Miscellaneous active electrical nonlinear devices – circuits – and – Specific identifiable device – circuit – or system – With specific source of supply or bias voltage
Patent
1997-07-25
1998-09-01
Callahan, Timothy P.
Miscellaneous active electrical nonlinear devices, circuits, and
Specific identifiable device, circuit, or system
With specific source of supply or bias voltage
327538, H04B 354
Patent
active
058015833
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a device for providing the on-board power supply in a bus coupler without a repeater for coupling to an information and power conducting bus of a bus system, in particular for building systems management.
BACKGROUND INFORMATION
Published International Patent Application No. WO-A 9,308,652 describes a bus coupler for coupling to an information and power carrying bus (bus drivers 1, 2) of a bus system. Such a coupler is based on the principle of reducing reflection on a line that is not closed. The bus coupler described therein works without a repeater.
There are bus systems in use in building systems management, for example, the bus system of the European Installation Bus Association, EIBA, where reflection on the open line is negligible due to its mode of operation.
In the past, bus couplers have been designed with repeaters (see, e.g., European Patents Nos. A 365,696 and A 379,902). The DC voltage for the on-board power supply is obtained from the bus with a repeater and a capacitor that function as an LC filter. With a low-resistance DC resistor of the inductance of the repeater, a low resistance is used for obtaining the DC current and a high-resistance inductive resistor is used for the AC load due to the information transmission. In such a design, there are limits to the miniaturization and integration into an integrated circuit (IC).
SUMMARY OF THE INVENTION
An object of the present invention is to provide a device for supplying the on-board system voltage in a bus coupler, without a repeater, for coupling to a bus that carries both information and power, where it is irrelevant whether or not measures are to be taken to reduce reflection.
In accordance with the present invention, a coupling circuit with a control input is connected to a triggering circuit via the control input, where the triggering circuit has inputs for a control criterion. The coupling circuit is designed and constructed so that it operates as a constant current source for the communications frequencies and as a control circuit in combination with the triggering circuit for lower frequencies. Such lower frequencies are caused by power consumption. The communications frequencies can be understood as the transmission speed in bits/second. Thus, for example, the bus of the European Installation Bus Association, i.e., the EIBA bus, operates at 9.6 kbit/sec, which corresponds to a frequency of 9.6 kHz. The coupling circuit is effectively connected in series with a capacitor for tapping the on-board voltage. The series connection is effectively connected to the bus drivers.
Since the highest control frequency is set lower than the lowest transmission frequency, it is ensured that the resistance of the coupling circuit is low enough for the on-board power supply and is high enough for communications signals. Therefore, communications on the bus are not attenuated by the on-board power supply. On the other hand, the power for the on-board power supply is obtained in an especially economical and low-loss manner. In practice, it is advantageous to set the highest control frequency lower than one-tenth of the lowest transmission frequency.
Such a design permits implementation in an integrated circuit (IC).
The coupling circuit may effectively have a transistor whose emitter across a resistor forms one terminal of the coupler circuit to which a capacitor is also connected and on the other side is connected to the base of the transistor that serves as a control input and whose collector in turn forms the other terminal of the coupling circuit. Such a design is especially simple and effective.
The triggering circuit is preferably connected at its inputs to the two terminals of the coupling circuit and is designed and wired so as to minimize the voltage drop of the coupling circuit. This permits control with minimal voltage drop at the coupling circuit and thus yields the highest possible efficiency.
The triggering circuit can be optimized in various regards. If the control system is
REFERENCES:
patent: 5546419 (1996-08-01), Zierhut
Callahan Timothy P.
Lam T. T.
Siemens Aktiengesellschaft
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