Phase-Shift Full-Bridge Converter Light Load Control
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Solution Overview
Problem
Conventional phase-shift full-bridge converters experience reduced conversion efficiency and increased switching losses at high frequencies, leading to electromagnetic interference and shortened component life, especially in light load operations where resonance energy is insufficient or zero, necessitating improved soft switching techniques.
Innovation Solution
The method involves detecting the magnetizing current of the transformer to switch between extended and modified control modes, optimizing soft switching by adjusting the magnetizing current and duty cycle, thereby reducing switching losses and enhancing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the switching frequency is increased to reduce volume and weight, then the volume and weight of the switching power converter are reduced, but the switching losses increase and conversion efficiency decreases
Solution Approach 1:
The patent applies zero voltage switching (ZVS) technology to change the switching characteristics of the power converter. By ensuring that the voltage across the power switch is zero during the switching transition, the patent enables high-frequency operation without proportionally increasing switching losses, thus resolving the contradiction between high frequency (for reduced volume) and switching losses.
2Volume of moving object
If the switching frequency is increased to reduce volume and weight, then the volume and weight of the switching power converter are reduced, but the conversion efficiency decreases
Solution Approach 1:
The patent employs zero voltage switching (ZVS) to change the energy dissipation characteristics during switching. By ensuring voltage is zero during the switching transition period, the patent enables high-frequency operation while maintaining high conversion efficiency, thus resolving the contradiction between reduced volume (via high frequency) and conversion efficiency.
3Device complexity
If conventional hard switching technology is used, then the circuit structure is simple, but switching losses increase and electromagnetic interference occurs
Solution Approach 1:
The patent transitions from hard switching to zero voltage switching (ZVS) by changing the switching parameters and timing. This ensures that voltage across the power switch is zero during switching transitions, eliminating voltage and current surges that cause electromagnetic interference, while the control circuit maintains reasonable complexity through phase-shift control.
4Volume of moving object
If the switching frequency is increased, then the volume and weight are reduced, but the use life of switch components is shortened
Solution Approach 1:
The patent applies zero voltage switching (ZVS) to change the stress characteristics on power switch components. By ensuring that voltage across the switches is zero during switching transitions, the patent reduces switching stresses and thermal losses, enabling high-frequency operation that reduces volume while extending the use life of the switch components.
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 significantly reduces switching losses, improves efficiency, and achieves electromagnetic compatibility by implementing optimal soft driving in light load operations, doubling the magnetizing current under modified control modes to minimize power switch switching losses.
Implementation Method 1
a first resonant circuit comprising a first resonant inductor and a first resonant capacitor connected in series between a first node and a second node, a second resonant circuit comprising a second resonant inductor and a second resonant capacitor connected in series between a third node and a fourth node
Implementation Method 2
a first resonant circuit comprising a first resonant inductor and a first resonant capacitor connected in series between a first node and a second node, a second resonant circuit comprising a second resonant inductor and a second resonant capacitor connected in series between a third node and a fourth node
Data Source
AI summary
A method of controlling a phase-shift full-bridge (PSFB) converter in a light load operation is provided to switch control modes of the PSFB converter by detecting magnetizing current of a transformer thereof. The method includes following steps: First, the PSFB converter is operated in an extended PSFB control mode when the magnetizing current is larger. Afterward, the PSFB converter is operated in a modified PSFB control mode when the magnetizing current is gradually reduced and electric charges transported by the residual magnetizing current near to or less than a half of the DC input voltage. Finally, the optimal degree of soft switching of the PSFB converter is implemented when the PSFB converter is operated at the modified PSFB control mode. Accordingly, it is to improve overall efficiency, reduce switching losses, and achieve electromagnetic compatibility.