Electric power conversion systems – Current conversion – Including automatic or integral protection means
Reexamination Certificate
2001-09-20
2002-10-08
Vu, Bao Q. (Department: 2838)
Electric power conversion systems
Current conversion
Including automatic or integral protection means
C363S096000, C363S136000
Reexamination Certificate
active
06462968
ABSTRACT:
FIELD ON THE INVENTION
The present invention concerns the field of power electronics. It relates to a reverse conducting GCT (
G
ate
C
ommutated
T
hyristor) in accordance with the preamble of claim
1
, and also to an application of such a GCT.
BACKGROUND OF THE INVENTION
For applications in current source inverters, as are disclosed in U.S. Pat. No. 4,545,002, for example, reverse blocking power semiconductor components such as e.g. thyristors, GTOs or IGCTs (
I
ntegrated
G
ate Commutated
T
hyristors) are used (with regard to an explanation of the function and the construction of IGCTs, reference is made e.g. to an article by Harold M. Stillman, “IGCTs—megawatt power switches for medium-voltage applications”, ABB Review 3 (1997)). In this case, it is possible to use both symmetrical components and a series circuit comprising an asymmetrical component and a diode. The problem in application is that a large overvoltage is induced by the commutation inductance during the turn-off into a positive voltage (in the case of GTOs and IGCTs). However, the commutation inductance can only be influenced to a limited extent since it is manifested by leakage inductances.
In the application, therefore, the overvoltage must either be controlled by the semiconductor component used, or be reduced by massive external circuitry. Both approaches lead to losses which limit the performance of the power converter.
SUMMARY OF THE INVENTION
It is an object of the invention, therefore, to provide a current source inverter which does not have the abovementioned disadvantages of known current source inverters and, in particular, whose performance is not impaired by the overvoltages produced during turn-off, and also to specify a power semiconductor component for use in such a current source inverter.
The object is achieved by means of the totality of the features of claims
1
and
3
. The heart of the invention consists in using, in the bridge paths of the inverter, a power semiconductor component which is avalanche-proof at least under loading in the forward direction. This obviates, in particular, the need for providing additional circuit measures in the inverter. A series circuit comprising a reverse conducting GCT (
G
ate
C
ommutated
T
hyristor) and a diode is preferably used.
In the reverse conducting GCT, in which a GCT section and a reverse-connected parallel diode section are integrated beside one another in a semiconductor substrate, the avalanche strength is achieved by virtue of the fact that the diode section is designed in such a way that its avalanche voltage is lower than the blocking voltage of the GCT section.
In accordance with a first preferred refinement of the GCT according to the invention, the diode section comprises, one above the other, a cathode emitter layer, a first base layer, and a first anode emitter layer, and the avalanche voltage or blocking voltage of the diode section is reduced by virtue of the cathode emitter layer being driven in a recessed manner into the semiconductor substrate or the first base layer.
Another preferred refinement is characterized in that the diode section comprises, one above the other, a cathode emitter layer, a first base layer, and a first anode emitter layer, and in that the avalanche voltage or blocking voltage of the diode section is reduced by virtue of the first anode emitter layer being driven in a recessed manner into the semiconductor substrate or the first base layer.
A further refinement of the GCT according to the invention is distinguished by the fact that the diode section comprises, one above the other, a cathode emitter layer, a first base layer, and a first anode emitter layer, and that the avalanche voltage or blocking voltage of the diode section is reduced by virtue of a reduction of the resistivity of the first base layer, the reduction of the resistivity of the first base layer preferably being effected by neutron irradiation.
Finally, it is also possible to effect the avalanche voltage or blocking voltage of the diode section by a reduction in the thickness of the semiconductor substrate in the region of the diode section.
Further embodiments emerge from the dependent claims.
REFERENCES:
patent: 3947726 (1976-03-01), DeCecco et al.
patent: 4516315 (1985-05-01), Przybysz et al.
patent: 4545002 (1985-10-01), Walker
patent: 4945463 (1990-07-01), Dangschat
patent: 5095220 (1992-03-01), Kaifler
patent: 5731967 (1998-03-01), Gruning
patent: 5982646 (1999-11-01), Lyons et al.
patent: 6225791 (2001-05-01), Fujii et al.
patent: 6242895 (2001-06-01), Fujii et al.
patent: 0 509 118 (1992-10-01), None
patent: 1395 528 (1975-05-01), None
ABB (Schweiz) AG
Burns Doane Swecker & Mathis L.L.P.
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