Abstract: In a PWM control type power supply apparatus, a modulation (high frequency) signal component is eliminated not only from AC input, but also AC output.

Abstract: In a PWM control type power supply apparatus, a modulation (high frequency) signal component is eliminated from an AC output.

Abstract: In a PWM control type power supply apparatus, there are provided a single-phase full-wave rectifier coupled to a power source having a low frequency, for rectifying a first AC (alternating current) voltage to produce a DC (direct current) voltage; a DC-to-AC inverter including a first pair of switching elements connected to an input terminal thereof, and a second pair of switching elements connected to an output terminal thereof and to the first pair of switching elements to constitute a bridge inverter circuit, for inverting the DC voltage into a second AC voltage to be applied to a load; and a switching controller connected to the DC/AC inverter for alternately turning ON/OFF the second pair of switching elements in response to a sync signal (SYC) in synchronism with the first AC voltage at the low frequency of the power source, and for alternately turning ON/OFF the first pair of switching elements in response to a PWM (pulse-width modulation) control signal obtained from the first AC voltage and the secon

Abstract: A security apparatus adapted to a power converter, including a power converting circuit connected between a DC power source and an AC system; a phase detector circuit for detecting the voltage phase of the AC system to provide a phase detection signal; a reference signal generator circuit for generating a voltage reference in accordance with the phase detection signal; a control circuit for controlling an output voltage of the power converting circuit in accordance with the voltage reference. The security apparatus is characterized by a disturbance generator circuit for applying a disturbance to the phase detector circuit; and a detector circuit for detecting an abnormal state in which the phase or frequency of the output voltage of the power converting circuit deviates from a normal one.