LED Phase-Shift Dimming Circuit for Power Supply Interference Reduction
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Solution Overview
Problem
Conventional LED controllers with pulse width modulation (PWM) cause abrupt changes in LED brightness, leading to reduced image quality and interference with power supply circuits due to synchronous ON and OFF timings across multiple LED channels.
Innovation Solution
Implementing a phase-shift dimming circuit that generates multiple phase-shifted PWM signals with asynchronous turn-ON timings for each LED channel, using delay locked loops or pulse width mirrors to shift the ON timings, ensuring that each LED channel turns ON and OFF at different times within a duty cycle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If all LED channels use synchronous PWM control with the same turn-ON timing, then the control circuit is simple, but the brightness changes too sharply causing reduced image quality and power supply interference
Solution Approach 1:
The patent segments the PWM control signals into multiple phase-shifted versions, where each LED channel receives a PWM signal with a different phase timing. This segmentation of the control signal timing distributes the turn-ON events across different time intervals, preventing simultaneous switching of all LED channels and thereby reducing abrupt brightness changes and power supply interference.
Solution Approach 2:
The patent implements periodic phase-shifted PWM signals where each subsequent LED channel is controlled by a PWM signal shifted in phase relative to the previous channel. This periodic variation in timing creates a staggered turn-ON sequence that maintains PWM dimming functionality while eliminating the harmful synchronous switching effect.
2Ease of operation
If all LED channels turn ON and OFF simultaneously according to the same PWM signal, then the control method is simple, but image quality deteriorates due to sharp brightness transitions
Solution Approach 1:
The patent introduces asymmetry in the timing control by applying different phase shifts to different LED channels. Instead of symmetric simultaneous control, each channel operates with an asymmetric timing offset, creating a staggered turn-ON sequence that smooths brightness transitions and improves image quality while maintaining ease of PWM-based control.
Solution Approach 2:
The patent applies preliminary action by pre-calculating and pre-applied phase shifts to each PWM signal before they reach the LED channels. This preliminary timing adjustment ensures that channels turn ON in a controlled sequence rather than simultaneously, smoothing the overall brightness transition and improving image quality without complicating the control methodology.
3Device complexity
If multiple LED channels are controlled by the same PWM signal, then the circuit design is simple, but power supply circuits experience increased interference
Solution Approach 1:
The patent segments the single PWM control signal into multiple phase-shifted signals, each controlling a different LED channel. This segmentation distributes the switching events across different time intervals, reducing the cumulative current demand changes that cause power supply interference while maintaining relatively simple circuit design through the use of phase-shifted PWM generation.
Solution Approach 2:
The patent ensures continuity of useful action by maintaining PWM dimming control across all LED channels while staggering their activation times. The phase-shifted signals ensure that as one channel turns OFF, another may be turning ON, creating a more continuous and stable power consumption profile that reduces power supply interference.
Data Source
AI summary
The present invention discloses an LED controller with phase-shift dimming function and an LED Phase-Shift dimming circuit and method thereof. The LED controller includes: a power circuit for supplying DC power to multiple LED channels; and an LED phase-shift dimming circuit for receiving a pulse width modulation (PWM) input signal and generating multiple phase-shifted PWM signals with a shifted phase between one another, wherein a turn-ON timing of each of the multiple phase-shifted PWM signals follows a turn-OFF timing of a previous PWM signal which is the input PWM signal or a previous one of the multiple phase-shifted PWM signals.