Hybrid NMOS-PMOS Pixel Circuit for Low-Swing Display Driving
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Solution Overview
Problem
Emissive display devices face high power consumption due to large voltage swings required to turn off transistors, leading to increased circuit complexity, reduced power efficiency, and potential reliability issues, along with luminance drift and image retention from light emitting element degradation.
Innovation Solution
A pixel drive circuit with a hybrid configuration of NMOS and PMOS transistors, reducing gate high voltages and voltage swings, and stabilizing the gate-source voltage of the drive transistor, thereby maintaining consistent current output and reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If large voltage swings are used to turn off transistors, then transistor switching is achieved, but power consumption increases
Solution Approach 1:
The patent changes the voltage parameter by introducing a compensation mechanism that adjusts the gate voltage to account for light emitting element degradation. This allows the transistor to be turned off with smaller voltage swings while maintaining proper switching function, thereby reducing power consumption.
Solution Approach 2:
The patent implements a feedback mechanism where the compensation scan signal is adjusted based on the degradation state of the light emitting element. This feedback loop enables the system to maintain reliable transistor switching while optimizing voltage levels to minimize power consumption.
2Reliability
If large voltage swings are used to turn off transistors, then transistor switching is achieved, but circuit complexity increases
Solution Approach 1:
The patent makes the compensation scan line serve multiple functions: it provides compensation for light emitting element degradation and simultaneously controls the switching of transistors. This multi-functionality reduces the need for separate high-voltage generation circuitry, thereby simplifying the overall circuit design.
Solution Approach 2:
The patent merges the compensation function and the transistor control function into a single compensation scan line. By combining these functions, the patent eliminates the need for separate high-voltage swing circuits, reducing circuit complexity while maintaining reliable transistor switching.
3Reliability
If large voltage swings are used to turn off transistors, then transistor switching is achieved, but peripheral circuitry demands increase
Solution Approach 1:
The patent changes the voltage parameter by using a compensation mechanism that reduces the required voltage swing for transistor switching. The compensation scan signal adjusts the gate voltage to account for light emitting element degradation, enabling proper transistor turn-off with lower voltage levels, thereby reducing demands on peripheral circuitry.
4Duration of action of moving object
If light emitting elements operate over time, then display function is maintained, but luminance drift and image retention occur
Solution Approach 1:
The patent applies preliminary action by compensating for light emitting element degradation before it causes significant luminance drift or image retention. The compensation scan signal is adjusted in advance based on the degradation state, preventing luminance instability rather than correcting it after it occurs.
Solution Approach 2:
The patent implements a feedback mechanism that continuously monitors the degradation state of light emitting elements and adjusts the compensation scan signal accordingly. This feedback loop maintains luminance stability over time by dynamically compensating for degradation effects, preventing image retention and luminance drift.
Data Source
AI summary
A display device is provided that includes a light emitting element and a pixel drive circuit connected to the light emitting element. The light emitting element is connected between a first power line configured to receive a first power voltage and a first node. The pixel drive circuit includes a drive transistor and a plurality of switching transistors. The drive transistor is an N-type transistor, and at least one of the plurality of switching transistors is a P-type transistor.