Patent ID: 9705394
Date: 2017-07-11
CPC Classifications: H02M,H03K

Claim:
1. An overcurrent protection power supply apparatus having a power supply circuit that supplies electric power from a DC power source to a load via a FET and a control circuit that controls the FET, the overcurrent protection power supply apparatus protecting the power supply circuit from overcurrents by turning off the FET, the apparatus comprising: a drain-source voltage detecting circuit configured to detect a drain-source voltage between a drain and a source of the FET generated by a drain current flowing through the FET, a malfunction preventing circuit configured to initiate a detecting operation of the drain-source voltage detecting circuit when the FET is turned on and after the drain-source voltage increases in accordance with an increase of the drain current of the FET, a first overcurrent protection signal generating circuit configured to generate and output a first overcurrent protection signal based on the drain-source voltage, and a second overcurrent protection signal generating circuit configured to generate and output a second overcurrent protection signal when a rate of increase of the drain-source voltage exceeds an excessive rate-of-increase threshold, wherein the control circuit is configured to turn off the FET when at least one of the following conditions is met: (i) the first overcurrent protection signal is output from the first overcurrent protection signal generating circuit or (ii) the second overcurrent protection signal is output from the second overcurrent protection signal generating circuit, and the second overcurrent protection signal generating circuit is configured to measure a time interval from when the drain-source voltage becomes larger than a first threshold value until when the drain-source voltage becomes larger than a third threshold value, which is larger than the first threshold value, and to set, based upon the measured time interval, a reference time interval that is longer than the measured time interval.