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Digital Control of Power Supply Systems with Reduced Standby Losses DigiPowerSave

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Nottingham July 2008 Control of AC-DC, HF DC-DC and Automotive DC-DC Converters ... Dept of Electrical and Electronic Engineering, University College Cork, Ireland ... – PowerPoint PPT presentation

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Title: Digital Control of Power Supply Systems with Reduced Standby Losses DigiPowerSave


1
Digital Control of Power Supply Systems with
Reduced Standby Losses DigiPowerSave
  • Background
  • Motivation
  • Technology Developed
  • Commercialisation

2
Background
  • Regenerative electronic load for testing
    microprocessor Voltage Regulator Modules (VRM)
    developed under PRP/00/PEI/02b, High Current/Low
    Voltage Converters for Environmentally Friendly
    Energy
  • System demonstrated at IEEE APEC and Electronica.
  • Detailed negotiations with companies to license
    this technology.
  • Elements of this technology are now being
    commercialised demonstrate MOSFET/Drivers.

3
2005 MOSFET Demonstrator
  • Follow-on project due completed in November 2006.
  • Observation It appears easier to sell
    technology development than to license
    technology ?

4
Motivation for DigiPowerSave
  • Off-line, or mains-fed power supplies consist of
    two parts,
  • a front-end rectifier or ac/dc converter, to draw
    raw power from the mains
  • a second precision dc/dc converter to feed the
    low voltage electronic circuits.
  • Arising out of PRP/00/PEI/02b , we had developed
    digital techniques for front-end ac/dc
    converters.
  • From our experience in industrial motor drive
    technology, it was clear that digital control
    would also extend to the dc/dc power supply
    world.
  • Digital control can bring major advantages to
    both of these converter technologies.

5
Potential for Digital Control in Off-Line Power
Supplies
  • Input AC/DC Converter Stage
  • Standby power in off-line power supplies uses 30W
    in every home in Ireland.
  • Up to 35 million, or 5 of residential
    consumption, is wasted every year, resulting in
    quarter of a million tonnes of CO2 generated.
  • Digital control enables the use of non-linear
    topologies to optimise efficiency and minimise
    standby loss.
  • Network communications facilitates remote power
    supply control.
  • Output DC/DC Converter Stage
  • Accurate and precise PWM control.
  • Potential for optimised adaptive control
    algorithms.
  • Reduced sensor requirements.
  • Digital communications with front-end ac/dc
    converter can help in overall system efficiency.

6
Typical power supply unit
  • Objectives-
  • To address the growing environmental issue of
    stand-by energy loss and maximise efficiency.
  • To optimise the advantages of emerging digital
    control techniques to produce a tightly
    controlled dc output voltage.
  • Applications include power supplies for a wide
    range of electronic products.

7
Innovation in Digital AC/DC Converter Control
ATRP/01/314 DigiPowerSave
  • Use of novel topologies
  • Digital technology allows non-linear control
    strategies not possible using analogue schemes
  • Alternative sensing arrangements can be
    implemented
  • Extra magnetics can be eliminated, improving
    manufacturability
  • Special standby modes
  • Burst operation when power levels are low
  • Introduction of low- power standby function
  • Reduction of intermediate bus voltage during
    standby
  • This also increases reliability of electrolytic
    capacitors
  • Hold-up capacities can be folded back

8
Topology Implementation
ATRP/01/314 DigiPowerSave
  • Two prototypes power supplies were developed
  • A 65W two-switch flyback
  • No power factor correction is required below 70W
  • Typical power level for dvd players and set-top
    boxes
  • Supply controlled by DSP on secondary
  • Secondary post regulation was used for standby
    operation
  • A 200W novel topology
  • 12V output to be cascaded with high spec dc-dc
  • Typical configuration for computer supplies
  • DSP on the primary, microcontroller on the
    secondary
  • Intermediate bus voltage reduced for standby
    operation

9
65W Two-Switch Flyback
ATRP/01/314 DigiPowerSave
  • Secondary Side DSP control
  • Low power TopSwitchtm-fed winding on the same
    transformer for start-up
  • Output filter inductor is used as a buck when in
    standby mode

