Electrical resistors – Shunt type
Reexamination Certificate
2002-09-09
2004-06-29
Pert, Evan (Department: 2829)
Electrical resistors
Shunt type
Reexamination Certificate
active
06756877
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The present invention relates to a shunt resistor configuration.
Shunt resistors are used to measure high currents (i.e., from a few amperes up to a few hundred amperes). Shunt resistors (hereinafter, “shunts”) are measuring resistors which are connected in series with the component to be measured. The current in the main current path can be derived from the voltage dropped across the shunt resistor. Shunt resistors are employed in DC systems, since it is not possible to use entirely inductive current transformers therein. In addition, the current detection is extremely reliable with regard to precision and susceptibility to interference.
At the present time, shunt resistors are constructed on separate, insulated bases. The connecting lines for the load current and the shunt voltage measurement are connected individually. In this case, the shunt resistor is generally disposed in direct proximity to the fuses of the DC system. The fuses are configured as low-voltage high-rupturing-capacity (LVHRC) fuse elements. Accordingly, the space requirement for two individual LVHRC fuse elements, for the separately constructed shunt resistor, and also for the associated outlay on material and installation is comparatively significant.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a shunt resistor configuration that overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and that has a higher degree of freedom in the layout configuration compared with conventional configurations and a smaller space requirement on the printed circuit board. In particular, the object is to realize the shunt resistor configuration with a comparatively low outlay and cost.
With the foregoing and other objects in view, there is provided, in accordance with the invention, a configuration having a first shunt resistor and at least one further shunt resistor connected in parallel with the first shunt resistor, whose load terminals disposed at the front side of the shunt resistors are disposed between a first and a second supply potential, and which each have a large-area rear-side contact connection to which different potentials are applied.
In accordance with another feature of the invention, the space-saving configuration is achieved by having the rear-side contact connections asymmetrically contact-connected to the load current terminals in such a way that the first shunt resistor is connected by its rear-side contact connection to a first conductor track, to which a first supply potential is applied, while the rear-side contact connection of at least one further shunt resistor is connected to another conductor track, to which a further supply potential is applied.
In other words, according to the invention, the rear-side contact connections of at least two shunt resistors are at different potentials of the load current path. The electrical connection to the conductor tracks is effected by bonding connections.
As a result of the asymmetrical configuration of the shunts, it is also advantageously possible for the contact area used as mounting area below the shunt to be utilized as a conductor track in the second plane.
In accordance with a further feature of the invention, a front side terminal and the rear-side contact connection of the shunt resistor are connected by through-plating.
In accordance with an added feature of the invention, the load terminal at the front side of a shunt resistor and the rear-side contact connection thereof may be electrically connected to one another by bonding wires.
In accordance with an additional feature of the invention, there is provided at least one semiconductor component connected in either parallel or series manner with the parallel circuit of the shunt resistors. The semiconductor component is electrically connected to at least one of the supply potentials.
The shunt resistor configuration is advantageously disposed in a component module. In accordance with yet another feature of the invention, the component module typically has further semiconductor components (for example diodes, MOSFETs, IGBTs, thyristors and GTOs) connected in parallel with the parallel circuit of the shunt resistors.
In accordance with yet a further feature of the invention, the shunt resistors are disposed in the load current path and have, in particular, a carrier material with good thermal conduction for the rear-side contact connection. A thin insulation layer is applied to the carrier material and at least one resistance layer is applied thereto. Sense bonding contact areas, at which the measurement voltage drop across the shunt resistor can be tapped off. Load current contact areas are provided on the front side of the shunt resistor, at which bonding connections produce the contact-making connection to conductor tracks of the load current path and to the supply voltage.
The carrier material, which (as a heat sink) serves for dissipating heat from the shunt elements and the semiconductor components, may be composed of copper. The insulation layer determines the dielectric strength of the shunt elements and has, for example, a ceramic that is electrically insulating, but has good thermal conductivity, or a ceramic containing a suitable plastic (e.g. epoxy resin) with these properties. The resistance layer applied is generally an alloy such as a Cu—Ni alloy, an Al—Cr alloy and a Cu—Mn alloy.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a shunt resistor configuration, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
REFERENCES:
patent: 41 15 328 (1991-11-01), None
patent: 1 009 030 (2000-06-01), None
patent: 07 307 202 (1995-11-01), None
patent: 11 097 203 (1999-04-01), None
Franke Torsten
Tschirbs Roman
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