GB1391952A - Data processing system with power supply - Google Patents

Abstract

1391952 D.C.-D.C.-converting RAYTHEON CO 26 Jan 1973 [7 Feb 1972] 4189/73 Heading H2F A data processing system comprises data storage means, and data retrieval means and includes a power supply in the form of a D.C.- D.C.-converter of the pulse width modulated switching type, the switching cycle of this converter being synchronized with the operating cycle of the data retrieval means which is preferably a C.R.T. dot matrix display. The power supply in outline is shown in Fig. 2, and has two inputs, a first for a regulated d.c. voltage and the second for a synchronizing clock input which is derived from the operating clocks of the data processing system. This pulsed input is applied to a monostable and Schmidt-trigger arrangement 210 to derive a square-wave signal of mark/space ratio of approx. 6. The circuit 210, depicted in more detail in Fig. 6 (not shown), is responsive to external synchronizing pulses to trigger the monostable, only if they lie in a discrete time period after the recovery of the monostable and before a triggering pulse is emitted by the Schmidt trigger, otherwise the triggering is done wholly internally. The synchronized output from circuit 210 is differentiated, amplified and limited at 104 where the output is applied to the base of transistor 520 and to the base of main switching transistor 440 through transformer 444. The transistor is thus turned "on" for relatively long periods and "off" for relatively short periods, the cycle time being, e.g. 64 msecs. The collector voltage at transistor 440 rises and is clipped at a value of e.g. 550 volts in the "off" periods by a Zener diode and diode series circuit 130, 129 in parallel with a capacitor 132 in series with a secondary winding of output transformer 216, and falls to, e.g. 140 volts in its "on" periods. The resulting waveform at secondary 122 consists of longer periods, e.g. of a steady +35 volts, and pulses of larger negative voltage. The positive voltage output is rectified at 120 and smoothed at 132 to be applied to the several loads in operation. The regulated D.C. input is derived from an unregulated source by a translator D.C. chopper device which is regulated by a feedback system. Suitable overcurrent and over-voltage protection circuits are employed and an auxiliary D.C. source employed in the event of operation of these circuits. The rectifier for producing the unregulated D.C. from an A.C. input is shown at 202, Fig. 5. A diode full-wave bridge 320-326 is provided and if the input is 230 volts, the switch 31873 in the position shown. If a 115 volt input is used, the switch is changed to take out diodes 322, 326 from the circuit and the remaining diodes together with capacitors 329, 330 provide a full-wave rectifying and voltage doubling circuit.