OLED Anode Voltage Holding Circuit for Power Reduction
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Solution Overview
Problem
Conventional electro-optical apparatuses with voltage driving modes continuously consume power, even when displaying black, due to the need for continuous current flow in transistors to maintain OLED anode voltage.
Innovation Solution
An electro-optical apparatus with an active-matrix drive circuit that includes a first transistor for driving the light-emitting element, a second transistor for setting the anode voltage, and a holding capacitor and third transistor to maintain anode voltage during emission, allowing for reduced power consumption by controlling the transistors' operation based on image signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a transistor is kept continuously on to hold the OLED anode voltage in voltage driving mode, then the anode voltage is maintained, but power is continuously consumed even when displaying black
Solution Approach 1:
The patent applies periodic action by using a holding capacitor to store the anode voltage during the light emission period, allowing the transistor to be turned off during non-emission periods (such as when displaying black). This converts the continuous operation into periodic operation, eliminating unnecessary power consumption while maintaining voltage when needed.
Solution Approach 2:
The holding capacitor is charged in advance during the light emission period to store the required anode voltage. This preliminary action ensures that the voltage is already stored and ready, eliminating the need for continuous transistor operation to maintain the voltage during subsequent non-emission periods.
2Use of energy by moving object
If a holding capacitor and third transistor are added to hold anode voltage during light-emission period, then power consumption is reduced, but device complexity increases
Solution Approach 1:
The patent segments the voltage holding function from the driving transistor by introducing a dedicated holding capacitor and third transistor. This segmentation allows the main driving transistor to be turned off completely during non-emission periods, reducing its power consumption, while the holding circuit maintains voltage only when needed during light emission periods.
Data Source
AI summary
An electro-optical apparatus is provided with an active-matrix drive circuit that applies a voltage based on an image signal tone to a light-emitting element, and includes: a first transistor for driving, a source of the first transistor being connected to an anode of the light-emitting element; a second transistor for setting an anode voltage, the second transistor being connected between the anode and a power source, and determining a voltage applied to the anode; and a holding capacitor and a third transistor connected to the anode for holding the anode voltage during a light-emission period.