Shared-Capacitor Buck-Boost Converter for Smooth Mode Transitions
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Solution Overview
Problem
Conventional buck-boost converters experience discontinuous voltage transitions, large voltage ripples, and slow dynamic response due to discontinuous inductor current during mode changes.
Innovation Solution
A cascaded structure of a boost unit and a buck unit is utilized, with the inductor of the buck unit coupled to the output terminal, allowing for smooth transitions and reduced output voltage ripple by controlling the capacitors and inductors through synchronized control signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the switch Q3 is turned off in boost mode and buck-boost mode, then the converter can achieve voltage step-up function, but the inductor current becomes discontinuous causing voltage ripple and slow dynamic response
Solution Approach 1:
The patent segments the single inductor current path into two separate current paths: one through the first inductor (L1) and another through the second inductor (L2). This segmentation allows the second inductor to provide continuous current to the output terminal even when the first inductor's current is discontinuous, thereby reducing voltage ripple and improving output stability while maintaining voltage step-up capability.
2Device complexity
If the switching cycles of the first control signal and the second control signal are the same, then the control is simplified, but the dynamic response speed is reduced
Solution Approach 1:
The patent implements dynamic control by allowing the switching cycles of the first control signal and second control signal to be different. The controller can independently adjust the switching frequency and duty cycle of each control signal, enabling flexible adaptation to different operating conditions. This dynamic adjustment capability improves the converter's response speed to load changes and input voltage variations without overly complicating the control structure.
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 achieves smooth transitions in DC output voltage, reduces voltage ripple, and improves dynamic response speed by ensuring continuous inductor current and efficient operation across various conversion modes.
Implementation Method 1
The inductor L is coupled between node SW1 and node SW2
Implementation Method 2
The input capacitor Cin is coupled between the input terminal and ground, and the output capacitor Cout is coupled between the output terminal and ground
Data Source
AI summary
The present disclosure relates to a buck-boost converter and a control method therefor. The buck-boost converter includes a boost unit and a buck unit. The boost unit has a first capacitor and a first group of switches. The buck unit has an inductor and a second group of switches. The buck-boost converter has a cascaded structure of the boost unit and the buck unit to achieve multiple voltage conversion modes. The inductor of the buck unit is coupled to the output terminal. Therefore, not only can it achieve a smooth transition of the DC output voltage, but also reduce voltage ripple and improve dynamic response speed.