Dual incandescent lamp fitting - has two diodes in antiparallel to supply lamps alternately and produce third more light than direct connection

摘要

The circuit is used to supply two conventional filament lamps (f1, f2) from the a.c. mains (v). One terminal of each lamp is connected to the neutral supply, while the other terminals are fed via series diodes (d1, d2) and a parallel CR circuit (c1, r1) from the live supply. The series diodes conduct in opposite directions, so that current is only flowing in one lamp at any time. The capacitor value depends on the resistance of the lamps, e.g. a 9 microfarad capacitor is suitable for lamps with a cold resistance of 30 ohms. The resistance (r1) is only a discharge pre-caution for safety purposes, so it can be a high value compared to the lamp resistance. The lamps are mounted as close to each other as possible in a single casing to reduce the flickering effect. The light output from such a circuit is some 33% higher than from identical lamps fed directly from the mains.