PWM Controller Duty-Cycle Blanking for Parasitic Effects
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Solution Overview
Problem
Parasitic inductance and impedance in control systems for electric motors can affect the performance of power components, leading to issues such as switch failure and increased parasitic effects, particularly when control signal components are too similar.
Innovation Solution
A method and system that determine if control signal components are within a threshold amount of each other, applying duty-cycle blanking to generate an adjusted control signal to limit parasitic effects by advancing or delaying signal components to ensure a sufficient difference, thereby reducing parasitic impacts on electric motor control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If duty-cycle blanking is applied to adjust control signals, then parasitic effects are limited and reliability is improved, but device complexity and control signal processing complexity increase
Solution Approach 1:
The controller performs preliminary analysis of the PWM control signal components before generating the final control output. By checking if components are within a threshold amount of each other and pre-adjusting them through duty-cycle blanking, the system prevents parasitic effects before they occur, improving switching reliability while managing complexity through proactive signal conditioning
Solution Approach 2:
The system dynamically changes the duty cycle parameter of the control signal based on real-time analysis. When two PWM components are detected to be within a threshold amount, the controller modifies the duty cycle of one or both signals to create sufficient separation, thereby limiting parasitic effects without requiring fundamental changes to the control architecture
2Measurement precision
If control signal components are kept similar, then control precision is maintained, but parasitic effects increase and switch failure risk increases
Solution Approach 1:
The controller applies different treatment to different components of the PWM signal based on their specific characteristics. By locally analyzing each pair of control signal components and selectively applying duty-cycle blanking only when necessary (when components are within threshold), the system maintains precision where needed while preventing parasitic effects in problematic areas
Solution Approach 2:
When two PWM control signal components are detected to be too similar, the system introduces asymmetric adjustment by applying duty-cycle blanking to one or both signals differently. This creates intentional asymmetry in the control signals to ensure sufficient separation and prevent simultaneous switching, thereby reducing parasitic effects while maintaining overall control precision
Data Source
AI summary
A method of controlling an electric motor includes determining a PWM control signal, analyzing the PWM control signal to determine if components of the PWM signal are within a threshold amount of each other, applying duty-cycle blanking to the PWM control signal, if the components of the PWM control signal are within the threshold amount of each other, to generate an adjusted PWM control signal, and controlling the electric motor with the adjusted the PWM signal to limit parasitic effects.