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High-Efficiency High-Power-Density DC-DC Module, Based on
Full Bridge Phase Shift Converter
H. Pisani
In order to develop a high-efficiency and high power density dc-dc module the CEI has created a methodology that takes into
account the power losses and size of semiconductors and magnetic components to find the optimal design. This method helps
during the design when it is necessary to make a trade-off between the efficiency and power density. The proposed method
has been validated and the implemented converter has efficiency as high as 91.8% (in nominal conditions) and power density
of 4.8 kW/dm3.
Project sponsored by:
Objective and Specifications
Selected Architecture
Substitute a commercial solution for a custom
with the following specifications:
 Nominal input voltage : 270V (180V-350V)
 Nominal output voltage : 48V ( 39V – 55V)
 Nominal output power : 600W
 Constant switching frequency: 80 – 105 kHz
 Possibility to put several modules in parallel
 Limited volume : 12.2 x 4.7 x 2.16 cm3
 Good utilization of magnetic material in transformer
 ZVS on the primary side
 MOSFET voltage clamped to Vin
Architecture Optimization
Multi-objective Optimization
System variables
Important Design Issues
Magnetic design
o Inductors
o Transformer
Capacitor design
o Size and number
Semiconductor design
o Selection of MOSFETs and diodes
o Number of MOSFETs and diodes in parallel
Non dissipative snubber
 Recycling energy of PCB’s parasitics
 Small components
 Low voltage ratings
Primary Side Clamping Diodes
Rectifier diode’s voltage
350V
 Helps to obtain ZVS at low loads
 Reduces oscillations at the secondary side
Design of Additional Inductor
 Helps to obtain ZVS
 Fast current slope  High core losses
High core temperature
Complex design
Maximum inductance hardly limited
Experimental Results
Designed Converter
Commercial Converter
Measured Efficiency
Variable Switching Frequency
Nominal Efficiency : 89 %
Output power limited by output
voltage and current limit
Power Density : 6 kW/dm3
CONCLUSIONS
A commercial converter has been replaced by a highly optimized custom made converter. In order to design it, a multivariable
optimization has been applied. The implemented converter operates at constant switching frequency, has higher efficiency than
the commercial design and can provide nominal power in full range of output voltage (which the substituted commercial
solution cannot do)
Centro de Electrónica Industrial (CEI) | Universidad Politécnica de Madrid | [email protected] | www.cei.upm.es