The 1st Symposium on SPC (S2PC) 17/10/2014

Recent Approaches to Develop
High Frequency Power Converters
Location

Fireworks

Much snow

TokyoNagaoka University of Technology, Japan
Prof. Jun-ichi ItohDr. Koji Orikawa (Presenter)
Power Electronics Lab.

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Power electronics laboratory☆Objectives
・Efficiency improvement & size reductionof all kinds of power sources.

AC to ACLaboratory
Laboratory

DC to ACPower Electronics Lab.

DC to DC

☆Research Subjects“Save the earth”
Four directions of energy conversion
AC to DC- Circuit topologies and controltechnique- Optimization of the circuit design- Development of directional
PowerPower Electronics
Electronics
technology on applications
Members
Associate Professor: Jun-ichi Itoh
PD: 1, Ph. D: 9, M：12, B: 5=> Total: 28 persons
Power Electronics saves the Earth2

Field of our research
Grid connected inverter
Power decouplingThree Ph. D students
Theme

Motor

Three Ph. D students-PV inverter, Micro inverter-Matrix converter for wind turbines-Multi-level converter-PFC(“Active buffer”)

etc.

- Motor drive(IM, PMSM)- Motor design(PM)- Parameter identification method- Flywheel energy storage system

etc.
High switching frequency
converter

Three Ph. D students
Today’s contents
Power Electronics Lab.

- PCB implementation techniques- Applications of SiC and GaN- DC-DC converter- Gate drive circuit- Wireless power transferetc.
- Pulse density modulation
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High switching frequency power conversion☆Key technology

High switching frequency

Fundamental technologies
DC bus bar analysis in printed circuit boards (PCBs)
High speed & Low power consumption gate drivers
Applications

Today’s contents

Wireless power transfer for gate drive supplies
of a medium-voltage inverter
High power density PWM Inverter with wide band-gap devicesFrequency multiplying circuit for MHz output frequency
Wireless charger for electric assisted bicycle using EDLCs
Wireless power transfer with a Rail system
Several-Hundred-kHz Single-phase to Commercial Frequency
Three-phase Matrix Converter
Power Electronics Lab.

4

Multiple gate drive supplies of a medium voltage inverter
Conventional： Special isolated transformers are usedProblems- High cost and bulky due to custom designs- Reduction of parasitic capacitances is difficult

Primary Secondary
Insulation air-gap：50 mm

Proposed method#1vout1

C1

Multiple wireless power transferwith transmission coils on PCBsfor multiple gate driver supplies

MV Inv.

vin1
S1

D1-4

S2C0S3S4vinv#2GDU

fsw = 2 MHz

Only PCBs are usedwithout solid magnetic cores····f = 2MHz#3#6GDU

Transmission Receiverboardboards(6ch)

Cost reduction & Downsizing of the isolation system
Power Electronics Lab.

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System configuration of wireless multiple power transfer
Transmission board #0
High frequency INV (2MHz)
Series resonance capacitor C0Transmission coil

Substrate spacing：50 mm
Clearance and creepage distanceare secured50mm

S1S2C0S3S4150mm48Vvinvfsw = 2 MHz

50mm

4Controller

300mm

Diode bridge rectifier
Series resonance capacitor C1
Receiver coil

50mm

Receiver boards #1~#6C1

vin1

60 mm
Power Electronics Lab.

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Experimental results (Operation with gate drivers)#1
Transmitting board#0
S1

DC G1-15V
PWM1

C0S3

S448V fsw = 2.18 MHz

#2

GDU 2

#3

GDU 3

G133nF

Gate drivers are connected
Capacitors are connectedassuming IGBTs········

C0=130 pF+15VDCC1

C1=70 pF D1-4

S2GDU 1vout1

Operation waveforms#6

GDU 6Enlarged view

G0Inverter output voltage(Transmitting board)
vinv 50 [V/div]
Input voltage(Receiving board #1)
vin1 25 [V/div]
Output voltage(Receiving board #1)
vout1 10 [V/div]
Gate-emitter voltage(Receiving board #1)
vGE1 20 [V/div]

00000000vGE1 50 [V/div]
200[nsec/div]

1kHz, ±15V

500 [us/div]

200 [ns/div]

A switching operation on all of receiver boards is confirmed
Power Electronics Lab.

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GaN-FET Inverter & EMC filter

M
GridGaN-FETGaN-FET Motor
EMC filter
PWMPWM
Advantage of GaN-FET
RectifierInverterFast switching
GaN-FET Inverter
Motor drive system using GaN-FETLDLCCX

GaN-FET inverter
Use a PWM rectifier
Sinusoidal input current

CYDownsizing

High frequency switching
Reduce the ripple current

Single stage EMC filter

Miniaturize the EMC filter by using high frequency carrier
Power Electronics Lab.

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Relationship between volume and carrier frequency

VolumeGrid

EMC filter

Cooling system
Carrier frequency

Volume of the system

RL loadLISN

EMCfilter

PWM
rectifierHeat sink

PWM
inverter

Stray capacitance

Conduction noise measurement system
Estimate the conduction noise

GaN-FET inverter system with high frequency carrierHigh frequency noise
Large switching loss
Smaller EMC filter
Larger cooling system
Each volume is calculated based on the simulation results
Relationship between the carrier frequency
and the total volume of GaN-FET inverter system is evaluatedPower Electronics Lab.

