GB1057563A - Improvements relating to apparatus for operating electric discharge devices - Google Patents

Abstract

1,057,563. Supply systems for discharge lamps. GENERAL ELECTRIC CO. July 18, 1963 [July 23, 1962], No. 28513/63. Heading H2H. [Also in Divisions G3 and H3] The current taken by a discharge lamp 12 from an A.C. supply 19, 20 is maintained constant by a variable impedance network comprising rectifier diodes D 1 . . D 4 , resistors R 1 , R 2 , Zener diode Z 1 and a transistor Q 1 , the network providing an instantaneously varying impedance during a part of each half-cycle of the supply to produce a current waveform which is approximately rectangular, Fig. 2 (not shown). Resistor R 2 is chosen so that the transistor Q 1 is driven to a low impedance state in the initial and final part of each half-cycle, the transistor impedance progressively increasing and decreasing during the intervening period to match the voltages across members R 1 , Z 1 , Fig. 3 (not shown). The network may be modified, Fig. 5 (not shown), by using two parallel-connected transistors, this combination including a resistor in series with each emitter and being connected across the rectifier bridge through a resistor in parallel with a switch to enable the lamp to be operated at either a normal or a lower level of illumination. Further levels may be obtained by use of a variable resistor. A starting circuit including a tuned . network and a momentary contact switch is connected across the lamp. In another modification using a transistor of lower voltage rating, the variable impedance network of Fig. 1 is connected between a supply terminal and a tapping of an auto transformer whose winding is in series with the lamp, Fig. 6 (net shown). This latter arrangement may be modified by using an ordinary transformer whose primary is in series with the lamp and whose secondary supplies the variable impedance network which, in this case, has a separate variable D.C. supply for the transistor base to progressively dim the lamp, Fig. 7 (not shown). Fig. 8 shows an arrangement in which a lamp 84 is connected through transformers T 7 , T 8 to an A.C. supply 82, 83, and the secondary windings S 11 , 8 12 of transformer T 8 bias one or other of transistors Q 7 , Q 8 into conduction according to the supply polarity, the variation in transistor impedance causing a " bucking " voltage to be applied to the lamp circuit via bridge 87 and windings P 9 , P 10 and S 9 , which voltage varies instantaneously to maintain the lamp current constant. In the circuit of Fig. 9 the lamp 99 is supplied from the source 102, 103 via a transformer T 9 , bridge 109 and transistors Q 9 , Q 10 which are controlled by a signal applied from terminals 106, 107 through a transformer T 10 , the value of a resistor R 10 determining the period during each half-cycle for which the voltage of winding 8 13 of transformer T 9 is varied by alteration of the impedance of transistor Q 9 or Q 10 to maintain the lamp current constant. The signal at terminals 106, 107 may be obtained from the winding S 13 (thus achieving unity lamp power factor), or any desired waveform of lamp current may be obtained by applying a signal having this waveform to the terminals 106, 107. 1,057,581. Switches held set and freed mechanically. MICRO-ELECTRIC A.G. July 31, 1963 [Aug. 17, 1962], No. 30427/63. Heading H2B. A switch of the type wherein a con tact arm 16 pivoted on an operating arm 10 is movable with a snap action between fixed contacts 6 and 8 by a tension spring 22 when a cam 11 or other operating member acts on follower 12 is provided with adjustment screw 19 for setting the precise point at which change-over occurs with respect to the cam 11. A plurality of switches may be mounted closely adjacent on a printed-circuit board 23 by means of terminal screws such as 24, or the terminals 1, 2 and 3 may be formed as lugs holding the switch parts on base 4 and connecting them into the planted-circuit board 23. The screw 19 is formed with an enlarged head 21 to accept the end of spring 22 and this head 21 is larger than the slot 13 in operating arm 10 so that it acts as a stop for the arm when the switch is not mounted. Additional followers such as 25 may be provided on arm 10 for operation by other cams, such as 26. Instead of adjusting the anchorage of spring 22, the pivot point 9 may be adjustable by means of a screw similar to screw 19.