Galvanically Isolated LED Driver Using Transformer Feedback
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Solution Overview
Problem
Galvanically isolated LED drivers require additional effort and cost to feedback information from the secondary side of the SELV barrier to the primary side, typically necessitating the use of an optocoupler.
Innovation Solution
A method and circuit design that allows for indirect detection of electrical parameters, such as current or resistance values, across a coding resistor on the secondary side of a transformer, using clocking parameters like frequency and duty cycle, eliminating the need for an optocoupler by using a measurement winding and a flyback converter for galvanically isolated transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If galvanic isolation is used in LED driver, then safety and electrical isolation are improved, but additional components like optocouplers are required increasing device complexity and cost
Solution Approach 1:
The patent combines the power transmission function and information feedback function into a single transformer component. The transformer not only provides galvanic isolation for power delivery but also enables bidirectional communication through its windings, eliminating the need for separate optocoupler components for feedback transmission.
Solution Approach 2:
The transformer is designed to serve multiple functions simultaneously: it provides galvanic isolation for safety, transmits power from primary to secondary side, and enables bidirectional information communication. The primary winding receives control signals while the secondary winding provides feedback, making the transformer a universal component that replaces multiple separate functions.
2Loss of information
If optocoupler is used for feedback transmission, then information can be transmitted across SELV barrier, but cost and device complexity increase
Solution Approach 1:
The feedback transmission function previously requiring a separate optocoupler is merged into the transformer's secondary winding. The transformer structure itself enables the feedback signal to cross the galvanic barrier without requiring additional isolation components, as the transformer windings inherently provide both power isolation and signal coupling.
Solution Approach 2:
The transformer acts as an intermediary that mediates both power and information transfer across the galvanic barrier. Instead of using an optocoupler as a separate intermediary for feedback, the transformer's magnetic coupling mechanism serves as the mediator for both energy and signal transmission, simplifying the overall system architecture.
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 information reading from an LED module without additional components like optocouplers, reducing costs and complexity while maintaining accurate parameter detection across the SELV barrier.
Implementation Method 1
galvanically isolated transmission of electrical power to the coding resistor located on the secondary side of a transformer
Implementation Method 2
indirect detection of the current through the coding resistor or the resistance value of the coding resistor based on a parameter detected on the primary side of the secondary side of the transformer
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The invention relates to a method for reading out information of an LED module (2), comprising the following steps: transmitting (21) electrical power to a circuit (6) on the secondary side of a transformer in a galvanically isolated manner in such a way there is a defined voltage on the circuit (6), wherein the circuit (6) is associated with the LED module (2), and indirectly sensing an electrical parameter of the circuit (6) or the change thereof over time on the basis of a parameter that is sensed on the primary side of the transformer (21).