Two-Stage Resonant Buck Power Converter for Soft Switching
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Solution Overview
Problem
Conventional non-isolated power converters suffer from high switching losses due to the use of hard switching technologies in both the front-stage and rear-stage conversion circuits, limiting energy transmission efficiency.
Innovation Solution
A power converter design that includes a front-stage conversion circuit with a buck circuit and an auxiliary circuit featuring negative coupling inductors, and a rear-stage conversion circuit with resonant capacitors and negative coupling output inductors, achieving zero-current and zero-voltage switching through resonant networks to reduce switching losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If hard switching technology is used in both front-stage and rear-stage conversion circuits, then the circuit structure is simple, but switching loss is high and energy transmission efficiency is low
Solution Approach 1:
The power converter is divided into two independent stages: front-stage conversion circuit and rear-stage conversion circuit. Each stage can be optimized independently for different functions. The front stage uses resonant inductors and capacitors to achieve soft switching, while the rear stage uses a parallel buck topology with phase-shifted control, allowing each segment to contribute to overall efficiency without requiring complete redesign of the entire system.
Solution Approach 2:
The patent introduces resonant inductors and capacitors to create oscillating current and voltage waveforms in the front-stage conversion circuit. This resonant vibration enables the switches to turn on and off when current or voltage is zero, eliminating switching losses. The resonant frequency is carefully designed to match the switching frequency, creating a vibration-based switching mechanism that replaces traditional hard switching.
2Power
If a two-stage circuit topology is used to achieve high voltage transformation ratio, then voltage reduction requirement is met, but current stress on transistors increases
Solution Approach 1:
The patent combines two different circuit topologies (front-stage resonant converter and rear-stage parallel buck converter) into a single two-stage system. The front stage handles the primary voltage transformation with isolated ground, while the rear stage performs secondary voltage adjustment with phase-shifted control. This merging allows the system to achieve high voltage transformation ratio while distributing current stress across multiple transistors in parallel configuration.
Solution Approach 2:
The rear-stage conversion circuit uses dynamic phase-shifted control where the switching duty cycles of the two parallel buck circuits are shifted by 180 degrees. This dynamic control strategy redistributes the current stress on transistors over time, ensuring that not all transistors bear maximum stress simultaneously. The duty cycle can be dynamically adjusted based on load conditions to optimize current distribution.
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 design enhances energy transfer efficiency by minimizing turn-on and turn-off losses in the switches, optimizing the front-stage and rear-stage conversion circuits through resonant inductance cancellation and phase-shifted control.
Implementation Method 1
the resonance generated by the resonant capacitor, zero-current switching functions of the switches in the front-stage conversion circuit can be achieved
Implementation Method 2
a first inductor and a second inductor of an auxiliary circuit are negative coupling. In the rear-stage conversion circuit, the dot-marked terminal of one of a first output inductor and a second output inductor is connected with the non-dot terminal of the other of the first output inductor and the second output inductor. Consequently, the large inductance of the inductor in the front-stage conversion circuit can be offset.
Data Source
AI summary
A power converter includes a front-stage conversion circuit and a rear-stage conversion circuit. The front-stage conversion circuit includes a buck circuit and an auxiliary circuit. The buck circuit includes a first inductor, a first switch and a first capacitor. A first terminal of the first inductor is electrically connected to an input positive terminal of the buck circuit through the first switch. A second inductor of the auxiliary circuit and the first inductor are negative coupling. The rear-stage conversion circuit includes a resonant capacitor, a first output inductor and a second output inductor. A dot-marked terminal of the first output inductor is connected with a non-dot terminal of the second output inductor and electrically connected with an output positive terminal of the power converter. The auxiliary circuit is electrically connected between an input negative terminal of the buck circuit and the resonant capacitor of the rear-stage conversion circuit.