Step-up/down DC Converter Ripple Filtering
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Solution Overview
Problem
Conventional step up/down DC converters experience higher ripple voltage output, leading to errors in load regulation due to diode-based rectification, which restricts efficiency improvements.
Innovation Solution
The implementation of a step up/down DC converter with a power isolating and converting unit, a ripple-filtering inductor, a power switch, and MOSFET-based rectification to reduce voltage drops and smooth ripple voltage, utilizing multiple windings for isolation and transformers to manage power flow paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If diode-based rectification is used in conventional step up/down DC converters, then the device complexity is reduced and manufacturing is simpler, but the conduction loss increases and efficiency deteriorates due to higher voltage drops
Solution Approach 1:
The patent changes the rectification component from diode to MOSFET, altering the electrical parameters (lower on-resistance, lower voltage drop) to reduce conduction loss. This parameter change directly addresses the energy loss issue while accepting increased device complexity as a trade-off for improved efficiency
Solution Approach 2:
The patent converts the previously harmful voltage drop across diodes into a benefit by using MOSFETs with much lower resistance. The body diode of the MOSFET provides a low-loss rectification path during reverse recovery, turning what was a source of loss into an efficient operation mode
2Object-affected harmful factors
If conventional step up/down DC converter topology is used, then the device structure is simpler, but the output ripple voltage increases causing load regulation errors
Solution Approach 1:
The patent segments the power conversion function into distinct stages with separate MOSFETs for rectification and switching. This segmentation allows each component to be optimized for its specific function, with the rectifying MOSFET handling voltage drop reduction and the switching MOSFET handling ripple reduction through controlled duty cycle
Solution Approach 2:
The patent introduces an intermediary MOSFET structure that provides both rectification and ripple filtering functions. The body diode of the rectifying MOSFET acts as an intermediary element that facilitates smooth current transition and reduces ripple voltage without requiring additional complex filtering components
3Loss of energy
If MOSFET-based rectification is implemented, then efficiency is improved by reducing voltage drops, but device complexity increases
Solution Approach 1:
The patent makes the MOSFET perform multiple functions: rectification during the off-state (using body diode), switching during the on-state, and ripple filtering through controlled duty cycle. This multi-functionality reduces the need for separate components, offsetting the inherent complexity of using MOSFETs instead of simple diodes
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
This configuration reduces conduction loss and enhances efficiency by using MOSFETs for rectification, minimizing voltage drops and improving ripple voltage smoothing, thereby stabilizing the output power to the load.
Implementation Method 1
The power isolating and converting unit is electrically connected to the ripple-filtering inductor and includes a plurality of windings for isolation an output stage electrically connected to the load from an input stage electrically connected to the power source
Implementation Method 2
The rectifying switch turns off when the power is conducted, thus the ripple-filtering inductor and the first inductor divide the electric power provided by the power source to smooth a ripple voltage conducted to the load
Data Source
AI summary
A step-up/down DC converter applied to achieve a characteristic of zero-ripple voltage, which ripple voltage is near zero, is disclosed. The converter includes a ripple-filtering inductor, a power isolating and converting unit, a power switch, a first inductor, a first capacitor, a second capacitor, and a rectifying switch. The power isolating and converting unit comprises windings for isolation an input stage connected to a power source from an output stage connected to a load. The power switch, the first inductor, and the first capacitor are arranged at the input stage, and the second capacitor and the rectifying switch are arranged at the output stage. The ripple-filtering inductor, which may be arranged at the input or output stage, and the first inductor divide the power supplied from the power source, thus the voltage drop of the first inductor is reduced for smoothing the ripple voltage at the output stage.