Lighting circuit of automotive lamp
AssigneeKoito Manufacturing Co., Ltd.
InventorsTomoyuki ICHIKAWA, Ryosuke MATSUHANA, Satoshi KIKUCHI, Naoki KAWABATA, Norito TAKAHASHI
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Abstract
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 VOUT across 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.
Claims14
A lighting circuit structured to turn on a plurality of semiconductor light sources, comprising:
- a plurality of current sources each of which is to be coupled to a corresponding semiconductor light source in series;
- a switching converter structured to supply a driving voltage across each of a plurality of series connection circuits each formed of the semiconductor light source and the current source;
- and
- a converter controller employing a ripple control method,
- wherein the plurality of current sources each comprise:
- a series transistor and a sensing resistor arranged in series with a corresponding semiconductor light source;
- and
- an error amplifier structured to adjust a voltage at a control electrode of the series transistor based on a voltage drop that occurs across the sensing resistor,
- and wherein the converter controller is structured to turn on the switching transistor of the switching converter in response to an output voltage of the error amplifier included in any one of the plurality of current sources satisfying a predetermined turn-on condition.
The lighting circuit according to 1, wherein, when the driving voltage exceeds a predetermined threshold value, the switching transistor is forcibly turned off.
Dependencies are inferred from the claim text.