Phase Shift Full Bridge Power Supply Light Load Efficiency
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Solution Overview
Problem
Full bridge converters experience a significant degradation in power conversion efficiency at light load conditions due to the inability to perform zero voltage switching smoothly for lagging leg switches, leading to reduced performance in these regions.
Innovation Solution
A phase shift full bridge power supply device that controls the switching time of lagging leg switches based on the load state, using a comparison unit to delay the switching on time of these switches when the load is low, thereby maintaining efficiency across varying load conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If switching time of lagging leg switches is fixed, then control is simple, but zero voltage switching cannot be maintained at light load
Solution Approach 1:
The patent implements feedback by having the control unit detect the actual load state and adjust the switching time of lagging leg switches accordingly. The control unit compares the detected load state with reference values and automatically modifies switching timing to maintain zero voltage switching, creating a closed-loop control system that balances simplicity with reliability.
2Loss of energy
If switching on time of lagging leg switches is delayed at light load, then power conversion efficiency is improved, but switching time becomes variable and control complexity increases
Solution Approach 1:
The patent makes the switching time dynamic rather than fixed, allowing it to vary between a first value at heavy load and a second value at light load. This dynamic adjustment is controlled by comparing detected load state with reference values, enabling efficiency optimization without requiring complex additional hardware.
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 effectively suppresses the reduction in power conversion efficiency at light loads by ensuring zero voltage switching is maintained, even in low load conditions, thus maintaining high efficiency across the entire load range.
Implementation Method 1
a transformer having a primary winding receiving power switched by the switch of the full bridge and a secondary winding electrically isolated from and magnetically coupled to the primary winding to form a preset winding ratio therewith, transforming the switched power according to the winding ratio
Implementation Method 2
based on resonance between the switch of the full bridge and an output capacitor and a parasitic inductor of a rectifying switch
Data Source
AI summary
There is provided a phase shift full bridge (PSFB) type power supply device controlling a switching on time of lagging leg switches according to a load state. The power supply device includes a power supply unit supplying preset DC power by switching input power using a full bridge by a phase shift method; and a control unit controlling a switching time of a switch of the full bridge according to a load state in which the DC power is received from the power supply unit.