LED Driver PWM Frequency Selection for Flicker and Cost Trade-off
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Solution Overview
Problem
Existing LED dimming technologies using pulse width modulation (PWM) face issues with flicker and interference due to the need for high PWM frequencies, which increase component and design costs, and can lead to stability problems and non-linearity in dimming control when PWM frequency is adjusted during dimming.
Innovation Solution
Selecting the PWM frequency based on the maximal dimming level set in the illumination system, ensuring a consistent PWM frequency throughout the dimming range to maintain a long enough switching period and avoid adverse effects, while keeping the frequency high enough to prevent flicker and interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high PWM frequency is used to avoid flicker and interference, then flicker and interference are prevented, but component costs and design complexity increase
Solution Approach 1:
The patent applies dynamics by making the PWM frequency adjustable rather than fixed. The system dynamically selects from multiple predefined PWM frequencies (e.g., 1 kHz, 2 kHz, 3 kHz) based on the dimming level requirements. This allows the driver to use lower frequencies at higher dimming levels where flicker is less noticeable, reducing component stress and costs, while switching to higher frequencies at lower dimming levels to prevent flicker.
Solution Approach 2:
The patent changes the PWM frequency parameter based on operating conditions (dimming level). By providing a set of predefined frequencies and selecting the appropriate one based on the dimming ratio, the system optimizes the balance between flicker prevention and component requirements. This parameter adaptation allows using lower frequencies when possible, reducing component costs while maintaining reliability when needed.
2Productivity
If PWM frequency is changed during dimming to optimize performance, then dimming efficiency improves, but stability problems and non-linearity occur
Solution Approach 1:
The system dynamically adjusts PWM frequency based on dimming level, but implements this change in a controlled manner by selecting from predefined frequency values. The microprocessor monitors the dimming ratio and switches between frequency sets accordingly, maintaining stability through structured transitions rather than continuous or arbitrary frequency changes.
Solution Approach 2:
The patent segments the dimming range into different zones, each associated with a specific PWM frequency set. By dividing the operating range and assigning appropriate frequencies to each segment, the system achieves efficient dimming in each zone while avoiding the stability issues that would arise from unstructured frequency changes across the entire range.
3Device complexity
If PWM frequency is reduced to lower component costs, then component costs decrease, but flicker and interference problems reappear
Solution Approach 1:
The patent changes the PWM frequency parameter based on operating conditions (dimming level). By providing a set of predefined frequencies and selecting the appropriate one based on the dimming ratio, the system optimizes the balance between flicker prevention and component requirements. This parameter adaptation allows using lower frequencies when possible, reducing component costs while maintaining reliability when needed.
Data Source
AI summary
A LED driver and a method in connection with a LED driver. The method comprising providing a controlled current to an output of the LED driver for providing controlled illumination from a LED light source, employing a pulse width modulator having a PWM frequency to produce the controlled current, setting a minimum effective value of the controlled current, setting the PWM frequency of the pulse width modulator on the basis of the set minimum effective value of the controlled current.