Miscellaneous active electrical nonlinear devices – circuits – and – Specific identifiable device – circuit – or system – With specific source of supply or bias voltage
Reexamination Certificate
1998-05-21
2001-02-06
Callahan, Timothy P. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Specific identifiable device, circuit, or system
With specific source of supply or bias voltage
C323S315000
Reexamination Certificate
active
06184742
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention concerns a current distribution circuit comprising:
a first at least DC current sinking branch, which is provided with the main current stream of a first controlled semiconductor having a first control input,
a second current sinking branch connected in parallel to the series arrangement of the first current sinking branch, which second current sinking branch is provided with a second control input, and
means for controlling the currents through the first and second current sinking branches, which controlling means are coupled to the first and second control inputs respectively.
The present invention also concerns a telecommunication device provided with a current distribution circuit.
Such a current distribution circuit and device are known from application note ETT/AN93015 on the TEA 1093 chip. In particular this note discloses a current distribution circuit comprising:
a first AC and DC current sinking branch, which is provided with the series arrangement of the main current stream of a first current controlled semiconductor having a first combined AC/DC current control input, and a stabilising circuit for providing a DC supply voltage,
a second AC current sinking branch connected in parallel to the series arrangement of the first current sinking branch, which second current sinking branch is provided with a second AC current control input, and
means for controlling said currents through the first and second current sinking branches, which controlling means are coupled to the first and second current control inputs respectively.
Such a current distribution circuit is being applied in telecommunication devices, such as for example a subscriber telephone, a handsfree telephone, a facsimile, a WEB-television having a telephone card, a personal computer having a telephone card etc. Usually such telephone ICs' are capable of controlling the AC-speech signals on the telephone line to facilitate communication between the telecommunication device and a central device. Furthermore they are equipped for processing the DC-line-current from the telephone line in the first current sinking branch. The stabilising circuit provides the DC supply voltage having a relative high magnitude. Processing a necessary maximum DC-line-current in the first current sinking branch of say for example approximately 140 mA would lead to an IC having a relatively large chip area for the DC current controlled semi-conductor transistor used in that first current sinking branch, because said transistor has to have a certain limited collector/emitter voltage. This collector/emitter voltage is limited and has to be kept limited because the DC supply voltage needs to have a relative high magnitude for controlling present day telephone add-on equipment, such as handsfree facilities, extra loudspeakers, and other peripheral devices.
SUMMARY OF THE INVENTION
It is an object of the present invention to sink the necessary maximum DC-line-current at all times under all operating conditions and with a minimal chip area.
Thereto the present invention is characterised in that the current distribution circuit comprises an at least DC current measuring means coupled to the controlling means for providing a measure for at least the DC-current in the first current sinking branch, and that the second current sinking branch is a second at least DC-current sinking branch whose second control input is connected to the controlling means for leading an excessive part of at least the DC-current through the second current sinking branch.
The idea underlying the present invention is that the first current sinking branch sinks a part of the line-current normally used for deriving a DC supply voltage there from, whereas the second current sinking branch is used to sink a surplus part of at least the DC-line-current. Because the second current sinking branch does not contain the stabilising circuit, sinking the surplus, excess or top-part of at least the DC-current of the first current sinking branch through the second current sinking branch can take place in said second current sinking branch at a relatively high collector/emitter voltage. As a consequence thereof the chip area for taking up such a relatively high magnitude of DC current at larger collector/emitter voltages is reduced.
A further advantage of the current distribution circuit and device according to the invention is, that controlling the AC-currents in the first and second current sinking branches is still possible. In fact a possible simultaneous AC/DC current control in both the first current sinking branch and the second current sinking branch provides for a double control function in in particular the second current sinking branch.
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Labbe Eric C.
Mulder Jacob
Thus Fransiscus J. M.
Callahan Timothy P.
Nguyen Hai L.
U.S. Philips Corporation
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