiplied, an inverter with a high control precision and high stability can be obtained.