Patent attributes
The present invention provides a light emitting device drive circuit which does not require complicated feedback control for shortening a rising response delay time in the transition from an extinction state of a light emitting device to a light emitting state so as not to increase a bias current, and for eliminating harmful effects due to the influence of a droop phenomenon. A circuit including a series of a coil 55 and a resistor 54 is connected in parallel with an LD 53. In this configuration, the LD 53 is subjected to supply of an overshoot drive current ILD for a time period determined by a time constant of the coil 55 and the resistor 54, i.e., a time period in which a high-frequency current is supplied in the transition from the extinction state to the light emitting state. Thus, a delay in rise time until light emission of the LD 53 can be decreased. The drive current ILD supplied to the LD 53 is increased in proportion to a decrease of a forward voltage Vop supplied to the LD 53 due to temperature rise. Thus, even if the light emitting state continues for a long period of time, the intensity of light emission from the LD 53 can be kept constant.
