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The following articles are to familiarize yourself with the
different technologies we have to offer. If you are unsure about a particular
section, please feel free to contact us for more help.
Introduction to Power Supplies
Virtually every electronic device in the world today is powered from a DC source; this
source may be either a battery or a power supply. Most electronic equipment requires not
only a DC power source, but also one that is well-filtered and well-regulated as well three
types of electronic power conversion devices in common use today: the AC/DC power supply,
the DC/DC converter, and the DC/AC inverter. Each has its own specific areas of application.
Of the three, AC/DC power supplies and DC/DC converters are the most commonly used and are
the subject of this technical section.
Power supplies have evolved through the years from the large rack-mounted units employing
vacuum tubes and dangerously high voltages, to today's compact solid state power supplies
with their lower, and relatively safe, DC voltages. Since power supplies and DC/DC converters
are so widely used in electronic equipment, these devices now comprise a worldwide segment
of the electronics market in excess of $5 billion annually. Furthermore, this market is growing
in step with the total worldwide electronics market. Power converters have not only evolved
into compact solid-state devices, but the basic technology has advanced from linear power
supplies to modern switching power supplies which are not only smaller and lighter, but also
much more efficient than their linear counterparts. Linear power supplies employ conventional
50/60Hz power transformers followed by a rectifier, filter, and linear regulator. These
supplies, still widely used, are about 40 to 55% efficient.
Switching power supplies, on the other hand, are generally "off-line" devices; that
is, they directly rectify and filter their AC Line voltage without first using a 50/60 Hz
transformer. Then the filtered DC is chopped by a power switch and high frequency transformer,
and is finally rectified and filtered again. Because of the fast switching rate, which is
from 20 KHz to 500 KHz, the transformer and capacitors are much smaller than their 50/60Hz
counterparts are. Switching power supplies are from 50 to 80% efficient.
DC/DC converters, similar to switching power supplies in their operation, are used
to change one DC voltage to another, and are usually well regulated. These devices are
important where electronic equipment must be operated from a battery or other DC source.
Power supply technology has changed rapidly over the past decade, and modern switching
power supplies and DC/DC converters are much more difficult devices to design and produce
reliably than were the simpler linear power supplies of the past.
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