GB1167920A - Control Arrangements for the Power Stabilisation of Metal Vapour Discharge Lamps. - Google Patents

Abstract

1,167,920. Supply systems for gas-discharge lamps. NOVELECTRIC A.G. 27 Oct., 1967 [27 Oct., 1966], No. 48983/67. Heading H2H. [Also in Division G3] In a lamp control circuit the power consumption of the lamp is controlled in dependence upon a signal which is generated as a function of the sum of lamp voltage and lamp current rather than as the product thereof. As shown, a high pressure discharge lamp 10 is supplied from an AC. input O, P by way of a choke D, a resistor R and back-to-back thyristors 12. A first signal, representative of lamp current and derived from resistor R, and a second signal, representative of the voltage across the lamp 10, are respectively applied to the primary windings of transformers T1, T2 the secondary windings of which are series connected to produce a resultant signal corresponding to the sum of the first and second signals. This resultant signal is compared in a controller 14 with a reference signal derived from a source 16, and the thyristors 12 are controlled by the output from controller 14 so that the power consumption of the lamp is maintained approximately constant. The Specification states that the use of such a resultant signal gives a sufficiently accurate control and yet allows the circuitry to be much simpler than that required to produce a true power-representarive signal, i.e. one derived by multiplying lamp current by lamp voltage. Thyratrons or a triac may replace the thyristors 12. In another embodiment (Fig. 2, not shown) the choke D and the lamp 10 are arranged in a bridge circuit with two resistors, and the required resultant signal for application to rhe conrroller 14 is derived from a transformer connected across one diagonal of the bridge.