Dimming System Frequency and Duty Cycle Adjustment
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Solution Overview
Problem
Existing dimming technologies, such as PWM and AM dimming, face limitations in dimming range and stability, causing visual flicker and restricted dimming capabilities due to frequency and duty cycle constraints.
Innovation Solution
A single-stage AC-to-DC converter system that adjusts both the frequency and duty cycle of a control signal in response to a dimming signal, allowing for enhanced dimming range and reduced electromagnetic interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If PWM dimming is used with high frequency control signal, then the light source can be effectively dimmed, but visual flicker and dark regions appear in specific situations
Solution Approach 1:
The patent changes the parameters of the control signal dynamically by adjusting both frequency and duty cycle simultaneously. The controller switches between different operating modes (first mode with first frequency and first duty cycle, second mode with second frequency and second duty cycle) to achieve effective dimming while avoiding the visual flicker problems associated with fixed-frequency PWM dimming.
2Illumination intensity
If AM dimming is used with varying loading magnitude, then dimming control is achieved, but the driving circuit produces unstable light source current due to too-low duty cycle
Solution Approach 1:
The patent implements dynamic control by allowing the controller to switch between different operating modes with different frequency and duty cycle combinations. This dynamic adjustment ensures that the duty cycle remains within stable ranges while achieving the desired dimming control, preventing the light source current instability that occurs in AM dimming when duty cycle becomes too low.
3Device complexity
If fixed frequency and duty cycle are used in control signal, then circuit configuration remains simple, but dimming range is limited
Solution Approach 1:
The patent extends the dimming range by implementing dual-mode operation where the controller can switch between different frequency and duty cycle combinations. This allows the system to adapt to a wider range of dimming requirements while maintaining relatively simple circuit configuration, as the same controller hardware supports multiple operating modes through parameter adjustments.
Data Source
AI summary
A dimming system comprises a controller and an AC-to-DC converter. The controller outputs a control signal in response to a dimming signal. The controller comprises a frequency adjustment circuit and a duty cycle adjustment circuit. The frequency adjustment circuit adjusts the frequency of the control signal in response to the dimming signal. The duty cycle adjustment circuit adjusts the duty cycle of the control signal in response to the dimming signal. The AC-to-DC converter converts an external power and to output a DC signal in response to the control signal so as to drive a light source by the DC signal. When the controller is operated at a first mode, the control signal has a first frequency and a first duty cycle. When the controller switches to a second mode, the control signal has a second frequency and a second duty cycle.