Active Detection Rectifier for LED Driver Current Sensing
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Solution Overview
Problem
Existing driver circuits for LED lighting systems require costly and complex arrangements to detect current on the secondary side, leading to detection errors, especially at high temperatures due to reverse current issues in diodes used as rectifiers.
Innovation Solution
The circuit design allows current detection on the primary side by using an active detection rectifier with four rectifier switches, which actively controls the rectification process to compensate for reverse currents, eliminating the need for additional detection inputs and reducing errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current detection is performed on the secondary side using a detection circuit and bridging element, then the illuminant current can be detected, but the circuit costs increase and the circuit arrangement becomes complicated
Solution Approach 1:
The patent inverts the conventional approach by performing current detection on the primary side instead of the secondary side. The detection circuit is integrated into the primary side converter winding, eliminating the need for separate secondary-side detection circuits and bridging elements. This inversion simplifies the overall circuit arrangement while maintaining detection capability.
Solution Approach 2:
The detection function is merged with the existing primary side converter winding. The same winding that performs power conversion also serves as the detection sensor, eliminating the need for separate detection components on the secondary side. This merging reduces component count and circuit complexity.
2Device complexity
If diodes are used as rectifiers in the detection circuit, then the circuit is simple, but detection errors occur at high temperatures due to reverse current
Solution Approach 1:
The patent extracts the rectification function from passive diodes and assigns it to active switches on the primary side. By removing the reliance on diode reverse current characteristics, the detection circuit becomes immune to temperature-induced detection errors while maintaining simplicity through the use of existing switch control signals.
Solution Approach 2:
The control unit uses the detected primary side current as feedback to actively control the rectifier switches. This active feedback control replaces the passive diode rectification, eliminating reverse current errors while maintaining circuit simplicity through coordinated switch operation.
3Measurement precision
If an auxiliary winding and detection circuit are provided on the secondary side, then current parameter detection is possible, but additional components increase circuit costs
Solution Approach 1:
The primary side converter winding serves dual functions: power conversion and current detection. This multi-functionality eliminates the need for separate auxiliary windings and detection circuits on the secondary side, reducing component count and manufacturing costs while maintaining detection precision.
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
This solution enables accurate current detection on the primary side, reducing detection errors and simplifying the circuit arrangement, while maintaining reliable operation across varying temperatures.
Implementation Method 1
the secondary side of the circuit is fed by electromagnetic coupling of the primary-side converter winding L2_1 and the secondary-side converter winding L22, L23
Implementation Method 2
The detection circuit E then detects, by means of the auxiliary winding Lh, a current induced on the secondary side of the circuit
Data Source
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AI summary
The invention relates to a drive circuit for operating an illuminant, preferably at least one LED, comprising an isolated converter which is clocked on the primary side by a control unit by means of at least one controlled switch unit, said converter supplying a rectifier starting from which the illuminant can be fed, a measurement circuit for indirectly measuring the current on the secondary side of the converter having a transformer with at least one winding on the primary side.