Multi-Level Buck-Boost Converter with Flying Capacitors
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Solution Overview
Problem
Battery-powered devices face inefficiencies in power conversion due to limited USB charging capabilities, leading to increased recharging times and potential hot spots from high inductor current ripple, especially with higher input voltages.
Innovation Solution
A compact power converter design utilizing an inductor and flying capacitors with a switching cell and control unit to enable efficient step-up and step-down conversions using a minimal number of switches, including an auxiliary switch for Boost conversion, and interleaving capacitors to reduce current ripple.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If higher input voltages (9V, 12V, 20V) are used for USB charging to increase power delivery, then charging power is improved, but inductor current ripple increases causing increased DCR losses and switching frequency issues
Solution Approach 1:
The patent divides the power conversion process into multiple stages using a multi-level converter architecture. Instead of a single large inductor handling the full voltage range, the system segments the voltage conversion into multiple smaller steps (e.g., 20V→12V→9V→5V), with each stage handling a narrower voltage differential. This segmentation reduces the current ripple in each individual inductor, thereby reducing DCR losses while still achieving high power delivery capability.
Solution Approach 2:
The patent introduces intermediate voltage levels as mediators between the high input voltage (20V) and the standard output voltage (5V). Flying capacitors and intermediate inductors serve as intermediary elements that step down the voltage in controlled increments. This intermediary approach allows the system to achieve high power conversion while maintaining lower current ripple in each conversion stage, reducing overall energy losses.
2Power
If inductor current ripple is increased to enable higher input voltages, then power delivery capability is improved, but hot spots and dissipation increase
Solution Approach 1:
The multi-level converter architecture segments the power delivery function across multiple conversion stages. Each stage operates with lower current ripple, generating less heat locally. The distributed architecture prevents concentration of thermal energy in a single component, thereby reducing hot spots and overall dissipation while maintaining high power delivery capability through the cascaded stages.
Solution Approach 2:
The patent employs dynamic switching control that adapts the switching frequency and duty cycle based on the operating conditions. During high power delivery modes, the controller dynamically adjusts the switching parameters to optimize efficiency and minimize thermal generation. This dynamic adaptation allows the system to maintain high power capability while actively managing temperature and preventing hot spots.
3Loss of energy
If switching frequency is increased to compensate for inductor current ripple, then power conversion efficiency may be improved, but dissipation and hot spots increase
Solution Approach 1:
The patent segments the high-frequency switching operation across multiple lower-frequency stages. Instead of one inductor operating at very high frequency to handle the full voltage range, multiple inductors operate at lower frequencies in a cascaded manner. This segmentation allows each stage to use optimized switching frequencies that balance efficiency with thermal management, reducing overall dissipation and hot spots while maintaining conversion efficiency.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides power-efficient, compact power conversion with reduced losses and stable output voltages, supporting a wide range of voltage levels and currents, while minimizing the number of switches and reducing recharging times for battery-powered devices.
Implementation Method 1
an inductor L having a first inductor port and a second inductor port
Implementation Method 2
a flying capacitor C having a first capacitor port and a second capacitor port
Data Source
AI summary
A power converter for converting an input voltage at an input port into an output voltage at an output port of the power converter is described. The power converter comprises an inductor having a first inductor port and a second inductor port, wherein the second inductor port is coupled to the output port. Furthermore, the power converter comprises a flying capacitor having a first capacitor port and a second capacitor port, and a switching cell. In addition, the power converter comprises a control unit to operate the switching cell in a first sequence of operation phases to perform step-up conversion; and in a second sequence of operation phases to perform step-down conversion.