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Ground Behind Power Supplies:
Different type of power
supply is used in electronics equipments. In starting high voltage capacity
power supply made directly from 220/230 AC supply. For generating low voltage
supply we use resistance in high voltage supply according to necessity,
capacitor and coil used for filling AC pulse and ripples. After few years
transformers used for making lower supplies, output voltage changes according
to input AC volts, it means when input AC voltage increase output DC voltage
also increases and if input AC voltage decrease output DC volts also decrease
and this type of power supply called unregulated power supply. But when we use
integrated circuit for making electronics equipments, this is necessary to use
regulated supply. First of all transistor are used as a series regulator,
problem of regulation not ended, because of working efficiency up to 25% to
40%. For example if we use 100watt as a input then we get only 25 watt to 40
watt as a output and rest of energy lost in power supply. So we can say there
is high loss of energy in this type of power supply and use of heavy
transformer in circuit is difficult. After few year we use SCR, which also loss
energy, because of this we can’t use SCR power supply in high rating, so there
is a necessary to use power supply having high working efficiency about to 80%
with less price.
Important Functions of
SMPS:
1. When
we give AC supply to any coil then there is magnetic field develop around the coil
which is called flux. AC supply having two half cycle, positive half cycle and
negative half cycle. When coil meets with postive half cycle then value of
developed magnetic field is maximum and when coil meets with negative half
cycle then value of develop magnetic field is minimum, so magnetic field varies
between maximum and minimum.AC supply have alternately positive and negative
half cycle, so we can say by giving AC supply to any coil, value of developed
flux varies around the coil and secondary winding develop voltage. Stable
magnetic flux can’t create voltage at secondary. For example if we connect
voltmeter at both ends of coil and place magnet near to coil, then meter shows
no definition. But when we moves magnet then meter shows deflection.
From above discussion this is clear,
if we give variable supply to coil, magnetic field developed around it and by
putting another coil in that region it generate voltage.
As
we know that value and direction of DC supply is constant, so when we give DC
supply to any coil then no magnetic field develop around the coil, that is the
only reason behind using transformer in AC supply but if we give different type
of DC supply to coil in which the value of DC supply rise continuously and when
it reaches to maximum we break DC supply suddenly and this method we get
current intermittently in the coil. In first position when value of DC voltage
rises from zero to maximum then value of current in coil rises from zero to
maximum.In second position when DC supply is stopped then current in coil fall
to zero. This is one type of variable current from which magnetic field develop
in the coil. So we can say that variable DC supply.develop magnetic field
around the coil.
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