EV Inverter PWM Timing Control Across Galvanic Isolation
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Solution Overview
Problem
Inverters for electric vehicles face challenges in converting High Voltage Direct Current (HVDC) to Alternating Current (AC) due to system delays and electrical noise, affecting pulse width modulation (PWM) signals and resulting in inefficient motor operation.
Innovation Solution
A system with a galvanic isolator separating high and low voltage areas, including a low voltage phase controller and a high voltage phase controller, which adjusts PWM signals based on feedback from a phase switch on-time measurement and clock reference alignment to ensure precise duty cycle matching, using a phase switch on-time detector, on-time comparator, and PWM delay trimmer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If galvanic isolator is used to separate high voltage and low voltage areas, then electrical noise and interference are reduced, but device complexity increases
Solution Approach 1:
The inverter controller is divided into separate high voltage and low voltage areas with a galvanic isolator between them. This segmentation isolates electrical noise in the high voltage area from the low voltage control circuits, reducing interference while maintaining functional separation.
Solution Approach 2:
A galvanic isolator is introduced as an intermediary component between the high voltage and low voltage areas. This mediator allows signal transmission while blocking electrical noise and ground loops, reducing harmful electrical interference without direct electrical connection.
2Measurement precision
If phase switch on-time detection and feedback control are implemented, then PWM signal accuracy is improved, but device complexity increases
Solution Approach 1:
The system implements feedback control by detecting the actual on-time of phase switches using on-time detectors and comparing it with the commanded duty cycle. The low voltage phase controller adjusts subsequent PWM signals based on this feedback to compensate for delays and ensure accurate duty cycle execution.
Solution Approach 2:
The system performs preliminary measurement of phase switch on-time before adjusting the PWM signal. By detecting the actual switching duration first and then making compensatory adjustments, the system ensures accurate PWM control while accounting for inherent delays in the power circuitry.
3Stability of the object's composition
If clock reference alignment between high and low voltage areas is implemented, then timing synchronization is improved, but device complexity increases
Solution Approach 1:
A clock reference signal serves as an intermediary timing reference between the high voltage and low voltage areas. Both areas synchronize their operations to this common clock reference, ensuring timing coordination across the galvanic isolator without requiring complex inter-area communication protocols.
4Productivity
If PWM signal adjustment based on on-time measurement is implemented, then inverter conversion efficiency is improved, but device complexity increases
Solution Approach 1:
The low voltage phase controller uses feedback from phase switch on-time measurements to adjust PWM signal parameters. This closed-loop control compensates for delays and losses in the power circuitry, improving the efficiency of DC to AC conversion by ensuring accurate duty cycle execution.
Solution Approach 2:
The system dynamically adjusts PWM signal parameters such as duty cycle and timing based on measured phase switch on-time. By changing these parameters in response to actual operating conditions, the inverter optimizes its conversion efficiency while adapting to variations in load and component characteristics.
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 pulse width modulation (PWM) signal from an inverter controller and adjust the received PWM signal based on a feedback signal; and a high voltage phase controller in the high voltage area, the high voltage phase controller configured to receive the adjusted PWM signal from the low voltage phase controller, provide the adjusted PWM signal to a phase switch, and provide the feedback signal based on an on-time measurement of the phase switch.