SMPS Controller Ripple Suppression and Feed-Forward Loop
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Solution Overview
Problem
Conventional switched mode power supply (SMPS) feedback loop designs introduce delays and phase lag, leading to reduced performance and difficulty in real-time control of output voltage, particularly when using the Voltage Feed-Forward (VFF) mechanism in multi-rate controllers.
Innovation Solution
A controller is designed to oversample both output and input voltages, generating feedback and feed-forward signals to combine into a duty cycle control signal, with a ripple component estimation module to suppress voltage ripple, thereby reducing latency and distortion in the feedback loop.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional feedback loop design is used, then the SMPS can regulate output voltage, but delays and phase lag occur reducing real-time control performance
Solution Approach 1:
The patent applies preliminary action by measuring the input voltage before it causes output voltage deviations, and using this feed-forward signal to proactively adjust the duty cycle. This allows the controller to compensate for input voltage changes before they manifest as output voltage errors, eliminating the need to wait for the feedback loop to detect and respond to deviations.
Solution Approach 2:
The patent combines feedback control with feed-forward control, where the feedback loop continuously monitors output voltage and adjusts the duty cycle to maintain regulation. This dual approach ensures both real-time correction of deviations and proactive compensation for anticipated changes.
2Speed
If Voltage Feed-Forward mechanism is used, then response to input voltage changes improves, but phase loss and distortion increase in multi-rate controllers
Solution Approach 1:
The patent implements dynamic adjustment of the duty cycle by continuously updating it based on both feedback error signals and feed-forward input voltage measurements. This dynamic control allows the system to adapt to changing conditions in real-time, maintaining optimal performance across varying operating conditions without fixed phase delays.
Solution Approach 2:
The patent changes the control parameter from fixed duty cycle to dynamically adjusted duty cycle based on real-time measurements. By continuously varying the duty cycle in response to input voltage changes and output voltage deviations, the system maintains accurate control without the phase loss associated with fixed or periodically updated parameters.
3Loss of time
If sampling frequency is increased to reduce delay, then real-time control improves, but system complexity and computational load increase
Solution Approach 1:
The patent introduces a feed-forward path as an intermediary control mechanism that processes input voltage measurements separately from the main feedback loop. This intermediary path provides proactive compensation without requiring increased sampling frequency in the feedback path, thereby reducing the computational burden while maintaining real-time control performance.
Data Source
AI summary
A controller, and related method, configured to generate a duty cycle control signal for controlling an output voltage of a switched mode power supply as a function of a reference signal. In one embodiment, the controller is configured to sample a signal indicative of the output voltage to generate a first sampled signal, filter out a ripple component of the first sampled signal to generate a filtered signal, and generate a feedback control signal based on the filtered signal. The controller is also configured to sample a signal indicative of an input voltage of the switched mode power supply to generate a second sampled signal, generate a feed-forward control signal based on the second sampled signal and a feed-forward reference voltage, and generate the duty cycle control signal based on the feedback control signal and the feed-forward control signal.