Discharge lamp lighting device and headlight using same

A discharge lamp lighting device comprising:

• a DC/DC converter configured to convert an input voltage input from a DC power supply into a voltage value that is necessary for lighting a discharge lamp by performing switching;
• a DC/AC inverter configured by a bridge circuit in which at least one series circuit of a first switching element disposed on a high potential side and a second switching element disposed on a low potential side is connected between output terminals of the DC/DC converter, and configured to convert a DC output of the DC/DC converter into an AC output and supply the AC output to a load including the discharge lamp;
• a drive unit configured to convert the DC output of the DC/DC converter into an AC output acquired by alternating polarity of the DC output at a predetermined period by alternately turning on the first switching element and the second switching element at the predetermined period at least at a time of stable lighting;
• a measurement unit configured to measure at least one of an output voltage and an output current for the load;
• and
• a control unit configured to, when a measured value acquired by the measurement unit is in an abnormal range, decrease power to be supplied to the discharge lamp to be lower than power to be supplied to the discharge lamp at a normal time,
• wherein the drive unit includes a capacitor that supplies, to a control electrode of the first switching element disposed on the high potential side, electric charge necessary for turning on the first switching element when the second switching element disposed on the low potential side is turned off,
• the capacitor is charged when the second switching element is turned on, and
• when the discharge lamp is started up, the capacitor is started to be charged before the DC/DC converter starts to be operated, and the control unit has a determination period for determining presence/absence of an abnormality based on the measured value acquired by the measurement unit in a state in which the DC/DC converter and the DC/AC inverter are operated after completion of the charging of the capacitor.