Dynamic PWM Frequency Control for LED Current Accuracy
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Solution Overview
Problem
Conventional LED driving systems face challenges in accurately controlling the frequency of pulse width modulation (PWM) signals, leading to inaccuracies in target output current, perceived flicker, and instability in waveform and chromaticity control.
Innovation Solution
A dynamic PWM frequency control system that includes current source circuitry, control switch circuitry, feedback circuitry, PWM frequency determination circuitry, and PWM generation circuitry to dynamically adjust PWM frequencies based on the state of the current, ensuring improved accuracy and stability by generating distinct PWM signals for DC and PWM currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed PWM frequency is used to control LED current, then the control circuit is simple, but the target output current accuracy deteriorates and perceived flicker increases
Solution Approach 1:
The patent implements dynamic PWM frequency adjustment based on the operating mode. The control circuit switches between a first PWM frequency for DC current mode and a second PWM frequency for PWM current mode, allowing the system to adapt to different operating conditions and maintain high current accuracy while avoiding the limitations of fixed-frequency approaches
Solution Approach 2:
The patent changes the PWM frequency parameter dynamically based on the detected current mode. By selecting different frequency values (first frequency for DC mode, second frequency for PWM mode), the system optimizes current control accuracy and eliminates flicker perception without requiring a overly complex control architecture
2Object-affected harmful factors
If PWM frequency is increased to reduce flicker, then perceived flicker decreases, but control precision and chromaticity stability deteriorate
Solution Approach 1:
The system dynamically selects PWM frequency based on operating mode rather than using a single high frequency. In PWM current mode, a second frequency is used that balances flicker reduction with chromaticity stability, while in DC current mode, a first frequency optimizes for precision. This dynamic approach resolves the trade-off between flicker reduction and control precision
Solution Approach 2:
The patent applies different PWM frequency characteristics to different operating modes. The first PWM frequency is optimized for DC current control precision, while the second PWM frequency is optimized for PWM current mode with flicker considerations. This localized optimization for each mode eliminates the need to compromise overall performance
3Stability of the object's composition
If DC current mode is used for LED control, then chromaticity stability is improved, but dimming precision and response speed deteriorate
Solution Approach 1:
The control circuit dynamically switches between DC current mode and PWM current mode based on the required operation. DC mode is used when chromaticity stability is the priority, while PWM mode is used when dimming precision and response speed are needed. This dynamic mode switching allows the system to achieve both chromaticity stability and fast dimming response in different operating conditions
Data Source
AI summary
The present disclosure provides a dynamic pulse width modulation (PWM) system that includes current frequency determination circuitry to determine a DC value of a source current, and to determine a frequency of the source current generate a plurality of pulses from an AC power source; and PWM generation circuitry to generate a first PWM signal having a first frequency based on the DC value of the current source; the PWM circuitry also to generate a second PWM signal having a second frequency based on the frequency of the current source; wherein the first frequency is less than the second frequency.