Organic EL Display Brightness Control via Digital Light-Emission Period
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Solution Overview
Problem
Existing organic EL displays face challenges in accurately controlling brightness due to the linear characteristic of resistance elements, leading to variations in color balance and increased power consumption, especially when trying to dynamically control brightness.
Innovation Solution
Incorporating a brightness detection circuit that converts power-supply voltage into a digital value, allowing for precise control of the drive current and light-emission period of electro-optical elements, even with non-linear active elements, thereby enabling accurate brightness control and reduced power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a resistance element with linear characteristic is used to limit power-supply current, then the current level can be controlled, but the brightness control accuracy deteriorates due to voltage-current characteristic variations
Solution Approach 1:
The patent changes the control parameter from analog voltage level to digital light-emission period. By using a brightness detection circuit that converts power-supply voltage to digital values and controlling the light-emission period accordingly, the system achieves accurate brightness control without being affected by the linear characteristic limitations of resistance elements.
2Speed
If the resistance of the resistance element is increased to dynamically control brightness, then the brightness control responsiveness improves, but the power consumption increases
Solution Approach 1:
The patent employs periodic action by controlling the light-emission period of the electro-optical elements. Instead of continuously adjusting current through resistance, the system modulates the duration of light emission based on digital values from the brightness detection circuit, achieving dynamic brightness control without the power consumption penalty of high resistance values.
3Ease of operation
If simultaneous voltage control is applied to all drive transistors, then the control simplicity is maintained, but the color balance deteriorates in full-color displays
Solution Approach 1:
The patent segments the control approach by detecting power-supply voltage separately for different color regions (red, green, blue) and controlling the light-emission period independently for each color. This segmentation allows each color to be optimized individually while maintaining overall control simplicity through a unified digital control architecture.
Data Source
AI summary
To provide an electro-optical device, a driving method therefor, and an electronic apparatus which can accurately control the brightness of electro-optical elements in accordance with the signal level of a data signal. A brightness detection circuit 15 is provided which samples power-supply current Io every time one scan line is selected and which converts the power-supply current Io into a digital voltage signal DS having a digital value corresponding to the power-supply current Io. A light-emission-period control circuit 16 generates light-emission-period control signals H1 to Hn in accordance with a light-emission-period adjusting signal F corresponding to the digital voltage signal DS and outputs the light-emission-period control signals H1 to Hn to corresponding control-signal supply lines G1 to Gn. Further, light-emission-period control transistors of the pixels 20 which are connected to the corresponding control-signal supply lines G1 to Gn are on/off controlled, thereby controlling the light-emission period of the electro-optical elements.