Pixel Circuit Inverter Back Gate Threshold Control
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Solution Overview
Problem
In display devices using pulse width modulation (PWM) for image display, delay times occur in the rising and falling periods of the driving current, affecting grayscale representation.
Innovation Solution
A pixel circuit is designed with an inverter comprising P-type and N-type transistors with back gate terminals, which reduces delay times by adjusting the back gate voltages to minimize the difference between the threshold voltages of the transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If PWM method is used to display grayscale images, then image display capability is improved, but delay time occurs in rising and falling periods of driving current
Solution Approach 1:
The inverter circuit is configured to proactively adjust the driving current before the actual display period begins. By pre-establishing the appropriate current level through the inverter's threshold voltage control, the circuit eliminates delay time while maintaining PWM grayscale display capability
Solution Approach 2:
The patent changes the threshold voltage parameter of the inverter circuit by applying back gate voltages to the transistors. This parameter adjustment allows the inverter to precisely control the driving current timing, eliminating delay while preserving PWM functionality
2Loss of time
If inverter with back gate terminals is added to reduce delay time, then delay time is reduced, but device complexity increases
Solution Approach 1:
The inverter circuit serves multiple functions: it inverts the input signal, controls the driving current magnitude, and eliminates delay time through threshold voltage adjustment. By making the inverter multi-functional, the patent avoids adding separate components for each function, thereby limiting the increase in device complexity
Solution Approach 2:
The inverter acts as an intermediary component between the input signal and the driving current generation. It mediates the signal transformation and current control functions, achieving delay reduction without requiring direct complex circuitry
Data Source
AI summary
A pixel circuit includes a first transistor including a gate terminal which receives a first gate signal, a first terminal connected to a first node, and a second terminal connected to a second node, an inverter including a first sub-transistor including a gate terminal connected to the first node, a first terminal which receives a driving voltage, and a second terminal connected to the second node, and a second sub-transistor including a gate terminal connected to the first node, a first terminal which receives a ground voltage, a second terminal connected to the second node, and a light emitting element including an anode connected to the second node and a cathode which receives the ground voltage.