NPSS Distinguished Lecturers
Program
Solid-state pulsed power on the move!
Luis M. S. Redondo
lmredondo@deea.isel.ipl.pt
Lisbon Engineering Superior Institute (ISEL)
Nuclear & Physics Center from Lisbon University (CFNUL)
EnergyPulse Systems, Lda (EPS)
Lisbon, Portugal
Outline
o Pulsed-Power
o what is it & some facts
o Industrial applications
o Pulse generation
o Concept - energy storage
o Switching - semiconductors
o Opening switch, inductive storage: SOS diodes
o Closing switch, capacitive storage: Thyristors,
MOSFETs, IGBTs, JFETs, …
o
o
o
o
Topologies/techniques for pulse generation
Protection, Triggering, thermal considerations
How to deal with semiconductor limitations
Future trends SiC …
o Example
o Summary
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Pulsed Power?
The science and technology of accumulating electrical energy over a
relatively long period of time, followed by its released in a single short pulse
or a repetitive sequence, thus increasing the instantaneous peak power,
enhancing the properties of a product or a technique.
High peak power
Low average power
Pulsed not ac or dc
Enhance bio & physic-chemical effects
What makes it so unique? The concept that extremely high peak powers
can be delivered during precise times without the demand for highly
average power sources, used in custom dc or ac power systems.
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Facts about Pulsed Power!
The German Erwin Otto Marx invented in 1923 the cascaded generator that
allows the generation of transient high voltages, known as the Marx generator.
1.2/50 Impulse voltage
TU Dresden, Germany
• Until ‘70s the research in Pulsed Power was confined to National Laboratories in the
US and USSR, and a few industries, but the results were generally secret. The research
was restricted to military and high energy physic applications.
• The first biennial Pulsed Power Conference was organized in Lubbock, Texas, in
1976, and the IEEE Transactions on Plasma Science becomes the official R&D journal
for Pulsed Power.
• With the end of the could war in 1989 the Pulsed Power community starts searching
for industrial pulsed power applications.
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Driving forces for R&D in Pulsed Power
Transfer from high energy single pulses to lower energies, repetitive
pulses, efficient and reliable systems
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→ Industrial applications
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Industrial applications in Pulsed Power
Where moderate
pulse energies,
repetitive pulses,
efficient,
portable,
reliable and
cost effective
modulators are
needed.
Loads:
R, liquids
RC, gases, plasmas
RL, inductor, transformer
In average: up to kHz, µs
to ms, kA, 10’s kV.
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Biological effects:
- food processing (extraction & sterilization)
- plasma sterilization
- medical treatment (e.g. cancer)
- crop growth
Streamer discharges in gases:
- exhaust gas treatment
- ozone generation
Discharges in liquid or liquid-mixture:
- water treatment
- engine ignition
Material processing:
- implantation & deposition (surface change)
- magnetic forming, welding & cutting
- nano particles synthesizing
- concrete recycling
- laser (material ablation & surface annealing)
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Pulse generation
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Pulse generation – concept
Fixed or
mobile
source of
electrical
power
Primary
Energy
Source
Energy
Storage
Switching
(Shaping)
Load
Pulse
technique
High/low
conductivity, RC
Inductive, L
Switching sets the performance
of the modulator & for Industrial
Applications
Solid-state switches:
Shamiloglu, E., Barker, R.J., Gundersen, M., and Neuber, A.A.
PROCEEDINGS OF THE IEEE, VOL. 92, NO. 7, JULY 2004
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- medium peak power
- high-repetition rate
- compactness
- long lifetime
- efficiency
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Pulse generation – storage vs switching
Capacitive storage
Closing switch
Capacitive vs inductive energy
density
Inductive storage
Opening switch
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Switching Technology
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Solid-state switches for industrial applications
SCR, silicon-controlled rectifier
GTO, gate turn-off thyristor
IGCT, integrated gate-commutated
thyristor
MOSFET, metal-oxide semiconductor
field-effect transistor
IGBT, insulated gate bipolar
transistor,
IEGT, injection-enhanced gate
transistor
JFET, Junction Field Effect Transistor
Families:
- HV PIN diode and SOS diodes
- Thyristors and turn off Thyristors devices: SCR, GTO/GCT, IGCT, MCT
- Metal Oxide Semiconductor technology: MOSFET, IGBT, IEGT
- Power JFETs and derived devices, normally on: SIT, SITh (SiC technology)
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Opening switch - SOS Diodes
Semiconductor Opening Switches (SOS) are
modified high-voltage diodes, PIN, using a
P+PN-N+ structure with gradual doped P layer.
They are optimized to exhibit relatively slow
reverse recovery (≈ 50-100ns) but abrupt
recovery (very fast reverse decay) ≈ 5ns.
Inductive energy storage
Switch kA in ns opening times, with
uniform distribution of reverse voltage
(kV) in series stacked devices, with
average power of 10’s kW.
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Closing switch – on & off Thyristors
Turn-off IGCT
Turn-on SCR
Turn-off GTO
Incorporate
distributed gate drive
Basic Trigger circuit
Modern optically activated
LTT, Light triggered Thyristor
or
LASCR, Light Activated SCR
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Closing switch – MOSFET vs IGBT
IGBT (hybrid device)
PT-IGBT, extra P+ layer in collector
NPT-IGBT, substituting N+ by a P+ layer
MOSFET (unipolar device)
Fast trise & tfall
Limited hold-off voltage (1 kV)
due to on-resistance
P+ injects holes in N- layer reducing voltage
droop by conductivity modulation.
Similar trigger circuits,
low power for
charge/discharge
input capacitance
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Closing switches – SIT & SITh
Normally-on switches, can be turned-off by a negative voltage on the
gate electrode.
