Electric lamp and discharge devices: systems – Surge generator or inductance in the supply circuit
Patent
1990-06-15
1991-10-15
Laroche, Eugene R.
Electric lamp and discharge devices: systems
Surge generator or inductance in the supply circuit
315244, 315290, H05B 3700
Patent
active
050577522
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a circuit arrangement for igniting and operating gas-discharge lamps, particularly metal-vapor lamps.
An almost endless variety of circuits for ballasts of gas-discharge lamps are known for a long time. Every one of these circuits employs for ignition the glow starter arranged in parallel with the lamp and, for current limitation during operation, the choke which is connected in series with the gas-discharge lamp. In these arrangements with glow starter and choke, no flicker-free instantaneous start is effected and, furthermore, lamp burning is not stable. The influence of mains voltage fluctuations on the lighting current of the lamp is likewise not inconsiderable. Since the glow starter comprises a mechanical switch which is a thermostatic bimetal switch, the risk of failure of the latter is relatively high.
Electronic ballasts have been developed to avoid these disadvantages. A circuit of this type is described in German Patent No. 31 52 342. Such circuit consists of a current source, an ignition circuit, a control element and an auxiliary voltage source. However, such a ballast requires a great deal of components and is therefore also quite susceptible to failure. Furthermore, it is conceived particularly for fluorescent lamps which require a lower ignition voltage than metal-vapor lamps. This ballast is thus entirely unsuitable for metal-vapor lamps.
The object of the invention is thus to provide an electronic ballast particularly for metal-vapor lamps requiring a high ignition voltage in the range of 2 kV to 5 kV.
The object is achieved by the invention. This is characterized in that a buffer capacitor, preferably an electrolytic capacitor, is connected to a rectified voltage, preferably the mains voltage rectified by means of a bridge rectifier, a choke-capacitor series circuit being in parallel with the buffer capacitor, whereby an electronic switch, preferably a transistor or thyristor, and a fast recovery diode forming part of the electronic switch are connected in parallel with the capacitor, and that the gas-discharge lamp provided with a parallel capacitor is connected by means of a further choke-capacitor series circuit to the parallel circuit consisting of capacitor, electronic switch and fast recovery diode. In this new type of ballast, the ignition circuit and the supply circuit are combined and can be considered as one unit. Therefore, a separate ignition circuit is also not required. Furthermore, the circuit operates independently of the supply voltage. Moreover, the gas-discharge lamp is always supplied with constant power. This even then when the lamp burning voltage changes, such burning voltage increasing with the age of the lamp.
An embodiment of the invention is characterized in that a further choke is provided in series with the parallel circuit consisting of capacitor, electronic switch and fast recovery diode. In this manner, the structural size of the two already existing chokes can be kept small.
It is advantageous that the choke of the further choke-capacitor series circuit is arranged in series with the parallel circuit consisting of capacitor, electronic switch and fast recovery diode. By virtue of this arrangement, the ballast according to the invention is excellently suitable for gas-discharge lamps with an ignition voltage less than 2 kV.
The invention will now be described in still greater detail in conjunction with the drawing.
FIG. 1 shows the basic circuit of the electronic ballast,
FIG. 2 shows the augmented circuit having three chokes, and
FIG. 3 shows the circuit for lamps with an ignition voltage of less than 2 kV.
In all three Figures there is a direct current voltage applied at the terminals 1, 2, which is normally the mains voltage rectified by means of a bridge rectifier. At this direct current voltage there is placed a buffer or smoothing capacitor C4.
This is generally an electrolytic capacitor having a high capacitance value. In the circuit depicted in FIG. 1, a choke-capacitor series circuit L1, C1 is connected in parallel with th
REFERENCES:
patent: 4461982 (1984-07-01), Fahnrich
patent: 4594531 (1986-06-01), Ganser et al.
patent: 4683404 (1987-07-01), Hitchcock
patent: 4958107 (1990-09-01), Mattas
Bitsche Otmar
Grabner Wolfgang
LaRoche Eugene R.
Stylux-Gesellschaft fur Lichtelektronik m.b.H.
Zarabian A.
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