US 3529207 A
Description (OCR text may contain errors)
Sept. 15, 1970 c. W B 3,529,207
FLUORESCENT LAMP CONTROL Fiied April 18, 1968 F]. E I INVENTOR. i PHILIP C. WEBB ATTORNEY United States Patent O" 3,529,207 FLUORESCENT LAMP CONTROL Philip C. Webb,.4752 Pin Oak Trail,
Jackson, Mich. 49201 Filed Apr. 18, 1968, Ser. No. 722,440 Int. Cl. Hb 39/00 US. Cl. 315-94 6 Claims ABSTRACT OF THE DISCLOSURE OUTLINE OF INVENTION The transistor is substituted for the usual current limiting ballast of fluorescent lights. A biasing connection to a control terminal of the transistor automatically regulates the transistor to pass the necessary high starting voltage to the lamp, and reduce the operating current and voltage in the lamp, when the internal resistance of the lamp is reduced as the lamp starts. The biasing connection to the transistor includes a resistor, which may be variable and used as a brightness control for the lamp, and a secondary coil of the power supply transformer of the lamp.
Unexpectedly, the transistor is conducting on both cycles of alternating current applied to the transistor and its biasing connection, so oppositely connected transistors are not required to provide substantially continuous energization of the lamp.
The drawings, of which there is one sheet show a preferred form of the control circuit connected to a fluorescent lamp.
FIG. 1 is a schematic wiring diagram of the connections to a fluorescent lamp with the control elements of the invention connected thereto.
FIG. 2 is a diagrammatic view showing the wave form of the current flowing through the lamp during operation.
The diagram shows the tubular envelope 1 of a fluorescent lamp with filaments 2 and 3 in its ends. An alternating current source indicated at 4 is selectively connectable by the switch 5 to the primary 6 of a transformer indicated generally at 7. One secondary winding 8 of the transformer is connected to one side of the power source and to filament 2. Another secondary winding 9 is connected to the other filament 3 and is connected through a transistor 10 to the opposite side of the power source through conductors 11 and 12.
The conductor 11 connects between the emitter 13 of the transistor and the opposite end of the primary winding 6. The conductor 12 connects between the collector 14 of the transistor and one side of the winding 9 and the filament 3. Together, the conductors 11 and 12 constitute a regulating conductor for filaments 3 and the lamp.
The base 15 of the transistor is connected by the conductor 16 to a resistor 17, which may be variable. The resistor is connected by conductor 18 in series with a third coil 19, which is connected to conductor 11 and the power source.
In operation of the lamp and its control, closing of the 3,529,207 Patented Sept. 15 1970 switch 5 provides heater current to the filament 2 at the alternating potential of one side of the power source. The other filament 3 is supplied with an approximately equal heating current by the winding 9. However, the potential of the filament 3 relative to the filament 2 is determined by the action of the transistor 10 and its control base 15. Generally, the absolute potential of filament 3 will approximate the alternating potential of the opposite side of the power source from filament 2; so that an operative potential is created between the filaments 2 and 3 considered as opposite electrodes of the lamp 1. The alternating potential of the side of the power source connected to switch 5 acts, in conjunction with current flow through conductors 11 and 12, to modulate and integrate the potentials and currents transmitted by the transistor, so that the resultant current through the lamp varies as is I CC indicated graphically in FIG. 2. The current through the lamp 1 does not vary in the same sinusoidal manner as the ordinary commercial alternating current such as is applied 0 the primary winding 6. Neither does the transistor act as a half wave rectifier to create intermittent voltage and current between the filaments. Instead, the current through the lamp 1 varies as shown by the graph in FIG. 2.
Considering the cycle of ordinary sixty cycle commercial current to be indicated by the lines 20 in FIG. 2, the
' resultant current in the lamp 1 rises from zero at 21 to an intermediate peak 22, followed by a small fluctuation 23. Following the fluctuation, the lamp current rises to a sharp and higher peak or positive value at 24. The current then falls rapidly to a second low, but still positive fluctuation, indicated by the dip 25. From this point the current decreases through zero to a negative peak 26. The cycle is completed by a rise (decrease of negative value) to the zero starting value. This cycle of current maintains practically constant transmission or emission between the filaments 2 and 3, and at the standard of sixty cycle commercial current provides illumination without noticeable flicker.
The following specific values or factors in the circuit provide an installation of a currently standard 40 watt F-40 type of fluorescent lamp in a 240 volt supply line. The windings 8 and 9 provide a heater voltage to the filaments 2 and 3 of 6.3 volts, which is somewhat higher than the 5 volts recommended for F-40 type lamps.
The resistor 17. if variable, will start and operate the lamp at 10,000 ohms, with a resultant brightening of the lamp. A fixed 8,000 ohm, 10 watt resistor starts and operates the lamp satisfactory, but with the development of considerable heat or lost energy in the resistor. The transistor may be of the type identified by the designation DTS-423. Winding 19 provides a biasing voltage of 6.3 volts to the base 15 through conductors 18 and 16 to the transistor. The third winding 19, in conjunction with resistor 17 provides a control voltage of about 7 volts be tween the base 15 and the emitter 13 of the transmitter.
- What is claimed as new is:
1. A control for a fluorescent lamp having spaced filaments comprising,
a transformer having a primary winding adapted to be connected to a source of alternating current,
a first secondary winding in said transformer connected to one side of said primary winding and having terminals adapted to be connected to the ends of a first of said filaments,
a second secondary winding in said transformer having terminals adapted to be connected to the ends of the other of said filaments,
a transistor having base, emitter and collector terminals,
a regulating conductor connecting said second second- 3 ary winding to the opposite side of said primary winding from said first secondary winding,
said regulating conductor having two sections connected in series through said emitter and said co1lector terminals of said transistor,
and a control circuit including a resistor connected bebetween the base of said transistor and the other side of said primary winding from said first secondary winding,
said control circuit extending through a secondary winding of said transformer.
2. A control as defined in claim 1 in which said resistor is variable.
3. A control as defined in claim 2 in which said variable resistor has both minimum and maximum resistances of finite values.
4. A control as defined in claim 1 in which said second secondary winding is connected to said regulating conductor between a terminal connection to said other of said filaments and said transistor.
7 4 Y e .0 5. A control as defined in claim 4 in which there is a third secondary winding in said transformer,
said third winding being connected in series with said resistor in said control circuit. 6. A control as defined in claim 5 in which said secondary windings supply voltages between 5 and 7 volts, and in which said resistor is variable between 5,000 and 10,000 ohms.
References Cited UNITED STATES PATENTS 3/1969 Miller et al. 315-94 US. Cl. X.R.