power supply design ppt

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Introduction to Power supply topologiesBy Manish


AGENDA : Power supply design

Introduction

Basic requirements

Regulator Classification

Switching Topologies


INTRODUCTION

Power converter

Transfers energy One V * I format to another V * I format.

A circuitry monitors Vout deviations related to Vin, I-out, T° etc.

If Vout deviates from its target, an error is created and fed-back

to the power stage for action.

The action is a change in the control variable: duty-cycle (VM),

peak current (CM) or the switching frequency.


INTRODUCTION CONTD.

Applications Overview

Analog + High speed design : PLL ( Low noise, low voltage) Dc motors ( High current ) Television Display LED / LCD drivers ( Very high voltage) Digital (Low voltages , Higher power – Load regulation )


Characteristics

Basic Design requirement

Voltage input Voltage Output Current Output Line regulation Load regulation Thermal Stability Efficiency Output Ripple voltage limit Source reflected Noise : EMI /EMC


Classification

Shunt regulator Series regulator Linear dropout regulator (LDO) Non-Isolated Switching topology

-Buck regulator-Boost regulator-Buck-Boost regulator-Inverting regulator

Isolated Switching topology-Fly back regulator-Push pull regulator-Full bridge regulator


BUCK topology

BUCK topology


Non Isolated topologies

BUCK topology BOOST topology

Inverting topology BUCK - BOOST topology


Isolated Topologies

FLYBACK topology

PUSH-PULL topology

FULL BRIDGE topology


Switching regulator parameter

Switching frequency Dynamic response Noise

Power dissipation Static power dissipation Dynamic power dissipation

Galvanic Isolation


Case study of Buck topology


Modulator


Case study continued

Error amplifier

* Generates Loop-back control voltage * Loop back gain

* Also contribute to stability of Supply control loop.

Output LC filter Detailed in next section


Basic Design Equation

Filter Inductor equation:

VOUT (VIN(MAX) - VOUT)L = ======================

VIN(MAX) x f x IOUT x LIR

where: f = switching frequency IOUT = maximum DC load current LIR = ratio of AC to DC inductor current,typically 0.3.

The peak current can be calculated by: VOUT * (VIN(MAX) - VOUT)

IPEAK = ILOAD + ——————————— 2 x f x L x VIN(MAX)

Filter Capacitor equation:

VNOISE(p-p) = IRIPPLE x (RESR + 1 / (2 x pi x f x CF))

Current sense resistors: Rsense = Vsense / Ipeak.


Modern regulator feature

Modern regulator feature

- Logic Shut-down control

- Synchronization control

- Soft-start

- Power sequencing

- Accurate Digital voltage control / Monitoring through communication protocol like I2C

- Self voltage monitored outputs

- Thermal / Over current / Short circuit protection

- High power ( low voltage ,High current , High Effi > 95% )


Advantages- Greater efficiency - Other advantages include smaller size and lighter weight

lower heat generation due to higher efficiency.

Disadvantages- Greater complexity,- Switching Noises back to main power.

Advantage & disadvantages


Buck: used the reduce a DC voltage to a lower DC voltage. Boost: provides an output voltage that is higher than the

input. Buck-Boost (invert): an output voltage is generated

opposite in polarity to the input. Flyback: an output voltage that is less than or greater than

the input can be generated, as well as multiple outputs. Also, some multiple-transistor converter topologies will be

presented: Push-Pull: A two-transistor converter that is especially

efficient at low input voltages. Half-Bridge: A two-transistor converter used in many off-

line applications. Full-Bridge: A four-transistor converter (usually used in off-

line designs) that can generate the highest output power of all the types listed.

power supply design ppt

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