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DC FLUORESCENT LAMP POWER SUPPLY

IP.com Disclosure Number: IPCOM000024906D
Original Publication Date: 1982-Oct-31
Included in the Prior Art Database: 2004-Apr-04
Document File: 2 page(s) / 88K

Publishing Venue

Xerox Disclosure Journal

Abstract

Figures 1 and 2 disclose a power supply circuit, in schematic form, which operates a fluorescent lamp in a pulsed DC mode. In Figure I, a control signal is applied to the circuit, turning on transistor 10 and generating an increasing current level in inductor 12. The control signal is reduced when a predetermined current level in the inductor is achieved. A voltage spike is then generated at the collector of transistor 10 due to the stored energy in the inductor 12 magnetic field. The circuit components are designed to create a spike of about 300 volts, sufficient to initiate operation of fluorescent lamp 14. Current through the lamp returns to the inductor through free-wheeling diode 16. Once lamp 16 is turned on, it can be kept in conduction if transistor 10 is switched on and off rapidly enough. Controlling the ratio of the on/off time of transistor 10 will determine the power delivered to lamp 16, and by monitoring either the current through the transistor or the lamp output, a feedback signal can be generated to control the lamp current or the light output.

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Page 1 of 2

DC FLUORESCENT LAMP POWER SUPPLY Proposed Lawrence J. Mason Classification

U.S. C1. 315/307 Int. C1. G05f 1/00

FIG. 1

16

B CONTROL

FIG, 2

Volume 7 Number 5 September/October 1982 307

[This page contains 2 pictures or other non-text objects]

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DC FLUORESCENT LAMP POWER SUPPLY (Cont'd)

Figures 1 and 2 disclose a power supply circuit, in schematic form, which operates a fluorescent lamp in a pulsed DC mode. In Figure I, a control signal is applied to the circuit, turning on transistor 10 and generating an increasing current level in inductor 12. The control signal is reduced when a predetermined current level in the inductor is achieved. A voltage spike is then generated at the collector of transistor 10 due to the stored energy in the inductor 12 magnetic field. The circuit components are designed to create a spike of about 300 volts, sufficient to initiate operation of fluorescent lamp 14. Current through the lamp returns to the inductor through free-wheeling diode 16. Once lamp 16 is turned on, it can be kept in conduction if transistor 10 is switched on and off rapidly enough. Controlling the ratio of the on/off time of transistor 10 will determine the power delivered to lamp 16, and by monitoring either the current through the transistor or the lamp output, a feedback signal can be generated to control the lamp current or the light output.

One of the advantages of this type of pulsed DC powering is that only a single filament is required at the cathod...