Koito Manufacturing Company, Ltd.

Ryosuke Matsuhana

Tomoyuki Ichikawa

Satoshi Kikuchi

Naoki Kawabata

Norito Takahashi

A lighting circuit turns on a plurality of semiconductor light sources. Multiple current sources are each coupled to a corresponding semiconductor light source. A switching converter supplies a driving voltage Vacross each of multiple series connection circuits each formed of the semiconductor light source and the current source. A converter controller employing a ripple control method turns on a switching transistor of the switching converter in response to a voltage across any one of the multiple current sources decreasing to a bottom limit voltage.

Lighting circuit of automotive lamp

A lighting circuit turns on multiple semiconductor light sources. Multiple current sources are each coupled in series with a corresponding one from among the semiconductor light sources. A switching converter supplies a driving voltage Vacross each of multiple series connection circuits formed of the multiple semiconductor light sources and the multiple current sources. A converter controller controls a switching transistor of the switching converter based on a relation between a voltage across one from among the multiple current sources and a reference voltage having a positive correlation with the temperature T.

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Shizuoka, Japan

Ryosuke Matsuhana