EE361-Electromechanical Energy Conversion

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# EE-361
# Introduction to Step-down(Buck) Converter

## Ozan Keysan

[keysan.me](http://keysan.me)

Office: C-113 <span class="meta">•</span> Tel: 210 7586

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# DC/DC Converters
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## Can be used to:
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## Step down the input voltage (Buck Converters)
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## Step up the input voltage (Boost Converters)

## or both (Buck-boost Converters)

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## Let's start with a simple Step down Converter
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<img src="./images/ee463/simple_dc_dc.png" alt="Drawing" style="width: 800px;"/>

## Can you design this converter?

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## Resistive Voltage Divider

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# Series Regulator (Transistor in linear mode)

### Efficiency= 50% !
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## Avoid lossy elements for high efficiency!

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# DC/DC Converter Applications
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## All Types of Power Supplies

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# Which components do you see?

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# Which components do you see?

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# Step-Down (Buck) Converter:

## Simplest Case

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# Step-Down (Buck) Converter:

## Simplest Case

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# Let's make the output voltage smoother
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## Add a Low Pass Filter (eg LC Filter)

### [Buck Converter Simulation](https://www.multisim.com/content/9zdN2fmAxbMcsVv46Ap9KX/buck-converter/)
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## Why do we have the diode for?

## Freewheeling Diode: Conducts when switch is off

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## Operating Modes of Buck Converter

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## Switch ON

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## Switch OFF

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## Operating Modes (in CCM)

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## Voltage and Current Waveforms

#### Assumptions:

- #### Converter working under steady state (\\(I\_{L}(0)=I\_{L}(T)\\))
- #### Capacitor is large so that output voltage (\\(V\_{o}\\)) is constant
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## Voltage Output Characteristics

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## Step-Down (Buck) Converter:
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#\\(V_o = D V_d\\)
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### Neglecting losses

#\\(I_o = I_d/D\\)

### Like a DC transformer with a turns ratio of \\(D:1\\) !

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## You can download this presentation from: [keysan.me/ee361](http://keysan.me/ee361)