Browse Prior Art Database

DC Operation of a Switchable Fluorescent Lamp

IP.com Disclosure Number: IPCOM000082832D
Original Publication Date: 1975-Feb-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 35K

Publishing Venue

IBM

Related People

Ernst, LM: AUTHOR [+2]

Abstract

A fluorescent lamp is rapidly switched from a low-light output state to a high-light output state by a DC control circuit.

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DC Operation of a Switchable Fluorescent Lamp

A fluorescent lamp is rapidly switched from a low-light output state to a high- light output state by a DC control circuit.

Fluorescent lamp 11 is switched from a low-light output state to a high-light output state by transistor 13 which operates as a switch which is off or saturated, depending on the presence or absence of a high frequency pulse train, V2, at the input to base drive pulse transformer 15. The alternating voltage, V1, when rectified and filtered by capacitor 17, provides a voltage source sufficient to start lamp 11 in the presence of an appropriate ground plane potential.

When transistor 13 is saturated due to the presence of V2, the lamp operating point is determined by the voltage on capacitor 17, the saturation voltage of transistor 13, the lamp current-voltage characteristics, and the resistor
19. When transistor 13 is off, lamp current is determined as above, except that the series resistance is the sum of resistors 19 and 21.

The values of resistors 19 and 21 are chosen to provide a large ratio between lamp light output in the low and high-output states and to provide sufficient arc current in the low-light output condition, to assure that the arc is not extinguished or unstable over the required range of lamp environments. Capacitor 17 is chosen sufficiently large to provide desirable arc current and light output.

Relay 23 is used to reverse the polarity of the voltage across lamp 11 each time t...