10
Efficiency in Normal Mode
ATRP/01/314 DigiPowerSave
11
Efficiency in Standby Mode
ATRP/01/314 DigiPowerSave
12
Power Flow in an Off-Line PSU
ATRP/01/314 DigiPowerSave
Required Output Power
Mains Input Power
Power stored in the bus caps
Power from bus caps
Power from bus caps
Power goes directly to the output
13
Novel 200W Topology
14
Topology Characteristics
  • Benefits
  • Only a single magnetic is required
  • 70 of the power requires only one conversion
  • No inrush current, no NTC thermister required
  • Intermediate bus voltage can be reduced
  • Drawbacks
  • 2 high-side gate drives required
  • Fast recovery rectifier diodes required
  • Primary leakage results in re-circulating energy
  • Discontinuous currents

15
200W Prototype
ATRP/01/314 DigiPowerSave
  • Only one custom magnetic component
  • Efficiency 83 to 87

16
Future possibilities
ATRP/01/314 DigiPowerSave
  • The digital strategies and technology developed
    in this project could also be applied to
  • Power supplies with integral UPS features
  • Integration of small scale generation with a
    household supply
  • Solar panels
  • Small wind turbines
  • Micro CHP
  • Integration of power supplies with building
    management systems

17
Digital control in dc-dc conversion
  • Divides into two separate applications
  • Digital control loop (high-frequency)
  • System monitoring/interfacing (low-frequency)
  • Project focus on digital control loop
  • Development of hardware modules
  • High-frequency, high-resolution pulse generation
  • Generation of multiple matched and phase-delayed
    signals requiring area-efficient implementation
  • FPGA-based architectures with frequency
    calibration capability
  • Algorithm development
  • Observer-based control

Power Electronics Research Laboratories, Dept of
Electrical and Electronic Engineering, University
College Cork, Ireland
18
Typical dc-dc buck converter architecture
Project development
Power Electronics Research Laboratories, Dept of
Electrical and Electronic Engineering, University
College Cork, Ireland
19
High resolution pulse generation
  • Delay line approach
  • Minimises required clock frequencies
  • Uses logic gates as delay elements
  • Difference in time delay between paths allows
    very high resolution pulses to be generated.

Power Electronics Research Laboratories, Dept of
Electrical and Electronic Engineering, University
College Cork, Ireland
20
High resolution pulse generation
  • UCC approach uses 3 delay granularities
  • Minimises required implementation area
  • Achieves very high resolution ( 255 ps)

Power Electronics Research Laboratories, Dept of
Electrical and Electronic Engineering, University
College Cork, Ireland
21
High resolution pulse generation
  • Architecture expanded to generate multiple
    outputs
  • Phased nature of outputs used to reduce
    implementation area compared to non- optimised
    architecture

Power Electronics Research Laboratories, Dept of
Electrical and Electronic Engineering, University
College Cork, Ireland
22
Commercialisation I
ATRP/01/314 DigiPowerSave
  • Two digitally controlled PSUs have been
    developed
  • A 65W supply for set-top box applications
  • A 200W single magnetic unit with integrated power
    factor correction.
  • Intellectual property
  • Novel single magnetic topology
  • Application of state space methods to PSU control
  • Potential for commercialisation
  • Discussions with large IC company regarding PSU
    digital control.
  • Support for Irish power supply companies wishing
    to incorporate digital control into their
    products
  • Licensing of novel topology to be further
    explored.

