Active Ripple Cancellation in LED Driver Systems
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Solution Overview
Problem
Battery-operated systems face inefficiencies and reduced battery run time due to AC ripple noise on the main system power rail, which causes increased RMS losses, heat dissipation, and premature termination of operations in noise-sensitive subsystems like LED backlighting.
Innovation Solution
Active ripple cancellation is achieved by modulating the output current of an LED driver in opposition to dynamic system loads, using a filter network to prevent modulation at visible frequencies and dynamically adjusting the LED luminescence based on sensed ripple signals, thereby reducing interference with ripple-sensitive subsystems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If LED driver output current is modulated to cancel ripple on the main power rail, then ripple noise is reduced and battery run time is extended, but LED luminescence may flicker at visible frequencies
Solution Approach 1:
The LED driver output current is dynamically modulated in response to detected ripple conditions, allowing the system to adaptively cancel ripple while maintaining stable LED luminescence through real-time adjustments that prevent visible flicker
Solution Approach 2:
The system uses feedback from ripple detection to control the LED driver modulation, creating a closed-loop system that monitors power rail ripple and adjusts LED current accordingly to cancel ripple while preventing visible flicker through controlled feedback response
2Object-affected harmful factors
If ripple cancellation modulation is applied to LED driver, then total system ripple on power rail is reduced, but power losses and heat dissipation increase due to additional modulation
Solution Approach 1:
The system converts the potentially harmful effect of additional modulation into a beneficial outcome by using LED driver modulation to cancel ripple, where the net effect reduces total power losses despite the added modulation complexity
3Illumination intensity
If filter network is used to prevent visible frequency modulation, then LED flicker is eliminated, but ripple cancellation effectiveness is reduced at certain frequencies
Solution Approach 1:
The filter network applies selective frequency treatment, allowing ripple cancellation to operate effectively at non-visible frequencies while blocking modulation at visible frequencies, creating different operational characteristics for different frequency ranges
Data Source
AI summary
Various embodiments of the invention allow for active AC ripple noise cancellation. In certain embodiments, noise cancellation is accomplished by modulating an LED driver output in a polarity opposite to the ripple, thereby, preventing interference with ripple-sensitive loads. Certain embodiments take advantage of a filter network to prevent the LED driver from modulating LED current in response to ripple that falls within a visible frequency range so as to prevent flicker in an LED backlight display. In addition to protecting ripple-sensitive loads from large ripple currents, efficiency is increased by reducing both I2·R losses and peak currents, thereby, extending the useful battery life time in mobile devices.