Block Diagram
and description
FIG: BLOCK DIAGRAM OF SWITCH MODE POWER SUPPLY
Input Rectifier Stage
It is used to convert an AC input into DC. A SMPS with dc input
does not require this stage. The rectifier produces unregulated dc which is
feed to the filter circuit.
Inverter Stages
The inverter stage
converts DC, whether directly from the input or from the rectifier stage
specified as, to AC by running it through a power oscillator, whose output
transformer is very small with few windings at a frequency of tens or hundreds
of kilohertz(KHz).
Output transformer:
If the
output required is to be isolated from input, the inverted AC is used to draw
the
primary
windings of a high frequency transformer. This converts the voltage up or down
to the required output level on it’s secondary winding.
Output rectifier:
If the dc output is
required, then the ac output from the transformer is rectified.
Regulation:
Feedback circuit monitor
the output voltage and compare it with the reference voltage.
Multiple output block
FIG: CONFIGURATION OF MULTIPLE OUTPUT CONCEPT
n For the regulating switched mode power supply there are possible
multiple output voltages are getting with either proper arrangement of
transformer turns ratio or ideal switching of the MOSFETs. Which is situated in
the fig. Of Primary portion.
n Where as output voltages
are possible at the other secondary portion of the circuit configuration. So,
the help of low pass filter with assembled with inductor and capacitor are make
connected across the load
Advantages and Disadvantages of SMPS
n The main advantage of this method has great efficiency because the
switching transistor dispel little power when it is outside of its active
region (i.e., when the transistor acts like a switch and either has a
negligible voltage drop transverse it or a negligible current through it)
n Other advantages include smaller size and lighter weight (from the
exclusion of low frequency transformers which have a high weight) because low
heat dissipation and reduces the harmonic.
n Disadvantages include greater complexity, the generation of
high-amplitude, high-Frequency energy that the low-pass filter might block to
procrastinate electromagnetic interference (EMI), Ripple Voltage at the
switching frequency.
n The Harmonic Frequencies thereof, very low cost SMPS may couple
electrical switching noise back onto the mains power line, that causing
interference with A/V equipment connected to the same phase.
Non-power-factor-Corrected SMPS also reason harmonic distortion.
APPLICATION
n Switched-mode power supply units (PSU) are used in PLCs, Audio and
Video applications, measuring instruments, security systems, and machine and
tools industries.
n In domestic products such as personal computers often have
universal inputs, meaning that They can accept power from mains supplies
throughout the world, nevertheless a manual voltage range switch may be
required.
n Switch -mode power supplies can tolerate a wide range of power
frequencies and voltages.
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