Isolated Interface for Dimmable LED Converter Safety
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Solution Overview
Problem
Conventional dimmable LED converters fail to maintain double insulation when connected with dimmers having only basic insulation, violating safety regulations and resulting in potential electrical shock hazards.
Innovation Solution
A dimmable converter design with a primary side switched isolated power converter stage, an isolated interface for dimming signals, and isolated signal transmission means using transformers or optocouplers to ensure galvanic isolation between the primary and secondary sides, maintaining SELV compliance and double insulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional dimmable LED converter is connected with a dimmer having only basic insulation, then the converter can operate with various dimmers, but the double insulation safety requirement is violated
Solution Approach 1:
An isolated interface stage is introduced as an intermediary component between the power converter stage and the dimming signal input. This interface stage includes an isolated control circuit that receives dimming signals through galvanically isolated signal transmission means (such as optocouplers or transformers), thereby maintaining the double insulation barrier while enabling compatibility with various dimmers having only basic insulation.
2Reliability
If galvanic isolation is implemented in the interface stage, then safety regulations are maintained, but the device complexity increases
Solution Approach 1:
The control circuit is segmented into two separate parts: a first control circuit on the primary side of the isolated power converter stage and a second control circuit on the secondary side. These two control circuits are galvanically isolated from each other through isolated signal transmission means. This segmentation allows the maintenance of double insulation safety requirements while managing the complexity through functional separation and standardized isolation components.
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 allows for safe operation with various dimmers, broadening the selection range while maintaining safety regulations and achieving linear dimming curves, independent of circuit topology, thus enhancing luminary design safety and performance.
Implementation Method 1
The isolated signal transmission means may use for example a current transformer for transmitting the current signal from the secondary side to the interface control circuit
Implementation Method 2
The further isolated transmission means may use for example an optocoupler for transmitting the control signal to the control circuit
Data Source
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AI summary
A dimmable converter (1) for driving an illuminant (14) such as an LED includes a primary side (4) switched isolated power converter stage. A switch is arranged on the primary side (4) of the isolated power converter stage and a control circuit (24, 24') controls an on/off switching of the switch. The control circuit (24, 24') is arranged either on the primary side (4) or on a secondary side (6) of the isolated power converter stage. An interface (8) isolated both against the primary side (4) and the secondary side (6) of the isolated power converter stage is supplied with a dimming signal (17.1, 17.2). The interface (8) comprises an interface control circuit (20) obtaining via an isolated signal transmission means (16) a current signal (19) indicating a current flow on the secondary side (6) of the isolated power converter stage from the secondary side (6) of the isolated power converter stage. The interface control circuit (20) generates a control signal transmitted to the control circuit (24, 24') of the isolated power converter stage.