Electric lamp and discharge devices: systems – Periodic switch in the supply circuit – Silicon controlled rectifier ignition
Reexamination Certificate
2000-01-31
2001-07-10
Philogene, Haissa (Department: 2821)
Electric lamp and discharge devices: systems
Periodic switch in the supply circuit
Silicon controlled rectifier ignition
C315S291000, C315S247000, C315S244000, C315SDIG007
Reexamination Certificate
active
06259213
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a circuit arrangement for operating at least one low-pressure discharge lamp.
PRIOR ART
A circuit arrangement of this type is disclosed for example in the European Patent Specification EP 0 253 224 B1. This patent specification describes a circuit arrangement for the high-frequency operation of low-pressure discharge lamps. The circuit arrangement has a mains voltage rectifier, an inverter, a load circuit designed as a series resonant circuit, and a harmonic filter which is provided for the purpose of reducing the mains current harmonic content. The harmonic filter has a series circuit of two diodes which are connected in the forward direction to the mains voltage rectifier, a capacitor which connects the centre tap between the diodes to the voltage output of the inverter, and a further capacitor which connects the centre tap between the diodes to a tap in the series resonant circuit. In addition, the harmonic filter has two further diodes, which are connected in parallel with the two diodes of the harmonic filter and whose centre tap is connected to the voltage output of the inverter.
The European Patent Application EP 0 679 046 A1 describes a circuit arrangement for operating low-pressure discharge lamps with comparatively high running voltages. This circuit arrangement has a high-frequency rectifier bridge which interrupts the charging of the smoothing capacitor, which feeds the inverter, with the switching rhythm of the inverter and as a result, in cooperation with a storage inductor connected upstream of the high-frequency rectifier bridge and with a capacitor arranged at the output of the mains voltage rectifier, in interaction with a back-up capacitor and a negative-feedback capacitor, permits virtually sinusoidal mains current drawing with a mains power factor of >0.98.
SUMMARY OF THE INVENTION
The object of the invention is to provide a circuit arrangement for operating at least one low-pressure discharge lamp which has a simplified harmonic filter with a smaller number of electrical components.
This object is achieved according to the invention by means of the characterizing features of Patent Claim
1
. Particularly advantageous embodiments of the invention are described in the subclaims.
The circuit arrangement according to the invention has a mains voltage rectifier, a capacitor connected in parallel with the DC voltage output of the mains voltage rectifier, an inverter with a load circuit connected downstream and designed as a series resonant circuit, a smoothing capacitor connected in parallel with the DC voltage input of the inverter, a harmonic filter having at least one diode and one capacitor. According to the invention, a first terminal of the at least one capacitor of the harmonic filter is connected to the resonance capacitor of the series resonant circuit, to a first electrode of the at least one diode of the harmonic filter and to the DC voltage output of the mains voltage rectifier. In addition, the second terminal of the at least one capacitor of the harmonic filter is connected to the voltage output of the inverter and the second electrode of the at least one diode of the harmonic filter is connected to the smoothing capacitor.
In this way, a circuit arrangement is provided which has a harmonic filter which is simplified and more cost-effective compared with the prior art and comprises a reduced number of electrical components. The capacitor connected in parallel with the DC voltage output of the mains voltage rectifier is advantageously dimensioned in such a way that its capacitance is at least 0.33 times the capacitance of the resonance capacitor. This advantageous dimensioning of the capacitances of the abovementioned capacitors means that even in the event that the voltage drop across the at least one low-pressure discharge lamp exceeds the voltage drop across the smoothing capacitor, virtually sinusoidal mains current drawing and a correspondingly low harmonic content are still ensured. In order to avoid undesirably high charging currents for the capacitors and thus a high loading on the electrical components, the capacitance of the capacitor connected in parallel with the DC voltage output of the mains voltage rectifier is advantageously at most as large as the capacitance of the resonance capacitor.
REFERENCES:
patent: 4808887 (1989-02-01), Fahnrich et al.
patent: 4959591 (1990-09-01), Hirschmann
patent: 5521467 (1996-05-01), Statnic et al.
patent: 5583399 (1996-12-01), Rudolph
Bessone Carlo S.
Philogene Haissa
Ratent-Treuhand-Gesellschaft fuer elektrische Gluehlampen mbH
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