DRIVE CIRCUIT FOR OPTICAL ELEMENT AND LIGHT EMITTING DEVICE AND ELECTRONIC DEVICE USING SAME

摘要

A detection resistor (R1) is provided in the path of an LED string (6). A controller (10) generates a gate pulse signal (G1) for which the duty ratio is adjusted such that the voltage drop (VR1) for the detection resister (R1) is the same as a prescribed reference voltage (VREF). In addition, the controller (10) receives a dimming control signal (PWMDIM) that dictates a burst dimming duty ratio and generates a burst dimming pulse (G2) according to this burst dimming duty ratio. A first driver (DR1) drives an output circuit (102) that generates a drive voltage (VDRV) based on the gate pulse signal (G1). A second driver (DR2) switches between connecting and disconnecting a drive current (IDRV) based on the burst dimming pulse (G2). A duty ratio detecting unit (30) controls the frequency of the gate pulse signal (G1) according to the duty ratio (a) dictated by the dimming control signal (PWMDIM).