Reverse-Coupled Inductors for Interleaved DC-DC Converters
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Solution Overview
Problem
Multi-phase three-level power converters face challenges with high output and inductor ripple currents and common mode noise, leading to reduced efficiency, increased costs, and decreased power density due to interleaved operation.
Innovation Solution
The implementation of a multi-phase three-level power converter with reverse-coupled inductors and a magnetic element design that includes inversely coupled coils, reducing circulating currents and common mode noise by canceling out circulating currents in the circulating current path, while maintaining the ripple cancellation effect of interleaving.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If interleaved operation is used to reduce output current ripple, then output current ripple is reduced, but inductor circulating current ripple increases abnormally
Solution Approach 1:
The patent applies reverse-coupled inductors that convert the harmful circulating current ripple into a beneficial effect. The reverse coupling creates a negative feedback mechanism where the inductors generate opposing voltages that cancel the circulating current ripple, transforming the harmful interleaving effect into a beneficial current suppression mechanism while maintaining output ripple reduction.
Solution Approach 2:
The reverse-coupled inductors act as intermediary elements between the interleaved power converter legs. These inductors mediate the circulating current by providing a controlled path with reverse coupling that suppresses the abnormal current ripple without interfering with the primary power conversion function and output current smoothing.
2Quantity of substance
If reverse-coupled inductors are added to reduce circulating current ripple, then circulating current ripple is reduced, but device complexity increases
Solution Approach 1:
The patent merges the reverse-coupled inductors with the existing power converter structure by integrating them into the circulating current path between interleaved legs. This combining approach reduces device complexity by consolidating multiple functions into unified components rather than adding separate independent systems.
Solution Approach 2:
The reverse-coupled inductors serve multiple functions simultaneously: they suppress circulating current ripple, maintain output current smoothing, and provide a unified solution that works across different interleaved power converter configurations. This multi-functionality reduces overall system complexity by eliminating the need for separate solutions for each problem.
3Stress or pressure
If three-level power converters are used for high voltage applications, then voltage stress on switches is reduced, but common mode noise is generated at switching frequency
Solution Approach 1:
The reverse-coupled inductors convert the common mode noise generated by three-level power converters into a beneficial suppression effect. By creating opposing voltage signals through reverse coupling, the inductors cancel the common mode noise at the switching frequency, transforming the harmful electromagnetic interference into a noise cancellation mechanism.
4Object-generated harmful factors
If CM filter is added to attenuate common mode noise, then common mode noise is reduced, but power density decreases due to increased volume
Solution Approach 1:
The patent extracts the common mode noise suppression function from the traditional bulky CM filter and integrates it into the reverse-coupled inductor structure. This extraction eliminates the need for separate large-volume filtering components while maintaining noise attenuation, thereby preserving power density.
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 significantly reduces output and inductor ripple currents, decreases common mode noise, and enhances power density by minimizing the size and weight of the power converter, allowing for more compact and cost-effective designs.
Implementation Method 1
reverse-coupled inductors having one coil in series with the inductor and another coil in series with the one coil in a circulating current path resulting from the interleaving of phases
Implementation Method 2
a magnetic element design that includes inversely coupled coils, reducing circulating currents and common mode noise by canceling out circulating currents in the circulating current path
Data Source
AI summary
Output current ripple is reduced in a three-level DC-DC power converter by connecting a plurality of phase legs in parallel between a source of input power and an output of the power converter and conducting power from the source of input power to the power converter output in an interleaved manner. The large current that results from such interleaved operation is reduced to acceptable levels, potentially less than the output current ripple of the power converter by providing inversely coupled inductors having a mutual inductance preferably greater than the inductor of the power converter in respective phase legs and in series in the circulating current path to avoid any need to increase the power converter inductance due to the circulating current. The inductor and inversely coupled inductors are preferably integrated into a single magnetic element of compact design.