Phase-Shift PWM Circuit for Stable Multi-String LED Dimming
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Solution Overview
Problem
Existing phase shift circuits for LED dimming fail to maintain uniform voltage across multiple LED strings, leading to instability in brightness control when all strings are activated simultaneously.
Innovation Solution
A phase shift circuit that generates multiple phase-shifted signals based on a single PWM signal, using an on signal generator, off signal generator, and channel signal generator to provide distinct phases to each LED string, ensuring stable dimming operations by adjusting the rising edges of the signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single PWM signal is provided to multiple LED strings, then the circuit complexity is reduced, but the voltage stability deteriorates
Solution Approach 1:
The patent divides a single PWM signal into multiple phase-shifted signals (first PWM signal, second PWM signal, third PWM signal) that are provided to different LED strings respectively. This segmentation of the control signal allows each LED string to be driven at different phases, preventing simultaneous activation and ensuring stable voltage distribution across all LED strings while maintaining a relatively simple circuit structure.
2Illumination intensity
If multiple LED strings are activated simultaneously, then the brightness control capability is improved, but the voltage uniformity deteriorates
Solution Approach 1:
The patent employs periodic phase-shifted PWM signals to drive multiple LED strings. The first LED string is activated during a first phase period, the second LED string during a second phase period, and the third LED string during a third phase period. This periodic activation ensures that not all LED strings are activated simultaneously, maintaining voltage uniformity across the power supply while still providing comprehensive brightness control capability for all strings.
3Stability of the object's composition
If phase-shifted signals are generated for each LED string, then the voltage stability is improved, but the device complexity increases
Solution Approach 1:
The patent merges the phase-shift generation function into a single integrated circuit that receives one PWM signal and internally generates multiple phase-shifted signals. Rather than using separate phase-shift circuits for each LED string, the invention combines all phase-shift generation logic into one device, reducing overall component count and circuit complexity while still providing the necessary phase-shifted control signals for stable voltage distribution.
Data Source
AI summary
A phase shift circuit includes an on signal generator, an off signal generator, and a channel signal generator. The on signal generator generates an on signal having a rising edge shifted by a predetermined phase based on a pulse width modulation (PWM) signal, the off signal generator generates an off signal based on the PWM signal and the on signal, and the channel signal generator generates a channel signal that is enabled in response to the rising edge of the on signal and disabled in response to a rising edge of the off signal.