Display Drive Circuit Power Reduction via Periodic Current
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Solution Overview
Problem
Display devices with self-luminous elements, such as organic EL, face challenges in reducing power consumption due to the need for amplifier circuits that require constant bias currents, leading to increased heat generation and limited power reduction, especially in small form factor devices with high pixel density.
Innovation Solution
A drive method that uses capacitors to output a constant current to data lines during a set driving period, eliminating the need for amplifier circuits and reducing power consumption by suppressing normally flowing currents, while compensating for threshold voltage variations using transistors and capacitors to maintain consistent voltage changes across data lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If amplifier circuits are used to drive data lines, then data voltage control is improved, but power consumption increases due to constant bias current flow
Solution Approach 1:
The patent applies periodic action by using a constant current source that operates only during a specific driving period (Tdr) rather than continuously. The current source is controlled to output current during the driving period and stop otherwise, eliminating the need for continuous bias current while still achieving accurate data voltage control through the capacitor charging mechanism during the active period.
2Use of energy by moving object
If constant current is output only during driving period, then power consumption is reduced, but data line voltage consistency may be affected
Solution Approach 1:
The patent implements feedback by using a compensation circuit that includes a compensation transistor and capacitor to detect and compensate for threshold voltage variations in the drive transistor. This feedback mechanism ensures that despite operating in periodic mode rather than continuous mode, the data line voltage remains consistent across different transistors and operating conditions by actively correcting for device variations.
3Use of energy by moving object
If amplifier circuits are eliminated, then power consumption is reduced, but threshold voltage variation compensation becomes more difficult
Solution Approach 1:
The patent extracts the essential function of threshold voltage compensation from the complex amplifier circuit structure and implements it through a simplified dedicated compensation circuit. This compensation circuit uses a compensation transistor and capacitor to isolate and compensate for threshold voltage effects separately from the main drive function, achieving the same compensation goal with reduced overall circuit complexity and lower power consumption.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach achieves low power consumption by eliminating the need for amplifier circuits and maintaining display quality by ensuring consistent data voltages across data lines, reducing heat generation and power consumption, especially in small form factor devices with high pixel density.
Implementation Method 1
a plurality of capacitors each provided between corresponding output node of a plurality of output nodes of the drive circuit and corresponding data line of the plurality of data lines
Data Source
AI summary
A display device includes a pixel circuit, a drive circuit that drives a data line connected to the pixel circuit, and a capacitor that is provided between an output node of the drive circuit and the data line. The drive circuit outputs a constant current to the output node during a driving period of which a length is set according to display data.