Electric lamp and discharge devices: systems – Surge generator or inductance in the supply circuit – Circuit interrupter in the inductance circuit
Reexamination Certificate
1999-09-07
2001-03-20
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Surge generator or inductance in the supply circuit
Circuit interrupter in the inductance circuit
C315S2090SC, C315S219000, C315S276000, C315SDIG005, C315SDIG007
Reexamination Certificate
active
06204611
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a circuit arrangement for igniting a lamp, comprising input terminals for connection to a power supply source,
a first capacitive element,
a first circuit component coupled to the first capacitive element and to the input terminals for generating a charging current from a power supply voltage supplied by the power supply source, said charging current being used for charging the first capacitive element
a transformer having a primary winding and a secondary winding,
a first branch shunting the first capacitive element and comprising a series arrangement of the primary winding and a switching element,
output terminals coupled to the secondary winding for connecting a load circuit comprising a lamp.
The invention also relates to an illumination unit.
A circuit arrangement as described in the opening paragraph is known from U.S. Pat. No. 4,342,948. The known circuit arrangement is very suitable for generating a voltage having a relatively high amplitude. In practice, it is often found for such a circuit arrangement that the voltage generated by the circuit arrangement has the shape of an attenuated AC voltage because the leakage inductance of the transformer resonates with the first capacitive element. The frequency of the attenuated AC voltage is often relatively high. Since the transport of charge carriers in the ignited lamp is relatively slow, the relatively high frequency of the attenuated AC voltage has the result that the maximum amplitude of the ignition voltage of the lamp is higher than the maximum amplitude of the attenuated AC voltage across the second capacitive element. The ignition behavior of the lamp is thereby influenced positively. A drawback of the relatively high frequency of the attenuated AC voltage is, however, that the ignition voltage is present across the lamp only for a relatively short time. The frequency of the attenuated AC voltage can be modified by modifying the dimensioning of the circuit arrangement. However, the latter would result in a relatively expensive and voluminous circuit arrangement. In practice, the relatively high frequency of the attenuated AC voltage has the result that some lamps do not ignite or only ignite after a relatively large number of attempts.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a circuit arrangement for igniting a lamp, with which the lamp can be ignited rapidly and effectively.
According to the invention, a circuit arrangement as described in the opening paragraph is therefore characterized in that the secondary winding is shunted by a second branch comprising a series arrangement of a unidirectional element and a second capacitive element.
During operation of the circuit arrangement, the second capacitive element is charged to a voltage which is equal to the maximum amplitude of the attenuated AC voltage which would be present across the second capacitive element in the absence of the unidirectional element. However, due to the presence of the unidirectional element, the voltage across the second capacitive element in a circuit arrangement according to the invention is a DC voltage instead of an attenuated AC voltage. In theory, an infinitely long voltage pulse is present across the second capacitive element. The DC voltage across the second capacitive element also constitutes the ignition voltage across the lamp. In practice, the voltage across the second capacitive element decreases because it is discharged by means of the leakage current of the unidirectional element and the leakage current of the second capacitive element. Although the maximum amplitude of the ignition voltage across the lamp which is generated by a circuit arrangement according to the invention is relatively low, the period of time during which this ignition voltage is present across the lamp is relatively long. It has been found that lamps of various types and power can be ignited rapidly and effectively by means of the circuit arrangement according to the invention.
The switching element may be constituted by a breakdown element which becomes conducting at a given value of the voltage across the first capacitive element. However, it has proved to be advantageous to make use of a switching element provided with a control electrode and to provide the circuit arrangement with a control circuit coupled to the control electrode for rendering the switching element conducting and non-conducting. A very reliable operation of the circuit arrangement can be realized in this way. More particularly, this has been found for embodiments of a circuit arrangement according to the invention in which the switching element is a thyristor. It has also been found that a good control of the conductivity state of the switching element is possible when the control circuit comprises a diac and/or a zener diode.
The unidirectional element preferably comprises a diode.
In a preferred embodiment of a circuit arrangement according to the invention, the output terminals are connected by means of a third branch comprising a series arrangement of the second capacitive element and the input terminals. The ignition voltage across the lamp is thus formed by the sum of the power supply voltage and the voltage across the second capacitive element.
A circuit arrangement according to the invention is very suitable for igniting a discharge lamp having a filling which mainly consists of neon. A discharge lamp having a filling which mainly consists of neon is herein understood to mean a discharge lamp having a filling comprising neon in such a way that red light is generated in the plasma of the lamp during stationary lamp operation, with the color point in the C.I.E. chromaticity diagram being in the range bounded by the lines y=0.300, y=0.350, y=−x+1 and y=−x+0.99. Such a lamp is very suitable for use in an illumination unit used, for example, as a signal light in a motorcar. Such an illumination unit is preferably provided with a housing having a reflecting surface and with means for positioning the lamp in the housing. If the illumination unit is not used as a brake light but, for example, as a blinker, the wall of the lamp is preferably provided with a luminescent coating.
REFERENCES:
patent: 3818253 (1974-06-01), Chafer et al.
patent: 4342948 (1982-08-01), Samuels
patent: 5621278 (1997-04-01), Chambers
patent: 5783908 (1998-07-01), Toda et al.
patent: 5821681 (1998-10-01), Wynn
patent: 5962985 (1999-10-01), Buij et al.
patent: 6008591 (1999-12-01), Huber et al.
Bouwman Lambertus J. M.
Van Den Berg Arjan
Franzblau Bernard
Tran Thuy Vinh
U.S. Philips Corporation
Wong Don
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