Patent ID: 6982689
Filing Date: 2006-01-03
Classification: H01S,H04B

Abstract:
1. A light-emitting element drive apparatus, comprising; a drive current generation circuit for outputting a drive current to a light-emitting element, the drive current causing the light-emitting element to emit light with a predetermined optical output based on a data signal; a sensing light-receiving element for receiving light from the light-emitting element and outputting a sense signal that corresponds to the optical output thereof; a first filter for smoothing the sense signal; a first comparison circuit for comparing the smoothed sense signal from the first filter and a pre-determined setup signal; a control circuit for generating, based on a comparison result of the first comparison circuit, a control signal that causes the drive current generation circuit to output the drive current such that the light-emitting element produces the predetermined optical output; a setup signal generation circuit that waveform-shapes the setup signal so that the setup signal has the same ripple component as the smoothed sense signal, and outputs the waveform shaped setup signal to the first comparison circuit in synchronization with the smoothed sense signal; a level adjustment circuit for receiving the setup signal from the setup signal generation circuit and attenuating the setup signal to a pre-determined level to generate a light-emitting element degradation setup signal; and a second comparison circuit for comparing the light-emitting element degradation setup signal and the smoothed sense signal from the first filter to determine whether the light-emitting element has degraded.