Patent ID: 7359649

Claim:
An infrared transmitter circuit, comprising: a light emission element; and a driving circuit which outputs a driving current, being constant, which causes the light emission element to emit light on the basis of a transmission signal constituted of a pulse, said driving circuit including: (a) a protection circuit for stopping supplying the driving current to the light emission element as a protection operation when the transmission signal is in a state which causes the light emission element to emit light for a certain time or more; and (b) a reference current source for generating a reference current so as to generate the driving current, wherein the protection circuit stops supplying the driving current and stops the reference current source, wherein the protection circuit includes: a capacitor element which is charged by flow of a current; a charging control circuit for allowing a charging current to flow to the capacitor element when the transmission signal is active; a first comparison circuit for comparing a first reference voltage with an inter-terminal voltage of the capacitor element; and a retention circuit for retaining a protection operation condition of the protection circuit when the reference current source stops, and the protection circuit begins the protection operation when the first comparison circuit determines the inter-terminal voltage to be not less than the reference voltage.