Lighting circuit utilizing DC power for a discharge lamp utilizing AC power
AssigneeKoito Manufacturing Co., Ltd.
InventorsGoichi Oda, Atsushi Toda, Masayasu Yamashita
Life of this patent
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Abstract
A lighting circuit converts the output voltage of a DC booster circuit to an AC voltage which is in turn supplied to a discharge lamp connected between AC output terminals. The lighting circuit comprises a short-circuit detector for detecting a change of a DC voltage from the DC booster circuit to a square-wave voltage when short-circuiting between one of the AC output terminals and ground occurs, and sends a detection signal via a hold circuit to a power cutoff relay circuit. As a result, a relay contact in the power cutoff relay circuit is opened to inhibit the operation of the lighting circuit.
Claims19
A lighting circuit for a discharge lamp comprising:
- a DC power supply circuit for boosting and/or decreasing a DC voltage;
- a DC-AC converter for converting an output voltage of said DC power supply circuit into a square-wave AC voltage and supplying said AC voltage to a discharge lamp;
- an abnormality detector for monitoring an output voltage of a DC booster circuit in said DC power supply circuit and an output voltage of said DC-AC converter to thereby detect an abnormality of said lighting circuit;
- and
- a protection circuit for inhibiting an operation of said lighting circuit or cutting off power supply to said discharge lamp when an abnormality is detected by said abnormality detector.
A lighting circuit for a discharge lamp comprising:
- a DC power supply circuit for boosting and/or decreasing a DC voltage;
- a DC-AC converter for converting an output voltage of said DC power supply circuit into a square-wave AC voltage and supplying said AC voltage to a discharge lamp;
- an abnormality detector for monitoring an output voltage of a DC booster circuit in said DC power supply circuit to thereby detect an abnormality of said lighting circuit, said abnormality detector including short-circuit detecting means for detecting a change of a DC voltage from said DC booster circuit to a square-wave voltage when short-circuiting between an AC output terminal and ground occurs;
- and
- a protection circuit for inhibiting an operation of said lighting circuit or cutting off power supply to said discharge lamp when short-circuiting between said AC output terminal and ground is detected by said short-circuit detecting means.
Dependencies are inferred from the claim text.