23
Commercialisation II
ATRP/01/314 DigiPowerSave
  • June, 2005, 'A digital PWM controller for
    multi-phase dc/dc converters' (DigiPowerSave).
    This patent was allowed to lapse as it was not
    licensed.
  • Discussions with large IC companies regarding the
    use of high resolution PWM generation

24
The comparative non-isolated bi-directional dc-dc
converter analysis
  • Marek Rylko

25
Aim of the work
  • Comparative half-bridge bi-directional high-power
    dc-dc converter analysis
  • Switching regimes (soft and hard switching)
  • Switching devices (MOSFET, IGBT, diode)
  • Materials (silicon, SiC, GaN)
  • Operating frequency limits
  • Volume and cost analyses
  • Magnetic design
  • An inductor
  • An transformer

26
Introduction
  • The hi-power dc-dc converter application
  • Automotive (power train)
  • Battery chargers
  • Fuel Cell stationary generators
  • Wind turbines (potentially)
  • Electric crafts

Regenerative Load
DC-DC Converter
Battery SuperCap
27
The Power Requirement
  • Power requirement depends on design i.e.
  • The automotive application for mid-size C class
    car 100kW peak for 30sec and 50kW continuous
    power competitive performance to present ICE
    cars
  • The battery charger - maximum charging current
    and voltage (charging regimes)
  • Consideration of the work-cycle is important to
    avoid an overestimated design

28
The Power Supply
  • The internal combustion engine with generator
    (gasoline, diesel, CNG, LPG, hydrogen, methanol)
  • Pollution (NOx, CO and CO2)
  • Crude Oil shortage
  • The fuel cell
  • Zero emission (excluding hydrogen production)
  • Refuelling problem, low social acceptance
  • Short Cycle Lifetime
  • The battery
  • Well established technology, clean but expensive
    and requires complex production process, contains
    toxic components, recycling problem
  • The solar panel
  • Low power density, solar radiation dependent

29
The Car Power Train
  • Classical solutions with IEC
  • Hybrid propulsion systems (IEC and electric
    motor)
  • Series Hybrid
  • Parallel Hybrid
  • Series-Parallel
  • Complex Hybrid
  • The battery electric vehicle
  • The fuel cell electric vehicle

30
The Hybrid Car Classification
31
The Fuell Cell
  • Fuell Cell types and properties
  • Types PEM, AFC, PAFC, MCFC, SOFC
  • fuel cell operates best at a 30 percent load
    factor due to issue of mass transport limitation
    (oxygen and hydrogen contact with membrane)
  • Ironically, the fuel cell does not eliminate the
    battery it promotes it.
  • The fuel cell needs batteries as a buffer.
  • Efficiency up to 65 at 30 of load (efficiency
    is output power reffered to LHV includes water
    vaporisation)
  • Complex auxiliary components system
  • Auxiliary system requires 10-15 of FC rated
    power
  • High cost

32
Batteries
  • The Battery - types and properties
  • Types Valve Regulated Lead Acid (VRLA), NiCd,
    NiZn, NiMH, Zn/Air, Al/Air, Na/S, Na/NiCl2,
    Li-Polymer, Li-ion,
  • High efficiency up to 99 (Li-ion polymer exclude
    converter)
  • Zero emission (energy generation not included)
  • Specific energy 330Wh/kg Li-ion superpolymer
    Electrovaya
  • Specific power 315W/kg at 80 discharge rate
    (Li-ion polymer)
  • Energy density 600Wh/liter Li-ion superpolymer
    Electrovaya
  • High cost (gt100/kWh Li-ion)
  • Short lifetime (800-1200 at 80 discharge rate
    Li-ion) or 3-7 years
  • Toxic component needs recycling policy
  • Battery terminal voltage varies with state of
    charge and discharge current (1.6-2.4V for
    VLRA, 3-4V for Li-ion)
  • Charging issues
  • Super Capacitor

33
The Load
  • 4-quadrant inverter with electric motor
  • Energy recovering
  • Energy conditioning for double-fed induction
    motor

34
The Converter
  • Isolated push and pull, full bridge
  • Non-isolated half-bridge buck-boost, cascade,
    buck, boost, CUK, Sepic/Luo, voltage multipliers
    (magnetic-less)
  • Hard switched (HS)
  • Soft switched (SS)
  • Simplicity
  • Bi- and uni-directional
  • Advantages and disadvantages