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Relationship between efficiency and power density
96

Three stages
Two stages

95 fcarrier=150kHz
Efficiency [%]High efficiency
High power density

High efficiency(fcarrier=150 kHz)Single stage
94
93

High power density(fcarrier=300 kHz)fcarrier=300kHz
fcarrier=450kHz

92
91
1

fcarrier=600kHz
2
3
Power density [kW/dm3]

High efficiency
High power density:fcarrier=150 kHz:fcarrier=300 kHz

4

EMC filter should be constructed by two stage filter
in order to achieve high power density and high efficiency
Power Electronics Lab.

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MHz band high-frequency power converter
Applications

Battery

Charger
ReceiverantennaTransmission antenna

Generation of plasma

Induction heating

Wireless power transfer

Wireless power transfer
Grid13.56MHz
HF powersource(Target)Transmissionantenna
Power Electronics Lab.

13.56MHz
RectifierDC
Battery

DC loadReceiverantenna

Requirements
for HF power source>High frequency>High efficiency>Downsizing
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Conventional method of high-frequency power converter
Ex) Class A, AB, C, etc…
Linear amplifier method
Vacuum tube, Power Transistor>Electromagnetic interference (EMI): Low>Efficiency: Low>Cooling system : Large sizenpnpnp

Switching amplification method
Power MOSFET>Efficiency: High>Cooling system : Downsizing
Employing wide band gap semiconductors: Silicon carbide(SiC), Gallium nitride(GaN)>Fast switching, low power loss
>Implementation of gate drive unit (GDU) : Complicated>Control gate-source voltage : Difficult
Power Electronics Lab.

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Concept of the proposed circuit and purpose of this study
ConceptHigh
Simple method
efficiency
Without wide band gap semiconductors,
only conventional Si devices are used
Low
>Conventional GDU can be usedswitching
SimpleHigh output frequency overfrequency
switching frequency
Frequency multiplying method is adoptedIu
VDC
2
VDCoVDC
2Power Electronics Lab.

Snuuv
Snvw
Snw

SpySpxSpwSpv

SpuVoutx
Snx

Vuo

Snyy13

Proposed circuit –Frequency multiplying method 1. Multiphase inverter with square wave drive using shifted gate signal
2. Multicore transformer is adopted
Sum of the inverter output voltage can achieve high output frequency
Iu
VDC
2
VDC

Vuo

DCo
VDC
2

Spy

Spx

Spw

Spv

Spu

VDC/2
U-phaseVuo
0voltage-V /2u

Snuv
Snvw
Snw

Voutx
Snx

SnyyTsw

72 deg.

VDC/2
V-phaseVvo
0voltage-VDC/272 deg.

VDC/2
W-phaseVwo
0voltage-VDC/272 deg.

VDC/2X-phase
Vxo
0voltage-VDC/272 deg.

VDC/2Y-phase
Vyo0voltage-VDC/2

1. Multi-phase inverter
2. Multi-core transformer
VDC/2Output
0Vout
Square wave drive
Primary : Parallel connection voltage-VDC/2
Secondary: Series connection

fout = N*fsw
Power Electronics Lab.

Ex.) fout = 2.5 MHz, N = 5Tsw/5

fout = 500 kHz
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Applying series resonance using resonance capacitanceMulti-phase inverter
SSppVuouu

VDC
2
VDCo
VDC
2SpySnnS
SSnnuuu
SunyLeakage Resonanceinductance capacitoruvwxy

Sinusoidalvoltage

Vvo
Vwo

Vout

Vxo
Vyo

A resonance capacitance is connected to the secondary side of multicore transformer
Leakage inductance is effectively used for sinusoidal output voltage
Power Electronics Lab.

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Experimental results (Series resonance, fout=2.5MHz)
rms value60(a)High output
5040 (b)Rload: 100 W
30
20
Rload: 33 W
10Rload: 50 W

Load voltage Vload [V]U phase voltage
Vuo(100V/div)0
U phase current
Iu0(2A/div)
Load voltage
Vload 0(100V/div)
Output current
Iout 0(1A/div)
400 (ns)

0100

200300400500600(a) Rload: 50W (Cr:100pF)

Resonance capacitance Cr [pF]

Load voltage and current
U phase voltage
V(100V/div)0Almost sinusoidal
U phase current
waveform
I0(2A/div)
Output voltage is changed by Output voltage
V0
resonance capacitance value(100V/div)
Output current
I0
Load resistance: Small(1A/div)
Quality factor for resonance: Large> Output voltage: Decreased
uou

out

out

Power Electronics Lab.

400 (ns)(b) Rload: 33W (Cr:100pF)
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Conclusion
Printed circuit board design
Power loss calculation(Semiconductors, passive components)

High frequency switching
Clarification ofdesign methods

Volume estimation(Passive components, heat sinks)

Applications

Combination

Wireless power transfer for gate drive supplies
of a medium-voltage inverter
High power density PWM inverter with wide band-gap devices
Frequency multiplying circuit for MHz output frequency
etc.
Power Electronics Lab.

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