Multi-phase Buck Converter with Coupled Inductors
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Solution Overview
Problem
Multi-phase buck converters experience sub-harmonic output ripple due to asymmetrical magnetic characteristics, which reduces efficiency and increases ripple current, especially in converters with an odd number of phases.
Innovation Solution
The implementation of a multi-phase converter design where pairs of converters are connected to coupled inductors wound around a common core, with a phase shift scheme to eliminate ripple, and at least one inductor remaining uncoupled to maintain symmetry and reduce ripple current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If multiple inductors are wound around a common core to achieve current cancellation and reduce ripple, then the peak-to-peak current through inductors is reduced and converter efficiency is improved, but the arrangement becomes inherently asymmetrical causing sub-harmonic output ripple
Solution Approach 1:
The patent applies asymmetry by intentionally creating an asymmetrical winding arrangement where inductors are wound in opposite directions around the common core. This asymmetrical configuration enables current cancellation between phases while maintaining symmetrical magnetic characteristics through careful design of the winding patterns and connections, thereby eliminating sub-harmonic ripple.
2Speed
If inductors are coupled together to reduce inductor size and improve transient response, then the converter responds faster to load changes, but asymmetrical coupling introduces sub-harmonic ripple
Solution Approach 1:
The patent uses asymmetrical winding directions for coupled inductors to achieve current cancellation while maintaining symmetrical magnetic properties. The inductors are wound in opposite directions around the common core, creating asymmetrical physical arrangement that translates to symmetrical magnetic characteristics and eliminates sub-harmonic ripple during transient responses.
3Power
If more phases are added to increase current rating, then the converter handles higher current loads, but the complexity of maintaining symmetrical magnetic characteristics increases
Solution Approach 1:
The patent segments the multi-phase converter into pairs of phases, where each pair uses coupled inductors with opposite winding directions. This segmentation approach simplifies the design of high-current multi-phase converters by breaking down the complexity into manageable pairs, making it easier to maintain symmetrical magnetic characteristics across multiple phases while achieving high current ratings.
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 design reduces sub-harmonic ripple, decreases RMS current per phase, minimizes output capacitance, and eliminates harmonic ripple, enhancing efficiency and transient response.
Implementation Method 1
current cancellation in a multi-phase voltage regulator such as a multi-phase buck converter can result in the reduction of ripple in the output current
Implementation Method 2
An inductor 12 is connected to each respective switched node 10 at one pole thereof and to an output node 14 at another pole thereof
Data Source
AI summary
A multi-phase converter comprising 2N+1 inductors; and 2N+1 switching converters parallel connected and each including a switched node; wherein N is an even integer, a pair of said inductors are coupled and wound about a common core and each said coupled inductor is connected at one pole thereof to a respective switched node and at another pole thereof to an output node, and at least one of said inductors is uncoupled from the other inductors.