Discharge-lamp lighting circuit
AssigneeKoito Manufacturing Co., Ltd.
InventorsMasayasu Ito, Jun Yabuzaki, Atsushi Toda
Life of this patent
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Abstract
A discharge-lamp lighting circuit has a switching power source portion (a DC—DC converter) for converting DC voltage and a control circuit for controlling output voltage of the converter by ON/OFF-controlling a switching device constituting the converter. The length of the ON-period of the switching device is changed with respect to a predetermined length of the OFF period to control the ratio of the two periods. In this manner, stable lighting of a discharge lamp and improved lighting efficiency are realized by the light circuit because a change in input/output conditions (change in the power source or a state of a load) of the lighting circuit of the discharge lamp cannot easily exert an influence.
Claims16
A discharge-lamp lighting circuit that produces an output voltage, comprising:
- a switching power source portion having a DC—DC converter structure for converting DC voltage, said switching power source portion comprising switching devices;
- and,
- a control circuit for controlling the output voltage by controlling ON/OFF of said switching devices, wherein
- said control circuit controls the ratio of an ON period and an OFF period of said switching device by changing the length of the ON period with respect to a constant length of the OFF period.
Dependencies are inferred from the claim text.