LED Display Channel Control Module for Low Gray Scale Linearity
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Solution Overview
Problem
As pixel spacing decreases and integration levels increase in LED display screens, the speed of turning on channels for PWM constant current driving decreases, leading to deterioration in gray-scale linearity and consistency when displaying low gray-scale images, affecting the display effect.
Innovation Solution
The LED display device incorporates a channel control module that adjusts the column-line voltage to a target voltage during a first time period when a pulse width modulation signal is active, and then controls constant current sources to provide driving currents in a second time period, improving constant current cut-in speed and linearity under low gray-scale conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If pixel spacing is decreased and integration level is increased, then display resolution is improved, but channel turn-on speed decreases leading to deterioration in gray-scale linearity
Solution Approach 1:
The patent introduces a pre-charging phase before the constant current driving phase. During this pre-charging phase, the column line voltage is rapidly charged to a target voltage value that is pre-calculated based on the LED's forward voltage characteristics and the desired current. This preliminary action eliminates the voltage buildup delay, allowing the constant current source to immediately establish the correct current when the PWM signal activates, thereby maintaining fast turn-on speed even as pixel spacing decreases and integration level increases.
2Use of energy by moving object
If PWM constant current driving is used, then power consumption is reduced, but gray-scale linearity and consistency deteriorate at low gray scales
Solution Approach 1:
The patent implements a feedback mechanism where the target voltage for the pre-charging phase is dynamically calculated based on the PWM duty cycle and LED forward voltage characteristics. The system continuously monitors the relationship between the PWM signal parameters and the required column line voltage to achieve accurate current control. This feedback ensures that even at low gray scales where PWM duty cycles are small, the pre-charged voltage is precisely set to ensure linear and consistent gray-scale rendering, while still maintaining the power efficiency of PWM constant current driving.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the speed and linearity of constant current cut-in when displaying low gray-scale images, improving the overall display effect by pre-charging column lines and setting target voltages based on minimum cut-in voltages, without increasing power consumption or circuit costs.
Implementation Method 1
the channel control module is configured to adjust a column-line voltage of a corresponding one of the plurality of column lines to a target voltage in a first time period when a corresponding one of the pulse width modulation signals is active
Implementation Method 2
A light-emitting diode (LED) is a diode that exploits light-emitting principle of recombining minority carriers and majority carriers in a PN junction. When a forward voltage is applied to the PN junction, the diode can be turned on, so that electrical energy can be converted into optical energy.
Data Source
AI summary
Disclosed is an LED display device, a driving method and a chip thereof. The LED display device comprises: a display array comprising row lines, column lines, and pixel units each comprising an LED connected to a corresponding one of the row lines and a corresponding one of the column lines; a row driver module, connected to the row lines and providing selection signals; a column driver module, connected to the column lines and providing driving signals corresponding to gray scale data according to pulse width modulation signals; a channel control module, connected to the column lines and adjusting a column-line voltage of a corresponding column line to a target voltage in a first time period when a corresponding pulse width modulation signal is active, thus improving constant current cut-in speed and improve consistency and linearity under low gray scale when an image with low gray scale is displayed.