Introduction to SMPS T.K.Santhosh Contents

• Introduction to Power Supplies and DC/DC Converters • Types & Technologies of Power Supplies and DC/DC Converters • Circuit Selection and Design • Circuit Performance and Protection Features • Thermal Requirements and Design Issues

KIOT - SMPS 2 I just had a look around!!

A closer look!!

KIOT - SMPS 3 What else..

A closer look!! A miniature vacuum cleaner!!

KIOT - SMPS 4 Digging out

My mobile had a charger Got a older mobile..

KIOT - SMPS 5 The list got bigger..

A power bank Closer look..

Another charger

KIOT - SMPS 6 Continued..

Solar charge controller A network router Adapter

KIOT - SMPS 7 Got curious!

Broke it I found a old trimmer charger

An SMPS.. Closer look

KIOT - SMPS 8 An old torch light

Broke it Closer look An SMPS..

KIOT - SMPS 9 It doesn’t stop there..

There is a charger I also had a failed one.. Broke it

An SMPS again!!

KIOT - SMPS 10 Other Applications-

By The original uploader was Smial at German Wikipedia - https://commons.wikimedia.org/w/index.php?curid=2958312

KIOT - SMPS 11 Other Applications- PLC Power Supply

Last year UG project

KIOT - SMPS 12 Looks like SMPS is everywhere!

So, What’s an SMPS?? SMPS Definition

• Switched Mode Power Supply • Owes its name to the dc-to-dc switching converter for conversion from unregulated input voltage to regulated output voltage. • Deals with conversion and control of • Power supplies are circuits that generate a fixed or controllable magnitude dc voltage from the available form of input voltage. • A single switch-mode power supply’s performance or its failure can affect the fate of a large, costly system.

KIOT - SMPS 14 Introduction to Power Supplies and DC/DC Converters

• Available/Raw Power Sources • AC or DC (frequency) • Un-regulated (changes with load, prime source, etc.) • Voltage (different level, polarity, isolation) • Non-protected (against over load, fault, temp., etc.) • Load Demand • Different AC or DC (frequency) • Regulated (against load, prime source, etc.) • Voltage (different level, polarity, isolation) • Protected (against over load, fault, temp., etc.)

KIOT - SMPS 15 Introduction to Power Supplies and DC/DC Converters –cont.

Desired power out Raw power in (V, I, P, F) Power & Electronic Circuits To loads: Battery Electronic ckts Fuel Cell Motor AC Outlet Computer Solar Equipment Power Supply

Control

KIOT - SMPS 16 Power Supplies and dc/dc Converters –Types & Technologies

• AC-DC Power Supply (or AC Adapter) • Change ac power into regulated dc power, e.g., a typical AC Adapter takes 230V ac input and converter it to regulated 5 Vdc. • DC/DC Converters • Change dc at one voltage potential to a dc at a different voltage potential • DC-AC Power Supply (for example, UPS, 12Vdc-120Vac adapter) • AC-AC Power Supply/Regulator (for example, line regulator)

KIOT - SMPS 17 AC-DC Power Supplies -Circuit Selection and Design • Using Linear Regulators • Using LDO Regulator http://www.national.com/pf/LM/LM78M05.html

120 V Step-down Regulator AC Xfmer

• For low power (several watts or below) applications. • Low efficiency, large size and weight (bulky step-down line ) • Low cost

KIOT - SMPS 18 AC-DC Power Supplies -Circuit Selection and Design • Using Switching-Mode • High efficiency • Small size and light weight • For high power (density) applications

TI Power Supply Technologies Poster

http://www.electronicproducts.com/ http://www.linear.com/index.jsp

http://www.linear.com/3770

KIOT - SMPS 19 Selecting the Right dc/dc Converter

• The Need for dc/dc Converters • E.g., a single AA alkaline battery produces 1.5 V when fully charged and its voltage drops to as low as 0.9 V when becoming depleted. • DC/DC Converter Types • Buck • Boost • Buck-Boost • DC/DC Converter Technologies • Linear Regulators • Switching Regulators The MCP1703 LDO is one type of dc/dc linear regulator • Charge Pumps

KIOT - SMPS 20 Selecting the Right dc/dc Converter –cont.

Dc/dc converter technology comparison Linear Switching Parameter Charge pump regulator regulator Efficiency Low High Medium

EMI Noise Low High Medium

Output current Low to medium Low to High Low

Boost (step-up) No Yes Yes

Buck (step-down) Yes Yes Yes

Solution size small Large Medium

KIOT - SMPS 21 Selecting the Right dc/dc Converter –cont.

VBAT = 3.7 V nom, BIN_BB = 1.2 V Load Current = 600 mA Linear regulators: Power delivered to load = 600 mA * 1.2 V = 720 mW •Inexpensive Power converted to heat = 720 mW * ((3.7/1.2) 1) = 1,500 mW •small footprint Total power consumed = •low part count 720 mW + 1,500 mW = 2,200 mW •low noise

32% goes to work, 68% goes to heating user hand and •high rejection ear when using a Linear Regulator for a mobile device

VBAT = 3.7 V nom; BIN_BB = 1.2 V Load Current = 600 mA Switching regulators: Converter efficiency = 90% •a bigger footprint Power delivered to load = 600 mA * 1.2 V = 720 mW •higher part count, Power converted to heat =720 mW * ((1/0.9) 1)=80 mW Total power consumed = 720 mW + 80 mW = 800 mW •more cost •prone to conducted 90% goes to work, 10% goes to heating user hand and ear and radiated EMI. When using a Switch-mode regulator for a mobile device. 22 KIOT - SMPS Specs, Performance and Protection

• Voltage ripple (+-50 mV, or 5%) • Isolation (e.g., 1,500 V ac for 1 min.) • Load regulation (e.g., 3%) • Dynamic response (transients, wake-up time, etc.) • Short circuit protection • OC protection • OV protection • OT protection

KIOT - SMPS 23 Power Losses and Thermal Design • For example, a 7815 linear regulator with input voltage of 20 V and output current of 1 A. The power loss is (20-15)Vx(1 A)=5 W.

• From the chip to the ambient, DTi can be calculated according to the thermal circuit using Ohm’s law (R=V/I), where R is the thermal resistance, V is the temperature and I is the power dissipation. Where: TT Tcase is case Temp. case ambient T is ambient Temp. RThcase ambient  ambient P is power loss Pdissipation dissipation Pin is input power Pout Pout is output power PPPPdissipation in  out   out op is efficiency under op given operating conditions

KIOT - SMPS 24 Example • Device : 7815 (Linear regulator)

• Vin=20V, Vo=15V, Io=1A

• W : (20-15)×1=5 watts

•Rth(j-c) : 5 °C/W

•Rth(c-f) : 0.5 °C/W, Greased surface An assortment of 78XX series

•Rth(f-a) :20 °C/W

° •Ta=25 C Tc=5×(0.5 + 20)+25=127.5 °C Tj=5×1+127.5=132.5 °C DTj=82.5-25=107.5°C An assortment of heat sinks

KIOT - SMPS 25 Let’s begin.. KIOT - SMPS 27