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US 8,044,920 B2Granted
Backlight control circuit with low brightness variation when light emitting devices not operating
AssigneeRichtek Technology Corporation
InventorsChiawei Liao, Jing-Meng Liu
Life of this patent
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Abstract
The present invention discloses a backlight control circuit, and a method for controlling light emission devices. The method comprises: providing a plurality of light emission device paths connected in parallel; and setting a total current of the paths connected in parallel to a constant.
Claims23
A backlight control circuit, comprising:
- a plurality of current matching circuits respectively controlling currents on corresponding plurality of light emission device paths;
- and
- a common node electrically connected with the plurality of current matching circuits, for electrically connecting with a total current setting circuit,
- wherein each of the plurality of current matching circuits includes a transistor, and one and the same operative amplifier is shared among the plurality of current matching circuits, the operative amplifier comparing a voltage at the common node with a reference voltage to generate an output controlling the transistor in each of the plurality of current matching circuits;
- and
- wherein when any light emission device is inoperative, the brightness of other operative light emission devices is passively increased to compensate the brightness lost by the inoperative light emission device.
3 more elements
A backlight control circuit, comprising:
- a plurality of light emission device paths;
- and
- a common node electrically connected with the plurality of light emission device paths, and also electrically connected with a total control current source, the total control current source controlling a total current on the plurality of light emission device paths,
- wherein the plurality of light emission device paths include light emission devices wherein at least three of the light emission devices form an array, and in the array every two non-diagonal neighboring light emission devices belong to two different light emission device paths, and when any light emission device is inoperative, the brightness of other operative light emission devices is passively increased to compensate the brightness lost by the inoperative light emission devices.
1 more element
A method for controlling light emission devices, comprising:
- (A) providing a plurality of light emission device paths connected in parallel;
- (B) setting a total current of the paths connected in parallel to a constant;
- and
- (C) providing a current matching circuit for each, of the plurality of light emission device paths, wherein the current matching circuits share a common operative amplifier which compares a voltage at a common node with a reference voltage such that currents in the current matching circuits match with one another when a total current is set to a constant, and when any light emission device is inoperative, the brightness of other operative light emission devices is passively increased to compensate the brightness lost by the inoperative light emission device.
1 more element
Dependencies are inferred from the claim text.