Flying Capacitor Primary Circuit for High-Voltage ZVS DC/DC Conversion
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Solution Overview
Problem
High power DC/DC converter circuits require larger switches to handle high voltage differences, leading to increased size and reduced power density, as well as slower switching due to higher output capacitances, which is inefficient and limits their performance.
Innovation Solution
A voltage converter circuit design with a primary side circuit featuring four switches and two capacitors, where a flying capacitor and transformer coil are used to distribute the voltage difference across multiple switches, reducing the voltage rating of each switch and enabling smaller, more efficient components with lower output capacitances, allowing for higher power density and faster switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If larger switches are used to handle high voltage differences, then the voltage handling capability is improved, but the device size increases and power density decreases
Solution Approach 1:
The patent divides the high voltage difference into multiple smaller voltage segments by introducing intermediate nodes with capacitors. Four switches are arranged in series, with each switch handling only a portion of the total voltage difference. The flying capacitor and other capacitors create intermediate voltage levels, so that instead of one switch handling the full high voltage, multiple switches each handle a fraction of that voltage, enabling the use of smaller switches and reducing overall device size.
2Strength
If larger switches are used to handle high voltage differences, then the voltage handling capability is improved, but the power density is reduced
Solution Approach 1:
By segmenting the voltage handling across multiple smaller switches, each switch can be optimized for its specific voltage level, resulting in smaller individual component sizes. This segmentation allows the overall circuit to achieve the required voltage handling capability while maintaining higher power density because the smaller switches occupy less space and have lower parasitic elements.
3Strength
If larger switches are used to handle high voltage differences, then the voltage handling capability is improved, but the switching speed decreases due to higher output capacitances
Solution Approach 1:
The patent segments the voltage handling function across multiple switches, where each switch handles a smaller voltage portion. This results in each switch having lower output capacitance compared to a single large switch handling the full voltage. Lower capacitance enables faster charging and discharging, thus achieving faster switching speeds while still maintaining the overall high voltage handling capability of the circuit.
Solution Approach 2:
The patent changes the voltage parameter distribution across the switches by introducing intermediate capacitive nodes. Instead of one switch handling the full voltage, the voltage is divided into segments, and each switch operates at a lower voltage level with corresponding lower capacitance. This parameter change enables faster switching while maintaining the required overall voltage handling capability.
4Volume of moving object
If smaller switches are used to reduce device size, then the device size is reduced, but the voltage handling capability decreases
Solution Approach 1:
The patent uses segmentation to allow smaller switches to collectively handle high voltage. By arranging multiple smaller switches in series with capacitive intermediate nodes, each switch handles only a portion of the total voltage. The series combination of these smaller voltage-handling segments achieves the overall high voltage handling capability while using smaller individual components, thus reducing device size.
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 reduced size and increased power density while enabling faster switching, specifically through zero voltage switching (ZVS), improving the efficiency and performance of high power DC/DC converters.
Implementation Method 1
a primary side transformer coil connected between the second switch output node and the second capacitor node of the first capacitor
Implementation Method 2
A flying capacitor is connected between first circuit node and a second circuit node
Data Source
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AI summary
A voltage converter circuit including a primary side circuit including four transistors connected in series between two voltage application nodes, and two capacitors coupled in series between the two voltage application nodes. A flying capacitor is connected between first circuit node and a second circuit node, where the first circuit node is between the first and second transistors in the transistor series, and the second circuit node is between the third and fourth transistors in the transistor series. A primary side transformer is connected between a third circuit node and a fourth circuit node, where the third circuit node is between the second and third transistors in the transistor series, and the fourth circuit node is between the first and second capacitors in the capacitor series.