Embedded Conference (Saturday May 21, Bangalore)

By

Ramesh KankanalaMicrochip Technology Inc.

Optimization of Power Converters Efficiency

Using Digital Technology

2

Agenda

What is power efficiency?

Factors affecting efficiency

Why is efficiency imperative?

Ways to digitally improve efficiency of power

converters

Digital Power Management

Processor Power Saving Options

3

Efficiency in power converters

The classical definition of efficiency is the ratio of power utilized by the load to the power consumed from the source, usually expressed as a percentage

In case of multiple power stages, the cumulative efficiency is the product of individual stage efficiencies

Efficiency consideration from power-converter perspective: Power requirement from the source Nature of power conversion Effect on upstream systems Overall power management

What is power efficiency?

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Component selection Internal resistance of active and passive components Active component Switching losses

Topology of power converter Switching frequency Number of stages in the power converter

Line harmonics – voltage and current Higher rated components Higher rated harmonic filters

Filter design Larger inductors and capacitors

Controller selection Operating clock frequency Device currents

Factors Affecting Efficiency

Why is Efficiency Imperative?

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Why is efficiency imperative?

Cost

BatteryLife

Density

Cost

BatteryLife

Density

Cost

BatteryLife

Density

Cost

BatteryLife

Density

Cost

BatteryLife

Density

Cost

BatteryLife

Density

Noise

BatteryLife

Loss

Regulations

GreenEnvironment

Heat

Cost

Harmonics

Density

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Why is efficiency imperative?

Lower Losses Will Lead to Lower heat dissipation lesser cooling requirements, like fans, heat sinks etc. Lower acoustic noise due to lesser cooling

requirements longer battery life in battery-operated systems

Higher Power Density Reduction in the cost of the system Lesser space requirements

Meeting Standards and Regulatory Needs Reduction in cost Greener environment due to lesser harmonics

Contribution to Greener Environment

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Heat and Power Loss LossHeat

Loss in switching elements Switching loss in MOSFETs Conduction loss in MOSFETs Diode/Rectifier losses

Loss in passive components DCR in inductors ESR in capacitors

Driver losses Loss due to poor PF

Operation at higher RMS and peak current More reactive energy returned to grid

Transmission and distribution losses

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Higher Power Density

Higher level of integration

Digital filters for noise reduction

RC time constant using S/W blanking

S/W dead-time configurations

Power control and communication

S/W protections / Fault handling

S/W-based output sequencing

On-chip clock, analog comparators and amplifiers

S/W-based feedback compensation

Density

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Battery Life

Low Power is required for battery-operated applications, such as Portable and Handheld devices

Hand Drill Electric Shaver Mobile Phones Toys

Handheld Medical Applications Glucometer Pulse Oximeter

Battery life directly depends on Device ON/OFF state power losses Power consumed by RTCC Power for operating internal/external clock Power for running Watchdog and Timers Power for driving the display Power for non-volatile memory operation

BatteryLife

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Going Green

Harmonics Reduction Single or Multiphase PFC

Improved Total Harmonic Distortion (THD) Line noise cancellation by operating PWM out of phase

Ripple Reduction Multiphase Buck

Output ripple cancellation by operating PWM out of phase

Switching noise reduction Soft Switching EMI Reduction

HarmonicsNoise

GoingGreen!

Ways to Improve Efficiency in Power Converters

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Interleaving Power Stages - PFC

PWM1

PWM2

IL1

IL2

90

-26

5V A

C

PWM1Is1

PWM2

IL2

Is2

ID2P

FC

ou

tpu

t

IC

IIN IL1 ID1 ILoad

When duty cycle is = 50%

(IL1 + IL2)t

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Interleaving Power Stages - Buck Converter

12V Input

3.3VOutput

GND

Q1Q2

Q3Q4

Q5Q6

120° 120° 120°

Q1

Q3

Q5

Drive Signals are Phase

Shifted by 120°

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Load Balance

Without Load Balancing Component and wiring differences cause some modules to

work harder than others The heavily loaded modules get hotter and reliability drops

causing failures – domino effect

With Load Balancing Share the load equally between the converters Reliability improvement by ensuring equal stresses

