Circuit arrangement for ignition and operation of a high pressure gas discharge lamp for motor vehicles

Claim 1

In a circuit arrangement for ignition and operation of a high pressure gas discharge lamp for motor vehicles of a type including: a) a DC/AC converter; b) a resonance ignition device coupled between the DC/AC converter and the high pressure gas discharge lamp; c) a power regulating device including: 1) a current measuring device in series with the high pressure gas discharge lamp, 2) a voltage measuring device in parallel with the high pressure gas discharge lamp, 3) a multiplier having inputs coupled to the voltage measuring device and the current measuring device and having an output coupled to the DC/AC converter; d) a phase control loop including: 1) a phase comparator, 2) a voltage controlled oscillator coupled to an output of the phase comparator which controls the DC/AC converter, 3) wherein a first input of the phase comparator is coupled to the voltage measuring device, and 4) a second input of the phase comparator is coupled to a connection between the voltage controlled oscillator and the resonance ignition device; the improvement wherein is further included: e) a desired power value determining device, f) an integrating comparator whose first input is coupled to the desired power value determining device and having a second input coupled to the output of the multiplier, g) a switching device which couples either the phase comparator or the integrating comparator with the voltage control oscillator, and h) a status recognition device coupled to the current measuring device for controlling the switching device in such a manner that when the high pressure gas discharge lamp is unignited the voltage controlled oscillator is coupled with the phase comparator and when the high pressure gas discharge lamp is ignited the voltage controlled oscillator is coupled to the integrating comparator.