Variable Frequency PWM LED Control Circuit for Strobe Prevention
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Solution Overview
Problem
Portable lights powered by pulsed or AC power can create a strobing effect when illuminating moving objects, leading to safety hazards as users may incorrectly perceive stationary objects, potentially causing injury or damage.
Innovation Solution
A control circuit and method that employs a pulse width modulated (PWM) drive signal with a frequency that varies continuously over a range of frequencies, preventing the strobing effect by ensuring moving objects appear to move rather than appear stationary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If pulsed or AC power is used to power the LED light source, then power conversion efficiency is improved, but a strobing effect occurs that causes moving objects to appear stationary
Solution Approach 1:
The patent applies dynamics by making the PWM frequency variable rather than fixed. The control circuit continuously varies the PWM frequency over a range of frequencies (e.g., 100-1000 Hz) to prevent the light from synchronizing with moving objects, thereby eliminating the strobing effect while maintaining power conversion efficiency through continued use of pulsed power.
2Use of energy by moving object
If a fixed frequency PWM signal is used to control the LED, then power conversion efficiency is maintained, but the strobing effect persists when the frequency matches moving object frequencies
Solution Approach 1:
The patent applies parameter changes by varying the PWM frequency parameter over time and across a range of values. The control circuit adjusts the frequency dynamically rather than maintaining a fixed frequency, which prevents synchronization with moving objects and eliminates the strobing effect while preserving power conversion efficiency.
3Object-affected harmful factors
If the PWM frequency is varied continuously over a range of frequencies, then the strobing effect is eliminated, but device complexity increases
Solution Approach 1:
The patent applies periodic action by implementing a control circuit that systematically varies the PWM frequency in a periodic manner across a defined range. This structured approach to frequency modulation eliminates the strobing effect while keeping the control circuit complexity manageable through use of standard PWM generation techniques with variable frequency control.
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
The solution effectively eliminates the strobing effect, enhancing user safety by accurately depicting the motion of moving objects and preventing potential injuries or damages.
Implementation Method 1
a pulse width modulator generating a pulse width modulated (PWM) drive signal having a PWM ON time ratio responsive to a control signal and having a PWM drive frequency that varies over a range of frequencies repeatedly and substantially continuously
Data Source
AI summary
A control circuit for a light source comprises: a light source, a drive circuit applying a pulse width modulated (PWM) drive signal to the light source; and a pulse width modulator generating the PWM drive signal having a PWM ON time ratio responsive to a control signal and a PWM drive frequency that varies over a range of frequencies repeatedly and substantially continuously. A method for controlling a light source comprises: applying a pulse width modulated (PWM) drive signal to the light source; generating the PWM drive signal having a PWM ON time ratio responsive to a control signal and having a PWM drive frequency that is varied over the range of frequencies repeatedly and substantially continuously. The PWM drive signal causes the light source to produce light at the varying frequency, whereby light at a frequency exhibited by a moving object does not continuously illuminate a moving object.