Dual Galvanic Isolation Circuit for EV Inverter PWM Noise Immunity
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Solution Overview
Problem
Inverters used in electric vehicles face electromagnetic interference issues, such as common-mode radio frequency interference, which compromise the operation of galvanic transceivers due to radio frequency noise being coupled or induced into high voltage operating planes.
Innovation Solution
A system with dual galvanic isolators, amplifiers, comparators, and a pulse reshape and envelope detector is employed to transmit Pulse Width Modulation signals across high and low voltage areas, utilizing a resistor average circuit and an out-of-range detector to mitigate common-mode noise and transient immunity interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If galvanic transceivers are used in high voltage operating planes, then power conversion functionality is achieved, but electromagnetic interference and common-mode noise compromise correct operation
Solution Approach 1:
The system divides the operating environment into distinct voltage domains (high voltage area and low voltage area) separated by galvanic isolators. This segmentation allows power conversion to occur in the high voltage area while protecting control and communication circuits in the low voltage area from electromagnetic interference and common-mode noise.
Solution Approach 2:
Galvanic isolators serve as intermediary devices between the high voltage and low voltage areas. These isolators transfer signals and power while blocking the propagation of electromagnetic interference and common-mode noise, enabling safe operation of galvanic transceivers in the high voltage environment.
2Reliability
If dual galvanic isolators with amplifiers and comparators are used, then common-mode noise rejection and CMTI tolerance are improved, but device complexity increases
Solution Approach 1:
The system combines multiple functional blocks (dual galvanic isolators, amplifiers, comparators, pulse reshape and envelope detector) into an integrated circuit architecture. This merging approach achieves superior common-mode noise rejection and CMTI tolerance while reducing the overall number of discrete components and simplifying the device structure.
Solution Approach 2:
The integrated circuit performs multiple functions simultaneously: galvanic isolation, signal amplification, comparative detection, pulse reshaping, and envelope detection. This multi-functionality enables the system to handle various signal conditions and reject common-mode noise across different operating scenarios without requiring separate dedicated circuits for each function.
Data Source
AI summary
A system includes an inverter including: a first galvanic isolator separating a low voltage area from a high voltage area, the first galvanic isolator having a first galvanic isolator output path; a second galvanic isolator having a second galvanic isolator output path; an amplifier connected to the first galvanic isolator via the first galvanic isolator output path, and connected to the second galvanic isolator via the second galvanic isolator output path, the amplifier having a first amplifier output path and a second amplifier output path; a comparator connected to the amplifier via the first amplifier output path and the second amplifier output path, the comparator having a first comparator output path and a second comparator output path; and a pulse reshape and envelope detector connected to the comparator via the first comparator output path and the second comparator output path.