Dimmer Conduction Angle Detection Circuit for Stable Light Output
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Solution Overview
Problem
Existing dimmer conduction angle detection circuits, such as RC filters and microcontroller-based systems, are sensitive to line voltage fluctuations and lack sufficient linearity in lamp light output regulation, leading to undesired changes in illumination levels.
Innovation Solution
A ballast circuit incorporating a conduction angle detection circuit with a comparator, input network, threshold supply circuit, and filter, which uses a power factor correction circuit's gate drive signal to provide a voltage-limited dimmer reference level signal, ensuring the dimmer setting is accurately represented and minimizing the impact of line voltage variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If an RC filter is used for conduction angle detection, then the circuit complexity is reduced, but the output becomes sensitive to line voltage fluctuations and lacks linearity
Solution Approach 1:
The patent introduces a current mirror circuit as an intermediary between the rectifier output and the filter. The current mirror (Q1, Q2, Q3, Q4) copies the dimmer conduction angle information to a separate circuit path, isolating the detection circuit from line voltage fluctuations. This allows the RC filter to process a stable copied signal rather than the directly fluctuating rectifier output, maintaining both simplicity and stability.
2Measurement precision
If a microcontroller is used for conduction angle detection, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces the microcontroller-based digital processing system with an analog circuit implementation. The current mirror circuit, comparator, and RC filter work together to detect and process the dimmer conduction angle information entirely in the analog domain. This substitution eliminates the need for microcontrollers while maintaining measurement precision through proper analog circuit design.
Solution Approach 2:
The current mirror circuit automatically copies the dimmer control signal characteristics to the detection path without requiring external intervention or complex processing. The circuit self-regulates to provide accurate conduction angle detection through the natural properties of matched transistors and passive components, eliminating the need for programmed logic.
3Device complexity
If the ballast circuit directly uses rectifier output for dimmer detection, then device complexity is reduced, but linearity of lamp light output regulation deteriorates
Solution Approach 1:
The current mirror circuit serves as an intermediary that creates a faithful copy of the dimmer conduction angle signal. This copied signal is then processed by the RC filter to generate a DC voltage that linearly represents the dimmer setting. The intermediary current mirror ensures that the detection circuit receives an accurate representation of the original dimmer control, preserving linearity without adding significant complexity.
Data Source
AI summary
A dimmer conduction angle detection circuit, and systems and methods incorporating the same, is disclosed. The circuit receives a gate drive signal from a PFC circuit and provides a dimmer reference level signal representative of a dimmer circuit's dimmer setting in response. The circuit includes a comparator with first and second inputs that provides a pulse-width modulated output in response to comparing signals received at the inputs. The pulse-width modulated output has a pulse width representative of the dimmer circuit's dimmer setting. The circuit also includes an input network, coupled to the comparator, to receive the gate drive signal and to provide an output, in response, to the comparator's first input. The circuit also includes a threshold supply circuit to provide a threshold voltage to the comparator's second input, and a filter, coupled to the comparator, to convert the comparator's pulse-width modulated output to the dimmer reference level signal.