Adaptive PWM Duty Cycle Control for Bus Voltage Fluctuations
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Solution Overview
Problem
Existing motor driving systems face challenges in managing bus voltage fluctuations, which can impact motor performance, and current solutions often incur high costs and complexity.
Innovation Solution
A method and circuit for adaptively adjusting the PWM duty cycle by sampling the direct current bus voltage, performing low-pass filtering, and calculating a new duty cycle based on voltage fluctuations, while also implementing under-voltage protection and weak magnetic control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If software damping control techniques are used to mitigate bus voltage fluctuations, then motor performance stability is improved, but device complexity and computational overhead increase substantially
Solution Approach 1:
The patent replaces complex software damping control algorithms with a simplified hardware-based detection and compensation mechanism. The controller directly monitors bus voltage fluctuations and adjusts PWM duty cycles through predefined compensation logic, eliminating the need for complex computational damping algorithms while maintaining motor performance stability.
Solution Approach 2:
The patent extracts the essential function of voltage fluctuation compensation from complex software control algorithms and implements it as a standalone, simplified control module. This extracted module independently handles bus voltage monitoring and PWM adjustment without requiring the full computational overhead of traditional damping control systems.
2Reliability
If voltage boost mechanisms are used to mitigate bus voltage fluctuations, then bus voltage stability is improved, but circuit cost increases due to additional peripheral circuits
Solution Approach 1:
The patent converts the harmful effect of bus voltage fluctuations into a beneficial control signal. By monitoring voltage drops and using them to trigger compensatory PWM duty cycle adjustments, the system transforms voltage instability into a useful feedback mechanism that automatically corrects itself without requiring additional voltage boosting hardware.
Solution Approach 2:
The patent makes the existing PWM controller perform multiple functions: it simultaneously controls motor operation and compensates for bus voltage fluctuations. The controller uses its existing PWM generation capability to implement voltage compensation by adjusting duty cycles, eliminating the need for separate voltage boost circuits while maintaining both motor control and voltage stabilization functions.
3Reliability
If PWM duty cycle is adjusted to compensate for bus voltage fluctuations, then motor performance is maintained, but risk of over-voltage increases if control is improper
Solution Approach 1:
The patent implements a closed-loop feedback mechanism where the controller continuously monitors bus voltage levels and uses this feedback to dynamically adjust PWM duty cycles. The system measures actual voltage fluctuations and applies compensatory duty cycle changes only when needed, ensuring that motor performance is maintained while preventing over-voltage conditions through real-time voltage-aware control.
Solution Approach 2:
The patent employs dynamic PWM duty cycle adjustment that adapts to real-time bus voltage conditions. Rather than using fixed compensation values, the system continuously modifies duty cycles based on instantaneous voltage measurements, enabling flexible compensation that maintains motor performance while automatically preventing over-voltage by reducing duty cycles when voltage rises.
Data Source
AI summary
The present application relates to a method, circuit, and motor driving system for adaptively adjusting a PWM duty cycle, comprising: sampling a direct current bus voltage and performing a low-pass filtering; determining whether the direct current bus voltage is under-voltage; if yes, entering an under-voltage protection state; and if not, executing the next step; calculating a new duty cycle and a new amplitude; determining whether the new duty cycle is greater than 100%; if yes, applying a weak magnetic control; and if not, adjusting a duty cycle of PWM signals through the new amplitude. Without altering the core current loop, torque loop, or speed loop of the motor driving system, this application adaptively adjusts the PWM duty cycle based on existing sine wave generators and PWM generators, effectively mitigating the impact of direct current bus voltage fluctuations on motor performance, ensuring straightforward operation, and significantly reducing costs.