| 摘要 |
A single comparison circuit detects load open circuit abnormality and load short circuit abnormality of a discharge lamp operating at a high-frequency driving voltage, with a small number of circuit elements. A discharge lamp drive control circuit includes an inverter control circuit, a positive change voltage detecting circuit which detects a positive change of voltage occurring in the secondary coil of a driving transformer, a negative change voltage detecting circuit which detects a negative change of voltage occurring in the secondary coil of the driving transformer, and the comparison circuit connected to the inverter control circuit. The outputs from the positive and negative change voltage detecting circuits are added to generate an added output, and the added output is supplied to the comparison circuit and compared with a reference voltage. When an abnormal operation occurs, the comparison circuit supplies an abnormal operation control signal to the inverter control circuit.
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