Patent ID: 7564197

Claim:
A discharge tube operation device comprising: a DC-AC conversion circuit which generates an alternating-current voltage by switching a direct-current voltage in accordance with a control signal; a resonance circuit which is supplied with the alternating-current voltage from said DC-AC conversion circuit and resonates with the alternating-current voltage thereby to flow a current through a discharge tube, which is an object of lighting, and light said discharge tube; a discharge tube current detection circuit which detects a current level of the current flowing through said discharge tube and outputs an electric signal level corresponding to the detected current level; an integration circuit which includes difference circuit for obtaining a difference between a reference level and the electric signal, a capacitor connected between an input terminal and output terminal of said difference circuit, and an element for setting a charging/discharging speed of said capacitor, and integrates the electric-signal; a control circuit which controls switching of said DC-AC conversion circuit in accordance with a signal level of an output signal of said integration circuit, thereby to output a control signal for controlling energy to be transmitted from said DC-AC conversion circuit to said resonance circuit; and a time division signal output circuit which generates a time division signal, which is a signal for repeatedly instructing a lit period and an unlit period of said discharge tube for time-division-driving said discharge tube and has a signal level that transmits energy capable of lighting said discharge tube from said DC-AC conversion circuit to said resonance circuit in a period in which lighting is instructed and that transmits energy incapable of lighting said discharge tube from said DC-AC conversion circuit to said resonance circuit ( 20 ) in a period in which non-lighting is instructed, and adds the time division signal to the signal level of the detection signal.