SWITCHING POWER SUPPLY DEVICE

PURPOSE:To supply a load device with the signals of arbitrary wave shape and frequency with high power efficiency by providing a switch means selecting first adn second states, in which either one of reference potential is output in response to outputs from two comparators, and a third state generating no output. CONSTITUTION:Triangular waves generated by an inclined wave generator 38 are input to the non-inverting input terminal of a comparator 34 and the inverting input terminal of a comparator 36. Sine waves generated from an arbitrary waveform generator 10 are input to variable offset circuits 30 and 32, and positive offset is applied. The output waveforms of the variable offset circuits 30 and 32 are input to the inverting input terminals and non-inverting input terminals of the comparator 34 and 36. The individual FETs 42 and 44 are in conduction with positive gate voltage and are cutoff with negative gate voltage. Accordingly, a waveform at a node 50 is formed in a waveform having a first state, in which voltage +V is output, a second state, in which voltage -V is output, and a third state outputting no voltage.