Low-Side Buck Converter Eliminates Isolation Transformer
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Solution Overview
Problem
Conventional buck converters for LED lighting require an isolation transformer, increasing cost, size, and complexity due to the high-side floating switch and ground-referenced current control, which complicates the control circuitry.
Innovation Solution
A buck converter design that eliminates the isolation transformer by using a primary inductor, primary inductor current sensing circuit, switch current sensing circuit, and controller to control the switch based on sensed current signals, allowing the switch to be connected between the load and ground, enabling direct control without the need for isolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an isolation transformer is used in the buck converter to control the high-side floating switch, then the switch can be properly controlled, but the cost, size, and complexity of the converter increase
Solution Approach 1:
The patent extracts and eliminates the isolation transformer from the conventional buck converter circuit. By using a low-side switch connected to ground reference instead of a high-side floating switch, the controller can directly sense current and control the switch without requiring galvanic isolation, thereby removing the transformer component entirely
Solution Approach 2:
The patent inverts the traditional switch placement from high-side (between input and load) to low-side (between load and ground). This inversion allows the switch to be ground-referenced, enabling direct control and sensing without isolation transformers, thus simplifying the overall circuit architecture
2Ease of operation
If an isolation transformer is used in the buck converter, then the controller can control the high-side switch, but the cost and size of the converter increase
Solution Approach 1:
The patent removes the isolation transformer from the component list by fundamentally changing the switch topology to low-side switching. This extraction eliminates the need for galvanic isolation since the controller and switch share a common ground reference, directly reducing component quantity
Solution Approach 2:
The low-side switch configuration allows the same controller circuitry to perform both control and sensing functions without requiring separate isolated power supplies or additional isolation components, making the control system more universal and efficient
Data Source
AI summary
A light fixture includes a converter operable to drive a light source of the light fixture. The buck converter is operable to provide a predetermined average current to the light source or load. A switch of the buck converter is located in the low side of the buck converters such that a controller of the buck converter may drive the switch directly without the use of an isolation transformer. The buck converter controls operation of the switch based on current through the switch and current through the primary inductor of the buck converter.