DC/DC CONVERTER CONTROL CIRCUIT, AND POWER SUPPLY APPARATUS, LIGHT EMITTING APPARATUS AND ELECTRONIC DEVICE USING THE SAME

摘要

An externally exited DC/DC converter control circuit wherein the output voltage is directly monitored to detect a short-circuit state and perform an overcurrent protection. A switching control part (10) of a control circuit (100) controls the switching operation of a switching transistor (Tr1) of an externally exited DC/DC converter (210). A voltage comparator (30) compares an output voltage (Vout) with a threshold voltage (Vth) to detect a short-circuit state. When the voltage comparator (30) detects a short-circuit state after an lapse of a predetermined activation time period of the externally exited DC/DC converter starting from the beginning of the activation thereof, the switching control part (10) halts the switching operation of the switching transistor (Tr1). On the other hand, before the lapse of the activation time period, the switching control part (10) nullifies the short-circuit state detection of the voltage comparator (30). After halting the switching operation of the switching transistor (Tr1) for a predetermined halt time period starting from the detection of the short-circuit state, the switching control part (10) resumes the activation of the externally exited DC/DC converter.