Light Emitting Device Area Drive Circuit Luminance Stability
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Solution Overview
Problem
Conventional backlight systems with active matrix driving experience luminance reduction when transitioning from minimum to maximum luminance due to incomplete carrier activation in the inversion layer of the drive transistor, leading to temporary luminance drops.
Innovation Solution
The implementation of a light-emitting device configuration with two holding capacitors and specific control transistors, where the second write control transistor maintains the data voltage pseudo-rewritten after the carrier activation time, ensuring consistent luminance by adjusting the write and stop periods to prevent luminance reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If active matrix driving is used to control LED luminance for each area, then luminance control precision is improved, but luminance reduction occurs in the frame period immediately after a sharp increase in target luminance
Solution Approach 1:
The patent applies preliminary action by extending the write period duration to ensure complete carrier activation in the inversion layer before the frame period begins. This preliminary extension of the write period allows carriers to fully activate in the drive transistor's inversion layer, preventing the luminance reduction that would otherwise occur when transitioning from minimum to maximum luminance. The write period is set to a duration that ensures carrier equilibrium is reached before display output begins.
2Reliability
If the write period is extended to ensure carrier activation, then luminance stability is improved, but frame period duration increases
Solution Approach 1:
The patent applies local quality by selectively extending the write period only for areas experiencing sharp luminance increases from minimum to maximum, rather than uniformly extending all frame periods. This localized approach ensures that carrier activation is completed only where necessary, maintaining luminance stability for affected areas while minimizing the overall frame period duration impact. The control circuit identifies and applies the extended write period selectively based on the luminance transition requirements of each area.
Data Source
AI summary
A light-emitting device includes a plurality of area drive circuits. The area drive circuits each include a first write control transistor and a second write control transistor. Each of the area drive circuits has a first write period in which the first and the second write control transistor are maintained in an on state, a first write stop period in which the first and the second write control transistor are maintained in an off state, and a second write period in which the first write control transistor is maintained in the off state and the second write control transistor is maintained in the on state, the periods being provided in this order in one frame period from when the first write control transistor changes from the off state to the on state to when the first write control transistor next changes from the off state to the on state.