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DC-DC Converters (choppers)

The objective is to convert a fixed DC voltage to a

variable DC voltage

It is possible to step up and step down voltage.

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Voltage step down (buc converter)

First, suppose L=0, E=0.

The diode is not needed.

Va=(ton/T)Vs

VRMS=k 1/2Vs

out=(kVs2

)/R 

k=ton/T is the dut! "!"#e

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!tep down converter with

"# load

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spi"e s"he$ati"s Step do%n d"&d" "on'erter 

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Voltage step up (boost)

convertern* $ode+ VL=L(di/dt)

* $ode+ -ssu$e

"urrent de"reases at a"onstant rate. Then

Vo=VsVL

To ensure "ontinuous "urrent

#o%, a "apa"itor is in"#uded.

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eror$an"e o a step up "on'erter %ith resisti'e #oad (=0).

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DC-DC Converter classification

$irst %uadrant converter

!econd %uadrant

converter &st and 'nd %uadrant

converter

rd and th %uadrantconverter

$our %uadrant converter

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!econd *uadrant Converter

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&-' and - %uadrant converters

1st uad+ S1,

2nd uad+ S, 1

3rd uad+ S3, 2

th uad+ S2, 3

o#arit! o the #oad EMF is

re'ersed.

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$our %uadrant converter