LED Current Adjustment Circuit Using Zero-Crossing Timing Control
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Solution Overview
Problem
Existing LED light source dimming technologies, such as CCM and DCM, face challenges with high costs, inductor saturation, harmonic current, and poor consistency among multiple LED light sources, leading to inconsistent dimming effects due to strong electromagnetic interference and parasitic parameter influences.
Innovation Solution
A current adjustment circuit that controls the zero-crossing phase of the switching cycle using a time control sub-circuit and a switch control sub-circuit, eliminating the influence of parasitic parameters and ensuring consistency among LED light sources by adjusting the switch-on and switch-off times of the dimming switch.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional DCM dimming is used, then the inductor current is properly reset during one switching cycle, but harmonic current is high and electromagnetic interference is strong
Solution Approach 1:
The patent implements periodic action by introducing a zero-crossing detection mechanism that triggers switching operations at specific phases of the AC cycle. The control circuit detects when the AC current crosses zero and uses this timing to initiate switching cycles, creating a periodic control pattern that synchronizes with the AC waveform. This periodic synchronization reduces harmonic current and electromagnetic interference while maintaining proper inductor current reset.
2Duration of action of stationary object
If CCM dimming is used, then the LED light source can be driven continuously, but inductor saturation is prone to occur and control is difficult
Solution Approach 1:
The patent employs periodic action by transitioning from continuous conduction mode to discontinuous conduction mode synchronized with AC zero-crossings. Each switching cycle is periodically initiated when the AC current crosses zero, allowing the inductor current to fully reset to zero before the next cycle begins. This periodic reset prevents inductor saturation while maintaining continuous LED operation through rapid cycling.
Solution Approach 2:
The patent applies parameter changes by dynamically adjusting the switching frequency and duty cycle based on the AC waveform phase. The control circuit modifies operating parameters (switching timing, on-time duration) to optimize performance at different points in the AC cycle, preventing inductor saturation while maintaining continuous LED operation.
3Quantity of substance
If a plurality of LED light sources are connected in a circuit, then the overall lighting coverage is improved, but the LED light sources have poor consistency resulting in large difference between dimming effects
Solution Approach 1:
The patent implements universality by designing a control circuit that simultaneously manages multiple LED light sources using a single synchronized control mechanism. The zero-crossing detection and timing control serve multiple parallel LED circuits uniformly, ensuring that all light sources receive identical switching commands and operate in sync, thereby achieving consistent dimming effects across all connected LED sources.
4Ease of operation
If brightness of LED light sources is adjusted according to user needs, then the usability is improved, but parasitic parameters of driving circuit affect the LED output current
Solution Approach 1:
The patent applies feedback by implementing a control circuit that monitors the actual LED output current and compares it with the desired current level. The zero-crossing detection provides timing feedback, and the control circuit adjusts switching duty cycle based on this feedback to compensate for parasitic parameter effects, maintaining precise LED output current control despite variations in driving circuit characteristics.
Data Source
AI summary
The present disclosure provides a current adjustment circuit. The current adjustment circuit includes a lighting sub-circuit, a dimming switch disposed in the lighting sub-circuit, a switch control sub-circuit connected to the dimming switch and the lighting sub-circuit, and a time control sub-circuit connected to the switch control sub-circuit. Time of switch-off period in a switching cycle of the current adjustment circuit is adjusted under control of the time control sub-circuit and the switch control sub-circuit. Brightness of the current adjustment circuit is adjusted based on the output current of the current adjustment circuit. The present disclosure may reduce or even eliminate influence of factors such as circuit parasitic parameters on an LED light source, ensure consistency of each light source, and optimize display effect of the LED light source.