EV Inverter Message Bus Isolation Against Coupled Currents
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Solution Overview
Problem
Existing communication architectures in high EM field applications, such as electric vehicle inverters, are susceptible to coupled currents, leading to malfunctions and delayed fault detection due to the inability to effectively tolerate induced currents, which compromises the control and management of power device switches.
Innovation Solution
A high-speed, bidirectional communication architecture utilizing a single-wire data bus with a galvanic interface and logic managers that define communication bits based on dominant and recessive phases, along with switched current sources and sinks, to maintain control and interrupt capabilities despite coupled currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional communication architectures are used in high voltage areas, then device complexity is reduced, but reliability deteriorates due to susceptibility to coupled currents
Solution Approach 1:
The communication architecture is segmented into multiple message managers (low voltage message manager, high voltage message manager, and point-of-use message manager) separated by a galvanic interface. This segmentation isolates the high voltage area from the low voltage area, preventing coupled currents from affecting the entire system while maintaining communication functionality through the galvanic interface.
Solution Approach 2:
A galvanic interface acts as an intermediary between the low voltage message manager and the high voltage message manager. This intermediary component enables bidirectional communication while providing galvanic isolation, thereby protecting the communication system from harmful coupled currents generated in the high voltage area during power device switching.
2Reliability
If galvanic isolation is implemented to separate high voltage and low voltage areas, then reliability improves by tolerating coupled currents, but device complexity increases
Solution Approach 1:
The message managers are designed with multi-functionality, handling both communication protocols and galvanic isolation coordination. The high voltage message manager and point-of-use message manager can operate independently or in coordination, providing universal communication capability across different voltage domains while managing the galvanic interface efficiently.
Solution Approach 2:
The communication protocol uses parameter changes in the single-wire data bus (dominant and recessive phases with different timing durations) to encode logic bits. This parameter-based encoding allows robust communication through the galvanic interface by using timing differences rather than voltage levels, making the communication more tolerant to electrical disturbances.
3Device complexity
If a single-wire data bus is used for communication, then device complexity is reduced, but reliability worsens due to susceptibility to coupled currents
Solution Approach 1:
The galvanic interface serves as an intermediary that protects the single-wire data bus from coupled currents. By placing the galvanic interface between the low voltage and high voltage message managers, the simple single-wire bus architecture maintains its low complexity while the intermediary component ensures reliability by isolating it from electrical disturbances in the high voltage area.
Solution Approach 2:
The communication protocol dynamically switches between dominant and recessive phases on the single-wire data bus, with timing parameters that can be adjusted. This dynamic phase switching allows the system to tolerate coupled currents by using time-based encoding rather than static voltage levels, maintaining reliability without requiring a complex multi-wire bus architecture.
Data Source
AI summary
A system includes an inverter configured to convert DC power from a battery to AC power to drive a motor, wherein the inverter includes: a galvanic interface configured to separate a high voltage area from a low voltage area; a low voltage message manager in the low voltage area; a high voltage message manager in the high voltage area, and configured to communicate with the low voltage message manager; and a point-of-use message manager in the high voltage area, and configured to communicate with the high voltage message manager.