Pixel Driving Circuit With Dynamic PWM for Low-Grayscale Stability
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Solution Overview
Problem
Existing display technologies using MiniLEDs and MicroLEDs face issues with uneven brightness and flickering during low grayscale display due to low current density, failing to meet the demand for high-quality display products.
Innovation Solution
A pixel driving circuit with a current driving circuit and grayscale control circuit that adjusts brightness through pulse width modulation, allowing for three levels of grayscale adjustment by controlling the duration of light emission using two types of transistors and pulse width selection circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional display technologies are used to drive MiniLEDs and MicroLEDs, then the display can show images, but the brightness becomes uneven and flickering occurs during low grayscale display due to low current density
Solution Approach 1:
The patent implements dynamic grayscale control by switching between different pulse width modulation modes (first PWM mode with longer duration and second PWM mode with shorter duration) based on the grayscale value. This dynamic adjustment optimizes current density at different grayscale levels, preventing flickering and brightness unevenness during low grayscale display while maintaining display stability.
Solution Approach 2:
The patent changes the pulse width modulation parameters (duty cycle and duration) based on grayscale values. By adjusting the PWM signal characteristics dynamically according to the displayed grayscale level, the system maintains optimal current density across all grayscale ranges, eliminating the flickering and brightness uniformity issues observed in conventional displays.
2Illumination intensity
If pulse width modulation is used to control grayscale, then brightness can be adjusted, but flickering occurs during low grayscale display due to insufficient current density
Solution Approach 1:
The system dynamically selects between first and second PWM modes based on the grayscale value. For low grayscale values, the first PWM mode with longer duration is used to maintain sufficient current density and eliminate flickering. For higher grayscale values, the second PWM mode is used for normal operation. This dynamic switching resolves the flickering issue while preserving grayscale control capability.
Solution Approach 2:
The patent changes the PWM signal parameters (duration and duty cycle) according to the grayscale level being displayed. By adjusting these parameters dynamically, the system ensures that sufficient current density is maintained during low grayscale display to prevent flickering, while still achieving precise grayscale control across the full range.
3Device complexity
If a single transistor type is used in the pixel circuit, then the circuit structure is simple, but the voltage gradient between grayscales is insufficient
Solution Approach 1:
The patent employs asymmetric transistor configuration by using both first-type transistors (e.g., N-type) and second-type transistors (e.g., P-type) in the pixel circuit. This asymmetric design enables better voltage control and creates a more pronounced voltage gradient between different grayscale levels, improving display contrast and brightness differentiation while maintaining reasonable circuit complexity.
Solution Approach 2:
The dual-transistor configuration enables dynamic voltage control during the display process. By utilizing the complementary characteristics of different transistor types, the circuit can dynamically adjust voltage levels to create sufficient voltage gradient between grayscales, enhancing display performance without excessive complexity.
Data Source
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AI summary
A pixel driving circuit, a pixel driving method, and a display panel. The pixel driving circuit includes: a current driving circuit (10), which is used for receiving a display data signal (D1) and a display control signal (EM), and upon receiving the display control signal (EM), outputting a driving current, which has an intensity corresponding to the display data signal (D1); and a grayscale control circuit (200), which is used for receiving the driving current, a pulse width selection signal (D2) and a pulse width modulation signal (PWM), and according to the pulse width modulation signal (PWM), driving a light emitting element (300) 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 (D2).