Resonant Power Converter Soft Switching Control
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Solution Overview
Problem
Existing resonance-type power converters face inefficiencies due to increased switching loss when output power is reduced by increasing the switching frequency, limiting the range of frequencies capable of soft switching.
Innovation Solution
The method involves a controller that secures a delay time within a predetermined range of switching frequency, allowing the switching element to perform soft switching over a wider frequency range by adjusting either the switching frequency or duty ratio, thereby reducing applied voltage and enhancing power-conversion efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If switching frequency is increased to reduce output power, then output power is reduced, but switching loss increases and soft switching cannot be performed
Solution Approach 1:
The patent applies dynamics by making the switching frequency variable rather than fixed. The control device dynamically adjusts the switching frequency within a range from a first frequency (lower than series resonance frequency) to a second frequency (higher than series resonance frequency) based on the required output power, enabling the system to adapt to different operating conditions while maintaining soft switching capability across the entire frequency range
Solution Approach 2:
The patent changes the parameter of switching frequency to resolve the contradiction. By varying the switching frequency parameter within a specific range that spans both below and above the series resonance frequency, the system maintains soft switching conditions across different power output levels, preventing switching loss increase even when output power is reduced
2Power
If switching frequency is increased to reduce output power, then output power is reduced, but the range of frequencies capable of soft switching is limited
Solution Approach 1:
The system dynamically adjusts switching frequency within an expanded range that includes frequencies both below and above the series resonance frequency. This dynamic frequency adjustment capability allows soft switching to be maintained across a broader frequency spectrum, enhancing the system's adaptability to different power output requirements
Solution Approach 2:
The control device achieves multi-functionality by enabling soft switching across a universal frequency range that encompasses both sub-resonant and super-resonant frequencies. This allows the same circuit topology to effectively operate across different frequency domains without requiring additional circuitry, making the system versatile for various power output conditions
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 approach expands the range of switching frequencies capable of soft switching, improving the efficiency of resonance-type power converters and reducing costs by allowing the use of lower-cost switching elements and eliminating the need for high-precision current sensors.
Implementation Method 1
a frequency lower than a resonance frequency of a series resonant circuit... at the resonance frequency
Data Source
Figure 1
Figure 2(a)~2(b)
Figure 3
AI summary
The present disclosure includes by controlling at least either one of a switching frequency of a switching element (S) or a duty ratio indicating an ON period of the switching element, securing delay time from voltage at both ends of the switching element reaches zero voltage by resonance of the resonant circuit (L0, C0) in an OFF state of the switching element until the switching element is turned on, and turning on the switching element within the delay time.