SWITCHING POWER SOURCE CONTROL CIRCUIT FOR DRIVING LIGHT-EMITTING ELEMENT, AND LIGHT-EMITTING DEVICE AND ELECTRONIC APPARATUS USING SAME

摘要

A current drive circuit (8) is connected to an LED terminal (LEDi) and generates an intermittent drive current (ILEDi) that corresponds to a light modulation pulse signal (PWMi). An error amplifier (22) generates a feedback voltage (VFB) that corresponds to an error between a detection voltage (VLEDi) and a predetermined reference voltage (VREF). A pulse modulator generates a pulse signal having a duty ratio that corresponds to the feedback voltage (VFB). An abnormality detection comparator (COMP_OPENi) generates an abnormality detection signal (OPEN_DET) asserted whenever the detection voltage (VLEDi) is lower than a predetermined threshold voltage (VOPEN_DET). After the operation of a switching power source (4) has been initiated, a forced switch-off circuit (80) discontinues the generation of the drive current (ILEDi) by the current drive circuit (8) for a predetermined period of time. An abnormality detection circuit (70) detects whether or not the abnormality detection signal (OPEN_DETi) has been asserted during the predetermined period of time.