Voltage Supply Circuit for LCD Flicker Compensation
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Solution Overview
Problem
Liquid crystal display devices experience flicker and image quality issues due to the overdrive effect caused by liquid crystal molecules being deflected in the same direction during polarity inversion adjustments, leading to differences in brightness between frames.
Innovation Solution
A voltage supply circuit with a power management integrated circuit, transmission branch, and voltage reduction branch is used to provide different operating voltages to the gate driver circuit in alternating frames, reducing the liquid crystal electric field and compensating for the overdrive effect by switching between conducting and cutoff states based on control signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polarity inversion is adjusted periodically to prevent polarization of liquid crystal molecules, then the liquid crystal display device can maintain proper switching, but brightness inconsistency between frames occurs causing image flicker
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the voltage level supplied to the pixel cell based on the frame number and inversion cycle. In the first frame of an inversion adjustment cycle, a first voltage is supplied, while in subsequent frames, a second voltage is supplied. This voltage parameter change compensates for the overdrive effect and ensures consistent brightness across frames while maintaining proper liquid crystal molecule polarization prevention.
2Ease of operation
If no polarity inversion is performed in the first frame of the next inversion adjustment cycle, then liquid crystal molecules are deflected in the same direction causing overdrive effect, but this leads to brightness difference and image flicker
Solution Approach 1:
The patent applies preliminary anti-action by anticipating the overdrive effect that occurs in the first frame of the next inversion adjustment cycle. A compensation voltage is pre-calculated and applied in advance to counteract the expected brightness increase. This prevents the overdrive effect from causing image flicker while maintaining the simplicity of the polarity inversion adjustment mechanism.
3Illumination intensity
If different voltages are supplied in different frames to compensate for overdrive effect, then brightness consistency is improved, but voltage supply circuit complexity increases
Solution Approach 1:
The patent applies dynamics by implementing a voltage supply circuit that can dynamically adjust the output voltage based on the operational state. The circuit includes a voltage selection mechanism that chooses between a first voltage and a second voltage based on the frame number and inversion cycle information. This dynamic voltage adjustment achieves brightness consistency while keeping the circuit structure relatively simple through controlled variability rather than complete redesign.
Data Source
AI summary
There is provided a voltage supply circuit, in which a signal output end of a power management integrated circuit, a signal input end of a transmission branch, and a signal input end of a voltage reduction branch are coupled to a first node; a signal output end of transmission branch and a signal output end of the voltage reduction branch are coupled to a second node; the power management integrated circuit supplies an initial voltage to the first node; the transmission branch is coupled to a control signal terminal, and switch between a conducting state and a cutoff state in response to control of a control signal, and write the initial voltage into the second node in the conducting state; and the voltage reduction branch performs voltage reduction on the initial voltage at the first node to obtain a reduced voltage to be written into the second node.