Backlight control circuit capable of distinguishing under current condition
AssigneeRichtek Technology Corporation
InventorsChiawei Liao, Xiaoyong Zhang, Jing-Meng Liu
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Abstract
The present invention discloses a backlight control circuit capable of distinguishing an under current condition, comprising: at least one light emission device path having a voltage node; at least one current source for controlling the current amount on the light emission device path; and at least one under current detection circuit for generating a first control signal according to the voltage at the voltage node, wherein when the first control signal changes its state, the under current detection circuit generates a second control signal to change the voltage on the voltage node if the light emission device path is normally connected.
Claims35
A backlight control circuit, comprising:
- at least one light emission device path having a voltage node;
- at least one current source for controlling a current amount on the light emission device path;
- and
- at least one under current detection (UCD) circuit for generating a first control signal according to the voltage on the voltage node to indicate whether the light emission device path is normally connected, wherein when the first control signal changes its state, the UCD circuit generates a second control signal to lower the current amount on the light emission device path such that when the light emission device path is normally connected the voltage at the voltage node is changed, and when the light emission device path is not normally connected the voltage at the voltage node is unchanged, to thereby verify whether the first control signal correctly indicates the connection of the light emission device path.
A light emitting device path status detection method, comprising:
- (A) providing at least one light emission device path having a voltage node;
- (B) generating a first control signal according to the voltage on the voltage node to indicate whether the light emission device path is normally connected;
- and
- (C) when the first control signal changes its state, lowering the current amount on the light emission device path such that when the light emission device path is normally connected the voltage at the voltage node is changed, and when the light emission device path is not normally connected the voltage at the voltage node is unchanged, to thereby verify whether the first control signal correctly indicates the connection of the light emission device path.
An under current detection (UCD) circuit comprising:
- a comparator for generating a control signal by comparing a node voltage on a path with a reference voltage;
- a pulse generator for generating a pulse according to the control signal when the control signal changes its state in a first manner and in a second manner;
- a verification circuit to verify whether the node voltage is correct by lowering a current through the path in response to the pulse, wherein when the control signal changes its state in the first manner and the node voltage is correct, the node voltage changes in response to lowering the current, and when the control signal changes its state in the second manner and the node voltage is correct, the node voltage remains unchanged in response to lowering the current.
Dependencies are inferred from the claim text.