Testing Virtual ECUs - Power Systems Design

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than NiMH, Li-ion batteries require significantly
more battery management (temperature
monitoring, cell balancing, etc.) which increases
the semiconductor content. IMS Research
estimates that the semiconductor content of a
LI-ion battery is currently five times that of an
equivalent NiMH battery, with the majority of
the difference coming from the number of ASSPs
needed for cell pack voltage monitoring.
Automotive OEMs have considerable intellectual
property tied up in the design of their internal
combustion engines. The same is true for
hybrid and electric vehicles on the market at
the moment, with the theory being that electric
motor control is one way of keeping expertise inhouse.
But is this really the ideal way of getting
the most out of an electric vehicle?
Much of the expertise needed to control high
speed electric motors can be found in the
industrial automation or motor industry. Players
in these markets are setting their sights on the
electric vehicle market, particularly with ‘offthe-shelf’
inverter modules. Not only do these
‘modules’ play to their strengths, but they give
vehicle OEMs the opportunity to reduce R&D
costs by outsourcing motor control design.
The automotive OEMs have a big decision to
make: do they go it alone on motor control
design to retain the “engine IP”, or do they work
with existing experts to take advantage of their
experience?
www.imsresearch.com
DESIGNtips
POWER SYSTEMS DESIGN JULY/AUGUST 2011
POWER SUPPLY DEVELOPMENT
DIARY PART XIV
By Dr. Ray Ridley
This article continues the series in which Dr.
Ridley documents the processes involved in
taking a power supply from the initial design to
the full-power prototype. The second layout of the PC board
incorporates significant changes in the power stage, changing
the number of outputs from three to five. Some of the issues
involved in the coupled-inductor magnetics design are
discussed.
T
hree Output Coupled-
Inductor Design
The original
specification for the
power supply design was as
follows:
1. Output 1 – 35 VDC @ 10A
isolated
2. Output 2 – 35 VDC @ 10 A
isolated
3. Output 3 – 15 VDC Bias
power and regulated output,
primary referenced
4. Maximum power 350 W (only
one output fully loaded at
a time, application is for
audio.)
5. Input – 180 – 265 AC
6. Power Topology: Two-switch
forward
Figure 1 shows the schematic
of the three-output forward
Figure 1: Forward Converter with Three Coupled-Inductor Outputs
converter. A single core inductor
is used with three windings,
one for each of the outputs.
This coupled-inductor approach
provides the best cross-regulation
between each of the outputs.
There are two major advantages
of coupled inductors – firstly, all
of the outputs are tied together
through the transformer action
of the inductor, preventing them
from having individual resonant
frequencies. Secondly, regardless
of individual loading on each
of the outputs, the coupled
inductor forces all of the outputs
WWW.POWERSYSTEMSDESIGN.COM
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