Patent ID: 8154215
Filing Date: 2012-04-10
Classification: H05B,Y02B

Abstract:
1. A discharge-lamp lighting apparatus comprising: a direct-current voltage input terminal through which a direct-current voltage having a first value is supplied; a direct current-direct current converter circuit arranged to convert the direct-current voltage having the first value into a direct-current voltage having a second value and that includes a switching element; an output-voltage detection circuit arranged to detect an output voltage from the direct current-direct current converter circuit; a direct current-alternating current inverter circuit arranged to convert the direct-current voltage output from the direct current-direct current converter circuit into an alternating-current voltage having an arbitrary frequency and that includes a switching element and an LC series circuit; a lamp-current detection circuit arranged to detect a lamp current flowing through a discharge lamp; and a control circuit arranged to control turning on-off of the switching elements of the direct current-direct current converter circuit and the direct current-alternating current inverter circuit in accordance with the value of the output voltage detected by the output-voltage detection circuit and the value of the lamp current detected by the lamp-current detection circuit; wherein the control circuit sweeps a switching frequency in the direct current-alternating current inverter circuit near a frequency having a value provided by dividing a resonant frequency of the LC series circuit by an odd number at startup of the discharge lamp and sets the switching frequency to a frequency near or greater than the frequency after the sweeping after the switching frequency is swept to control an on-off duty ratio of the switching element in the direct current-alternating current inverter circuit and, after the operation at startup of the discharge lamp is repeated once or more times, the control circuit sets the switching frequency to less than the frequency after the sweeping to light the discharge lamp.