Totem-Pole PFC Current-Sampling Unit Demagnetization
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Solution Overview
Problem
The totem-pole power factor corrector (PFC) experiences inaccurate current detection and reduced conversion efficiency due to the non-fully demagnetized condition caused by the too-small resistance of the sampling resistor, leading to superimposed operations and ineffective power factor correction.
Innovation Solution
The totem-pole power factor corrector incorporates a current-sampling unit with a full-bridge rectifying unit, a magnetizing inductor, a demagnetizing component, and a sampling resistor, where the sampling switches are controlled to form different current sampling paths during positive and negative half cycles, ensuring accurate current detection and increased demagnetization efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a small resistance sampling resistor is used in the current-sampling unit, then the voltage drop across the sampling resistor is reduced, but the current detection accuracy deteriorates and the magnetizing inductor cannot be fully demagnetized
Solution Approach 1:
The patent introduces a demagnetizing component as an intermediary element connected in parallel with the secondary-side winding. This component provides a dedicated demagnetizing path that is independent of the sampling resistor, allowing the sampling resistor to maintain its low resistance for minimal voltage drop while the demagnetizing component ensures complete demagnetization through its own resistance value, thereby resolving the contradiction between low voltage drop and adequate demagnetization.
2Loss of energy
If the sampling resistor resistance is too small, then power loss is reduced, but superimposed operations occur and conversion efficiency decreases
Solution Approach 1:
The patent segments the current path by introducing a demagnetizing component that operates independently from the sampling resistor. This segmentation allows the sampling resistor to be optimized for minimal power loss (low resistance) while the demagnetizing component handles the demagnetization function separately, preventing superimposed operations and maintaining high conversion efficiency throughout the switching cycle.
3Loss of energy
If the sampling resistor resistance is reduced, then the voltage drop and power dissipation are minimized, but the demagnetization process becomes incomplete
Solution Approach 1:
The demagnetizing component serves as an intermediary that specifically addresses the demagnetization requirement. By connecting this component in parallel with the secondary-side winding, the system ensures that the demagnetization process is handled by a dedicated path with appropriate resistance characteristics, while the sampling resistor maintains its low resistance for minimal voltage drop, thus resolving the contradiction between voltage drop minimization and demagnetization completeness.
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 solution improves current detection accuracy and enhances conversion efficiency by effectively providing power factor correction and reducing superimposed operations, thereby increasing the overall performance of the power conversion circuit.
Implementation Method 1
The current-sampling unit includes a primary-side winding and a secondary-side winding, wherein the secondary-side winding is coupled to the primary-side winding
Implementation Method 2
The full-bridge rectifying unit has a first input end, a second input end, a first output end, a second output end
Data Source
AI summary
A totem-pole PFC and a current-sampling unit of the totem-pole PFC are provided. The totem-pole PFC is electrically connected to an AC power source and a DC-to-DC converter, and is electrically connected to a load through the DC-to-DC converter. The current-sampling unit has a first sampling switch and a second sampling switch. The first sampling switch and the second sampling switch are controlled to be turned on and turned off so that a magnetizing current flows through the magnetizing inductor when a magnetizing inductor is magnetized and a demagnetizing current does not flow through the sampling resistor when the magnetizing inductor is demagnetized, thereby increasing the demagnetization efficiency and overcoming superimposed operations to improve current detection and increase conversion efficiency of the power conversion.