Switching Power Supply Resonant Coupling and ZVS
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Solution Overview
Problem
Existing switching power supply devices face challenges in increasing power conversion efficiency due to limitations in magnetic coupling and frequency control, which hinder compactness and controllability, especially at high frequencies, leading to reduced efficiency and EMC issues.
Innovation Solution
A switching power supply device with a constant switching frequency on the primary side and adjustable on-period proportion, utilizing LC resonant circuits on both sides for magnetic and electric field coupling, enabling zero voltage switching and efficient power transmission by resonating at a frequency higher than the specific resonant frequency, thereby increasing output power and reducing losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a transformer utilizing electromagnetic induction is used to increase power conversion efficiency, then the degree of magnetic coupling must be increased, but magnetic saturation or physical constraints prevent further increase in coupling degree
Solution Approach 1:
The patent changes the operating parameters by using a resonant frequency higher than the specific resonant frequency, which alters the impedance characteristics of the circuit. This parameter change enables the system to operate in a regime where the switching elements can achieve zero voltage switching, thereby reducing switching losses and improving power conversion efficiency without being constrained by magnetic coupling limitations or magnetic saturation issues.
2Ease of operation
If frequency control and PFM control are used for output control, then a smoothing circuit must be designed according to the minimum operating frequency, but this hinders compactness
Solution Approach 1:
The patent employs dynamic control by adjusting the on-period proportion of multiple switching circuits while maintaining a constant switching frequency. This dynamic adjustment of duty cycles allows for flexible output power control without requiring frequency variation, thereby eliminating the need for large smoothing circuits designed for minimum frequency operation and achieving compact device design.
3Volume of moving object
If operation frequency is increased to the order of MHz for miniaturization of magnetic components, then frequency changes cause significant problems in output controllability and EMC
Solution Approach 1:
The patent maintains operation at a constant high switching frequency (MHz order) for miniaturization while achieving output control through dynamic adjustment of the on-period proportion (duty cycle) of multiple switching circuits. This separates the frequency function (miniaturization) from the control function (output power regulation), thereby achieving both compact magnetic components and excellent output controllability without EMC issues associated with frequency modulation.
4Productivity
If switching frequency is changed to adjust output power, then output control is achieved, but this results in significant EMC problems and reduces controllability at high frequencies
Solution Approach 1:
The patent achieves output power adjustment by dynamically changing the on-period proportion (duty cycle) of multiple switching circuits while maintaining a constant switching frequency. This dynamic duty cycle control provides precise output power adjustment capability without the electromagnetic compatibility problems that arise from frequency modulation, thereby achieving both productivity and EMC compliance.
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 enhances power transmission efficiency, reduces switching losses, and allows for compact and lightweight design while maintaining stable output voltage, achieving high-efficiency operation across a wide load range.
Implementation Method 1
a LC resonant circuit composed of an inductor Lr and a capacitor Cr
Implementation Method 2
the magnetic flux generated by a current flowing through the primary winding is linked to the secondary winding to cause a current to flow through the secondary winding
Implementation Method 3
switching elements are turned on and off at a frequency higher than a specific resonant frequency thereof at which an input impedance becomes minimum
Data Source
Figure 1~2
Figure 3~4
Figure 5(A)~6
AI summary
A first resonant circuit composed of Lr-Cr and a second resonant circuit composed of Lrs-Crs are caused to resonate with each other to cause sympathetic vibration of each resonant circuit, and thereby power transmission is performed by utilizing two types of coupling, namely, magnetic field coupling and electric field coupling between a primary winding (np) and a secondary winding (ns). In addition, operation at a switching frequency higher than a specific resonant frequency of an overall multi-resonant circuit allows a ZVS operation to be performed, enabling a significant reduction in switching loss and high-efficiency operation. Thus provided is a switching power supply device with reduced size and increased power conversion efficiency.