Switched Converter Feed-Forward Control for 100 Hz Ripple
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Solution Overview
Problem
Existing switched converters fail to effectively reduce output current ripple, particularly the 100 Hz ripple, due to limitations in feedback control mechanisms, especially in isolated converters like LLC converters, which are optimized for slower transients and cannot fully compensate for frequency-related ripples in DC bus voltage.
Innovation Solution
Implementing a feed-forward control (FFC) block with a faster response time than the feedback loop controller, which analyzes load current and DC signals to add a ripple compensation signal, adjusting the switching frequency or period to minimize ripple, and using adaptive gain settings based on actual ripple values and operational conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If feedback control is used to regulate LED current, then the average current can be controlled to nominal value, but 100 Hz ripple in DC bus voltage cannot be fully compensated
Solution Approach 1:
The patent applies preliminary action by detecting the 100 Hz ripple in the DC bus voltage and proactively generating a compensating signal before the ripple can significantly affect the LED current. The feed-forward controller anticipates the disturbance and counteracts it in advance, rather than waiting for the feedback loop to detect and correct the resulting current deviation.
Solution Approach 2:
The patent introduces an intermediary feed-forward control signal that mediates between the ripple detection and the LED current regulation. This intermediate signal is generated by detecting the ripple frequency and amplitude, then combining it with the feedback control signal to produce a composite control signal that addresses both the average current requirement and the ripple rejection need.
2Adaptability or versatility
If DC/DC converter is integrated to power DALI bus, then additional functionality is provided, but ripple on DC bus voltage is introduced that affects LED current
Solution Approach 1:
The patent applies feedback by continuously monitoring the LED current and detecting deviations caused by the DC/DC converter's ripple. The feedback controller adjusts the switching parameters to compensate for these deviations, while the feed-forward controller detects the ripple pattern and proactively generates compensating signals to prevent ripple propagation to the LED current.
Data Source
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AI summary
The invention relates to a switched converter, supplied with a DC voltage originating from an AC voltage, preferably mains voltage. The switched converter comprises output terminals for supplying an LED load, a feed-back loop controller configured to generate an output signal setting a switching frequency of at least one switch of the converter for controlling a load current on a nominal value, based on a signal indicating the load current and supplied to the feedback loop controller and a feed-forward control, FFC, block, wherein a response time of the FFC block is faster than a response time of the feed-back loop controller. The FFC block is configured to analyze, preferably in time increments said load current sensing signal and/or the DC signal a ripple amplitude component present in said signals and to add, based thereon, a ripple compensation signal to said output signal of the feed-back loop controller.