Patent-Treuhand-Gesellschaft Fuer Elektrische Gluehlampen Mbh

Patent-Treuhand-Gesellschaft F. Elektrische Gluehlampen Mbh

Ludwig Reiser

Klaus Fischer

Harald Schmitt

Walter Hirschmann

Ulrich Roll

Werner Bernhard

Peter Haeussinger

In an operating circuit for a low-pressure discharge lamp, the lamp current is controlled depending on the lamp temperature or the luminous flux.

Starting circuit for low-pressure discharge lamp

A circuit arrangement for operating a load, in which in normal operation control energy for activating the switching element or switching elements (T.sub.a, T.sub.b) is obtained from the energy content of the freewheeling current anti-parallel relative to this switching element, and the ON duration is determined by the time constants of control energy storage elements which are assigned to the switching elements, or by the storage time of bipolar transistors.

Switching control of an operating circuit

The invention relates to a circuit arrangement for operating a lamp (EL), particular a low-pressure discharge lamp, with a load circuit which has at least one inductor (L2) and at least one capacitor (C7, C8, C9), and with an invertor which may be configured as a half-bridge arrangement with two switching elements (T1, T2), and with a drive circuit (AS) for driving the switching elements (T1, T2). The invention provides that the drive circuit (AS) has at least one LC parallel tuned circuit (L3C3, L4C4). The circuit arrangement according to the invention can be produced without separate cost-intensive wound parts.

Circuit arrangement having LC parallel tuned drive circuitry

To eliminate the necessity for a saturated or air gap inductance to provide feedback circuit for a self-exciting oscillator including two active electronic switches (T1, T2) , for example MOSFETs, an auxiliary winding (HW1, HW2, . . . HW11) is inductively coupled to the resonance inductance (L2) present in the circuit for the discharge lamp (LP) anyway; and a pulse shaping - phase shifting network (R3, C3; R4, C4 . . . ) , devoid of inherent resonance, coupling the auxiliary winding to the active switching elements. The pulse shaping - phase shifting network is formed of a one or multiple-stage RC low-pass circuit, connected serially between the auxiliary winding and the control input, for example the gate, of the active switching element. The RC network can be constructed with variable elements, for example including PTC resistors, a varistor or the like, and may include a current source, protective circuits to protect against voltage peaks including Zener diodes. The low-pass characteristics of the pulse shaping - phase shifting network permits switching of the active semiconductor switches after the maximum current flow.

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Gersthofen, Germany

Ludwig Reiser