Direct Parallel Switch Control for Automotive Power Converters
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Solution Overview
Problem
High power electric drive systems in electric and hybrid vehicles face current limitations due to commercially available power devices, and paralleled phase legs often experience circulating current and imbalanced current issues, which are exacerbated by piece-to-piece variation and differing gate control propagation delays, necessitating the use of inductors and dead time to mitigate these problems, but this increases system size.
Innovation Solution
The implementation of direct parallel power switches with integrated current sensors and control circuitry that generates state signals based on current thresholds to prevent switch activation, eliminating the need for inductors and dead time, allowing for efficient operation of voltage source inverters/converters without circulating current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If inductors and dead time are used to mitigate circulating current and imbalanced current issues in paralleled phase legs, then current balance and system reliability are improved, but system size and complexity increase
Solution Approach 1:
The patent extracts and removes the inductors from the paralleled phase leg configuration. By using direct parallel connection of switches with integrated current sensors and control circuitry, the inductors that previously were necessary to mitigate circulating current are eliminated, reducing system size while maintaining current balance through active control
Solution Approach 2:
The patent implements feedback control through integrated current sensors on each switch that continuously monitor current flow. The control circuitry uses this real-time current information to dynamically adjust switch activation, preventing circulating current and imbalanced current distribution without requiring passive inductors
2Reliability
If inductors are added to paralleled phase legs to prevent circulating current, then current distribution is improved, but system cost and size increase
Solution Approach 1:
The patent removes the inductors from the system by using direct parallel switch connection with active current monitoring and control. The current sensors and control circuitry replace the function previously performed by inductors, eliminating the need for these passive components and reducing overall system component quantity
Solution Approach 2:
The patent replaces the passive mechanical/electrical inductor-based current balancing approach with an active electronic control system. Integrated current sensors and control circuitry use electronic feedback to regulate current distribution, substituting the physical inductor function with electronic control mechanisms
3Device complexity
If direct parallel switches are used without inductors, then system size is reduced, but circulating current and shoot-through conditions may occur
Solution Approach 1:
The patent applies preliminary action by using control circuitry to predict and prevent harmful conditions before they occur. The system monitors current through integrated sensors and proactively prevents shoot-through conditions and circulating current by controlling switch activation timing, eliminating the need for protective inductors
Solution Approach 2:
The patent implements real-time feedback control through integrated current sensors that continuously monitor switch current. The control circuitry uses this feedback to dynamically adjust switch operation, detecting and preventing circulating current and shoot-through conditions as they develop, maintaining safety without passive protection components
Data Source
AI summary
An automotive power converter includes positive and negative DC rails, a pair of phase legs each having first and second switches connected in series, an output electrically connected between the first and second switches of each of the phase legs, and control circuitry configured to prevent turn on of the first switches responsive to current through either of the second switches exceeding a predefined threshold.