LED Controller Circuit Dimmer Detection via Transistor On-Time Analysis
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Solution Overview
Problem
Conventional LED controller circuits require additional pins and comparators to detect dimmer type and conduction angle, leading to increased cost and complexity, and are dependent on input voltage amplitude.
Innovation Solution
An LED controller circuit that uses a processor to determine dimmer characteristics, such as type and on/off states, by analyzing the transistor on-time or switching period, eliminating the need for direct access to dimmer circuit outputs and reducing the IC pin count.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If voltage comparators are used to detect dimmer type and conduction angle, then detection accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts the dimmer detection function from the traditional voltage comparator approach and implements it through processing the transistor's on-time information. Instead of using multiple comparators to directly detect dimmer characteristics, the system extracts the necessary information (dimmer type and conduction angle) from the timing data already generated by the transistor switching operation, thereby eliminating the need for additional comparison hardware.
Solution Approach 2:
The transistor's on-time information serves dual purposes: it controls the power converter operation and simultaneously provides the data needed for dimmer type and conduction angle detection. The system uses its own operational timing data for detection purposes, eliminating the need for separate detection hardware that would require additional pins and comparators.
2Adaptability or versatility
If additional pins and comparators are added for dimmer detection, then detection capability is improved, but manufacturing cost increases
Solution Approach 1:
The transistor on-time parameter serves multiple functions: it controls the power conversion process and simultaneously provides the detection data for dimmer type identification and conduction angle measurement. This multi-functionality eliminates the need for dedicated detection hardware, reducing pin count and component count, which directly lowers manufacturing costs while maintaining universal dimmer compatibility.
3Measurement precision
If direct access to dimmer circuit outputs is used for detection, then detection accuracy is improved, but device complexity increases
Solution Approach 1:
The transistor on-time acts as an intermediary that indirectly provides dimmer detection information without requiring direct access to dimmer circuit outputs. Instead of connecting comparators directly to the dimmer output signal, the system uses the transistor's switching timing as a mediator to convey the necessary dimmer characteristics, simplifying the hardware architecture while maintaining detection accuracy.
Data Source
Figure 1A~2B
Figure 3A
Figure 3B~4
AI summary
An LED controller circuit for use in an LED drive circuit in which a coil current control scheme is used to deliver power to an LED arrangement from a phase cut dimmer. The controller circuit includes means for determining, based on an analysis/signal processing of the on-time of the transistor, the dimmer characteristics, including the on state and off states of the ac dimmed voltage signal. This avoids the need for the controller circuit to process the dimmer output.