Multi-Level Totem-Pole PFC Converter With Parallel Switching Cells
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Solution Overview
Problem
Current power converters face challenges in achieving high efficiency, high power density, and low electromagnetic interference (EMI) while maintaining high power conversion levels, as they often result in unbalanced currents and increased size and weight due to limited semiconductor device capabilities and single high frequency switching cells.
Innovation Solution
A power converter topology featuring multiple high frequency switching cells connected in parallel, magnetically coupled inductors, and a low frequency switching cell, which allows for pulse-width modulation control and current sharing, reducing total harmonic distortion (THD) and improving power factor (PF) through multi-level operation and EMI filtering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the number of semiconductor devices is increased to achieve high efficiency, then efficiency is improved, but power density decreases and size increases
Solution Approach 1:
The power converter is divided into multiple high frequency switching cells connected in parallel, where each cell handles a portion of the total power. This segmentation allows the system to achieve high efficiency through multiple devices while maintaining power density by distributing the power handling across smaller, parallel units rather than requiring one large device
Solution Approach 2:
The patent transitions from a single-phase topology to a multi-level topology by adding voltage levels through series-connected switching cells within parallel branches. This dimensional change in voltage structure allows efficient power conversion without proportionally increasing the physical size, as the voltage multiplication occurs in the electrical domain rather than requiring larger magnetic components
2Volume of moving object
If switching frequency is increased to improve power density, then power density is improved, but current ripple increases and EMI worsens
Solution Approach 1:
Multiple high frequency switching cells operate in parallel with phase-shifted control, dividing the total switching frequency burden across multiple cells. This segmentation of the switching function allows the system to maintain high effective switching frequency for power density while each individual cell operates at a manageable frequency, reducing current ripple and EMI through the distributed switching action
Solution Approach 2:
The patent employs periodic phase-shifting of control signals across multiple switching cells, where each cell is activated in a staggered sequence. This periodic action distributes the switching events over time, reducing peak current ripple and spreading EMI emissions across multiple frequency components, thereby mitigating the harmful effects of high frequency switching
3Power
If power conversion level is increased to handle higher current rates, then current handling capability is improved, but semiconductor device availability is limited and power density decreases
Solution Approach 1:
The power converter uses multiple high frequency switching cells connected in parallel, where each cell handles a fraction of the total current. This segmentation of current paths allows the system to achieve high current handling capability without requiring individual semiconductor devices with extremely high current ratings, thereby maintaining power density and using readily available devices
Solution Approach 2:
Multiple switching cells are merged in parallel configuration, combining their current handling capabilities to achieve the required total current capacity. This merging of parallel paths allows the system to scale current handling by adding more parallel cells rather than upgrading to larger, less available semiconductor devices, thus preserving power density
4Device complexity
If conventional totem-pole topology with single high frequency switching cell is used, then device count is reduced, but current ripple is high and filtering elements are large
Solution Approach 1:
The single high frequency switching cell is segmented into multiple parallel switching cells, each contributing to current synthesis. This segmentation of the switching function creates multiple current waveforms that can be combined to reduce ripple content, thereby reducing the size of filtering elements required without significantly increasing overall device complexity
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 configuration enhances efficiency and power density by reducing current and voltage stresses on components, achieving lower THD and higher PF, and simplifying the control structure, while also reducing EMI emissions.
Implementation Method 1
at least one inductor of the plurality of inductors is magnetically coupled to at least one other inductor of the plurality of inductors. The plurality of inductors is configured to inductively couple a common connection point on an input side with at least a first connection point connected to a midpoint of the first high frequency switching cell
Data Source
AI summary
A power conversion apparatus employs multi-level techniques and wide band-gap semiconductor switching devices to achieve high efficiency in a converter system having high power density. The apparatus may be configured as a bi-directional conversion system capable of operating as both an inverter, configured to receive DC power and produce AC power, and as a rectifier configured to receive AC power and produce DC power. The apparatus is especially suitable for electric vehicle (EV) applications.