LCD Data Driver Circuit PWM Gray Level Control
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Solution Overview
Problem
Existing LCD driving circuits face challenges due to the large area and high cost of resistive digital-analog converters (R-DACs) used for generating gray level voltages, which also produce excessive heat, reducing the lifespan of the circuits.
Innovation Solution
The proposed solution involves an LCD driving circuit that adjusts gray levels by modulating the duty ratio of pulse voltage signals, eliminating the need for R-DACs and incorporating a shift register, data register, comparator, and buffer to generate pulse voltage signals for pixel regions, thereby reducing the circuit area and heat production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If R-DAC is used to convert binary data signals to analog gray level voltages, then gray level voltages can be provided for LCD driving, but the circuit area and cost increase significantly
Solution Approach 1:
The patent extracts and eliminates the R-DAC component from the data driver circuit. Instead of using resistive networks to generate gray level voltages, the invention uses a pulse width modulation (PWM) approach where a single voltage level is generated and varied by duty ratio, thereby removing the need for multiple resistors and reducing circuit area.
Solution Approach 2:
The patent changes the parameter used for gray level control from voltage amplitude (analog) to duty ratio (temporal). By modulating the duty ratio of a single voltage level signal, multiple gray levels are achieved without requiring multiple voltage generation circuits, thus reducing the circuit area.
2Adaptability or versatility
If R-DAC is used to provide multiple gray level voltages, then voltage output capability is improved, but the number of resistors increases and cost increases
Solution Approach 1:
The patent removes the resistor-based R-DAC structure entirely. Instead of using multiple resistors to create voltage dividers for different gray levels, the invention uses a single voltage source combined with PWM control, eliminating the need for resistor networks and reducing component count.
Solution Approach 2:
The patent makes a single voltage generation circuit serve multiple functions by using duty ratio modulation to produce different gray levels. This universal approach replaces what would traditionally require multiple dedicated voltage generation circuits with a single multi-functional component.
3Adaptability or versatility
If R-DAC is used to generate gray level voltages, then voltage output is achieved, but excessive heat is produced reducing circuit lifespan
Solution Approach 1:
The patent extracts and removes the resistive heating problem by eliminating the R-DAC structure. The PWM-based approach uses switching elements rather than resistive networks, significantly reducing heat generation and improving circuit reliability and lifespan.
Solution Approach 2:
The patent converts the harmful effect of resistive heating into a beneficial PWM switching approach. Instead of using resistors that continuously dissipate heat, the invention uses switching elements that transfer charge capacitively, converting the heat problem into an efficient switching-based voltage generation method.
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 reduces the area and cost of the data driver circuit, decreases heat generation, and extends the lifespan of the LCD driving circuit while maintaining adjustable gray levels without altering the voltage values.
Implementation Method 1
a shift register for shifting and outputting a clock signal
Implementation Method 2
a comparator for comparing signals inputted to the first and second inputs, and outputting a pulse voltage signal according to the comparison result
Implementation Method 3
a latch unit for latching and outputting data signals according to enable signals
Implementation Method 4
a data register for receiving data signals from the timing controller according to the first enable signal
Implementation Method 5
a buffer for buffering and outputting the pulse voltage signal to a data line
Data Source
AI summary
An exemplary data driving circuit includes a data register, a counter, and a comparator. The data register is configured for receiving serial gray level signals in turn, and outputting the plurality of gray level signals in parallel. The counter is configured for outputting counting signals. The comparator is configured for receiving the gray level signals and the counting signals, and outputting pulse voltage signals according to the gray level signals and the counting signals. A variety of duty ratios of the pulse voltage signals correspond to a variety of gray levels.