EE463-Static Power Conversion-I

class: center, middle

# EE-463 STATIC POWER CONVERSION-I

# An Introduction to DC/DC Converters

## 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
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# Step up the input voltage

# or Both

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

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## DC/DC Converter Applications
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## Renewables: PV

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## DC/DC Converter Applications

## Electric Cars/Traction

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## DC/DC Converter Applications

## Electric Cars/Traction

### [200 kW SiC DC/DC Converter](https://www.iisb.fraunhofer.de/de/research_areas/vehicle_electronics/dcdc_converters/projects/200_kw_full_sic_dcdc_converter.html)

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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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# Let's make the output voltage smoother
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## LC Filter Characteristics (More in the following weeks)

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## Why do we have the diode for?

## Freewheeling Diode: Conducts when switch is off

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## Operating Modes (in CCM)

CCM: Continuous Conduction Mode
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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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# Transition to DCM
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# Transition to DCM

### Boundary Current between CCM and DCM
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## \\(I\_{LB}= \dfrac{D T\_s}{2L} (V\_d - V\_o)\\)
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## when D=0.5

## \\(I\_{LB\_{max}}= \dfrac{T\_s V\_d }{8L}\\)
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# Transition to DCM

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# Transition to DCM

### Minimum Inductance for Continuous Current

### \\(L\_{min}= \dfrac{(1-D) }{2 f\_s} R\\)
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### Current Ripple for a given inductance

### \\(\Delta i\_{L}= (\dfrac{V\_s - V\_o}{L}) DT = \dfrac{V\_o (1  - D)}{L f\_s} \\)

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# Discontinuous Conduction Mode
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### Details and derivations are in the textbook.

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# Discontinuous Conduction Mode

### Output voltage is increases in DCM if Vd and D is kept constant

### Critical current is max, when D=0.5

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# Discontinuous Conduction Mode

### or duty cycle needs to be reduced to keep Vo constant

### Critical current is max, when D=0.5

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# Voltage Ripple
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# Voltage Ripple
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### \\(\Delta V\_o = \dfrac{\Delta Q}{C}\\)
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### \\(\Delta V\_o = \dfrac{\Delta i\_L T\_s}{8C}\\)

### \\( \dfrac{\Delta V\_o}{V\_0}= \dfrac{(1-D) T\_s^2 }{8LC} \\)
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## Can you put it in a much nicer form?

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# Voltage Ripple

### \\( \dfrac{\Delta V\_o}{V\_0}= \dfrac{(1-D) T\_s^2 }{8LC} \\)
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### \\( \dfrac{\Delta V\_o}{V\_0}= \dfrac{\pi^2 (1-D) }{2} {\bigg(\dfrac{f\_c}{f\_s}\bigg)}^2 \\)

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# Effect of Capacitor ESR
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## \\( \Delta V\_{o, ESR} = \Delta i\_{c} r\_{c} = \Delta i\_{L} r\_{c} \\)

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# Synchronous Buck Converter
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### What is the purpose of the extra MOSFET?
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### Increased efficiency due to reduced diode loss.
### ( \\(R\_{ds-on}\\) instead of \\(V\_{forward}\\) )

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# Design Decisions 
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## Small Volume is desired:
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- ## Increase \\(f_s\\), LC filter gets smaller.
- ## Switching loss is increased (also increases heatsink volume)

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# Design Decisions

## High Efficiency is desired:
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- ## Limit  \\(f_s\\), switching loss is reduced.
- ## LC filter gets bigger

- ## Use Synchronous Buck (Can achieve higher \\(f_s\\) for same efficiency)
- ## Cost of the converter is increased

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# Step-Up (Boost) Converter
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<img src="./images/ee463/boost_converter.png" alt="Drawing" style="width: 700px;"/>
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# Step-Up (Boost) Converter

## Can you plot the on & off states?
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<img src="./images/ee463/boost_on_off.png" alt="Drawing" style="width: 800px;"/>
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### Mechanical Analogy: Ram Pump

