LC Filter Current-Slope Control for Flying Capacitor Balance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing multi-level converter technologies face challenges in balancing flying capacitor voltages due to non-ideal input power supplies and inconsistent gate drive signal delays, leading to increased stress on switch tubes and reduced output voltage quality.
Innovation Solution
A multi-level converter control method that collects inductive current within a drive pulse cycle to determine and adjust duty cycles of switch tubes based on slopes of rising and falling periods, thereby balancing flying capacitor voltages by adjusting the duty cycles of the switch tubes connected in series.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If flying capacitor voltage is controlled by directly detecting voltage of each flying capacitor, then voltage balance can be achieved, but detection circuit complexity increases and floating voltage detection becomes difficult
Solution Approach 1:
The patent uses inductive current as an intermediary parameter to indirectly control flying capacitor voltage balance. Instead of directly detecting flying capacitor voltages, the method detects the inductive current in the LC filter and uses its rising and falling slopes to determine which flying capacitors need voltage adjustment. This intermediary approach simplifies the detection circuit while maintaining voltage balance control effectiveness.
Solution Approach 2:
The patent replaces the direct voltage detection mechanism with a current-based control mechanism. By substituting voltage sensing with current slope analysis, the system avoids the complexity of floating voltage detection circuits while achieving the same voltage balance objective through a different physical quantity measurement.
2Ease of operation
If gate drive signal delay is not consistent, then switching operation becomes simple, but flying capacitor voltage balance deteriorates
Solution Approach 1:
The patent implements a feedback mechanism by continuously monitoring the inductive current slopes and using this information to adjust the duty cycles of switch tubes. The current slope feedback provides real-time information about flying capacitor voltage deviations, allowing the system to compensate for inconsistent gate drive signal delays and maintain voltage balance dynamically.
Solution Approach 2:
The patent changes the control parameter from direct voltage measurement to current slope measurement. By monitoring the rising and falling slopes of the inductive current, the system can detect voltage imbalances and adjust switch tube duty cycles accordingly, making the control system more robust to timing variations in gate drive signals.
3Manufacturing precision
If duty cycle of switch tubes is adjusted to balance flying capacitor voltage, then voltage balance improves, but output voltage quality may deteriorate due to inductive current ripple
Solution Approach 1:
The patent applies partial adjustment to the duty cycles of switch tubes rather than uniform adjustment. By selectively adjusting only the duty cycles of switch tubes associated with unbalanced flying capacitors (determined through current slope analysis), the system achieves voltage balance with minimal disturbance to the overall output voltage, thereby reducing inductive current ripple while maintaining balance.
Data Source
AI summary
A multi-level converter control method is provided that includes: acquiring an inductive current of an LC filter in a driving pulse period; determining a to-be-adjusted first switch tube and a first duty ratio adjustment amount of the to-be-adjusted first switch tube based on a slope of a rising period of the inductive current, and adjusting a duty ratio of the to-be-adjusted first switch tube based on the first duty ratio adjustment amount; and determining a to-be-adjusted second switch tube and a second duty ratio adjustment amount of the to-be-adjusted second switch tube based on a slope of a falling period of the inductive current, and adjusting a duty ratio of the to-be-adjusted second switch tube based on the second duty ratio adjustment amount.