Parallel circuit comprising a plurality of IGBTs

Details Parallel circuit comprising a plurality of IGBTs Parallel circuit comprising a plurality of IGBTs

2001-09-07

2003-02-11

Cunningham, Terry D. (Department: 2816)

Miscellaneous active electrical nonlinear devices, circuits, and

Gating

Utilizing three or more electrode solid-state device

C327S434000, C327S112000

Reexamination Certificate

active

06518821

ABSTRACT:

FIELD OF THE INVENTION
The present invention concerns the field of power electronics. It relates to a parallel circuit comprising a plurality of IGBTs.
BACKGROUND OF THE INVENTION
For a relatively long time power electronic semiconductor modules have been commercially available in which up to six high-power IGBTs with corresponding reverse-connected parallel diodes are arranged and interconnected in such a way that they can either form the individual arms of a three-phase power converter bridge or can be combined by being connected in parallel to form a single phase arm with three-fold current-carrying capacity. Modules of this type are offered by the applicant under the general type designation LoPak5 and have, by way of example, a collector-emitter voltage V
CE
of 1200 V and a collector current I
c
of 300 A (see the data sheet 5SYA1528 from ABB Semiconductors AG relating to the module type 5SNS030OU120100 of Jul. 1, 2000).
The parallel circuit comprising such high-power IGBTs on the power side (i.e. by connecting the collector-emitter paths of the individual IGBTs in parallel) throws up various problems:
If the IGBTs with their associated gate drive circuits (“gate drives”) are only connected in parallel on the power side without further measures, considerable unequal distribution of the currents between the individual IGBTs can occur dynamically due to different delays in the gate drive circuits during the switching of the IGBTs. Since the individual gates of the IGBTs are not connected to one another, the positive transistor behavior of the IGBTs does not help either.
If the gates of the IGBTs are likewise connected in parallel, the IGBTs, owing to their fundamental transistor behavior, naturally have the tendency to statically divide the currents identically among themselves: identical transistors have identical I
CE
/V
CE
characteristics and - since they have the same V
CE
and the same gate voltage - they must also draw the same collector-emitter current I
CE
. Dynamically, however, the currents can differ considerably. The absolute values of the gate resistances as well as the ratio of individual and common resistances in the module influence the balance between the currents.
The output stage of a gate drive circuit used for such IGBTs is usually a push-pull stage constructed with two MOSFETs (p-channel and n-channel MOSFETs). If two gate drive circuits are connected in parallel, it must be ensured that one gate drive circuit does not break down to the other and that one gate drive circuit does not “charge” the other. The simplest solution is to use individual gate resistors for decoupling the gate drive circuits. However, such a solution can only be realized for two gate drive circuits connected in parallel.
SUMMARY OF THE INVENTION
It is an object of the invention, therefore, to specify a parallel circuit comprising high-power IGBTs in which more than two gate drive circuits are connected in parallel.
The essence of the invention is that the MOSFETs in the output stages of the gate drive circuits are in each case connected to a positive or negative supply terminal via a constant-current source and the outputs of the gate drive circuits are interconnected via a connecting line. In this case, the constant-current sources are designed as “weak” constant-current sources and are constructed in a manner known per se from a transistor or MOSFET and diodes and/or resistors.
In order that the power supplies of the gate drive circuits are at least uniformly loaded, it is advantageous if the positive and negative supply terminals of the gate drive circuits are respectively interconnected by connecting lines.


REFERENCES:
patent: 5949273 (1999-09-01), Mourick et al.
patent: 6323717 (2001-11-01), Omura et al.
patent: 6326819 (2001-12-01), Carlson
patent: 0 818 889 (1998-01-01), None
“IGBT Module LoPak5 SPT 5SNS0300U120100 Marketing Information”, ABB Semiconductors AG, Jul. 10, 2000, pp. 1-4.

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