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Browse Prior Art Database

Current Regulator for Fluorescent Lamp Control

IP.com Disclosure Number: IPCOM000088794D
Original Publication Date: 1977-Aug-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 2 page(s) / 53K

Publishing Venue

IBM

Related People

Chacon, CC: AUTHOR [+2]

Abstract

This circuit provides rapid turn-on of a fluorescent lamp by controlling current such that in the OFF state the lamp current is reduced to a low level (i(L) Approximately = 1 ma) but not completely extinguished. The circuit operates at two controlled current levels, the ON state current being typically about 100 na. A block diagram is shown in Fig. 1, and a circuit schematic in Fig. 2.

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Current Regulator for Fluorescent Lamp Control

This circuit provides rapid turn-on of a fluorescent lamp by controlling current such that in the OFF state the lamp current is reduced to a low level (i(L) Approximately = 1 ma) but not completely extinguished. The circuit operates at two controlled current levels, the ON state current being typically about 100 na. A block diagram is shown in Fig. 1, and a circuit schematic in Fig. 2.

In Fig. 1, note that diode D(5) prevents the reverse discharge of capacitor C(4) through the lamp, thus avoiding a tendency to extinguish the lamp. Also note that resistor R(13) provides a path for the leakage current of transistor Q(6) such that the OFF current of the lamp is not affected by Q(6) leakage. Thus, lamp OFF current is set by trickle resistor R(12) and ballast resistor R(b), while lamp ON current is set by the regulator.

To turn the lamp ON, the logic signal at the base of transistor Q(1) is pulled low. When Q(1) is cut off, all of the collector current of transistor Q(2) flows through resistor R(6). The voltage developed at R(6) is high enough to bias transistor Q(4) on and thus supply base current to transistor Q(6). When Q(6) turns on, capacitor C(4) is discharged through R(3). As C(4) discharges, the potential across R(b) increases, which forces the lamp current to increase. The current continues to increase, as does the output of operational amplifier OP1, until it reaches the upper threshold voltage of the discrete S...