Article Power MOSFETs 650V CoolMOS™ CFD2

A new 650V Super Junction Device with rugged body diode for hard
and soft switching applications
A)
A)
B)
B)
M.-A. Kutschak , W. Jantscher , D. Zipprick , A. Ludsteck-Pechloff ,
A) Infineon Technologies Austria AG, Siemensstraße 2, A-9500 Villach, Austria
B) Infineon Technologies AG, Am Campeon 1-12, D-85579 Neubiberg, Germany
Abstract
With the new CoolMOS™ 650V CFD2 technology a new benchmark is set for high voltage power
MOSFETs with a high performance body diode of the MOSFET. The transistor combines a high blocking voltage of 650V with lowest Rdson and low capacitive losses together with an improved body diode
ruggedness during reverse recovery especially for hard and soft switching applications. Together with
the improved performance a specification of the max-value of the Qrr and trr in the datasheet will be introduced. This article investigates the influence factors for improving the body diode ruggedness. The
benefit of this new Superjunction device family with fast body diode is especially shown for a HID halfbridge topology.
1.
Introduction
With the increasing demand for higher power
density, especially soft switching topologies like
half-bridge (e.g. HID half-bridge or LLC) and fullbridge concepts (e.g. ZVS bridge) seem to be
the ideal solution. These topologies reduce the
switching losses and increase the reliability of
the system due to less dynamic di/dt and dv/dt
stress on the power device. Such high stresses
occur predominantly in light-load operation [1]. It
is already shown that Superjunction devices like
the CoolMOS™ help to overcome this problem
by inherent optimized charge carrier removal
during reverse recovery and eliminating the problem of latch-up of the parasitic npn-bipolar transistor [2]. A significant reduction of the reverse
recovery charge can be achieved by an enhanced recombination rate of the injected carriers resulting in lower reverse recovery peak currents during turn-off and strongly reduced reverse recovery charge by almost a factor of 10.
For optimized body diode (Fig.1) performance in
hard switching conditions, especially the shape
of the resulting reverse recovery waveform and
the design conditions of the printed circuit board
are important [3-4]. The new CoolMOS™ 650V
CFD2 is designed in this manner with improved
reverse recovery behavior together with increased safety margin in breakdown voltage.
Fig. 1. Schematic cross section of the CoolMOS high voltage power MOSFET and
its integral body diode
2.
Reverse Recovery Behavior
The reverse recovery behavior of the new CoolMOS™ 650V CFD is shown in Fig. 2. It appears
that the new CoolMOS™ 650V CFD devices
have a very low reverse recovery charge Qrr, reverse recovery time trr and maximum reverse recovery current Irrm when compared to the standard device.
4. Dependence of Qrr and trr
with temperature
40
Id C6
Id C3
30
Of utmost importance for the designer is the dependence of Qrr and trr on temperature. The Qrr
and trr values tend to increase with temperature,
due to increased carrier generation in the device.
This dependence is shown in Fig. 4 for the
310mΩ 650V CFD2 device. A linear increase of
Qrr and trr with temperature is observed.
I [A]
20
New CFD Device
10
0
0.12
0.22
0.32
0.42
0.52
0.62
0.72
0.82
-10
160
-20
0.9
t [µs]
0.8
150
0.7
Fig. 2. Measured reverse recovery waveforms
at di/dt=100A/µs, 25°C, Vr=400V. The
new CFD device shows very low Qrr, trr
and Irrm when compared to the standard
device.
At the same time, the waveforms of the new device still show a soft characteristic, in spite of the
strongly reduced Qrr, trr and Irrm. This characteristic is highly desirable during hard commutation in
order to avoid voltage overshoot and to ensure
reliable device operation.
3.
Commutation Ruggedness
The commutation ruggedness of the CoolMOS™
650V CFD2 device is demonstrated in reverse
recovery measurements in Fig. 3, where the devices were tested up to di/dt  2000A/µs.
500
40
Vr
If
400
30
Trr (ns)
0.6
130
0.5
120
0.4
0.3
110
Trr
100
Qrr
90
20
30
40
50
60
70
80
90
100
110
120
130
0.2
0.1
0
140
T(°C)
Fig. 4. Dependence of Qrr and Trr with temperature for the 310mΩ 650V CFD device
5. Dependence of Qrr and Trr
with Rdson
Another important aspect to be considered is the
dependence of Qrr and trr on the device Rdson.
This can be seen in Fig. 5 and Fig. 6, respectively, where the new 650V CFD2 device is compared with the former Infineon’s CoolMOS™ fast
diode technology.
20
Test Conditions:
Vr=400V, If=12A, Tj=125°C
di / dt = 1000 A/µs
2.5
200
10
100
0
C3
C6
I [A]
U [V]
300
140
Qrr (µC)
Standard Device
2
-10
0.6
0.62
0.64
0.66
0.68
-100
0.7
0.72
0.74
-20
Qrr (µC)
1.5
0
1
t [µs]
Fig. 3. Measured reverse recovery waveforms
for the new CoolMOS 650V CFD2 device. The devices could not be destroyed
even at the maximum capability of the
tester
No device could be destroyed under these conditions and the waveforms show still a soft characteristic, compared to snappy waveforms for other
superjunction devices. This is a clear advantage
for the designer, once one can optimize its application for maximum performance without being
concerned with device destruction during hard
commutation of the body diode.
