Dynamic PWM Signal Adjustment for High-Power LED Flicker Control
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Solution Overview
Problem
High-power LED dimming systems experience flickering issues during camera shooting due to rapid on and off states of the LED light, leading to insufficient dimming smoothness and camera flicker, primarily caused by the high refresh rate required to prevent over-exposure.
Innovation Solution
A method and system for dynamically adjusting PWM signals by presetting standard signal periods and duty ratios, allowing for two adjustment modes: adjusting signal periods when the target duty ratio is lower and keeping signal periods constant when it's higher, to maintain smooth dimming and prevent camera flicker.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the refresh rate of the LED light is increased to prevent camera flicker, then camera flickering is reduced, but the dimming smoothness deteriorates due to hardware performance limitations
Solution Approach 1:
The patent applies dynamics by making the PWM signal period adjustable rather than fixed. The control system dynamically adapts the signal period based on operating conditions to optimize both camera flicker prevention and dimming smoothness. This resolves the contradiction by allowing the system to flexibly adjust the refresh rate within hardware capabilities rather than being constrained to a fixed high refresh rate.
Solution Approach 2:
The patent changes the parameter of PWM signal period from a fixed value to a variable parameter that can be adjusted within a range. By modifying the signal period parameter adaptively, the system can prevent camera flicker when needed while maintaining smooth dimming performance, thus resolving the technical contradiction between these two requirements.
2Object-affected harmful factors
If the PWM signal period is shortened to increase refresh rate, then camera flicker is prevented, but the resolution becomes insufficient due to hardware limitations
Solution Approach 1:
The system dynamically adjusts the PWM signal period based on real-time conditions rather than using a fixed short period. This allows the refresh rate to be increased only when necessary to prevent camera flicker, while maintaining longer periods when high resolution is needed, thus resolving the contradiction between flicker prevention and dimming resolution.
Solution Approach 2:
The patent transforms the fixed PWM period into an adjustable parameter within a specific range. By adaptively changing the period parameter, the system can achieve sufficient refresh rate to prevent camera flicker without excessively shortening the period to the point where hardware resolution becomes insufficient.
3Object-affected harmful factors
If the duty ratio adjustment is made by changing signal period, then camera flicker is reduced, but the dimming smoothness deteriorates when brightness is high
Solution Approach 1:
The control system dynamically selects the adjustment strategy based on current brightness levels. When brightness is low, it adjusts by changing signal period to prevent camera flicker. When brightness is high, it switches to adjusting duty ratio with fixed period to maintain smooth dimming. This dynamic strategy selection resolves the contradiction between flicker prevention and dimming smoothness.
Solution Approach 2:
The patent applies different adjustment strategies to different brightness conditions (local conditions). For low brightness, it uses period adjustment; for high brightness, it uses duty ratio adjustment with fixed period. This localized approach resolves the contradiction by optimizing for the specific operating condition rather than using a single approach for all conditions.
Data Source
AI summary
A method for dynamically adjusting a PWM signal includes steps of: presetting a standard signal period and a standard duty ratio of an effective pulse; receiving a target duty ratio entered by a user and comparing the target duty ratio with the standard duty ratio; adjusting a duration of a signal period relative to the standard signal period while keeping a duration of the effective pulse unchanged to cause a duty ratio to reach the target duty ratio, when the target duty ratio is smaller than the standard duty ratio; adjusting the duration of the effective pulse while keeping the duration of the standard signal period unchanged to cause the duty ratio to reach the target duty ratio, when the target duty ratio is larger than the standard duty ratio, when the target duty ratio is equal to the standard duty ratio.