LED Dimming Circuit Using Segmented Pulse Signals
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Solution Overview
Problem
Conventional LED dimming control methods using pulse width modulation (PWM) result in long pulse lengths and low frame rates due to limited frequency, making it inefficient for high-resolution gray level displays.
Innovation Solution
A signal generating method and circuit that combine two types of pulse signals, allowing for a mixed pulse width modulation signal with adjustable duty ratios and amplitudes to represent gray level information, significantly shortening the pulse length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the frequency of the pulse width modulation signal is not high (for cost down considerations), then the cost is reduced, but the length of the pulse width modulation signal becomes longer when more control bits are used
Solution Approach 1:
The patent segments the 16-bit gray level control into two separate 8-bit PWM signals. The first PWM signal uses 8 bits to control the high byte of the gray level, and the second PWM signal uses another 8 bits to control the low byte. This segmentation allows each PWM signal to have a shorter length (256 levels instead of 65536 levels), reducing the overall time required while maintaining the full 16-bit resolution through combination.
2Measurement precision
If more control bits are used to achieve higher gray levels (65536 levels), then the resolution is improved, but the length of the pulse width modulation signal becomes longer
Solution Approach 1:
The patent introduces a time dimension by using two sequential PWM signals instead of one long PWM signal. The first PWM signal transmits the high byte (8 bits) and the second PWM signal transmits the low byte (8 bits). By stacking these two 8-bit signals in time sequence, the system achieves equivalent 16-bit resolution without requiring a single 16-bit long PWM signal, thus reducing the length of each individual pulse train.
3Loss of information
If the length of the pulse width modulation signal is long, then more gray levels can be represented, but it takes more time to display a frame
Solution Approach 1:
The patent divides the frame display time into two sequential phases: the first phase displays the high byte PWM signal for 8-bit gray levels, and the second phase displays the low byte PWM signal for another 8-bit gray levels. This segmentation reduces the time required for each phase while preserving the full 16-bit gray level information through the combination of both phases, thereby reducing the total frame display time.
4Productivity
If the frame rate is increased to reduce display time, then the productivity is improved, but the pulse width modulation signal length must be reduced
Solution Approach 1:
The patent segments the gray level control into two separate 8-bit PWM signals transmitted in sequence. Each PWM signal has a length corresponding to 256 levels (8 bits) instead of 65536 levels (16 bits), reducing the length by a factor of 256. This allows the frame rate to be increased by a corresponding factor while maintaining the full 16-bit gray level resolution through the combination of both segmented signals.
Data Source
AI summary
The present disclosure provides a signal generating method and a circuit for controlling dimming of an LED. The method comprises generating a first pulse signal, the first pulse signal comprising information of P bits gray levels, P being an integer, wherein the minimum pulse-width of the first pulse is N, N is an integer; generating a second pulse signal after the first pulse signal, the second pulse signal comprising information of Q bits gray levels, Q being an integer, wherein the amplitude of the second pulse signal is different from the amplitude of the first pulse signal, the minimum pulse-width of the second pulse is the same as the minimum pulse-width of the first pulse; and utilizing the first pulse signal and the second pulse signal to represent gray levels information of the LED.