Two-wire electronic dimming ballast for fluorescent lamps

Claim 2

A two-wire electronic ballast arrangement for fluo-rescent lamp dimming comprising: a source of direct current; a source of variable square wave voltage; inverter means adapted to be fed by said source of direct current and modulated by said variable square wave voltage said inverter means including resonant inductor-capacitor circuit means having inductive coil means and first capacitor means connected in series adapted-to resonate at their natural frequency and to provide a sinusoidal voltage across said capacitor means as the output of said inverter means to the fluo-rescent lamps; auxiliary winding means associated with said inductive coil means, said auxiliary winding means being adapted to be connected to the filaments of one or more fluorescent lamps for heating, such that the voltage supplied to heat the filaments of said one or more lamps remains substantially constant during dimming of said one or more fluorescent lamps, said fluorescent lamps further being adapted to be connected across said first capaci-tor means.

Claim 3

The apparatus of claim 1 wherein said source of variable square wave electric power is a pulse width modulated drive and said dimming is accomplished by varying the pulse width thereof.

Claim 4

The apparatus of claim 1 wherein said source of direct current is a full wave bridge rectifier.

Claim 5

The apparatus of claim 3 further comprising means for varying the alternating current input to said rectifier.

Claim 6

The apparatus of claim 1 wherein said inverter means further comprises: a pair of series connected transistors connected across said source of direct current, the emitter of one transistor being tied to the collector of the other; a pair of series connected filter capacitors connected across said source of square wave power; and wherein one end of said inductor coil is connected to the junction of said series connected transistors, and the other end is connected to the junction of said filter capacitors through a resonating capacitor.

Claim 7

A two-wire electronic ballast arrangement for fluo-rescent lamp dimming comprising: a source of variable direct current power; inverter means adapted to be fed by said source of variable direct current power, said inverter means including resonant inductor-capacitor circuit means including inductive coil means and capacitor means connected in series adapted to resonate at their natural frequency and to provide sinusoidal voltage across said capacitor means as the output of said inverter Means to the fluo-rescent lamps; auxiliary winding means associated with said inductive coil means, said auxiliary winding means being adapted to be connected to the filaments of one or more fluorescent lamps for heating disposed such that the voltage supplied to heat the filaments of said one or more lamps remains substantially constant during dimming of said one or more fluorescent lamps, said fluorescent lamps further being adapted to be connected across said capacitor means.

Claim 8

A two-wire electronic ballast arrangement for fluo-rescent lamp dimming comprising: a source of variable direct current power; inverter means adapted to be fed by said source of variable direct current power, said inverter means including resonant inductor-capacitor circuit means including inductive coil means and capacitor means connected in series adapted to resonate at their natural frequency and to provide sinusoidal voltage across said capacitor means as the output of said inverter Means to the fluo-rescent lamps; auxiliary winding means associated with said inductive coil means, said auxiliary winding means being adapted to be connected to the filaments of one or more fluorescent lamps for heating disposed such that the voltage supplied to heat the filaments of said one or more lamps remains substantially constant during dimming of said one or more fluorescent lamps, said fluorescent lamps further being adapted to be connected across said capacitor means.

Claim 9

The apparatus of claim 6 wherein said source of direct current includes a full wave bridge adapted to be connected to a variable alternating current source and a filter circuit means to produce a filtered direct current output.

Claim 10

The apparatus of claim 6 wherein said inverter means is a self-oscillating, two-transistor inverter.

Claim 11

The apparatus of claim 8 wherein said self-oscillation system of said inverter means comprises: a triggering element for initially producing an input direct current to the base of a first transistor; positive feedback loops associated with said first and a second transistor means including feedback coil means and capacitor means and series diode means in parallel with said diode means, said positive feedback loops being connected between the base and emitter of each of said transistor means.

Claim 12

The apparatus of claim 6 further comprising clamping circuit means to limit circuit voltage and current upon removal of one or more of said lamps during operation of said system.

Claim 13

The apparatus of claim 10 wherein said clamping circuit further comprises a pair of series diodes connected across the conductors of said DC power and an inductor coil connected from the common of said series diodes and one of the conductors connecting said one or more lamps across said first capacitor means.

Claim 14

The apparatus of claim 7 including means for varying the alternating current source.

Claim 15

A two-wire electronic ballast arrangement for flu-crescent lamp dimming comprising: a source of variable direct current; self-oscillating inverter means adapted to be fed by said source of variable direct current, said inverter means including a main resonant L-C circuit means having a main inductive coil means, connected in series with a first capacitor means, said first capacitor means, being connected across the filaments of said one or more fluorescent lamps and second capacitor means connected in series with the filaments of said one or more fluorescent lamps; wherein said first and second capacitors are selected to resonate with the main inductor to provide tuned sinusoidal input to said one or more fluorescent lamps at substantially the natural frequency of the circuit; auxiliary tuned circuit means having parallel-connected inductor and capacitor means connected across said first capacitor means in series with said one or more fluorescent lamps wherein said auxiliary tuned circuit means is tuned to the same frequency as the input to said one or more fluorescent lamps and adapted to pre-vent oscillation of said inverter upon removal of any of said lamps during operation of the ballast.

