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摘要

1406895 D.C.-D.C. conversion TEXAS INSTRUMENTS Ltd 24 Nov 1972 54384/72 Heading H2F [Also in Division H3] A television line time base and D.C. supply circuit comprises deflection coils L1 connected in a resonant circuit with a storage and supply capacitor C3 and a parallel capacitor C2, a switching circuit comprising a diode D1 and a transistor ET1 connected across the resonant circuit by a diode D2, the transistor being connected to the supply through the primary winding of a transformer N1 the secondary of which is connected to the storage capacitor via a diode D3, a diode D4 being connected to the primary winding to prevent current flow from a secondary winding to the primary winding through diodes D2 and D3. During the second part of the sweep, a current builds up in the deflection coils from a storage capacitor C3 via transistor VT1. At the end of the sweep the transistor is switched off and resonant reversal of the deflection current takes place whereafter the first part of the next sweep is produced by current flowing from the coil through D1. While the transistor is conducting, current builds up in the primary winding N1 and when it goes off the back e.m.f. causes current to flow from the secondary winding to store the charge lost from C3. The voltage across C3 which may be used for external circuits, may be stabilized by controlling the conduction period of VT1 in dependence upon the voltage. EHT may be derived from a transformer T1 or a winding coupled to N1. Capacitor C3 may be chosen to effect S- shaping. In Fig. 9, not shown, the winding N2 is connected through D3 directly to the storage capacitor and a lower voltage may thus be produced thereacross.