Discharge lamp lighting device with a delayed-output oscillation circuit
AssigneeNew Nippon Electric Co., Ltd.
InventorIsao Kaneda
Life of this patent
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Abstract
A high frequency and high voltage generating circuit for a discharge lamp lighting device controls its initial output at the starting time of a discharge lamp to prevent applying a high voltage to the discharge lamp in the "cold cathode" state. The circuit comprises in combination an oscillation circuit having an oscillation capacitor, a non-linear inductor and a thyristor, and an initial output limiter for delaying the output supply until the lamp filament is sufficiently preheated for preventing sputtering and for extending the operational life of the discharge lamp. The output control is formed as a bias circuit for the nonlinear inductor and includes a thermistor with a negative or a positive temperature coefficient.
Claims11
A discharge lamp lighting device, comprising an a.c. power source, a current limiting means, discharge lamp means connected in series with said power source through said current limiting means, high voltage generating means operatively connected across said discharge lamp means, wherein said discharge lamp means comprise respective filament means, and wherein said high voltage generating means comprise an oscillation circuit (15) including a first series circuit of a nonlinear inductor (8) and a thyristor (9), and a second series circuit including an oscillation capacitor (7), a thermistor (12) having a negative temperature coefficient, and a biasing coil means (18), said second series circuit being connected in parallel to said first series circuit, and means operatively connecting said first oscillation circuit (15) to said filament means of said discharge lamp means for generating a high frequency high voltage, whereby said thermistor (12) operates for restricting the high voltage output at the beginning of operation for a given length of time, whereby the operational life of said discharge lamp means is improved.
A discharge lamp lighting device, comprising an a.c. power source, current limiting means, discharge lamp means connected in series with said a.c. power source through said current limiting means, high voltage generating means operatively connected across said discharge lamp means, wherein said high voltage generating means comprise an oscillation circuit including a parallel connection of an oscillation capacitor and a series circuit of a nonlinear inductor (8) and a thyristor, wherein said discharge lamp means comprises a filament operatively connected to said high voltage generating means for preheating by the output of said high voltage generating means, and output control means comprising negative and positive bias circuit means operatively connected to said nonlinear inductor for changing the magnetic flux density amplitude of said nonlinear inductor in such a manner that said output of said high voltage generating means is restricted to be below the lamp starting voltage when the discharge lamp means is in the cold cathode state and above the lamp starting voltage when the discharge lamp means is in the hot cathode state.
A discharge lamp lighting device, comprising an a.c. power source, current limiting means, discharge lamp means connected in series with said power source through said current limiting means, high voltage generating means operatively connected across said discharge lamp means, output control means operatively connected to said high voltage generating means for restricting the high voltage output at the beginning of operation for a given length of time, wherein said discharge lamp means is a hot cathode type discharge lamp having a filament, and wherein said high voltage generating means includes a first oscillation capacitor (7), a series circuit of a thyristor (9) and a nonlinear inductor (8), a second intermittent oscillation capacitor (11) connected in series with said series circuit which in turn is connected in parallel with said first oscillation capacitor (7), and wherein said control means comprise means connected for deactivating said second intermittent oscillation capacitor at the starting time of said discharge lamp, said deactivating means including a positive temperature coefficient thermistor (23) connected in parallel to said intermittent oscillation capacitor whereby the operational life of said discharge lamp means is is improved.
Dependencies are inferred from the claim text.