Patent ID: 6292284
Filing Date: 2001-09-18
Classification: H04B

Abstract:
A light emitting element driving apparatus, comprising:a driving unit driving a light emitting element by means of a driving signal while performing automatic light power control, said light emitting element being capable of converting an input electric signal containing data information into an optical signal;a reference voltage generation unit generating a reference voltage from said input electric signal, said reference voltage being used obtaining a light output comprising a specified power from said light emitting element in a normal condition;a monitoring voltage generation unit generating a monitoring voltage signal corresponding to power of an optical signal outputted from said light emitting element;a light power control unit comparing said reference voltage from said reference voltage generation unit with said monitoring voltage signal from said monitoring voltage generation unit and controlling, based on a result of said comparison, said driving unit by a discrete control amount such that a light output from said light emitting element can have said specified power; andan initial value setting unit setting a raising component as an initial value in a control signal comprising said discrete control amount supplied from said light power control unit to said driving unit, whereinsaid light power control unit comprises a comparison unit comparing said reference voltage from said reference voltage generation unit with said monitoring voltage signal from said monitoring voltage generation unit, an up-and-down counter circuit performing up-counting/down-counting for a result of comparison from said comparison unit in synchronization with a counting clock, and a digital/analog conversion unit converting into an analog amount a count value obtained by up-counting/down-counting performed in said up-and-down counter circuit and outputting said analog amount as a control signal comprising said discrete control amount, andsaid initial value setting unit corn a voltage generation unit generating a voltage signal to be used as said preset initial value and an analog/digital conversion unit converting said voltage signal generated in said voltage generation unit into a digital signal, and presets said digital signal from said analog/digital conversion unit in said up-and-down counter circuit of said light power control unit.