EV Inverter Oscillator Calibration Across Galvanic Isolation
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Solution Overview
Problem
Inverters for electric vehicles face inefficiencies due to disparities in oscillator frequencies, leading to distorted PWM signals and communication uncertainties between high and low voltage domains, which can result in delayed fault detection and potential damage to components.
Innovation Solution
A system is implemented with a galvanic isolator separating high and low voltage areas, and includes clock reference samplers and calibrators to align oscillator frequencies across controllers, using a command bus for initial alignment and a message bus for subsequent adjustments, eliminating the need for non-volatile memory and reducing component count.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If galvanic isolator is used to separate high voltage and low voltage areas, then safety and electrical isolation are improved, but communication reliability and timing synchronization deteriorate due to oscillator frequency disparities
Solution Approach 1:
A clock reference sampler circuit is introduced as an intermediary component that receives the clock reference signal from the high voltage domain, samples it, and generates a synchronized clock signal for the low voltage domain. This mediator eliminates timing discrepancies without compromising the galvanic isolation barrier, thereby maintaining both safety and communication reliability.
Solution Approach 2:
The system adjusts the oscillator frequency parameter in the low voltage domain to match the sampled clock reference from the high voltage domain. By dynamically changing the frequency parameter based on actual measurements, the system achieves precise timing synchronization while maintaining electrical isolation between voltage domains.
2Loss of information
If traditional clock synchronization methods are used, then communication between domains is maintained, but device complexity increases due to need for non-volatile memory and additional external components
Solution Approach 1:
The patent extracts and eliminates the requirement for non-volatile memory and external calibration components from the traditional synchronization architecture. The clock reference sampler performs all necessary calibration and synchronization functions using only standard in-system resources, thereby reducing device complexity while maintaining communication reliability.
Solution Approach 2:
The clock reference sampler circuit performs self-calibration by automatically sampling the high voltage clock reference and adjusting its own operation accordingly. This self-service capability eliminates the need for external calibration equipment and additional memory components, simplifying the overall device architecture.
Data Source
AI summary
A system comprises an inverter configured to convert DC power from a battery to AC power to drive a motor, wherein the inverter includes: a galvanic isolator separating a high voltage area from a low voltage area; a low voltage phase controller in the low voltage area, the low voltage phase controller configured to receive a clock reference signal; and a high voltage phase controller in the high voltage area, the high voltage phase controller configured to align a clock reference signal of the high voltage phase controller with the clock reference signal of the low voltage phase controller.