SIT
SITh
5.5kv/600A
Candidate for replacing multiple MOSFETs.
Ron similar to MOSFET!!!!
Used for pulse generation
as an opening switch in
inductive circuits, like SOS
diode. The SITh behaves
as a controlled diode.
High power capability (better than MOSFET) and relatively
fast switching performance (better than IGBT).
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Cascode
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Semiconductor stacks - Series
To overcome the power semiconductor’s limited hold-off voltage:
Guarantee synchronization
& voltage sharing:
- Static, R
- Dynamic, RC
Independently trigger
Higher
complexity
Commercial
Series switch
Cascode
topologies
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Semiconductor stacks - Parallel
To overcome the power semiconductor’s limited current ratings:
Guarantee current sharing
and synchronization:
Bipolar devices
Temperature coefficient:
- positive, MOSFETs, SITs
- negative, diodes, SCR, GTO, IGBTs
solution
- matched devices
- current sharing transformers or
coupled inductors
- current feedback control techniques
- small resistors in series
IGBTs
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MOSFETs
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Protection
TVS, Zener
Protections:
MOV, TVS
- Snubber circuis:
- L in series for decreasing di/dt;
- RC in parallel for lowering dv/dt;
- TVS/MOV/zeners in parallel for over-voltage
Zener, TVS
IGBT series
Transistor with RCD&L
SCR with RC&L
Static & dynamic
voltage sharing
&
dv/dt protection
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Protection
Hard switch-off
Protections:
- Fuses!!!
- vce monitoring for over-current
protection
Drive circuits with integrated
protections
Soft switch-off (limits over-voltage)
IR
Concept
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Technology future trends
Si solid-state is not dead ... long live SiC solid-state.
SiC is one of the wide band-gap
semiconductor materials (AsGa, C, GaN)
Switching:
Compactness, high-speed,
high-efficiency, …
But:
SiC still low power
as compared with
Si devices
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Thermal management
Switching losses
Heat sink
More power
More heat
Static thermal model
Needs dissipation
Natural convection
Forced air
Liquid cooled
Heat sink thermal resistance Rθ
+
(ºC/W)
The lower Rθ the better
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Pulse generation techniques
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Pulse generation – inductive storage
Voltage peak depends on load
impedance, better for capacitive loads
For opening devices, ns pulse generation:
Basic
circuit
For 10’s kV and
kA, dozens of
series and
parallel devices
Enhanced circuit
tp = L/R
Kotov, et al., IEEE Pulsed Power
Conf., pp.134 -139 1993
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IEEE Transactions Plasma Sci.,
Vol. 28, no. 1, Feb. 2000
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Pulse generation – direct capacitive discharge
Square pulses independent of load if store energy >> pulse energy (≈10x):
v
V
∆v 0
R LC dc
t
Ex: Vdc=20kV, 50 µs/1600Hz pulses into RL=1kΩ.
What is Cdc for ∆v= 5%?
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Pulse generation – associations
Use of series switches to increase
the hold-off voltage level.
Direct series stack
Adder circuit
v0=Vdc
Marx generators
Marx topologies for
positive and/or
negative pulses for
any load conditions
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v0=nVdc
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Pulse generation – using transformers
… for further increase the voltage output.
Transformer stacking
ringing!
Limitations:
- Average voltage zero condition imposes reset circuit;
- Parasitic elements ( distributed capacitance and leakage
inductance) deforms pulse shape;
- Load impedance must be matched;
- Low flexibility for changing pulse width and frequency.
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Pulse generation – Pulse Forming Line
Use of transmission lines for short pulse widths lower than 100 ns
Single line (pulse voltage ≈ Vdc/2)
50 Ω cables
5m →50ns
50 Ω matched load
Pulse Forming Networks,
PFNs
Line
Z0 =
impedance
L
C
Transit
l ε r Pulse width ≈ 2t
0
t0 =
time
c
Lumped parameters line, for pulse
widths >100 ns and different load
impedances
Blumlein (pulse voltage ≈ Vdc)
100 Ω matched load
+ stacked lines and line transformers (100 Ω multiples matched loads).
+ strip lines for compact systems and other load impedances, lower ones.
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Pulse generation - Bridge topologies
Half-bridge
Full-bridge
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Stack associations
nVdc
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Triggering issues
Trigger pulse generation:
- FPGA, PLC, Microprocessor, Microcontroller
& analog circuits (noise immunity mandatory)
Pulse signal sent to devices via:
- Pulse transformers (galvanic insulation and
power)
- RC dividers
- Optic fibers (galvanic insulation, low parasitic
capacitance, need auxiliary power)
Inverter + ring
transformers
Aux. Power from main circuit
ABB IGCT series switch assembly
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Example
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Solid-state pulsed power on the move!
10 kV / 150 A pulse
and 3.5 kW
Industrial applications,
Food processing
Marx type solid-state
mobile modulator (80 l)
1200 V
off-the-shelf
IGBTs
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Summary
o Pulsed Power is pushing R&D in several scientific areas: environment,
biomedical applications, food processing, industry;
o Semiconductor switches are contributing to bring pulsed power closer to
people: compact, portable & efficient devices;
o It is important to chose the right switch and pulse technique for the
application, but more general modulators are a key issue;
o New material can push forward the technology;
o Pulsed Power includes many scientific fields, from electric engineering to
physics, from the technology to the applications;
o Still it is not easy the acceptance of the technology in the industry, more
work and more people are needed;
o Other technologies for switching are available for industrial applications
that complement solid-state. For example magnetic switches, able to
handle higher power and still high repetition rates.
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