Speisespannungsgeraet zum Liefern eines Gleichstromes an eine sich periodisch aendernde Belastung

摘要

1309661 Converting PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd 7 April 1970 [25 April 1969 4 Nov 1969] 16342/70 Heading H2F [Also in Divisions H3 and H4] In TV apparatus, power supply and drive to the line output stage is obtained from a pulseduration modulated switched mode supply operating at line frequency. As shown, a voltage Vi is derived by rectifying the mains at 1 and is arranged to drive a pulsating current into the primary 8 of a transformer 9 under control of a switching transistor 2 pulsed at line frequency. A rectifying diode 7 becomes conductive during the inter-pulse interval. The resulting current charges capacitor 10 so as to provide the supply voltage for the line deflection stage 17. The output from secondary winding 14 is also used as base drive to the line output transistor 16 which supplies deflection coils 18 and EHT winding 20. The collector/base diode of transistor 16 may form the efficiency diode of the line output stage. Components 21 ... 25 are used to expedite the turn-off of transistor 16 at the end of each sweep as described in Specification 1,302,754. The supply to the line output stage is compared with a reference at 12 and used to control a pulse modulator at 5 so as to stabilize the supply voltage Vo. A parabolic field voltage 28 may be introduced for the correction of pincushion distortion. The beam current may be arranged to flow through a voltage-dependent resistor having a quadratic characteristic so that variation of voltage Vo may be proportional to the root of the variation in EHT voltage so that the line deflection remains constant. S-correction may be obtained by reducing the size of capacitor 10. The CRT heater may be supplied from transformer 9.