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Numerical problems
1.
A step up chopper has an input voltage of 150V. The voltage output needed is 450V. Given, that the
thyristor has a
conducting time of 150μseconds. Calculate the chopping frequency.
Solution −
The chopping frequency (f)
The new voltage output, on condition that the operation is at constant frequency after the halving the
pulse width.
Halving the pulse width gives −
2.
In
a type A chopper, the input supply voltage is 230 V the load resistance is 10Ω and there is a
voltage drop of 2 V across the chopper thyristor when it is on. For a duty ratio of 0.4, calculate the
average and rms values of the output voltage. Also find the chopper efficiency
3.
A step-up chopper supplies a load of 480 V from 230 V dc supply.
Assuming the non conduction
period of the thyristor to be 50 microsecond, find
the on time of the thyristor
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Buck regulator
With power being a key parameter in many designs, step down or "buck" regulators are widely used.
Although a resistor would
enable voltage to be dropped, power is lost, and
in applications such as the
many battery powered items used today, power consumption is a crucial element.
As a result step down switch mode converters or as they are more commonly termed, buck regulators are
widely used.
Linear step down
The most basic form of step down transition is to use a resistor as a potential divider or voltage dropper.
In some cases a zener diode may also be used to stabilize the voltage.
Figure: 3.19 Potential divider circuits
The issue with this form of voltage dropper or step down converter is that it is very wasteful in terms of
power. Any voltage dropped across the resistor will be dissipated as heat, and any current flowing through
the zener diode will also dissipate heat. Both of these elements result on the loss of valuable energy.
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