### [How the ram pump works?](https://www.youtube.com/watch?v=i31hGJ93OTg), [How to make a ram pump](https://www.youtube.com/watch?v=0S2u_tdZkHs), [Largest ram pump](https://www.youtube.com/watch?v=pORYUjKoSuA)
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# Step-Up (Boost) Converter
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## Can you plot the voltage & current waveforms?
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## Can you find the relation between \\(V_o\\)  and \\(V_d\\)?
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## [Plexim Simulation](https://www.plexim.com/academy/power-electronics/boost-conv)
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# Step-Up (Boost) Converter
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# Step-Up (Boost) Converter
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## \\(V\_d t\_{on} + (V\_d-V\_o)t\_{off}=0\\)
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## \\( \dfrac{V\_o}{V\_d} = \dfrac{T\_s}{t\_{off}} = \dfrac{1}{1-D} \\)
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## \\( \dfrac{I\_o}{I\_d} = (1-D) \\)

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# Transition to DCM
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<img src="./images/ee463/boost_boundary.png" alt="Drawing" style="width: 650px;"/>
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# Transition to DCM
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# DCM
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### Occurs at light loads

<img src="./images/ee463/boost_dcm.png" alt="Drawing" style="width: 650px;"/>
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# DCM
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### In order to keep Vo constant

<img src="./images/ee463/boost_dcm2.png" alt="Drawing" style="width: 600px;"/>
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# Ideal vs. Reality
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## What is Vo as D goes to 1?
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## Output Ripple
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### Can you derive the operating modes?
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<img src="./images/ee463/boost_ripple.png" alt="Drawing" style="width: 600px;"/>
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## Can you obtain the operating modes of this converter?
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# Buck-Boost Converter

## [Plexim Simulation](https://www.plexim.com/academy/power-electronics/buckboost-conv) 
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# Buck-Boost Converter
## Operating Modes
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### Switch is ON (Inductor Charges)
<img src="https://www.allaboutcircuits.com/uploads/articles/4B-Converter-in-Equilibrium-2_(4).png" alt="Drawing" style="width: 750px;"/>

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# Buck-Boost Converter
## Operating Modes
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### Switch is OFF (Inductor Discharges)

<img src="https://www.allaboutcircuits.com/uploads/articles/4B-Converter-in-Equilibrium-2_(5).png" alt="Drawing" style="width: 750px;"/>
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# Buck-Boost Converter

## Output Voltage
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#\\(V_o = \dfrac{D}{(1-D)} V_d\\)

### Notice the reverse polarity of Vo in the circuit

### [Practical Design Exercise](http://www.ti.com/power-management/non-isolated-dc-dc-switching-regulator/overview.html)

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## Non-Inverting Buck-Boost Converter
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## Uses two synchronized switches
## Both switches turn on and off simultaneously

### [Design tips for an efficient non-inverting buck-boost convertee](http://www.ti.com/lit/an/slyt584/slyt584.pdf)
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## Non-Inverting Buck-Boost Converter

## It is also possible to use as a buck converter

## Q2 always off, Q1 is controlled

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## Non-Inverting Buck-Boost Converter

## It is also possible to use as a boost converter

## Q1 always on, Q2 is controlled

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## Generalized Version: 4-switch buck-boost

<img src="./images/ee463/4_switch.png" alt="Drawing" style="width: 800px;"/>
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- ### Buck Mode: Q1, Q2 are controlled, Q3 is OFF, Q4 is ON
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- ### Boost Mode: Q3,Q4 are controlled, Q1 is ON, Q2 is OFF
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- ### Buck-Boost Mode: Q1 & Q3 are simultaneously ON, when Q2 & Q4 are simultaneously OFF, and vice versa.

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## Can you [compare](https://www.eetimes.com/document.asp?doc_id=1273276&page_number=1) the input/output noise level?

<img src="./images/ee463/input_output_noise.png" alt="Drawing" style="width: 600px;"/>
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## Ways to Reduce Noise

- #### [Achieving low noise and low EMI performance with DC/DC switching regulators](https://training.ti.com/understanding-measuring-and-reducing-output-noise-dcdc-switching-regulators)
- #### [Reducing noise on the output of a switching regulator](https://www.ti.com/lit/an/slyt740/slyt740.pdf)

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<img src="http://legendsrevealed.com/entertainment/wp-content/uploads/2015/10/future-continued.jpg" alt="Drawing" style="width: 350px;"/>

## EE464

- ## Flyback Converter
- ## Ćuk Converter
- ## SEPIC Converter
- ## Resonant Converters

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## You can download this presentation from: [keysan.me/ee463](http://keysan.me/ee463)