Feedforward Correction for Multilevel Output Mode Transitions
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Solution Overview
Problem
Multilevel power converters experience nonlinearities and mode-dependent output resistance variations due to flying capacitor discharge characteristics, leading to discontinuities in output impedance during mode transitions, which existing systems struggle to correct effectively.
Innovation Solution
A feedforward correction block is implemented in the multilevel output system to detect mode transitions, capture loop filter outputs before and after transitions, and determine a transition-specific compensation function to apply to the feedforward input signal, thereby minimizing the impact of mode-dependent output resistance variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a multilevel power converter is used to generate switching voltages, then power efficiency is improved, but mode-dependent output resistance variations and discontinuities in output impedance occur during mode transitions
Solution Approach 1:
The patent applies preliminary action by detecting mode transitions before they complete and preemptively adjusting the duty cycle of switching elements. The correction block monitors flying capacitor voltages and anticipates impedance discontinuities, modifying control signals in advance to maintain continuous output impedance. This prevents the harmful effect rather than reacting after it occurs.
Solution Approach 2:
The patent implements feedback by continuously monitoring flying capacitor voltages and output impedance characteristics, then using this information to dynamically adjust duty cycles. The correction block receives feedback about mode transitions and capacitor discharge states, processing this information to generate compensating control signals that maintain stable output impedance across mode transitions.
2Adaptability or versatility
If duty cycle is varied to control output voltage, then output voltage control flexibility is improved, but nonlinearities due to flying capacitor discharge characteristics worsen
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the duty cycle parameter based on detected mode transitions and flying capacitor discharge characteristics. When a mode transition is detected, the correction block modifies the duty cycle parameter to compensate for nonlinearities, ensuring linear output voltage control across all operating conditions while maintaining the flexibility to vary output voltage.
Solution Approach 2:
The patent applies preliminary anti-action by predicting nonlinear effects from flying capacitor discharge and applying counteracting duty cycle adjustments before the nonlinearities manifest. The correction block anticipates voltage droop and impedance changes, applying compensating duty cycle changes that preemptively counteract the nonlinear effects, maintaining linear control characteristics.
Data Source
AI summary
A feedforward correction block for use in a multi-level output system may include circuitry configured to determine an occurrence of a mode transition between operating modes of the multi-level output system, capture a loop filter output of a signal path of the multi-level output system occurring before and after the occurrence of the mode transition, and based on the transition and a change in the loop filter output responsive to the transition, determine a transition-specific compensation function to apply to a feedforward input signal of the signal path that is combined with the loop filter output.