Light emitting diode luminance system having clamping device
AssigneeIML International
InventorsYung-Hsin Chiang, Yi-Mei Li
Life of this patent
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Abstract
A light emitting diode luminance system includes a first power source, a voltage divider, a first switch, a clamping device, a plurality of current sources and a feedback circuit. The voltage divider is coupled to the first voltage source. The first switch is coupled to the voltage divider and a ground. The clamping device includes a plurality of transistors each coupled to a respective set of light emitting diodes and the voltage divider. The plurality of current sources is coupled to the plurality of transistors respectively. The feedback circuit is coupled to the plurality of transistors and the plurality sets of light emitting diodes.
Claims14
A light emitting diode luminance system, comprising:
- a first power source for providing a first voltage;
- a voltage divider coupled to the first voltage source;
- a first switch coupled to the voltage divider and a ground;
- a clamping device comprising a plurality of transistors, each transistor of the plurality of transistors having a first end respectively coupled to a second end of each of a plurality sets of light emitting diodes, a control end coupled to the voltage divider, and a second end;
- a plurality of current sources respectively coupled to the second end of each of the plurality of transistors;
- and
- a feedback circuit coupled to the second end of each of the plurality of transistors, and coupled to a first end of each of the plurality sets of light emitting diodes.
A method of controlling a light emitting diode luminance system, the light emitting diode luminance system comprising a first power source, a voltage divider, a first switch, a clamping device, a plurality of current sources and a feedback circuit, the first power source being used for providing a first voltage, the voltage divider being coupled to the first voltage source,
- the first switch being coupled to the voltage divider and a ground, the clamping device comprising a plurality of transistors, each transistor of the plurality of transistors having a first end respectively coupled to a second end of each of a plurality sets of light emitting diodes, a control end coupled to the voltage divider, and a second end, the plurality of current sources respectively being coupled to the second end of each of the plurality of transistors, and the feedback circuit being coupled to the second end of each of the plurality of transistors and coupled to a first end of each of the plurality sets of light emitting diodes, the method comprising:
- turning on the first switch for the voltage divider outputting a divided voltage to the control end of each of the transistors;
- turning off the first switch;
- and
- enabling the short circuit protection controller for detecting a voltage level of the second end of each of the plurality of transistors;
- wherein a period of the short circuit protection controller being enabled and a period of the first switch being turned off are at least partially overlapped.
Dependencies are inferred from the claim text.