Galvanically Isolated LED Converter Primary-Side Control
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Solution Overview
Problem
Existing converters for dimmable light sources, particularly those using LEDs, face challenges in efficiently regulating output current intensity across a SELV barrier without increasing circuitry complexity or costs, while maintaining efficient power transfer and wide-range dimmability.
Innovation Solution
A converter design featuring a primary-side clocked half-bridge circuit and LLC resonant circuit, where output current intensity is regulated based on a controlled variable detected on the primary side, eliminating the need for secondary-side feedback via a separate isolator, and utilizing a comparator to compare the controlled variable with a reference for dimming adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If feedback control is implemented on the secondary side with separate isolators, then output current regulation precision is improved, but device complexity and installation space increase
Solution Approach 1:
The patent divides the converter into primary-side and secondary-side circuits with galvanic isolation. The control function is segmented to operate primarily on the primary side, using the controlled variable detected there to regulate output current, thereby avoiding the need for complex secondary-side feedback isolators while maintaining regulation precision
Solution Approach 2:
The patent uses an intermediary approach by detecting the controlled variable on the primary side and using it to control the half-bridge circuit, which in turn regulates the secondary-side output current. This intermediary control method eliminates the need for direct secondary-side feedback isolators, reducing device complexity while maintaining precision
2Manufacturing precision
If secondary-side switches and isolators are added for feedback control, then dimming control accuracy is improved, but manufacturing costs increase
Solution Approach 1:
The patent extracts the feedback control function from the secondary side and relocates it to the primary side. By taking out the need for secondary-side isolators and switches, the patent reduces component count and manufacturing complexity while maintaining dimming control accuracy through primary-side controlled variable detection and control
Solution Approach 2:
The primary-side controlled variable detection and control mechanism serves multiple functions: it enables both output current regulation and dimming control accuracy. This multi-functional approach eliminates the need for separate secondary-side control components, reducing manufacturing costs while maintaining precision
3Device complexity
If primary-side controlled variable detection is used for regulation, then device complexity is reduced, but adaptability to secondary-side conditions decreases
Solution Approach 1:
The patent implements a feedback mechanism where the controlled variable detected on the primary side is used to continuously adjust and regulate the output current. This feedback loop ensures that the converter adapts to secondary-side load conditions (such as LED variations) while maintaining simplicity by operating the control logic on the primary side without requiring complex secondary-side sensing
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 configuration allows for efficient energy transfer and wide-range dimmability with reduced circuitry complexity and costs, enabling consistent current levels for varying LED loads without requiring secondary-side switches or isolators, thus simplifying control and reducing load-dependent fluctuations.
Implementation Method 1
a transformer connected to the resonant circuit
Implementation Method 2
resonant circuit fed by the inverter, a transformer connected to the resonant circuit
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
A galvanically isolated transformer (59) for energizing a lamp (5) comprises a primary circuit (60) including a half-bridge circuit that has two reciprocally clocked switches (21, 22), and including an LLC resonant circuit (25-27). The transformer (59) further comprises a secondary circuit (30) including an output (35) for supplying energy to the lamp (5). A control device (14) is designed to control the half-bridge circuit in accordance with a control variable (ipeak) detected in the primary circuit (60) in order to adjust a current intensity supplied to the lamp (5) by the secondary circuit (30) to a desired value.