Non-isloated HS converter
Non-isolated SS converter
Isolated converter
35
Hard and Soft Switching
The Hard Switching
Switching losses limit the maximum operating
switching frequency and may result in significant
device derating.
The soft switching constrains the switching of
the power devices to time intervals when the
voltage across the device or the current through
it is nearly zero.
The Soft Switching
36
Semiconductor Devices
  • Materials
  • Silicon
  • Silicon Carbide (SiC)
  • Gallium(III) Nitride (GaN)
  • Devices
  • MOSFET (CoolMOS)
  • IGBT (Trench, Planar)
  • BJT
  • Thyristor

37
Magnetics
  • Inductor
  • High inductance dc inductor with small
    ac-component small current ripple
  • Low inductance dc inductor with high ac-component
    high current ripple
  • Transformer
  • Magnetising inductance issue
  • Power loss associated
  • Core (histeresis, eddy currents)
  • Windings (eddy currents skin and proximity
    effect)

38
Soft-Switching Converter
The converter has been made by adding an
auxiliary cell to the classical half-bridge
bi-directional converter.
39
Soft-Switching Converter
  • The presented soft-switched converter is
    quasi-resonant with an auxiliary commutation cell
  • Benefits of solution are
  • Use intrinsic MOSFET body diodes
  • High efficiency over a wide load range up to
    97.6
  • High operating frequency leading to size
    reduction
  • Very robust, topology ensuring safe operating
    region by hardware design
  • Works above audible frequency 100kHz
  • Disadvantages
  • More elements than classical solution
  • Auxiliary signals
  • Complicated design process

For V1/V2 0.5
40
The Duty Cycle Analysis
  • The converter is assumed to operate under fixed
    bus voltage conditions and the converter average
    output current gain is investigated
  • The pole-voltage wave shape is affected by the
    turn-on and turn-off mechanisms
  • The converter current gain can differ
    significantly from the idealised HS case

Pole voltage
HS ideal
SS cell
41
The Duty Cycle Numerical Verification
The HS and the SS case differs due to SS Vs
loss Gray points represents PSpice simulation
results
42
Converters comparison
  • Three converters have been built and tested
  • Soft-switched MOSFET based low ripple
  • Hard-switched MOSFET based high ripple

43
Converters comparison
  • Hard-switched IGBT based low ripple

Table I. Converters comparison
44
Converters comparison
  • Switching Devices
  • MOSFET - Infineon type SPW47N60 (CoolMOS)
  • IGBT - International Rectifier type IRGP50B60
    (WARP2)
  • Auxiliary MOSFET - Infineon type SPP12N50C3
    (CoolMOS)
  • Inductors
  • Low-ripple inductor made of solid wire
  • ø1.5mm, 19 turns, 200?H, core EE65,
  • material 3F3, total airgap 1.44mm
  • High-ripple inductor made of Litz wire
  • 25xø0.315mm, 7 turns, 28?H, core
  • EE65, material 3F3,
  • total airgap 2.38mm

45
Converters comparison - results
46
The Test Rig
Inductor
Main pole
The Soft-switching cell
Control board
47
The Soft-Switching Cell
48
The Main Pole
49
The Control Board
Based TMS320F2808
50
Conclusions
  • Bi-directional converters have been investigated
    only
  • The three converters, which have been presented,
    achieve high efficiency of order 96-97 over a
    wide load range
  • Low-ripple HS MOSFET on test shows efficiency of
    order 88 due to the poor intrinsic diode
  • The IGBT transistor with the soft-switching cell
    did not demonstrate any significant efficiency
    improvements
  • The HS-converters with the IGBT transistors are
    preferred at frequencies up to 150kHz due to
    lower cost and simplicity
  • Beyond 150kHz MOSFETs indicates superiority over
    IGBTs
  • High-ripple converter, despite great efficiency
    results, cause serious challenge for magnetic
    design due to significant current AC component

51
Continuing work
  • Converters comparison at higher frequency
    200kHz-500kHz
  • IGBT operation frequency limits under hard and
    soft switching regime
  • A uni-directional dc-dc converter comparison with
    different switching devices at 100kHz-500kHz
    (IGBTSi/SiC, MOSFETSi/SiC)
  • Inductor design for the converter at
    100kHz-200kHz and 100kW
  • Cost analysis
  • Interleaved converter

52
The End
  • Thank you for your attention.
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