Download - Embedded Conference (Saturday May 21, Bangalore) By Ramesh Kankanala Microchip Technology Inc
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Embedded Conference (Saturday May 21, Bangalore)
By
Ramesh KankanalaMicrochip Technology Inc.
Optimization of Power Converters Efficiency
Using Digital Technology
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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
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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
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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!
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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
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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
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Thank You