Title:
BALLAST CIRCUIT FOR OPERATING A DISCHARGE LAMP
Document Type and Number:
WIPO Patent Application WO2002021884
Kind Code:
A3
Abstract:
A ballast circuit for a discharge lamp capable of protecting the circuit when the lamp reaches its end of life with a cost effective circuit arrangement. The circuit includes a DC voltage sensing network for sensing a DC voltage which appears as a consequence of the lamp reaching its end of life. Upon the sensed DC voltage exceeding a threshold, a control is made to limit or stop supplying an output power to the lamp for protecting the ballast circuit from an otherwise generating excessive current. The sensing network is composed of a DC sensing capacitor and a resistor which are connected in circuit outside of a resonant circuit responsible for generating a high frequency voltage to operate the lamp. Thus, the DC sensing capacitor can be kept free from the high voltage generated by the resonant circuit and be of less cost for reducing a manufacturing cost.
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Inventors:
NISHIMOTO KAZUHIRO (JP)
HAMAMOTO KATSUNOBU (JP)
MIZUKAWA HIROMITSU (JP)
HAMAMOTO KATSUNOBU (JP)
MIZUKAWA HIROMITSU (JP)
Application Number:
PCT/JP2001/007680
Publication Date:
May 10, 2002
Filing Date:
September 05, 2001
Export Citation:
Assignee:
MATSUSHITA ELECTRIC WORKS LTD (JP)
NISHIMOTO KAZUHIRO (JP)
HAMAMOTO KATSUNOBU (JP)
MIZUKAWA HIROMITSU (JP)
NISHIMOTO KAZUHIRO (JP)
HAMAMOTO KATSUNOBU (JP)
MIZUKAWA HIROMITSU (JP)
International Classes:
H05B41/24; H05B41/285; H05B41/298; H05B41/392; (IPC1-7): H05B41/285; H05B41/298
Domestic Patent References:
| WO1999034647A1 | 1999-07-08 |
Foreign References:
| EP0681414A2 | 1995-11-08 | |||
| US6023132A | 2000-02-08 | |||
| DE3401653A1 | 1984-07-26 |
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