Regulated power source circuit and regulated power source device

Abstract

In the regulated power supply circuit, an overcurrent detection circuit detects the flow of an overcurrent through a transistor acting as an output control element and supplies a result of the detection to a cut-off operation prohibition circuit. During non-startup time of the regulated power supply circuit, the cut-off operation prohibition circuit simply relays a result of the overcurrent detection circuit detecting an overcurrent to a cut-off circuit without introducing any changes to the result. The cut-off circuit increases a base potential of the transistor according to the result of the detection of an overcurrent to cut off the output of the transistor. It is ensured that the output voltage rises even if the overcurrent detection circuit has activated the cut-off circuit upon detection of the overcurrent temporarily passing through the transistor during a startup. Therefore, the cut-off operation prohibition circuit prohibits the cut-off circuit from performing the cut-off operation from the outset to the end of the startup. Hence, a regulated power supply circuit can be provided which, even if an overcurrent is detected, develops no loss in the transistor during non-startup time.

Dependencies are inferred from the claim text.