Display Device Threshold Voltage Compensation Circuit
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Solution Overview
Problem
The operation of canceling the influence of threshold voltage dispersion in driving transistors of organic EL display elements increases power consumption, which is undesirable for electronic apparatus.
Innovation Solution
A display device with a capacitor unit and switching transistors that hold and manage a voltage corresponding to the threshold voltage of the driving transistor, allowing for reduced power consumption by minimizing the frequency of operations that hold this voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the operation of canceling the influence of threshold voltage dispersion is performed every time a video signal is written, then image brightness uniformity is improved, but power consumption increases
Solution Approach 1:
The patent implements periodic action by performing the threshold voltage compensation operation only at specific intervals (e.g., once per frame or at predetermined timings) rather than continuously with every video signal write. This reduces the frequency of compensation operations while maintaining adequate image uniformity, thereby lowering power consumption compared to continuous compensation.
Solution Approach 2:
The patent applies preliminary action by pre-charging capacitors and preparing compensation voltages in advance during specific time periods before they are actually needed for threshold voltage cancellation. This allows the compensation operation to be performed more efficiently and less frequently, reducing overall power consumption while maintaining the ability to correct threshold voltage dispersion when necessary.
2Illumination intensity
If the active matrix method is used to drive the display element, then image brightness can be made high, but device structure becomes complicated
Solution Approach 1:
The patent applies universality by designing the capacitor unit and switching transistor to serve multiple functions: they not only maintain the gate voltage for the driving transistor but also participate in threshold voltage compensation and video signal writing operations. This multi-functionality reduces the need for additional dedicated components, thereby managing structural complexity while achieving high brightness through active matrix driving.
Solution Approach 2:
The patent merges the functions of voltage holding, threshold voltage compensation, and video signal writing into a single integrated capacitor unit and switching transistor structure. By combining these functions that could have been implemented with separate components, the patent reduces overall device complexity while maintaining the high brightness capability of active matrix driving.
Data Source
AI summary
The display element includes a current-driven light-emitting unit, a capacitor unit including a first capacitor and a second capacitor, an n-channel driving transistor that causes a current corresponding to a voltage held by the capacitor unit to flow through the light-emitting unit and a first switching transistor that writes a video signal voltage to the capacitor unit. In a state in which the first capacitor holds a voltage corresponding to a threshold voltage of the driving transistor, a video signal voltage is written to the second capacitor through the first switching transistor in a conducting state.