Light source module and lighting circuit
AssigneeKoito Manufacturing Co., Ltd.
InventorsTomoyuki Ichikawa, Atsushi Ozawa, Mariko Miwa, Yutaka Matsumoto
Life of this patent
Estimating the term…
Abstract
There is provided a rear sign lamp capable of enhancing safety. An LED string (502) includes four LEDs (504_1 to 504_4) connected in series. An LED driver circuit (610) receives a battery voltage (VIN) and supplies a drive current (ILED) stabilized at a target current (IREF) to the LED string (502). A bypass circuit (620) is provided in parallel with a bypassed portion (503) including two adjacent LEDs (504_3 and 504_4) of the LED string (502), and sinks a bypass current (IBYPASS) according to a battery voltage (VIN).
Claims9
A light source module comprising:
- an LED string including four LEDs (light-emitting diodes) connected in series;
- an LED driver circuit that receives a battery voltage and supplies a drive current stabilized at a target current to the LED string;
- a bypass circuit that is provided in parallel with a bypassed portion including two adjacent LEDs of the LED string and sinks a bypass current according to the battery voltage, and a break detection circuit that disables the bypass circuit when a break of the bypassed portion is detected, wherein when the battery voltage drops below a predetermined voltage, the bypass circuit sinks the bypass current, the bypass circuit comprises a first voltage comparator and a transistor, the first voltage comparator turning on the transistor based on a comparison of the battery voltage and a first threshold voltage, and the break detection circuit comprises a second voltage comparator that detects the break of the bypass portion based on a comparison of a voltage of the bypass portion and a second threshold voltage.
A lighting circuit that drives an LED string including four LEDs (light-emitting diodes) connected in series, the lighting circuit comprising:
- an LED driver circuit that receives a battery voltage and supplies a drive current stabilized at a target current to the LED string;
- a bypass circuit that is provided in parallel with a bypassed portion including two adjacent LEDs of the LED string and sinks a bypass current according to the battery voltage, and a break detection circuit that disables the bypass circuit when a break of the bypassed portion is detected, wherein when the battery voltage drops below a predetermined voltage, the bypass circuit sinks the bypass current, the bypass circuit comprises a first voltage comparator and a transistor, the first voltage comparator turning on the transistor based on a comparison of the battery voltage and a first threshold voltage, and the break detection circuit comprises a second voltage comparator that detects the break of the bypass portion based on a comparison of a voltage of the bypass portion and a second threshold voltage.
Dependencies are inferred from the claim text.