Importance

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Abstract

A failure detection system detects a failure in a by-pass switch of a power converter. The by-pass switch switches the electric power supply so that electric power is supplied from a standby power source to a load instead of from a power converter. A switch operation circuit turns the by-pass switch on and off. A first current detector detects the inverted output current of the power converter. A second current detector detects the load current flowing through the load. An operational amplifier adds the outputs of the first and second current detectors. A comparator detects a failure of the by-pass switch. If the addition result given by the operational amplifier is outside a predetermined range of values when the switch operation circuit is turned off, the comparator concludes that the by-pass switch has a failure. In this failure detection system, it is possible to detect a failure of the by-pass switch used to transfer the electric power to the load from the standby power source instead of from the power converter, without having to detect the current flowing through the by-pass switch. Thus, it is possible to reduce the size and the cost of the system.

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First Claim