PWM-controlled power supply capable of eliminating modulation-frequency signal components from ground potentials.

摘要

In a PWM control type power supply apparatus (100), a modulation (high frequency) signal component is eliminated from an AC output (V2). The PWM control type power supply apparatus (100) includes: AC-to-DC converting means (2:3) coupled to an AC (alternating current) power source (1) capable of supplying a first AC voltage (V1) having a low frequency from a pair of output terminals (L:N), for converting the first AC voltage (V1) to obtain a positive DC (direct current) voltage (E1) from a positive half cycle of the first AC voltage appearing at one output terminal (L) and a negative DC voltage (E2) from a negative half cycle of the first AC voltage appearing at one output terminal (L) with a common voltage appearing at the other output terminal (N); and, DC-to-AC inverter means (6) including a pair of first and second switching elements (61:62), and a PWM (pulse width modulation) controller (9) for controlling switching operations of the first and second switching elements (61:62) in a PWM control mode so as to invert the positive and negative DC voltage (E1:E2) into a second AC voltage (V2) having a modulation frequency higher than the low frequency with respect to the common voltage output terminal (N), whereby the second AC voltage (V2) contains no modulation frequency component.