Circuit arrangement for starting and for operating high-pressure lamps

#This application is closely related to the simultaneously submitted application with the internal file reference 99 P 5529.

#The invention proceeds from a circuit arrangement for starting and for operating high-pressure lamps. Particularly at issue here are high-pressure and extra-high-pressure discharge lamps which are becoming increasingly widespread in all sectors of lighting engineering, because of their good luminous efficiency. Owing to their specific properties, they are mostly difficult to start and operate. This holds, in particular, for sodium high-pressure lamps with a relatively high xenon pressure. Because of their outstanding luminous efficiency, these lamps are particularly well suited for street lighting. In this case, they frequently replace existing systems with a substantially lower efficiency, for example mercury-vapor lamps. In addition, in this formulation of the problem, it is also necessary to solve the problem of power reduction (in conjunction with an identical luminous flux), the result of all this being a saving in energy.

#DE-A 34 26 491 has already disclosed a circuit arrangement for starting and for operating high-pressure lamps, in which a series element is connected downstream of the dc output of the rectifier unit either directly or at most via a series element. The former series element contains an inductive filter in addition to the high-pressure discharge lamp. It is therefore possible to start lamps with a high cold filling pressure only with difficulty.

#The invention is to be explained below in more detail with the aid of a plurality of exemplary embodiments. In the drawing:

#FIG. 1 shows the outline circuit diagram of a circuit arrangement according to the invention, and

#FIGS. 2 to 7 show further exemplary embodiments of a circuit arrangement.

#The basic circuit design is illustrated in FIG. 1. The lamp L to be started and operated therewith is, for example, a sodium high-pressure lamp with a power of 70 W. The circuit arrangement comprises four circuit blocks.

#Firstly, the line voltage (240 V) present between the terminals CE1 and CE2 is filtered by means of the switching circuit NF. This is not mandatory for the functioning of the circuit arrangement according to the invention. The first circuit block can, however, comprise still further switching means such as a phase-gating or phase-cutting circuit (preferably by means of a triac or thyristor) and, possibly, a current-limiting inductor.

#Thereafter, line rectification is performed by means of a Grätz bridge GB, as known per se.