Pixel Driving Circuit With PWM Precharging for Grayscale Stability
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Solution Overview
Problem
Existing display technologies using glass substrate driven MiniLED/MicroLEDs face issues with uneven brightness and flickering during low grayscale display due to low current density, failing to meet the requirements of high-quality display products.
Innovation Solution
A pixel driving circuit with a current driving circuit and grayscale control circuit that adjusts brightness by controlling the duration of driving current based on pulse width modulation, allowing for three levels of grayscale adjustment through alternate or differential duration control of transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If pulse width modulation is used to control brightness, then grayscale adjustment is improved, but current density becomes too low causing uneven brightness and flickering
Solution Approach 1:
The patent segments the driving process into multiple stages: a pre-charging stage where current is accumulated before the actual light emission, and a main driving stage. This segmentation allows the light emitting element to receive sufficient total current while using PWM for brightness control, preventing low current density during the emission phase and eliminating flickering.
Solution Approach 2:
The patent applies preliminary action by introducing a pre-charging phase before the main light emission. During this pre-charging phase, current is accumulated in the light emitting element before the PWM-driven emission begins. This ensures that when the light emitting element starts emitting, it has sufficient charge to maintain stable brightness without flickering, while still allowing PWM control for grayscale adjustment.
2Loss of energy
If driving current is reduced for low grayscale display, then energy consumption is lowered, but current density becomes too low causing flickering
Solution Approach 1:
The patent uses periodic action through PWM (pulse width modulation) to control the driving current. By periodically switching the current on and off at high frequency, the light emitting element receives sufficient total current over time while maintaining low instantaneous current density during emission. This periodic control enables low grayscale display with reduced energy consumption while preventing flickering through proper timing.
Solution Approach 2:
The preliminary charging phase accumulates sufficient charge in the light emitting element before the PWM-driven emission begins. This ensures that even when PWM reduces the instantaneous current for low grayscale display, the light emitting element maintains sufficient charge to emit steadily without flickering, achieving both energy savings and display stability.
3Measurement precision
If transistor switching duration is extended for grayscale control, then brightness control precision is improved, but response time increases
Solution Approach 1:
The patent applies dynamics by making the transistor switching duration adjustable based on the required grayscale level. The control circuit dynamically sets the duration of the pre-charging phase and the main driving phase according to the desired brightness. This allows precise brightness control for different grayscale levels while optimizing the response time by not unnecessarily extending the switching duration, achieving both precision and speed.
Data Source
AI summary
A pixel driving circuit, a pixel driving method, and a display panel. The pixel driving circuit includes: a current driving circuit, which is used for receiving a display data signal and a display control signal, and upon receiving the display control signal, outputting a driving current, which has an intensity corresponding to the display data signal; and a grayscale control circuit, which is used for receiving the driving current, a pulse width selection signal and a pulse width modulation signal, and according to the pulse width modulation signal, driving a light emitting element for a preset duration, where the preset duration is a first duration, a second duration or a third duration corresponding to the pulse width selection signal.