N-Level Power Factor Converter Segmentation
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Solution Overview
Problem
Conventional power factor improving converters face limitations in miniaturization due to increased component losses when trying to reduce common mode noise, and the size of noise filters becomes larger, making it difficult to effectively minimize common mode current.
Innovation Solution
An n-level power factor improving converter is designed with (n−1) circuit blocks, each including a first and second series circuit with rectifier and switching elements, and a capacitor, where the input terminals are connected to form a choke, allowing for reduced voltage applied to the choke and increased apparent frequency, thereby minimizing the choke and noise filter size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the switching frequency is increased to miniaturize the power factor improving converter, then the inductance of the choke can be reduced, but the switching loss and component loss increase
Solution Approach 1:
The power factor improving converter is divided into multiple circuit blocks (first circuit block, second circuit block, etc.) connected in series. Each block contains switching elements (MOSFETs, diodes) and capacitors that operate independently to generate different voltage levels. This segmentation allows the converter to achieve miniaturization without increasing switching frequency, as each block operates at lower voltage stress, reducing switching loss and component loss while maintaining overall power factor improvement functionality.
2Volume of moving object
If the switching frequency is increased to reduce the choke size, then the converter becomes more compact, but the common mode noise increases
Solution Approach 1:
The converter is segmented into multiple circuit blocks with distributed switching elements. This segmentation reduces the voltage change rate (dV/dt) across each individual switching element, thereby reducing common mode noise generation. The choke can be miniaturized through the multilevel voltage structure without requiring increased switching frequency, thus avoiding the common mode noise problem that plagues conventional single-stage converters.
Solution Approach 2:
Capacitors are introduced as intermediary elements between the switching elements and the choke. These capacitors act as voltage buffers that smooth the voltage transitions, reducing the high-frequency voltage spikes that generate common mode noise. The intermediary capacitors allow the choke to be smaller while maintaining low common mode noise levels.
3Volume of moving object
If the voltage applied to the choke is reduced, then the choke size can be minimized, but the apparent frequency decreases
Solution Approach 1:
The converter uses multiple circuit blocks operating in series to create a multilevel voltage structure. This segmentation allows the voltage applied to the choke to be reduced in steps rather than as a single large voltage change. The apparent frequency is maintained through coordinated switching of multiple blocks, enabling choke miniaturization without sacrificing frequency response.
Solution Approach 2:
The switching elements in different circuit blocks are operated in a periodic, coordinated manner to generate the multilevel voltage waveform. This periodic action maintains the apparent frequency required for choke operation while keeping the peak voltage applied to the choke reduced, thereby enabling miniaturization without frequency degradation.
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 common mode noise without increasing heat resistance or switching loss, enabling the miniaturization of the choke and noise filter, while maintaining effective power factor improvement.
Implementation Method 1
a first series circuit including a first rectifier element and a first switching element, a second series circuit including a second rectifier element and a second switching element
Implementation Method 2
a first series circuit including a first rectifier element and a first switching element, a second series circuit including a second rectifier element and a second switching element
Implementation Method 3
a first series circuit including a first rectifier element and a first switching element, a second series circuit including a second rectifier element and a second switching element, and a capacitor
Implementation Method 4
A choke and a series circuit formed by connecting the other input terminal and the one input terminal of adjacent ones of the plurality of circuit blocks are connected to the AC power supply
Data Source
AI summary
Provided are a plurality of circuit blocks each including: a first series circuit including a first rectifying element and a first switching element which are connected in series; a second series circuit including a second rectifying element and a second switching element which are connected in series; and a capacitor, wherein output terminals are connected to both ends of the first series circuit, both ends of the second series circuit, and both ends of the capacitor. Input terminals of the respective circuit blocks are connected in series. An AC power source is connected thereto via a choke, thereby solving the problem.