LED Power Converter Control for Stable Pulsed Dimming
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Solution Overview
Problem
Existing electronic power converters for light-emitting diodes (LEDs) face challenges in maintaining stable brightness and color consistency due to color drift and flicker issues, especially at low brightness levels, and conventional pulse-width modulation methods disrupt control loops, leading to instability and stroboscopic effects.
Innovation Solution
A method and circuit that allow the electronic power converter to generate pulsed or periodically modified output variables without interrupting the physical power flow or control loop, using a dual-target value system where the first target value specifies continuous output power and the second target value modifies the pulse pattern, ensuring the control loop remains adjusted and stable.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If pulse-width modulation is used to reduce brightness at low levels, then brightness control is achieved, but flicker and stroboscopic effects occur
Solution Approach 1:
The patent applies periodic action by using pulse-width modulation to switch the LED current on and off at high frequency (above 100 Hz, preferably above 1 kHz). The duty cycle of these periodic pulses is adjusted to control the average brightness, while the high frequency ensures the periodic nature is not perceptible to humans, thereby avoiding flicker and stroboscopic effects.
2Stability of the object's composition
If current is continuously reduced to control brightness, then color drift is minimized, but control loop stability deteriorates at very low brightness
Solution Approach 1:
Instead of continuously reducing current, the patent uses periodic pulsed action where the current is switched on and off. This maintains a minimum current level during the on-phase, ensuring the LED operates in a stable region with consistent color characteristics, while the periodic switching enables brightness control without entering the unstable very-low-current region.
Solution Approach 2:
The patent changes the control parameter from continuous current reduction to periodic duty cycle adjustment. By maintaining a minimum current amplitude and varying only the duty cycle (ratio of on-time to total period), the LED operates within a stable current range, preserving color consistency while achieving brightness control through parameter transformation.
3Illumination intensity
If very short current pulses are used for low brightness, then brightness control is achieved, but edge switching speed requirements increase
Solution Approach 1:
The patent transforms the control approach by changing from varying pulse amplitude to varying duty cycle at a fixed minimum amplitude. This parameter change allows the use of longer pulse durations with lower switching frequency requirements, reducing the edge switching speed demands while maintaining effective brightness control through duty cycle modulation.
4Illumination intensity
If duty ratio is reduced to control brightness, then brightness control is achieved, but manufacturing complexity increases
Solution Approach 1:
The patent implements brightness control through simple periodic switching with duty cycle modulation. This approach uses basic on/off switching logic that can be implemented with simple timers and comparators, avoiding complex PWM generation circuits. The periodic nature allows use of straightforward frequency dividers and counter-based duty cycle control, reducing overall system complexity.
Data Source
AI summary
A method for operating clocked and regulated electronic power converters may be contained in operating devices for light-emitting diodes. An associated regulating circuit may include at least one regulating amplifier having at least two regulating inputs, from the output of which a negative feedback network runs to one of its regulating inputs, a first input for the signal for a target value of the average of the output power to be regulated, and a second input which forwards a signal for the target value of a waveform or of a pulse pattern for the output power to be regulated to one of the regulating inputs via a DC current-blocking high-pass filter.