0.5
0
0
100
200
300
400
Rdson (mOhm)
500
600
700
Fig. 5. Dependence of Qrr on Rdson, measured at
25°C and for the 80, 310 and 660mΩ
650V CFD2 devices in comparison with
the former 600V CFD technology
230
C3
C6
210
190
D-S Voltage T3
D – Current T3
G-S Voltage T3
D-Current T2
trr (ns)
170
150
130
110
90
70
50
0
100
200
300
400
500
600
700
Rdson (mOhm)
Fig. 6. Dependence of trr on Rdson, measured at
25°C and for the 80, 310 and 660mΩ
650V CFD2 devices in comparison with
the former 600V CFD technology
The new 650V CFD2 device clearly offers an
even better trade-off then the former technology
between dynamical characteristics (Qrr,trr) and
lowest Rdson.
6. Performance Evaluation in
HID-Bridge
We have also compared the performance of the
new devices with the commercial available
SPD07N60C3 in a HID half-bridge application.
Using the new CoolMOS™ CFD2 devices, the
diodes D2, D3, D4 and D5 can be eliminated and
allow reduced system costs (Fig. 7).
Fig. 7. Typical HID Half-Bridge circuit. By replacing the transistors T2 and T3 with the
new CoolMOS™ 650V CFD2 device, the
diodes D2 to D5 can be eliminated.
Lamp Current
Fig. 8. Circuit wave forms during the turn-off
phase of transistor T3 with SPD07N60C3
as switch and the diodes D2 – D5. An efficiency of 91,81% is achieved.
For reference Fig. 8 shows, the wave forms obtained by using the SPD07N60C3 device as
transistors T2 and T3 and additionally the diodes
D2, D3, D4 and D5. With this setup, we achieved
an efficiency of 91,81%.
By removing the diodes in series to the transistors, the additional voltage drop in forward operation is eliminated. This solution requires, however, an even superior performance of the internal
body diode of the MOSFET once the switching
losses increase due to the reverse recovery
charge stored in the MOSFET. This situation is
depicted in Fig. 9.
D-S Voltage T3
D – Current T3
G-S Voltage T3
D-Current T2
D-S Voltage T3
D – Current T3
G-S Voltage T3
D-Current T2
Lamp Current
Lamp Current
Fig. 9. Circuit wave forms during the turn-off
phase of transistor T3 with SPD07N60C3
without the diodes D2–D5. An efficiency
of 89,72% is achieved.
Fig. 10. Circuit wave forms during the turn-off
phase of transistor T3 with
IPD65R660CFD without the diodes D2–
D5. An efficiency of 92,81% is achieved.
In addition to increased switching losses, this setup also has the disadvantage that the MOSFET’s can eventually be destroyed due to the
high reverse recovery current.
A superior solution is achieved by using the new
IPD65R660CFD device. Due to the superior performance of the internal body diode of the MOSFET, it is possible to implement a solution without
the diodes D2-D5 and obtain at the same time a
considerably better efficiency. This is shown in
Fig.10.
The optimized construction of the internal body
diode of the new IPD65R660CFD device combined with a very low reverse recovery charge
also enable reliable device operation.
7.
Conclusion
Infineon’s new CoolMOS™ CFD2 device, offers
the lowest Rdson combined with a high blocking
voltage of 650V. This new device features also a
very low reverse recovery charge combined with
a robust integral body diode. A specification of
the max-values of the Qrr and trr will be available
in the datasheet. We have also evaluated the
performance of this new device in a typical HID
Half-Bridge circuit, leaving out four diodes and
getting superior efficiency. Due to the breakdown
voltage of 650V and the robust construction of
the integral body diode, this new device offers
additional safety against destruction during hard
commutation of the MOSFET.
8.
[1]
[2]
[3]
[4]
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converters: analysis and reliability improvements”, Proc. INTELEC 1998, pp. 30-40,
San Francisco, Oct. 1998
W. Frank, F. Dahlquist. H. Kapels, M.
Schmitt, G. Deboy, “Compensation MOSFETs with fast body diode – Benefits in Performance and Reliability in ZVS Applications“, Proceedings-CD of the International
Power Electronics Component Systems Applications Conference (IPECSA), San Francisco, California, March 29 – April 1, 2004
R.
Ng,
F.Udrea,
K.Sheng,
G.A.J.Amaratunga, “A Study of the CoolMOS Integral Diode: Analysis and Optimization”, The 24th International Semiconductor
Conference; CAS 2001, October 2001, Sinaia, Romania.Grütz, A.: Jahrbuch Elektrotechnik '98. Berlin-Offenbach: VDE-Verlag,
1997.
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Model”, Power Electronics Specialist Conference, 2003. PESC '03. 2003 IEEE 34th
Annual.
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