Schaltungsanordnung zum Erzeugen einer gegenueber der Netzspannung niedrigen Speisegleichspannung

摘要

958,069. Transistor sawtooth current generators; automatic phase control systems. MULLARD Ltd. Oct. 26, 1961, No. 38368/61. Headings H3A and H3T. [Also in Division H2] In a sawtooth current generator of the so called " retrace driven " type employing a silicon controlled rectifier as the switching device and in which during the long stroke the rectifier is non-conductive and energy is returned to the supply, part of the voltage across the output transformer during the long stroke is rectified to provide a D.C. voltage for semi-conductor devices in associated apparatus such as a television receiver or an oscilloscope. Fig. 1 shows a circuit for generating a saw-tooth current in a deflection coil L D , of the basic type described in Specifications 821,517 and 904,443 modified as described in Specifications 949,535 and 957,882 to minimize the magnetization of the transformer core and to quench the SCR. By the addition of components 8, 11, 12, part of the transformer voltage during the forward stroke is rectified to provide a supply of from 1-16 V. for the associated semi-conductor apparatus. The opposite polarity D.C. voltage may be obtained if a separate winding is used or if the SCR is of the opposite conductivity type. The Fig. 1 circuit is a selfoscillator in which timing is effected mainly by a capacitor 17 which is charged negatively during the flyback and which, during the long stroke (when the SCR is non-conductive), discharges through resistor 18. During this period C1 is also being charged. Capacitor 17 becomes completely discharged and then charges positively offsetting the feedback voltage from coil 15 until the combined effect of the charging of the two capacitors causes the SCR to conduct to produce the flyback, during which C 1 is discharged and 17 is charged negatively by the regenerative feedback coil L 2 . Synchronization is effected by a phase discriminator 22 which controls the charging of capacitor 17. In Fig. 4 timing is effected by a capacitor 26 which, during the long stroke, discharges through resistors 25, 27 and 28. This continues until the voltage at the left hand plate is sufficient to cause an SCR S1 to fire. The recharging current for capacitor 26 now causes the output SCR S to fire. The recharging of capacitor 26 is effected resonantly through choke 24 and the SCR S1 is extinguished when the capacitor is charged. Synchronization is effected by a phase comparator 21 which compares pulses from coil 23 with input pulses to produce a voltage for controlling the firing point of SCR S1.