Patent ID: 7282866

Claim:
A discharge lamp lighting apparatus for lighting a discharge lamp having two electrodes, comprising: a first drive circuit connectable to one of the two electrodes to supply a first alternating current to the discharge lamp, the first alternating current having a frequency and a first effective value; a second drive circuit connectable to the other of the two electrodes to supply a second alternating current to the discharge lamp, the second alternating current having the frequency and a second effective value, the second alternating current having an opposite phase to the first alternating current; and a control circuit for generating first and second drive pulses to drive the first and second drive circuits, respectively, the first and second drive pulses having a phase difference therebetween; and a detector for detecting the first effective value to generate a first output value, the detector detecting the second effective value to generate a second output value, wherein, the control circuit compares the first output value with the second output value, and adjusts the phase difference so as to increase a smaller one of the first and second output values and decrease a greater one of the first and second output values, thereby matching the first and second effective values.