Pulse or digital communications – Pulse width modulation
Patent
1998-02-06
1999-08-24
Vo, Don N.
Pulse or digital communications
Pulse width modulation
375258, 327 34, 327174, 327178, 332110, H03K 708, H03K 908, H04B 300
Patent
active
059433663
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention is directed to a transmission stage for a transceiver of a subscriber station of a bus system, and in particular of a bus of the European Installation Bus Association, EIBA.
BACKGROUND INFORMATION
Essentially symmetrical AC voltage information is superposed as bit information on a DC voltage of the bus. In a line that is under an inductive load, a DC voltage potential of the line is pulled, in,each case in an active pulse, to the potential of another line. Subsequently, an equalizing pulse is formed for the purpose of energy recovery. Bus couplers of this type are discussed in such references as European Published Applications 0 365 696, 0 379 901, and 0 379 902. Bus couplers of this type usually operate with transformers. In such systems, the DC voltage potential of a line that is under an inductive load is pulled, in each case in an active pulse, to the potential of another line. In the transmitter of a EIB transceiver, the bit pulse on the bus is generated in such a way that an active pulse having an amplitude of about 7 volts is superposed in each case on the bus DC voltage of about 24 volts, as described in European Published Patent Application 0 365 696. This arrangement operates with a turns ratio of about 3:1.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a transmission stage that operates without transformers.
According to the present invention, the active pulse of the bit information at a bit frequency is in this case formed from individual pulses of higher frequency. Specifically, the active pulse of the bit information at a bit repetition rate is obtained in a generator for generating individual pulses of higher frequency. In this case, the generator, in combination with a capacitor of an internal on-board electrical supply, is designed as a high-frequency step-up regulator. The voltage source for the step-up regulator is the bus, and the regulating criterion for the step-up regulator is the voltage dip during the active pulse. In an advantageous manner, use is made of a very high frequency, relative to the bit repetition rate, with the result that the transformer can be reduced to a very small inductance in the form of an inductor.
The transmission stage for the transceiver of the subscriber station of a bus system therefore operates with a generator for generating individual pulses of higher frequency than the bit repetition rate. The voltage drop during an active pulse is in this case simulated by high-frequency current pulses in a switched-mode power supply or by means of a transmission transistor, with ripple but in principle with a rectangular waveform. The higher the frequency of the individual pulses, the better the simulation of a rectangular waveform. The arrangement operates with a generator which is designed as a high-frequency step-up regulator.
European Published Patent Application 0 487 874 describes a multiplex device without energy recovery, which operates with a plurality of messages, and in which a bit pulse is not simulated.
In contrast, with the transmission stage of the present invention, energy recovery is carried out by the operation of the step-up switched mode regulator, which is designed in such a way that instead of regulating the output voltage, it regulates the dip in the input voltage. In other words, the active pulse is regulated in terms of its amplitude. By doing this, the input capacitance in comparison with a customary step-up switched-mode regulator can be reduced toward zero or even right down to zero. This is particularly advantageous because the bus should not be capacitively loaded.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates a transmission stage.
FIG. 2 illustrates a current profile in a transmission valve of the transmission stage during an active pulse.
FIG. 3 represents, in the upper curve profile, the bus voltage during superposition by an active pulse and, underneath that, the bus current during the superposition by an active pulse, together with subsequent
REFERENCES:
patent: 5020154 (1991-05-01), Zierhut
patent: 5546419 (1996-08-01), Zierhut
Park Albert
Siemens AG
Vo Don N.
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