Buck Phase 1

LoadLoad Equalization

Routine

Buck Phase 2

Buck Phase 3

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Phase Shedding

Power management : phase shedding with adaptive control Reduction in switching losses Reduction in reverse-recovery losses Reduction in inductor core losses Improves light-load efficiency

Phase angle control Reduction in the ripple

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Phase Angle Control

In multiphase PFC converters Phase shedding at light loads should be

accompanied by Adaptive phase adjustment, depending on number

of phases being shed EMI filter size will be minimized

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Absence of switching losses for the power switches

Operation at higher frequencies

Smaller magnetic components and filter components

Low levels of EMI/EMC emissions

Smaller heat sinks, reduction in size and weight

Higher overall efficiency at a given power

Resonant Conversion

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Motor Control Applications

Efficiency Improvement in Motor Control: Center-Aligned Mode of PWM

Reduces EMI problems Activation of PWM outputs such that centers of active

periods are aligned Sensorless Control

Eliminates mechanical feedback sensors Velocity and position information derived from motor

currents Single-Shunt Current Sensing

Eliminates up to two shunt resistors Derives current information from precise PWM

switching

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Digital HID Ballast

Improve performance, such as lamp life, color property and lumen maintenance Centralized control, advanced algorithm, precise power

control Improve precision and dynamic from startup

centralized real-time control loop algorithm High efficiency

High frequency, variable frequency, quasi resonant Flexibility

Topology, protection Insure IP protection Reduce aging and temperature drift caused by

components

Digital Power Management

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SMPS Digital Power Conversion

Digital Power

Power control: Controlling the power flow in the converter by digitally adjusting the duty cycle, period, dead time, etc.

Power management: Communicating with external peripherals, fault detection, monitoring, data logging, etc.

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Advantages of Digital Power Management

• Design reusability

• Modular in design

• Redundancy

• On-site parameter changes

• Easy maintenance

• Better thermal management

• Reliability

• Ease in component selection

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Power-Supply Sequencing

3.3v

5.0vV

T

simultaneous

3.3v

5.0vV

T

sequential

3.3v

5.0vV

T

ratio metric

3.3v

5.0vV

T

offset

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Dynamic Control of Gains

Change of compensator parameters based on Line voltage variations Load changes

Optimal dynamic performance in the entire operating region No hardware change Reduces passive-component size Improved step/transient response

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Vo

DC

Sync gate

driveGate drive

Half BridgeHalf wave

RectificationActive clamp

converter

Highest level of Integration

Full

Bridge

Sync

Rectification

Push

Pull

I Vout

Full Wave

Rectification

Aux. PSU

Vin

DC

Sync Rect.

current

doubler

Over

temperatureRemote

ON/OFF

Ext

Sync

(DSC) dsPIC33FJ16GS502Analog controller

Load

share

External

communication

PulsatingAC

PSFB

Load share

Load share IC

Microcontroller

External data communication

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No-Load Efficiency Improvement Techniques

Fan-speed control based on temperature rise, to optimize fan power consumption

Shutting down of fans in the case of multiple-fan cooling arrangement

Burst-mode PWM generation to reduce switching loss under light loads

Dropping individual converters in the multiple-converter systems, at light loads

Switching-frequency reduction at light loads

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Non-linear control techniques

Adjustable dead time to improve efficiency

Dead-time insertion in PWM to avoid cross conduction between the upper and lower MOSFETs

Adaptive control of dead time to minimize the freewheeling diode conduction period

Industry claims about 1 to 5% gain in the efficiency, because of adaptive dead-time control

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Processor Power Saving Options

Processor power consumption affects the overall efficiency

Various Power-Saving Options:SLEEP MODE

Ultimate in power reduction, everything disabled Both the processor clock and the peripheral clock will

be completely disabled IDLE MODE

Processor clock will be disabled Peripheral clock can be kept active, optionally

DOZE MODE Best of both worlds Processor clock can be operated at a fraction of the

frequency of the peripheral clock

Thank You