Light Dimming Device Zero-Cross PWM Control
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Solution Overview
Problem
Existing light-dimming devices face instability in controlling the lighting load due to poor charging of electrolytic capacitors, leading to unstable operation of the controller and difficulty in maintaining a consistent lighting state.
Innovation Solution
A light-dimming device with a switch, controller, and power supply module that includes a zero-cross detection circuit and PWM signal generation to control the conduction angle of the switch, ensuring stable operation by charging the capacitor within a prescribed period shorter than the AC voltage half cycle, thereby preventing current flow issues and maintaining a stable lighting state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the switch conducts from OFF state when absolute value of AC voltage is non-zero, then light output can be adjusted, but current may not flow through the lighting load depending on conduction angle, causing unstable control operation
Solution Approach 1:
The patent implements periodic switching action where the switch conducts from OFF state at specific intervals during the AC voltage cycle. By controlling the switch to turn on when the absolute value of AC voltage is non-zero and maintaining conduction for a controlled duration, the system achieves both light output adjustment and stable control operation through periodic on-off cycles.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution stabilizes the operation of the controller and maintains a consistent lighting state, reducing noise and allowing for a wider range of lighting loads to be effectively dimmed.
Implementation Method 1
a zero-cross detection circuit configured to detect zero-cross of an AC voltage from the AC power supply
Implementation Method 2
the electrolytic capacitor of the control power supply is charged by the control power for a certain period of time within time from the OFF state to turn-on of the switch
Implementation Method 3
The control circuit is configured to generate a PWM signal that defines an on-duty ratio corresponding to the conduction angle
Data Source
Figure 1
Figure 2
AI summary
Light-dimming device (10) includes: first and second terminals (1, 2); switch (3) including switching device (7) connected between terminals (1, 2); adjuster (6) for varying conduction angle of switch (3); controller (4) for controlling switch (3) and power supply module (5) for supplying power to controller (4). Controller (4) includes zero-cross detection circuit (9) for detecting zero-cross of AC voltage (Va), control circuit (11) for generating PWM signal of on-duty ratio corresponding to conduction angle from adjuster (6), and driver circuit (8) for turning device (7) on and off by PWM signal. Controller (4) allows device (7) to conduct and then turn off within variable period of time, from start of half cycle of AC voltage, shorter than half cycle. Circuit 11 starts generation of pulse in PWM signal when prescribed period of time, shorter than variable period of time, from zero-cross of voltage Va elapses.