ES354664A1 - Battery-operated Television Receiver - Google Patents

Abstract

A television receiver adapted for supply from a battery includes switching means which in a normal position ensures a normal power supply to the receiver circuits whilst in an economy position ensures a greatly reduced power supply from the battery to at least some of the circuits of the receiver, only a part of the display tube's screen being scanned in the economy position, the filament supply for the display tube being kept substantially constant when the switching means is in either the normal or economy position. In a first embodiment, Fig. 1, the battery is divided into two groups of cells la and 1b which are connected in series in the normal position of ganged switching means S 1 , S 2 and S 3 (as shown) and in parallel in the economy position. The filament 9 of tube 10 is connected between terminals 2 and 3 of the battery and thus the filament voltage is independent of the switching means. H.F. and I.F. circuits 12, the video and deflection circuits 13 and the sound circuits 14 are connected as shown. With this arrangement the dimensions of the picture both in the horizontal direction and in the vertical direction decrease to 0À7 of the value of the normal position. In a second embodiment, Fig. 2, which is adapted to prevent the sound reproduction intensity decreasing in the economy position, and arranged to operate with a picture tube having a directly heated cathode 91 (filament and cathode constructed as a single wire), the two groups 1a and 1b are always connected in series. In this embodiment the sound circuits 14, the H.F. and I.F. circuits 12 and the video circuits 16 always receive the full supply voltage E. By means of switch S 1 half voltage É may be supplied to the vertical deflection stage 20 and to the horizontal deflection circuit comprising synchronization pulse oscillator 21 and line output stage 22. In line output stage 22 ganged switch S 2 is arranged to make connections to two different taps 33 and 34 on transformer 25. The transformer 29 has two secondary windings, one for the supply of the directly heated cathode 91 of tube 10, and one for the filament supply of diode 28. This latter secondary winding is not required if diode 28 comprises a selenium rectifier. By switching between the two taps 34 and 33, the filament voltage remains constant when the supply voltage is reduced from E to É. Additional power saving is achieved by incorporating a control circuit operating according to the chopper principle in the power supply circuit, Fig. 3 (not shown), a control switching signal for the chopper being supplied by an oscillator. When the switching means is in the economy position, the duration of the switching signal which blocks the chopper is extended relative to the duration during which the chopper is released compared with the switching signal which is supplied by the oscillator in the normal position of the switching means. In a further embodiment, Fig. 4 (not shown), the decrease of consumed power takes place indirectly by switching the switching means, the decrease being exclusively for the line output stage 22 and the vertical deflection circuit 20.