Gas discharge lamp switch-on circuit e.g. for motor vehicle

摘要

A circuit to drive a gas discharge lamp uses a DC supply with a converter to produce a square waveform voltage at the lamp terminals. There is an abnormality detector to monitor this voltage with a protective circuit to interrupt the lamp supply should an abnormality occur. The detector acts as a short-circuit detector, monitoring for a change in the direct voltage should the converter output voltage short to earth. The detector compares a first voltage tapped off from the direct voltage entering the converter with a second voltage obtained by smoothing the first voltage and which is therefore normally the same value, and a binary signal is formed from the difference.