U N I KASSEL
V E R S I T Ä T
Photovoltaic Converter Topologies Suitable for SiC-JFETs
Authors: Benjamin Sahan, Samuel V. Araújo, Thomas Kirstein, Lucas Menezes, Peter Zacharias
Evolution of power devices
Fig 1: Hg-Thyratron,
ca. 300V,20A,Höhe 1m
Bj. 1958; Quelle: EVS, Uni Kassel
Switching performance
In a first test the switching performance of the
JFET (1200V, 0.13Ohm) was compared to
a Trench IGBT using a switching cell.
The turn-off losses were only 30uJ which
was about 90% lower than the IGBT
at the same current and voltage.
Fig 2: SiC-JFET Chip
1200V,15A, Fläche: ca 6mm^2,
tr=20ns; Quelle: Infineon AG
8
400
Voltage
200
4
Current
0
Voltage [V]
SiC features
Silicon Carbide (SiC) is characterized by
electrical field strength almost 9 times
higher than Si, allowing the design of
semiconductor devices with high blocking
voltage,very thin drift layers and as a
consequence low on-state resistance and
reduced switching losses.
Curr ent [A]
Introduction
SiC semiconductors offer several interesting
characteristics and can be considered as a
future trend in photovoltaic converter
technology.
The vertical JFET is an example of a
very promising device, mainly due to its
relative structural simplicity.
Nevertheless, its inherent normally-on
characteristic calls for specially tailored
topologies that has been presented and
discussed in this publication.
Decorated with the
Best Paper Award
at the
0
0
200
Time [ns]
400
Fig 4: Switching waveforms of the investigated JFET 3x total loss reduction compared to an IGBT
Fig 3: Switching cell for the investigation
of the dynamic performance of the switch
L1
S1
+
+
S2
+
UN
-
C2
D1
+
-
S3
S1
S3
S4
C1
C1
S5
-
D1
+
D2
-
Fig 5: Indirect Current Source inverter with a
single JFET
C2
S2
L1
+
UN
-
S4
Fig 6: Phase leg of Neutral Point Clamped
inverter with JFETs
L1
Inverter test board
Finally, a 1kW laboratory prototype inverter
was shown featuring very high efficiency
(98.9%) using only one fast (SiC-JFET)
switch which highlights the interesting potential
for the future application of SiC-JFET devices
in PV systems.
iN
C2
iL1
C1
iC2
S1
S2…S5
Fig 7: Testboard of Indirect Current Source
inverter with JFET
Some impressions from PCIM Conference...
Fig 8: Waveforms of testboard
Nightshift at the Lab...
The Award