Nixdorf Computer Ag

Siemens Aktiengesellschaft

Harald Schreiber

Hartmut Lubcke

Martin Backhaus

A buck type switching DC converter having coupled thereto a square-wave signal generator that modulates the pulse width of the control signal for the regulating switch depending on the output voltage of the DC converter given a fixed frequency, the square-wave signal generator being dynamically and selectively directly coupled to the control input of the regulating switch, for example, via a parallel circuit comprising a capacitor and an additional controllable switch.

Switching DC converter

A method of integrating one or more accessory function modules in telecommunication systems is disclosed, especially digital telephone extension systems, where communication between two user terminals is achieved using time division multiplexing by assigning a pair of time slots through a central exchange, and by preassigning at least one particular time slot which can be accessed to allow communication between the accesory function module or modules and the user terminals.

Method of integrating one or more accessory function modules in

A circuit for remote supply of subscriber line terminals in telecommunication systems, especially suitable for employment in digital telecommunication systems, is described. The circuit comprises a supply circuit (10) at the beginning of the subscriber line (11), which circuit has a negative internal resistance operative when a preassigned supply amperage is exceeded. Between the subscriber line (1) and the terminal, a current converter cirucit (12) is provided, containing an energy reservoir (40) on the primary side and a switch-on circuit (41-44) operating in dependence upon its charge voltage for the switch pulses required for start-up. The operating current for the switch pulses is then delivered by a secondary winding (57) of the converter transmitter (27). A pulse width modulation of the switch pulses is effected, in addition to a control voltage derived from the secondary side of the converter transmitter (27), in the switch-on process, by a rising ramp-like direct current voltage preventing too violent a discharge of the condenser (40) at the input of the current converter (12). When switched on, the entire arrangement brings about a slow rise of the current on the subscriber line (11). Furthermore, the condenser meets the exaggerated energy demand upon start-up of the current converter (12) and compensates for fluctuations in energy demand during operation. The switch-on circuit (41-44) is kept switched on after the current converter (12) has been switched on by way of a direct current voltage derived form the secondary side, even if the input voltage drops below the switch-on circuit (41-44) switch threshold operative in the switched-off condition.

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Salzkotten, Germany

Harald Schreiber