Phase-Shifted Full Bridge Converter Circulating Current Reduction
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Solution Overview
Problem
Phase-shifted full-bridge (PSFB) converters experience efficiency losses due to circulating currents, which are particularly significant in applications with wide input and output voltage ranges, as these currents do not contribute to power transfer across the transformer.
Innovation Solution
A controller circuit generates drive signals for the transistors in a PSFB converter, implementing a phase shift between the drive signals of the two half-bridges, ensuring that the high-side transistor in one half-bridge is switched off when the high-side transistor in the other half-bridge is turned on, and the low-side transistor in one half-bridge is switched off when the low-side transistor in the other half-bridge is turned on, thereby reducing the duration of circulating currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the phase shift between drive signals is increased to reduce circulating currents, then efficiency improves, but output voltage regulation becomes more difficult
Solution Approach 1:
The controller circuit dynamically adjusts the phase shift between drive signals based on operating conditions. The temporal offset between switching events is optimized to eliminate circulating currents while maintaining adequate output voltage regulation capability across varying load and input voltage conditions.
Solution Approach 2:
The control strategy modifies the timing parameters of the drive signals, specifically the phase shift and duty cycle, to optimize the switching sequence. By changing these temporal parameters, the converter achieves reduced circulating currents while maintaining stable output voltage regulation.
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 minimizes the duration of free-wheeling phases and associated losses, maintaining high efficiency across varying input and output voltage conditions by adjusting the phase shift to regulate the output voltage effectively.
Implementation Method 1
The first and the second drive signal are phase shifted-with respect to the third and the fourth drive signal
Implementation Method 2
The first drive signal and the second drive signal are periodic with a cycle period and pulse-width modulated
Implementation Method 3
A PSFB converter provides voltage conversion as well as galvanic isolation from the input line voltage since this converter topology includes a transformer
Implementation Method 4
Like other resonant or quasi-resonant converters, a PSFB converter can be operated to perform so-called Zero-Voltage-Switching (ZVS) with regard to the power transistors
Data Source
AI summary
A phase-shifted full bridge (PSFB) switching converter includes a transistor full-bridge having first and second half-bridges. Each half-bridge includes a high-side transistor and a low-side transistor. A controller circuit is configured to generate a drive signal for each transistor. The (first/third and second/fourth) drive signals for the transistors of each half-bridge are periodic with a cycle period, pulse-width modulated and have a temporal offset to each other that equals half of the cycle period. The drive signals for the half-bridges are phase shifted-with respect to one another. The controller circuit also is configured to generate the first drive signal so that the first high-side transistor is switched off when the third drive signal indicates to switch on the second high-side transistor, and to generate the second drive signal so that the first low-side transistor is switched off when the fourth drive signal indicates to switch on the second low-side transistor.