Isolated Switched Resonant Converter for LED Flicker Reduction
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Solution Overview
Problem
Existing LED converters lack accurate and flexible current sensing methods, leading to inefficiencies and potential issues like LED flickering.
Innovation Solution
An isolated switched resonant converter with a detection mechanism that senses differential current between the secondary winding and resonance capacitor, using a sense transformer and rectifier stages to provide a feedback signal for precise control of the switching stage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current sensing is performed using traditional methods with sense transformers and rectifier stages, then the converter can operate, but the current sensing accuracy and flexibility are insufficient leading to LED flickering
Solution Approach 1:
The patent introduces an intermediary signal processing stage that extracts the differential current component from the total current signal. By using a differential sensing approach where the sense transformer measures the difference between input and output currents, the system isolates the actual LED load current from other current components, thereby improving measurement accuracy and eliminating flickering issues
Solution Approach 2:
The patent replaces traditional mechanical/electrical current sensing methods with a signal-based differential measurement approach. Instead of directly measuring current through invasive shunt resistors or complex rectifier circuits, the system uses the differential current signal extracted from the transformer windings to derive accurate LED current information, simplifying the sensing mechanism while improving precision
2Measurement precision
If a sense transformer with multiple windings is used for current detection, then current sensing capability is improved, but the device complexity increases
Solution Approach 1:
The sense transformer is designed with multi-functionality, serving both as the isolation transformer for the resonant converter and as the current sensing element. The differential windings on the transformer simultaneously provide galvanic isolation and enable differential current measurement, eliminating the need for separate sensing transformers and reducing overall device complexity
Solution Approach 2:
The patent merges the isolation transformer function with the current sensing function into a single integrated transformer structure. The differential windings are combined with the main power transfer windings, allowing the same magnetic core and winding structure to perform both power isolation and current measurement functions, thereby reducing component count and simplifying the circuit
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
Enables accurate and flexible detection of current through the LED load, preventing flickering and ensuring efficient operation by allowing precise setting of operational parameters.
Implementation Method 1
detection means configured to detect a signal representing a differential current based on a difference between a first current flowing through the secondary side winding and a second current flowing through the capacitor
Implementation Method 2
the detection means comprises a sense transformer configured to detect the signal representing the differential current and a first rectifier stage configured to rectify the signal representing the differential current
Data Source
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AI summary
The disclosure relates to an isolated switched resonant converter for suppling a LED load, comprising a switching stage having at least one switch driven by a control circuit of the converter, a resonance circuit supplied by the switching stage, a transformer as an isolation stage, a resonance capacitor, wherein the capacitor is arranged in parallel to a secondary side winding of the transformer, wherein the secondary side winding is arranged to supply output terminals of the converter supplying the LED load, and detection means configured to detect a signal representing a differential current based on a difference between a first current flowing through the secondary side winding and a second current flowing through the capacitor, wherein the signal representing the differential current is supplied to the control circuit.