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Figure 1:
Battery Output Voltage Variations
will be a suitable regulator available
off-the-shelf to meet the voltage
requirements.
Obviously, the regulator must be
able to deliver the power required
by the load. Regulator power is
typically specified by a maximum
output current.
Input and Output Ranges
Although applications often require
a specific voltage, others will
require an adjustable output. This
might be because the loads change
– for example in a piece of test
equipment – or it may be that the
load is supplied by a long cable, and
the voltage needs to be trimmed
a little higher than required by the
load to compensate for the voltage
drop across the cable.
Input voltage ranges are particularly
important for applications such as
battery-powered systems. In an
automotive application, a nominal
12V battery might deliver 12.5V at
full charge and drop to 10V or less as
the battery discharges. A regulator
with a narrow input range may
no longer function as the battery
voltage drops, meaning that the full
capacity of the battery cannot be
used. Ensuring a sufficiently wide
input range is therefore an important
criterion for selecting your regulator.
Choosing wide input regulators also
has another benefit: they can also
reduce inventory costs as a single
regulator can be used in a variety of
different situations.
Efficiency
Efficiency is one of the criteria for
most power systems designed
today. Selecting a regulator with
high power losses can make it almost
impossible to meet efficiency goals.
It’s important to also remember
that regulator efficiency is not
constant: typically, the efficiency of
the regulator will fall dramatically
as the step-down or step-up ratio
increases and as the current drawn
from the output decreases.
Modern regulators, such as those
based on Vicor’s Zero Voltage
Switching (ZVS) topology offer
inherently high efficiency and are
more consistent across the whole
operating range.
Noise
Switching
regulators
provide
high efficiency, but the switching
circuit generates noise. In some
systems, particularly those with
sensitive analog components,
the power supply noise can limit
overall performance. Unnecessary
electronic noise can also make
it more difficult to achieve EMC
certification.
As with efficiency, the regulator
topology is key to achieving low
noise: it’s much easier to use a
component that doesn’t generate
noise than it is to try to filter that
noise out. ZVS, for example, is
54 l New-Tech Magazine Europe