Miscellaneous active electrical nonlinear devices – circuits – and – Specific signal discriminating without subsequent control – By shape
Reexamination Certificate
1998-09-11
2001-05-01
Callahan, Timothy P. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Specific signal discriminating without subsequent control
By shape
C327S014000, C327S165000
Reexamination Certificate
active
06225832
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a circuit for recovering a digital signal from an input signal received by way of galvanic separation, comprising two input terminals for the input signal and one output terminal for the recovered digital signal.
In the transmission of electrical signals between two systems A and B, it is frequently required that systems A and B must not be galvanically (metallically) connected to one another, that is to say there must not be a direct metallic connection between systems A and B. To galvanically isolate systems A and B, which are intended to exchange signals with one another, the insertion of a capacitor in each of the signal transmission lines or the use of a transformer for a pair of signal lines is possible in line-connected signal transmission. Accordingly, the coupling elements of capacitor or transformer, respectively, allow the transmission of signals between systems A and B without connecting these to one another galvanically.
However, the use of the coupling elements causes a change in the signal variation so that in the transmission of a signal from system A to system B, a device must be provided in system B by means of which the signal variation originally output by system A can be recovered. This is required especially in the case of digital signals because the digital signal processing devices in the receiving system B only operate reliably with defined signal structures.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a signal regeneration circuit, which overcomes the abovementioned disadvantages of the heretofore-known devices and methods of this general type and which allows a digital signal supplied to a receiver system by way of metallic isolation to be recovered from the received signal.
With the foregoing and other objects in view there is provided, in accordance with the invention, a signal regeneration circuit for recovering a digital signal from an input signal supplied via metallic isolation, comprising:
two input terminals receiving an input signal;
one output terminal outputting a recovered digital signal; and
a current direction sensor connected to the two input terminals for detecting a current direction prevailing between the two input terminals and outputting a signal representing the prevailing current direction.
In accordance with an added feature of the invention, the current direction sensor includes a voltage clamping configuration for fixing a voltage between the input terminals and a current mirror comprising an output driver configuration outputting the signal representing the prevailing current direction.
In accordance with an additional feature of the invention, the voltage clamping configuration includes a first series circuit of at least two diodes each connected in a given direction and a second series circuit of at least two diodes each connected in a direction opposite the given direction, the first and second circuits being connected to one another at a center node.
In other words, a preferred signal regeneration circuit has a current direction sensor which detects the current direction prevailing between the input terminals and outputs a signal corresponding to the prevailing current direction. In this configuration, the current direction sensor detects the direction of the current which flows between the two input terminals. The current direction sensor preferably includes a voltage clamping configuration and a current mirror. The voltage clamping configuration fixes the voltage between the input terminals to a predetermined maximum value. The current mirror detects the current flowing between the input terminals and supplies the detected current value to an output driver configuration at which the output signal can be picked up. It is especially preferred in this configuration that the voltage clamping configuration has a first and a second series connection of in each case at least two diodes connected in the same direction. In this configuration, the diodes of the first series circuit are connected in the opposite direction to the diodes of the second series circuit, and the series circuits are connected to one another at a center node.
In accordance with another feature of the invention, the current mirror includes a first current mirror circuit and a second current mirror circuit, the first current mirror circuit reflecting a current flow through the voltage clamping configuration in a first current flow direction and the second current mirror circuit reflecting a current flow through the voltage clamping configuration in a second current flow direction.
In accordance with again an added feature of the invention, the current mirror further includes a third current mirror circuit and a fourth current mirror circuit, the third current mirror circuit being connected to an output current path of the first current mirror circuit and the fourth current mirror circuit being connected to an output current path of the second current mirror circuit.
In accordance with again another feature of the invention, a connecting node connects an output current path of the third current mirror circuit with an output current path of the fourth current mirror circuit, the output current paths of the third and fourth current mirror circuits form the output driver configuration, and the connecting node outputs the output signal representing the prevailing current direction.
These foregoing features define a further, especially preferred exemplary embodiment of the signal regeneration circuit. The current mirror of the current direction sensor thereby has a first and a second current mirror circuit. In this configuration, the first current mirror circuit reflects the current flow through the voltage clamping configuration in a first current flow direction and the second current mirror circuit reflects the current flow through the voltage clamping configuration in a second current flow direction. In addition, it is especially preferred that the current mirror includes the third and fourth current mirror circuits. Here, the third current mirror circuit is connected to the output current path of the first current mirror circuit and the fourth current mirror circuit is connected to the output current path of the second current mirror circuit. The embodiment in which the output current path of the third current mirror circuit and the output current path of the fourth current mirror circuit are connected to one another and form the output driver configuration is especially preferred. The output signal can then be picked up at the connecting node of the output current paths of the third and fourth current mirror circuit.
In accordance with yet an added feature of the invention, the voltage clamping configuration includes a center node and a reference potential is added at the center node of the voltage clamping configuration. In this configuration, the reference potential is fixed with respect to the ground potential of the current direction sensor and thus of the signal-receiving system. The circuit structures of the current mirror can then be designed with respect to the ground potential of the receiving system.
In accordance with yet another feature of the invention, the reference potential has a value that lies within a range of threshold potentials of CMOS transistors in an integrated circuit.
In accordance with yet an additional feature of the invention, the current direction sensor is constructed with a plurality of transistors including bipolar transistors and CMOS transistors. In accordance with yet a further feature of the invention, the input signal is supplied to the inputs via capacitive coupling where capacitances are connected upstream of the two inputs in the signal flow direction.
In accordance with a concomitant feature of the invention, the current direction sensor comprises a buffer for temporarily storing a last prevailing current direction. In a preferred embodiment the buffer is constructed as a flip flop.
Other features which
Callahan Timothy P.
Greenberg Laurence A.
Infineon - Technologies AG
Lerner Herbert L.
Nguyen Hai L.
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