Bridgeless PFC Circuit Reduces Inrush Current Stress
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Solution Overview
Problem
Conventional power factor correction (PFC) circuits experience high losses and stress due to large inrush currents during startup, which lead to component degradation and inefficiency, particularly due to the use of diode-based rectifiers and inductors that require higher ratings and increased costs when using SiC and GaN switches or active rectification schemes.
Innovation Solution
A circuit arrangement with electronic switching devices and an inductor, controlled by a controller to manage current paths and flow directions, allowing for reduced inrush currents by using AC input nodes to charge the capacitor without relying on rectified unidirectional currents, thereby minimizing stress on components and reducing losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a diode-based full wave rectifier is used in a boost converter PFC circuit, then the circuit can provide power factor correction functionality, but large inrush currents occur during precharging which cause high current stress and losses
Solution Approach 1:
The patent removes the traditional diode-based full wave rectifier from the PFC circuit topology. Instead, it uses a bridgeless configuration with electronic switching devices (MOSFETs or IGBTs) that directly perform both rectification and power factor correction functions, eliminating the harmful precharging current path through diodes and reducing conduction losses.
Solution Approach 2:
The patent employs dynamic switching control of electronic devices to manage current flow paths. The switching devices are controlled to conduct during specific portions of the AC cycle, dynamically redirecting current to charge the output capacitor while maintaining power factor correction, thereby avoiding the static limitations of diode-based rectifiers.
2Loss of energy
If SiC and/or GaN switches or active rectifying schemes are used to reduce bridge rectifier losses, then efficiency is improved, but costs increase significantly
Solution Approach 1:
The patent designs a bridgeless PFC circuit where the same electronic switching devices perform multiple functions: they act as both rectifiers and PFC switches. This multi-functionality eliminates the need for separate rectifier components and reduces the overall component count, thereby lowering costs while maintaining efficiency improvements.
Solution Approach 2:
The patent changes the operating parameters and topology of the PFC circuit by eliminating the bridge rectifier configuration. This topological change allows the use of standard silicon-based electronic switches instead of expensive SiC or GaN devices, as the reduced voltage stress and simplified circuit architecture enable cost-effective implementations while still achieving lower losses.
3Reliability
If a large output capacitor is charged via three rectifying elements during operation, then the PFC circuit can maintain output voltage, but substantial losses occur due to current flowing through multiple PN junctions
Solution Approach 1:
The patent removes the multi-diode charging path for the output capacitor. In the bridgeless topology, the capacitor is charged directly through the electronic switching devices and inductor with fewer conduction paths, eliminating the need for current to pass through three rectifying elements and thereby reducing conduction losses while maintaining output voltage stability.
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 effectively reduces inrush currents and associated losses, enhancing the efficiency and reliability of PFC circuits by managing current flow directions and using AC input voltages to charge the capacitor, thus preventing inductor saturation and component stress.
Implementation Method 1
an inductor coupled between the first electronic switching device and the second electronic switching device
Implementation Method 2
a first electronic switching device coupled between the first AC input node and an output node; a second electronic switching device coupled between the second AC input node and the output node
Data Source
AI summary
In various embodiments a circuit arrangement is provided which may include: a first AC input node and a second AC input node; a first electronic switching device coupled between the first AC input node and an output node; a second electronic switching device coupled between the second AC input node and the output node; an inductor coupled between the first electronic switching device and the second electronic switching device; a controller configured to control the first electronic switching device and the second electronic switching device to, in a first mode, provide a first current path from the first AC input node to the output node via the inductor in a first current flow direction through the inductor; and, in a second mode, provide a second current path from the second AC input node to the output node via the inductor in a second current flow direction through the inductor, the second current flow direction being different from the first current flow direction.