Multi-Level Switching Converter With Self-Balancing Flying Capacitor Control
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Solution Overview
Problem
Conventional three-level buck converters require additional sensing circuits and compensation loops for flying capacitor voltage balancing, leading to increased complexity and inefficiency.
Innovation Solution
A multi-level switching converter circuit employing valley current mode control, which regulates and balances flying capacitor voltage without additional sensing circuits or compensation loops, using a power stage circuit with power switches and a conversion control circuit to generate control signals for duty ratio determination based on current sensing and feedback signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional three-level buck converters use additional sensing circuits and compensation loops for flying capacitor voltage balancing, then voltage balancing is achieved, but device complexity increases
Solution Approach 1:
The valley current mode control automatically balances the flying capacitor voltage through the inherent characteristics of the multi-level switching operation. The control circuit uses only current sensing signals and feedback voltage signals, without requiring separate voltage sensing circuits for the flying capacitor. The automatic balancing is achieved through the valley current detection mechanism that naturally regulates the capacitor voltage to one (k-1)th of the input voltage.
Solution Approach 2:
The invention extracts and eliminates the unnecessary flying capacitor voltage sensing circuit from the conventional control architecture. By using valley current mode control with only current sensing and output voltage feedback, the patent removes the complex voltage sensing and compensation loop components while maintaining effective flying capacitor voltage balancing.
2Reliability
If conventional three-level buck converters use additional sensing circuits and compensation loops, then voltage balancing is achieved, but manufacturing cost increases
Solution Approach 1:
The valley current mode control makes the system self-regulating for flying capacitor voltage balancing, eliminating the need for additional sensing circuits and compensation loop components. This reduction in component count directly lowers manufacturing costs while maintaining reliable voltage balancing through the inherent control mechanism.
Solution Approach 2:
By removing the flying capacitor voltage sensing circuit and compensation loop components from the design, the invention reduces bill of materials costs and assembly complexity, making the converter more cost-effective to manufacture while achieving the same voltage balancing function through simplified means.
3Device complexity
If valley current mode control is used to determine duty ratios, then control loop is simplified, but control precision must be maintained
Solution Approach 1:
The valley current mode control incorporates feedback mechanisms where the valley current detection signal is compared with a reference signal to generate PWM duty ratio control. The feedback loop ensures precise duty ratio determination while maintaining simplicity, as the valley current points naturally indicate the optimal switching moments for regulation.
Solution Approach 2:
The invention replaces complex voltage sensing and multi-loop compensation mechanisms with a simpler current-mode control approach. The valley current detection method uses current waveform characteristics instead of voltage sensing, substituting a simpler measurement approach that maintains precision through the natural timing information provided by current valleys.
Data Source
AI summary
A multi-level switching converter circuit for converting a first voltage to a second voltage or convert the second voltage to the first voltage, includes: a power stage circuit and a control circuit. Through a valley current mode control, the conversion control circuit generates a first ramp signal to determine a first duty ratio of the first control signal, and generates a second ramp signal to determine a second duty ratio of the second control signal, thereby a switching node connected to one end of an inductor is switched between two of k levels of voltages, such that the first voltage or the second voltage is regulated to a predetermined target level, and a flying capacitor voltage across the flying capacitor is regulated and balanced at one (k−1)th of the first voltage.