Voltage Sensing in Isolated Converters via Primary Winding
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Solution Overview
Problem
Isolated power converters face challenges in controlling output voltage due to the isolation barrier between input and output stages, leading to unreliability, added complexity, and increased cost in existing methods for voltage sensing and feedback.
Innovation Solution
A system using a first transformer with a primary and secondary coil, a feedback winding coupled to the output inductor to form a second transformer, and a monitor circuit that calculates the output voltage by combining voltages across the output inductor's feedback winding, primary coil, and transformer turns ratios, allowing feedback control without direct comparison across the isolation barrier.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If isolated operational amplifiers are used for voltage sensing, then voltage feedback control is achieved, but device complexity and cost increase
Solution Approach 1:
The patent extracts the voltage sensing function from the isolated output side and brings it to the input side by measuring the voltage across the primary winding. This eliminates the need for isolated operational amplifiers on the output side, reducing device complexity while maintaining reliable feedback control through the transformer's inherent isolation.
Solution Approach 2:
The primary winding of the isolation transformer serves dual functions: power transfer and voltage sensing. By utilizing the existing primary winding for both purposes, the patent eliminates the need for separate sensing components, thereby reducing overall device complexity while maintaining control reliability.
2Reliability
If additional feedback windings are added to the isolation transformer, then voltage feedback is enabled, but device complexity and cost increase
Solution Approach 1:
The patent makes the primary winding multi-functional by using it for both power transfer and voltage sensing. This eliminates the need for additional feedback windings, reducing device complexity while maintaining reliable voltage feedback control through the same transformer component.
3Reliability
If optical isolation with digitization is used, then voltage feedback across isolation barrier is achieved, but device complexity and cost increase
Solution Approach 1:
The patent extracts the voltage measurement function from the isolated output side and performs it on the input side by measuring primary winding voltage. This eliminates the need for complex optical isolation and digitization systems, maintaining isolation barrier integrity while significantly reducing device complexity.
Solution Approach 2:
The patent replaces complex optical isolation and digitization systems with a simple electrical measurement approach. By measuring the voltage across the primary winding directly, the system achieves the same feedback control function without requiring optical components or digital conversion, reducing complexity while maintaining isolation.
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 approach provides a lightweight, reliable method for sensing output voltage, enabling effective control of the input circuit while maintaining isolation, thus reducing complexity and cost.
Implementation Method 1
an isolation transformer between an input power stage and an output power stage. This allows energy to be transferred from the input stage to the output stage
Implementation Method 2
a feedback winding coupled to the output inductor to form a second transformer
Data Source
AI summary
A system for sensing voltage in an isolated converter includes an input circuit isolated from an output circuit using a first transformer, the first transformer having a primary coil and a secondary coil, wherein the output circuit includes an output inductor and an output capacitor, and wherein the input circuit includes a power source that provides power to the output circuit through the first transformer; a feedback winding coupled to the output inductor to form a second transformer; and a monitor circuit that calculates a voltage across the output capacitor using a voltage across the feedback winding, a voltage across the primary coil of the first transformer, a turns ratio of the first transformer, and a turns ratio of the second transformer in order to provide feedback to control the input circuit.