PS-ZVT Bridge Converter Switching Sequence Control
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Solution Overview
Problem
Phase-shifted zero-voltage-transition converter circuits face an imbalance in power dissipation among switching devices, with some devices dissipating more power than others, necessitating the use of higher-wattage devices to handle maximum dissipation, which is costly and inefficient.
Innovation Solution
The switching sequence of the bridge transistors is alternated between two modes, periodically reversing the switching sequence for diagonally opposed devices to balance their average power dissipation, allowing identical lower-wattage devices to be used by averaging the power dissipation over extended operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed switching sequence is used in PS-ZVT converter, then the converter operates with simple control logic, but power dissipation becomes unbalanced among switching devices
Solution Approach 1:
The patent applies periodic action by alternating between two switching sequences in a cyclical manner. The controller switches between sequence set A and sequence set B over successive operating cycles, ensuring that each switching device periodically experiences both high-power-dissipation and low-power-dissipation roles. This periodic alternation balances the average power dissipation across all devices without requiring complex real-time adjustments.
Solution Approach 2:
The patent implements dynamics by making the switching sequence adaptive rather than fixed. The controller dynamically selects between different switching sequences based on operational needs, allowing the system to adjust its behavior to achieve balanced power dissipation. This dynamic approach transforms the static control logic into a flexible system that can optimize performance characteristics.
2Reliability
If higher-wattage devices are used to handle maximum power dissipation, then all switching devices can tolerate peak loads, but system cost and device size increase
Solution Approach 1:
By periodically alternating switching sequences, the patent ensures that no single device continuously bears the maximum power dissipation burden. Each device experiences peak power conditions only during specific intervals when its associated switch is active, while experiencing reduced power dissipation during other intervals. This temporal distribution allows the use of lower-wattage devices that would be insufficient for continuous peak operation but are adequate when peak loads are intermittent and balanced across the system.
3Ease of manufacture
If identical devices are used for all bridge transistors, then manufacturing and assembly are simplified, but devices must be oversized to handle maximum dissipation
Solution Approach 1:
The patent enables the use of identical devices for all bridge transistors by implementing periodic alternation of switching sequences. This approach distributes the power dissipation burden evenly across all devices over time, allowing each device to be sized for the average power dissipation rather than the peak power dissipation. The periodic switching ensures that each device experiences both high and low power conditions in a balanced manner, making it possible to use uniform, lower-wattage devices throughout the bridge circuit.
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 approach reduces the average power dissipation in each transistor by over 21%, improving durability, reducing operating temperature, and enabling cost-effective design and packaging savings.
Implementation Method 1
utilizing the effects of parasitic capacitance in switching devices such as MOSFETs and IGBTs
Implementation Method 2
parasitic and/or additional inductance to ensure that the switching devices each transition to a conductive state when the switched voltage is essentially zero
Data Source
AI summary
The switching sequence of a phase-shifted zero-voltage-transition (PS-ZVT) full bridge converter circuit is alternated between two modes by periodically reversing the switching sequence for diagonally opposed switching devices (Q1, Q4/Q2, Q3) of the bridge. Over a period of operation, each of the switching devices (Q1-Q4) periodically conduct the entire free-wheeling current that occurs during load current reversal transitions so as to balance their average power dissipation and reduce the overall power dissipation of the converter circuit.