Switched Mode Power Supply _SMPS_

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Switched Mode Power Supply _SMPS_ Powered By Docstoc
					?SMPS stands for Switched Mode Power Supply or switching-mode power supply.
SMPS is a power supply unit (PSU) for electronic use that contains a switching
regulator. While a linear regulator maintains the desired output voltage by dissipating
excess power in a "pass" power transistor, the SMPS switches a power transistor at
the faster rate between saturation (full on) and cutoff (completely off) with a variable
duty cycle whose average is the desired output voltage. This process gives rectangular
waveform as a result which is filtered by a low-pass filter with using inductor and

The supreme benefit of using this process In SMPS is that it gives a better efficiency.
It is because of the small dissipation of the power by the switching transistor in the
saturated state and the off state compared to the semiconducting state (active region).
Other advantages of Switch Mode Power Supply (SMPS) include smaller size and
lighter weight which is greater in low frequency transformers which have a high
weight. Moreover it generates lower heat from the higher efficiency.

Disadvantages of SMPS are:

Greater complexity,

The generation of high amplitude

High frequency energy that the low-pass filter must block to avoid
electromagnetic interference (EMI)

Ripple voltage at the switching frequency and the harmonic frequencies..

SMPS can be categorized into four different types on the basis of its input and output
waveforms, as follows.

AC in, DC out: rectifier, off-line converter input stage.

DC in, DC out: voltage converter, or current converter, or DC to DC converter

AC in, AC out: frequency changer, cycloconverter

DC in, AC out: inverter

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