Variable Air-Gap Inductor for Light-Load PFC Efficiency
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Solution Overview
Problem
Existing power supply systems face inefficiencies in the critical conduction mode, particularly in the light load phase, due to high on/off losses in the power factor correction circuit, which affects the overall operating efficiency of the power supply system.
Innovation Solution
The design incorporates an inductor with a magnetic core featuring segmental air-gaps, including a solid air-gap and an air air-gap, whose total air-gap varies with current magnitude, allowing for adjustable inductance to optimize power factor correction circuit efficiency across load phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a fixed air-gap structure is used in the inductor, then the inductance value remains constant, but the power factor correction circuit suffers from high on/off losses during light load phases
Solution Approach 1:
The patent applies the dynamics principle by making the air-gap structure changeable based on operating conditions. The solid air-gap material is positioned such that it can be saturated by magnetic flux under different load conditions, causing the effective air-gap length to vary dynamically. During light load phases, the solid air-gap remains unsaturated, providing a smaller effective air-gap and larger inductance, which reduces on/off frequency and losses. During heavy load phases, the solid air-gap saturates, increasing the effective air-gap and decreasing inductance, which increases on/off frequency and maintains efficiency.
Solution Approach 2:
The patent applies the parameter changes principle by utilizing the magnetic saturation characteristic of the solid air-gap material to change the inductance parameter dynamically. The magnetic induction intensity of the solid air-gap is designed to be greater than that of the magnetic core middle column, ensuring that the solid air-gap saturates at different current levels. This causes the total air-gap length to change with current magnitude, thereby adjusting the inductance value to optimize power factor correction circuit efficiency across different load phases.
2Productivity
If the on/off frequency is increased to improve power factor correction, then the correction efficiency improves, but the on/off losses increase during light load phases
Solution Approach 1:
The patent dynamically adjusts the inductance through the variable air-gap structure, which automatically adapts the on/off frequency to load conditions. During light load phases, the larger inductance (smaller effective air-gap) naturally reduces the on/off frequency, thereby reducing on/off losses while maintaining adequate power factor correction. During heavy load phases, the smaller inductance (larger effective air-gap) increases the on/off frequency, improving power factor correction efficiency. This dynamic adaptation resolves the contradiction between correction efficiency and energy losses.
3Speed
If the air-gap size is increased to reduce inductance, then the on/off frequency increases, but the inductance becomes too small for light load efficiency
Solution Approach 1:
The patent uses parameter changes by leveraging the magnetic saturation特性 of the solid air-gap material. The magnetic induction intensity of the solid air-gap is designed to exceed that of the magnetic core middle column, causing the solid air-gap to saturate at higher current levels. This creates a current-dependent air-gap effect: at low currents (light load), the solid air-gap contributes minimally to the total air-gap, maintaining small effective air-gap and large inductance for efficiency. At high currents (heavy load), the solid air-gap saturates and contributes fully to the total air-gap, increasing effective air-gap and decreasing inductance to raise on/off frequency.
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 on/off losses in the power factor correction circuit during light loads and increases frequency during heavy loads, enhancing the overall efficiency of the power supply system and meeting high-efficiency requirements.
Implementation Method 1
When a magnetic flux increases, the solid air-gap is to be in a magnetic flux saturation state earlier than the magnetic core middle column. When a magnetic flux in the solid air-gap is saturated, the magnetic flux in the solid air-gap attenuates rapidly, and the solid air-gap serves as an air air-gap.
Implementation Method 2
The coil winding is disposed around the winding unit. The winding unit may include a magnetic core middle column and at least two air-gaps distributed in the first direction, and a direction of an axis of the magnetic core middle column is parallel to the first direction.
Data Source
AI summary
An inductor, a power factor correction circuit, and a power supply system. The inductor includes a coil winding and a magnetic core. The magnetic core includes a first outer magnetic core, a second outer magnetic core, and a winding unit. The first outer magnetic core and the second outer magnetic core are disposed opposite to each other in a first direction, the winding unit is disposed between the first outer magnetic core and the second outer magnetic core, and the coil winding is disposed around the winding unit. The winding unit includes a magnetic core middle column and at least two air-gaps distributed in the first direction. The inductor can improve the operating efficiency of the power factor correction circuit and can optimize efficiency of the power supply system in the light load phase.