Backlight Device Pulse Width Modulation Noise Control
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Solution Overview
Problem
Conventional liquid crystal display devices face issues with noise generation due to low pulse frequencies in their backlight systems, which affect image quality and grayscale display capabilities.
Innovation Solution
A backlight device comprising light strips, switch components, a pulse storage circuit, a pulse generator circuit, a voltage adjuster circuit, and a pulse modulation control circuit that adjusts pulse width and voltage to maintain frequencies above a threshold, preventing noise and enhancing grayscale display.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If pulse frequency is reduced to enable dimming control, then brightness adjustment capability is improved, but noise generation increases
Solution Approach 1:
The patent changes the control parameter from pulse frequency to pulse width (duty cycle). Instead of varying frequency to control brightness, the system maintains a high frequency above the audible threshold and adjusts the pulse width (on-time versus off-time within each cycle) to achieve dimming control, thereby eliminating noise while preserving brightness adjustment capability
Solution Approach 2:
The patent employs periodic pulse width modulation where the backlight is switched on and off in regular cycles at a frequency above the audible range. By controlling the duty cycle (ratio of on-time to total period), the system achieves average brightness control without producing audible noise, as the periodic switching remains inaudible to human ears
2Object-generated harmful factors
If pulse frequency is increased to prevent noise, then noise generation is reduced, but grayscale display capability deteriorates
Solution Approach 1:
The patent introduces dynamic adjustment of pulse width within each fixed high-frequency cycle. The system dynamically varies the duty cycle (pulse width ratio) to control brightness levels, enabling fine grayscale control through continuous adjustment of the on-time portion while maintaining the overall high frequency to prevent noise
Solution Approach 2:
The patent applies partial action by controlling only the active portion (pulse width) of each cycle rather than the entire cycle frequency. By adjusting the duty cycle to represent a fraction (e.g., 30% on, 70% off) of each high-frequency period, the system achieves grayscale control without needing to lower the overall frequency, thus maintaining noise-free operation while enabling precise brightness levels
Data Source
AI summary
A backlight device and a dimming control method thereof are provided. The method includes the following steps: supplying power to a plurality of light strips and a plurality of first switch components; storing an initial pulse signal in a pulse storage circuit; determining whether or not a frequency of the initial pulse signal is smaller than a frequency threshold by a pulse modulation control circuit, and if yes, outputting a pulse width modulation control signal and a voltage adjusting control signal; adjusting a pulse width of the initial pulse signal according to the pulse width modulation control signal to output a pulse width modulation signal to each of the first switch components by a pulse generator circuit; and outputting a voltage adjusting signal to each of the first switch components according to an adjustment ratio of the initial pulse signal to the pulse width modulation signal.