Patent GB-1387207-A (GB)
Title: Repeater power-supply system
IPC: H02M3/156
Filed: 1972-04-12
Abstract: 1387207 Repeater power supply TELECOMMUNICATIONS RADIOELECTRIQUES ET TELEPHONIQUES 12 April 1972 [15 April 1971] 16840/70 Heading H4R [Also in Division G3] A remote power supply system for repeaters includes at one end of the transmission line a direct voltage generator providing the power for all repeaters over a supply line and further includes a power supply unit situated at each repeater, the system being characterized in that the supply units are connected in parallel to the power supply line and that each of the power supply units includes a D.C.-D.C. converter of a type which is provided with a time-controlled electronic switch incorporated in a control loop. The power supply line may be the phantom circuit in the case of a telephone connection employing four transmission lines, and each D.C.-D.C. converter may supply a direct voltage of 12 volts at a substantially constant current level of 80 mA. Fig. 1 shows the general arrangement of a system including voltage generator G, power supply units B 1 -B n , and reaters A 1 -A n , the resistors R/2 representing the line impedances between repeaters. A detailed analysis of the voltage and current characteristics of the system is described with respect to Figs. 3 and 4 (not shown). Fig. 7 shows the circuit of one of the power supply units and incorporates a known D.C.- D.C. converter comprising the components, transistor 6, inductor 8, diode 9 and capactior 7, for converting the line D.C. voltage applied at the terminals 1, 2 to a lower putput voltage generated at terminals 3, 4. The D.C. voltage produced at terminals 3, 4 is governed by the on-off times of transistor 6 which is switched by a multivibrator 14 via a pulse repeater and amplifier circuit 10. The cut-off period T 1  of transistor 15 in the multivibrator 14 is determined by the fixed time constant of resistor 16, and capacitor 17 and hence transistor 6 has a fixed on period T 1 . The period T 2  during which transistor 6 is off is governed by the cut-off period of transistor 18, and this is governed by the variable time constant which is obtained by capacitor 19 and transistor 20 forming a control circuit arranged as s current injector and being driven by an error signal provided by the differential amplifier 21; the base of transistor 22 in the differential amplifier 21 is connected to a reference voltage and the base of transistor 23 is connected to a voltage which due to Zener diode 28 is highly dependent on variations in the output voltage at terminal 3. By this arrangement the output voltage is regulated. An integration circuit 29 is provided between the differential amplifier 21 and the control circuit for the multivibrator 14 which makes it possible to initially delay the operation of the control thereby building up the output voltage gradually when the system is switched on. Under normal working conditions the multivibrator and differential amplifier are powered from the output of the D.C.-D.C. converter via diode 35. However when the system is first energized these circuits are powered via a supply 36 from the input voltage. Once the output voltage of the D.C.-D.C. converter has built up transistor 37 in power supply 36 turns off and the circuits are supplied from the D.C.-D.C. converter output. The pulse repeater and amplifier circuit 10 is always powered by the input voltage. The arrangement of Fig. 7 is capable of suppling an output voltage of 12 volts stabilized on 1% for input voltages which vary between 30 and 160 volts. (For Figures see next page.)