Claim 16

A two-wire electronic ballast arrangement for flu-crescent lamp dimming comprising: a source of variable direct current; self-oscillating inverter means adapted to be fed by said source of variable direct current, said inverter means including a main resonant L-C circuit means having a main inductive coil means, connected in series with a first capacitor means, said first capacitor means, being connected across the filaments of said one or more fluorescent lamps and second capacitor means connected in series with the filaments of said one or more fluorescent lamps; wherein said first and second capacitors are selected to resonate with the main inductor to provide tuned sinusoidal input to said one or more fluorescent lamps at substantially the natural frequency of the circuit; auxiliary tuned circuit means having parallel-connected inductor and capacitor means connected across said first capacitor means in series with said one or more fluorescent lamps wherein said auxiliary tuned circuit means is tuned to the same frequency as the input to said one or more fluorescent lamps and adapted to pre-vent oscillation of said inverter upon removal of any of said lamps during operation of the ballast.

Claim 17

The apparatus of claim 13 including a plurality of series connected fluorescent lamps, said apparatus further comprising: auxiliary secondary winding means connected across the com-monly connected filaments of said series connected flu-orescent lamps, said auxiliary secondary winding being adapted to substantially maintain the filament heating voltage during dimming of said lamps.

Claim 18

The apparatus of claim 13 wherein said self-oscillating inverter means includes a plurality of series connected transistor means having positive feedback coils associated with each transistor means which share a common core with the inductor of said auxiliary tuned circuit such that oscillation of said inverter stops when a lamp is removed during the operation of the ballast.

Claim 19

The apparatus of claim 15 wherein said self-oscillating system of said inverter further comprises: a triggering element for initially producing an input of direct current to the base of first transistor of a pair of series connected transistor means; and starting resistor means associated with the second transis-tor of said pair of transistor means.

Claim 20

The apparatus of claim 13 wherein said source of variable DC current is a full-wave bridge rectifier.

Claim 21

The apparatus of claim 14 wherein said source of variable DC current is a full-wave bridge rectifier.

Claim 22

The apparatus of claim 17 including means for varying the AC input to said rectifier to accomplish dimming of said lamps.

Claim 23

The apparatus of claim 18 including means-for varying the AC input to said rectifier to accomplish dimming of said lamps.

Claim 24

A two-wire electronic ballast arrangement for flu-orescent lamp dimming comprising: a source of variable direct current power; inverter means adapted to be fed by said source of variable direct current electric power, said inverter means including resonant inductor-capacitor circuit means having inductive coil means adapted to be connected in series with the filaments of one or more fluorescent lamps and capacitor means connected in series with said inductor means and in series with the terminals of the filaments of each of said fluorescent lamps; wherein said capacitors are adapted to resonate with the inductor at about the natural frequency of the circuit, prevents substantial variation in the heating voltage to the cathode filaments of said one or more lamps, and prevents over-voltage and over-current in the circuit should one or more lamps be removed during the operation thereof.

Claim 25

A two-wire electronic ballast arrangement for flu-orescent lamp dimming comprising: a source of variable direct current power; inverter means adapted to be fed by said source of variable direct current electric power, said inverter means including resonant inductor-capacitor circuit means having inductive coil means adapted to be connected in series with the filaments of one or more fluorescent lamps and capacitor means connected in series with said inductor means and in series with the terminals of the filaments of each of said fluorescent lamps; wherein said capacitors are adapted to resonate with the inductor at about the natural frequency of the circuit, prevents substantial variation in the heating voltage to the cathode filaments of said one or more lamps, and prevents over-voltage and over-current in the circuit should one or more lamps be removed during the operation thereof.

Claim 26

The apparatus of claim 19 wherein said source of direct current includes a full wave bridge adapted to be connected to a variable alternating current source and a filter circuit means to produce a filtered direct current output.

Claim 27

The apparatus of claim 20 including means for varying the alternating current source.

Claim 28

The apparatus of claim 19 wherein said inverter means is a self-oscillating, two-transistor inverter.

Claim 29

The apparatus of claim 22 wherein said self-oscillation system of said inverter means comprises: a triggering element for initially producing an input of direct current to the base of a first transistor; positive feedback loops associated with said first and a second transistor means including feedback coil means and series diode means in parallel with said coil means, said positive feedback loops being connected between the base and emitter of each of said transistor means.