Symmetrical Boost Converter Topology for Balanced Isolation Voltages
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Solution Overview
Problem
Existing DC-to-DC boost converters in electric vehicles powered by fuel cells create an undesired asymmetry in isolation voltages to the vehicle chassis, leading to reduced component service life and non-compliance with clearance and creepage distance requirements.
Innovation Solution
A symmetrical DC-to-DC boost converter with separate negative and positive DC voltage inputs, chokes, and symmetry capacitors is introduced, ensuring no direct connection between the fuel cell and high voltage internal electrical system, achieving a symmetrical voltage distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional DC-to-DC boost converter is used with direct connection between fuel cell terminals and high voltage internal electrical system, then the voltage conversion function is achieved, but asymmetry in isolation voltages occurs leading to reduced component service life and non-compliance with safety standards
Solution Approach 1:
The converter is divided into two symmetrical half-bridges (positive and negative), each with its own switch, diode, and capacitor. This segmentation creates balanced isolation voltages between the fuel cell and high voltage internal electrical system, eliminating the asymmetry that reduces component service life while maintaining the voltage conversion function
Solution Approach 2:
Two capacitors (C1 and C2) are introduced as intermediary elements in the circuit. These capacitors serve as mediators that balance the isolation voltages by providing symmetrical voltage division, thereby improving reliability and component service life without significantly increasing overall device complexity
2Reliability
If a conventional DC-to-DC boost converter is used with direct connection between fuel cell terminals and high voltage internal electrical system, then the voltage conversion function is achieved, but clearance and creepage distance requirements are not met
Solution Approach 1:
The converter topology is segmented into two symmetrical half-bridges with separate positive and negative switches (S1, S2) and capacitors (C1, C2). This segmentation creates balanced isolation voltages that ensure adequate clearance and creepage distances between high voltage terminals and the vehicle chassis, meeting safety standards
Solution Approach 2:
The patent applies asymmetry in reverse - it deliberately creates a symmetrical structure where the positive and negative half-bridges are mirror images of each other. This symmetry ensures that isolation voltages to the vehicle chassis are balanced, thereby meeting clearance and creepage distance requirements for safety standards compliance
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 reduces asymmetry in isolation voltages, enhancing component longevity and compliance with safety standards, thereby improving the reliability and performance of the vehicle's electrical system.
Implementation Method 1
the chokes are coupled magnetically
Implementation Method 2
a first symmetry capacitor connected to the negative DC voltage input and the negative DC voltage output, as well as a second symmetry capacitor connected to the positive DC voltage input and the positive DC voltage output
Data Source
AI summary
A symmetrical DC-to-DC boost converter includes a DC input voltage source with a negative DC voltage input and a positive DC voltage input, a negative DC and positive DC voltage output, at least four switches, and two chokes, one of which is connected to the negative DC voltage input and two adjacent switches, and the other of which is connected to the positive DC voltage input and two other adjacent switches, such that a symmetrical topology with separate DC voltage inputs is obtained. Furthermore, there is an input capacitor between the voltage inputs and a first symmetry capacitor connected to the negative DC voltage input and the negative DC voltage output, as well as a second symmetry capacitor connected to the positive DC voltage input and the positive DC voltage output.