Multilevel DC/DC Converter Topology for Lower Switching Losses
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Solution Overview
Problem
Existing DC/DC-converters face challenges in achieving improved switching characteristics, higher efficiency, and reduced losses, particularly when using lower breakdown voltage semiconductors and multiphase technology.
Innovation Solution
A DC/DC-converter design utilizing multilevel technology with a transformer having primary and secondary coils, connected in polygon arrangements, and converter circuits that function as inverters and rectifiers, allowing for phase-shifted alternating current generation and resonance decoupling, along with controlled switching to minimize losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If multilevel technology is used, then switching characteristics are improved and losses are reduced, but device complexity increases
Solution Approach 1:
The converter circuit is divided into multiple independent converter legs (first converter leg, second converter leg, third converter leg), each handling a portion of the power conversion. This segmentation allows parallel processing of power conversion tasks, reducing overall switching losses while distributing the complexity across modular units rather than concentrating it in a single complex circuit.
Solution Approach 2:
The patent transitions from conventional 2-level voltage switching to multilevel voltage switching (3-level or higher), adding a voltage level dimension to the switching operation. This dimensional change enables smoother voltage transitions, reduced dv/dt stress on semiconductor devices, and lower switching losses, while the modular leg structure manages the increased circuit complexity.
2Object-generated harmful factors
If multiphase technology is used, then ripple cancellation is achieved, but device complexity increases
Solution Approach 1:
The converter is divided into multiple converter legs (at least three phases), with each leg producing an output current that is phase-shifted relative to the others. This segmentation enables the harmful ripple components from each phase to cancel each other out through phase opposition, while the modular structure manages the complexity of coordinating multiple phases.
Solution Approach 2:
Each converter leg operates with a phase shift of 360°/Number of legs relative to adjacent legs, creating periodic current waveforms that are offset in time. This periodic action with specific phase relationships causes the ripple components to align in such a way that they cancel each other at the output, eliminating harmful ripple while maintaining manageable complexity through regular phase progression.
3Loss of energy
If lower breakdown voltage semiconductors are used, then figure of merit is improved, but voltage handling capability is reduced
Solution Approach 1:
The patent introduces multiple voltage levels (beyond the conventional 2-level structure) in the converter legs, creating a voltage dimensionality expansion. This multilevel structure allows the use of lower breakdown voltage semiconductor devices by distributing the total voltage stress across multiple series-connected semiconductor switches within each leg, thereby improving the figure of merit (RdsonxQ) while maintaining the required voltage handling capability through the combined series arrangement.
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 design achieves lower losses, improved switching characteristics, and efficient ripple cancellation, enabling higher switching frequencies and reliable operation in both forward and backward modes.
Implementation Method 1
a transformer that comprises a primary side and a secondary side, wherein the primary side comprises a number of n primary coils and the secondary side comprises a number of n secondary coils
Implementation Method 2
The polygon connection of the resonance capacitors in the input stage provide lower current stress on the capacitors compared to a star connection
Data Source
AI summary
A DC/DC-Converter, including a transformer that includes a primary side which includes n primary coils and a secondary side which includes n secondary coils, wherein the primary side is terminated by n primary capacitors, which are connected in a first polygon arrangement, each primary capacitor connecting two of the primary coils. The first converter circuit is connected in between primary side of the transformer and two primary side contacts, and includes a first multilevel converter configured to work as a inverter when the DC/DC-converter is used in a forward mode, a second converter circuit connected in between the secondary side of the transformer and two secondary side contacts and is configured to work as a rectifier when the DC/DC-converter is used in a forward mode; and a control circuit configured to control the first multilevel converter of the first converter circuit to work as the inverter in the forward mode.