Multi-path LED backlight system and constant-current control circuit and method thereof
A technology of constant current control circuit and backlight system, applied in the field of circuits, can solve problems such as screen flickering phenomenon, and achieve the effect of improving current matching accuracy
Pending Publication Date: 2021-02-12
ON BRIGHT ELECTRONICS SHANGHAI
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Problems solved by technology
When the brightness of the LED is small, increasing the LED brightness by increasing the duty cycle of the LED drive current for each LED channel will not affect the matching of the maximum LED drive current for each LED channel, but the screen will flicker , which has certain effects on the health of the eyes
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[0019] Features and exemplary embodiments of various aspects of the invention will be described in detail below. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without some of these specific details. The following description of the embodiments is only to provide a better understanding of the present invention by showing examples of the present invention. The present invention is by no means limited to any specific configurations and algorithms presented below, but covers any modification, substitution and improvement of elements, components and algorithms without departing from the spirit of the invention. In the drawings and the following description, well-known structures and techniques have not been shown in order to avoid unnecessarily obscuring the present invention.
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The invention provides a multi-path LED backlight system and a constant-current control circuit and method thereof. The constant current control circuit comprises a channel setting current generator which generates a plurality of channel setting currents according to a reference voltage and an external resistor; a plurality of channel voltage generators generating a plurality of channel voltages according to the plurality of channel setting currents; and a plurality of LED channel drivers generating a plurality of LED driving currents for the plurality of LED channels according to the plurality of channel voltages. Each LED channel driver includes an operational amplifier. The operational amplifier comprises operational amplifier input geminate transistors, offset voltage storage geminatetransistors and an offset voltage storage capacitor, and the offset voltage storage geminate transistors store offset voltage of the operational amplifier input geminate transistors on the offset voltage storage capacitor before the operational amplifier generates LED driving current. When the operational amplifier generates the LED driving current, the offset voltage of the operational amplifierinput geminate transistors is superposed to the operational amplifier input geminate transistors, so that the influence of the offset voltage of the operational amplifier input geminate transistors onthe LED driving current is eliminated, and the matching between channel currents is improved.
Description
technical field [0001] The invention relates to the field of circuits, in particular to a multi-channel LED backlight system and its constant current control circuit and method. Background technique [0002] In a multi-channel light-emitting diode (LED) backlight system, in order to ensure uniform brightness across the screen, it is required that the LED drive currents for each LED channel must be precisely matched. [0003] In an LED backlight system using a low-frequency (for example, 100Hz to 1000Hz) pulse width modulation (PWM) dimming method, after setting the maximum LED drive current for each LED channel, by adjusting the LED for each LED channel The duty cycle of the driving current is used to adjust the brightness of the LED. Current matching is done for the maximum LED drive current for each LED channel. When the brightness of the LED is small, increasing the LED brightness by increasing the duty cycle of the LED drive current for each LED channel will not affect...
Claims
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Login to View More IPC IPC(8): G09G3/34
CPCG09G3/3406H05B45/345
Inventor 李萌翟向坤朱力强
Owner ON BRIGHT ELECTRONICS SHANGHAI