Starter for a high-pressure gas discharge lamp

Details Starter for a high-pressure gas discharge lamp Starter for a high-pressure gas discharge lamp

1997-07-30

1999-04-06

Wong, Don

Electric lamp and discharge devices: systems

Periodic switch in the supply circuit

Silicon controlled rectifier ignition

315241P, 315290, 315241S, 315291, 315205, 315289, 315 82, 315 77, 354415, H05B 3702, H05B 4132

Patent

active

058923322

DESCRIPTION:

BRIEF SUMMARY
RELATED ART

The invention is based on an ignition apparatus for a high-pressure gas discharge lamp, particularly for use in headlights of motor vehicles, of the type having an ignition transformer whose primary winding can be supplied with a voltage, and whose secondary winding ignites the high-pressure gas discharge lamp with the stepped-up value of the voltage, and wherein a capacitor is provided in parallel to the series connection of the primary winding and a controllable switch or the primary side, the capacitor is charged when the supply voltage is activated, and, when a certain voltage is attained, the capacitor is discharged by the switching on of the controllable switch for releasing the voltage.
A known ignition apparatus of this type, as described in DE 40 17 415 C2, includes an ignition transformer whose primary winding is supplied with a voltage. The secondary winding steps this voltage up to the voltage required to ignite the lamp. On the primary side, a capacitor is disposed in parallel to the series connection of the primary winding and a controllable switch formed by, for example, a thyristor. For ignition, this capacitor is charged to a voltage that is present and effective at that time. When a specific voltage is attained, the controllable switch is switched on and the capacitor is discharged for emitting the ignition pulse.
In this known ignition apparatus, a single capacitor supplies the total ignition energy and the energy required in the critical phase of the transfer of the high-pressure gas discharge lamp from the ignition operation into the burning operation. This capacitor must therefore be able to be charged to a very high voltage level, on the one hand, and, on the other hand, have the necessary capacity. This necessitates a costly and complex component that also has a considerably large space requirement.


SUMMARY AND ADVANTAGES OF THE INVENTION

In contrast, the ignition apparatus for a high-pressured gas discharge lamp according to the invention claim 1 has the advantage of improving the transfer behavior, because energy can be supplied later in the critical range of the transition of the high-pressure gas discharge lamp from the ignition operation to the burning operation. This is advantageously effected in that the total ignition energy need not be made available at the high voltage level due to the graduated capacitor discharge. This permits an economical utilization of space in the use of less expensive and smaller components. This leads to savings in space and costs.
In accordance with the invention, this is essentially achieved in that a second capacitor that is connected in series with a diode is provided in parallel to the capacitor, that this second capacitor can be charged to a lower voltage than the first capacitor, and that this second capacitor is then discharged by way of the correspondingly-polarized diode, and the switched-on, controllable switch is discharged into the primary winding if its voltage has become greater than that of the first capacitor during its discharge.
In a useful embodiment of the invention, the capacity of the second capacitor is approximately 2 to 5 times the capacity of the first capacitor.
In an advantageous modification of the invention, the voltage that charges the first capacitor is greater, preferably about two to five times greater, than the voltage that charges the second capacitor.
The invention can have two particularly advantageous embodiments. In one embodiment, the first capacitor can be charged by a separately-supplied voltage. This can also be referred to as the 3-conductor concept. In the other embodiment, which is to be referred to as the 2-conductor concept, the second capacitor can be charged by an internally-obtained voltage that is preferably smaller, by the voltage difference of a Zener diode, than the voltage with which the first capacitor can be charged.
In a further advantageous embodiment of the invention, it is provided that resistors are connected in series with the two capacitors, which resistors aid in th

REFERENCES:
patent: 3810212 (1974-05-01), Biber
patent: 4082985 (1978-04-01), Bolhuis
patent: 5036256 (1991-07-01), Garrison et al.
patent: 5084655 (1992-01-01), Van Zanten
patent: 5264895 (1993-11-01), Takahashi et al.
patent: 5426346 (1995-06-01), Allison

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