<p>A discharge lamp ballast includes a power converter and a control circuit. The power converter includes: a converter that includes a switching element and converts voltage from the power source into DC voltage; and an inverter that includes switching elements and inverts the DC voltage from the converter into square wave voltage. In case of high power control, the control circuit controls the on/off period of the switching element of the converter so as to increase a lamp current provided by component of at least a half-period of the square wave voltage while the number of half-period pulses of the square wave voltage reaches a specified number of times.</p>
