Multiphase LLC Converter Active Passive Current Sharing
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Solution Overview
Problem
High-efficiency AC/DC power supplies with multiple phases face challenges in current sharing, leading to uneven power distribution and stress on individual phases, particularly as the number of phases increases, which affects performance and reliability.
Innovation Solution
A multiphase LLC DC-DC power converter with both active and passive current sharing methods, utilizing multiple LLC power trains and control circuits to regulate and synchronize current among phases, ensuring efficient power distribution and minimizing ripple current through phase managers and current mode controllers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If multiple power trains are used in parallel to minimize current stress, then current stress per phase is reduced, but current sharing becomes uneven and control complexity increases
Solution Approach 1:
The system divides the power conversion into multiple independent power trains (phases), each with its own control circuit. This segmentation allows current stress to be distributed across phases while maintaining independent control capability for each phase, resolving the contradiction between reduced current stress and control complexity.
Solution Approach 2:
Each power train is equipped with current sensing and control circuits that provide feedback on the current status. This feedback mechanism enables automatic current sharing regulation, reducing the complexity of manual coordination while ensuring balanced current distribution across all phases.
2Power
If the number of phases is increased to improve power density and efficiency, then power density increases, but current sharing balance deteriorates
Solution Approach 1:
Each phase is designed with identical circuit topology and control parameters, ensuring local quality consistency. This uniformity in design across all phases, combined with individual current sensing, enables scalable phase addition while maintaining current sharing balance and system reliability.
Solution Approach 2:
The control system dynamically adjusts operating parameters such as switching frequency and duty cycle for each phase based on real-time current measurements. This parameter adaptation allows the system to maintain optimal current distribution even as the number of phases increases, preserving both power density and reliability.
3Loss of energy
If active phase shedding is used to achieve flat efficiency curves, then efficiency performance improves, but control complexity and current management difficulty increase
Solution Approach 1:
The system implements dynamic phase enabling/disabling control based on load conditions. During light load, fewer phases are active to maintain efficiency; during heavy load, all phases are engaged. This dynamic configuration, managed by coordinated control circuits, achieves flat efficiency curves while the control complexity is mitigated through systematic phase management protocols.
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
The solution achieves high efficiency and reliable operation by ensuring balanced current sharing across phases, reducing stress on individual phases and maintaining flat efficiency curves across varying load ranges, thereby enhancing power density and performance.
Implementation Method 1
Each of the power trains includes a plurality of switching elements and a resonant circuit having an associated resonant frequency
Data Source
AI summary
A multiphase DC-DC converter includes multiple groups of first and second LLC power trains coupled in parallel which collectively provide an output voltage to a load. A voltage feedback control loop senses an output voltage for the LLC converter and generates an identical reference current signal for each of the multiple groups of power trains, the signals representing a reference current based on the sensed output voltage, wherein an active current sharing operation is provided between each of the groups. A local current control loop for each of the groups generates PWM control signals to each of the respective first and second power trains based on the reference current, the PWM control signals having an identical frequency but out of phase with respect to each other, wherein a passive current sharing operation is provided within each of the plurality of power groups.