LLC Resonant Converter Pre-Conduction for Wide Voltage Range
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Solution Overview
Problem
LLC resonant converters used in electric vehicle charging piles face efficiency reduction due to increased quality factor, leading to damage in resonant inductors and transformers, as they struggle to supply a wide output voltage range without excessive temperature increase and phase shift angle reduction.
Innovation Solution
A resonant converter with a pre-conduction mechanism, featuring a circuit configuration with multiple switches and a control strategy that allows the fourth low-side switch to be switched from zero voltage, even with large phase shift angles, reducing the quality factor and enhancing efficiency by widening the output voltage range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the quality factor of the resonant tank is increased to enable switching when voltage is zero, then the converter can supply voltages within the wide output voltage range, but the resonant inductor and transformer are more easily damaged and efficiency is reduced
Solution Approach 1:
The fourth low-side switch is turned on before the second low-side switch is turned off, creating a pre-conduction interval. This preliminary action ensures that the fourth low-side switch is already conducting when needed, enabling zero-voltage switching without requiring excessive quality factor increase, thereby resolving the contradiction between wide output voltage range and efficiency
2Adaptability or versatility
If the quality factor of the resonant tank is increased to reduce phase shift angles, then the converter can supply voltages within the wide output voltage range, but the resonant inductor and transformer are more easily damaged
Solution Approach 1:
By turning on the fourth low-side switch in advance (pre-conduction), the circuit is prepared for the upcoming switching event. This preliminary action allows the switch to operate under favorable conditions (zero voltage) without requiring large phase shift angle reductions, thus maintaining component reliability while achieving wide output voltage range
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 resonant converter achieves a wider and lower output voltage range, reducing damage to components and improving efficiency by mitigating the quality factor, thus enhancing the voltage regulation performance.
Implementation Method 1
LLC resonant convertors can be switched at a high frequency and volumes of the LLC resonant convertors can be smaller than other types of the converters
Data Source
AI summary
A resonant converter having a pre-conduction mechanism for realizing a wide output voltage range is provided. The resonant converter includes a first circuit and a second circuit. The first circuit includes a plurality of primary-side switches. The plurality of primary-side switches includes a first high-side switch, a second high-side switch, a first low-side switch and a second low-side switch. The second circuit includes a plurality of secondary-side switches. The plurality of secondary-side switches includes a third high-side switch, a fourth high-side switch, a third low-side switch and a fourth low-side switch. When the second low-side switch and the first low-side switch are turned on and a current time reaches a preset on time, the fourth high-side switch and the third low-side switch are turned on.