PWM Controller Transient Response via Ripple Propagation
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Solution Overview
Problem
Conventional PID controller circuits for PWM signal generators experience delays in transient response due to averaging current ripple, leading to reduced performance and stability when controlling inductive loads.
Innovation Solution
Removing the averaging circuit from the control loop and updating controller parameters at a frequency significantly higher than the PWM signal frequency, allowing PWM ripple to propagate through the control loop, thereby improving transient response and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current ripple is averaged out before subtraction from set point, then measurement smoothness is improved, but transient response speed deteriorates
Solution Approach 1:
The patent segments the control loop into two distinct paths: one for average current measurement (using the averaging circuit for smooth feedback) and one for ripple signal processing (allowing ripple to propagate through the controller). This segmentation enables both smooth measurement and fast transient response by handling different signal components separately.
Solution Approach 2:
The patent introduces an intermediary approach by feeding the ripple signal directly to the controller while maintaining the averaging circuit for overall current measurement. The controller processes both the averaged current feedback and the ripple signal, using the ripple information to improve transient response without sacrificing measurement smoothness.
2Speed
If PWM ripple propagates through control loop, then transient response speed is improved, but control loop stability may deteriorate
Solution Approach 1:
The patent employs feedback mechanisms where the ripple signal propagating through the controller is fed back into the control loop. This feedback allows the controller to anticipate and compensate for ripple effects, improving transient response while maintaining stability through proper feedback gain adjustment.
Solution Approach 2:
The patent adjusts controller parameters (such as PID gains) to optimize performance when ripple propagation is enabled. By carefully tuning these parameters, the system achieves fast transient response while preventing instability that could arise from ripple propagation.
3Measurement precision
If controller parameters are updated at higher frequency than PWM signal, then control accuracy is improved, but computational load increases
Solution Approach 1:
The patent implements periodic updating of controller parameters at a frequency higher than the PWM signal frequency. This periodic high-frequency updating improves control accuracy by capturing rapid changes, while the structured periodic nature of the updates helps manage computational load through predictable timing patterns.
Data Source
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AI summary
A PWM signal generator (12) configured (D) to provide a supply current (ILOAD) to an electrical load (L) generates PWM signals at a first frequency (fPWM), the PWM signals having a duty cycle. Operating the generator involves: - receiving a set point signal (SP) indicative of a target average value for the supply current (ILOAD), - sensing (20) a sensing signal indicative of a current actual value of the supply current (ILOAD), - performing a closed-loop control of the supply current (ILOAD) targeting the target value (SP) for the supply current via a controller (14; 141, 142, 143, 144) such as a PID Controller which controls (PID) the duty cycle of the PWM signals generated by the PWM signal generator (12) as a function of the offset (18) of the sensing signal with respect to the set point signal (SP).