High frequency gas discharge lamp dimming ballast

Claim 2

An electronic ballast for a gas discharge lamp; said electronic ballast being dimmable over a large range; said ballast comprising: an a-c input circuit; a rectifier having a-c terminals connected to said a-c input circuit and having d-c output terminals; a filter capacitor connected across said d-c output terminals; a gas discharge lamp connected in circuit relation with said d-c output terminals and deriving its total energy therefrom; a single semiconductor switching means having a control electrode and first and second power terminals; a current sensing means; a control circuit connected to said control electrode and operable to turn said switching means on and off at a controlled duty cycle rate; a dimming level set circuit connected to said control circuit to set said duty cycle to a value related to a given degree of dimming of said lamp; said current sensing means being connected to said control circuit and operable to adjust said duty cycle to a value which maintains the current through said current sensing means at a value related to that called for by said dimming level set circuit; an energy storage inductor and a coupling capacitor; said d-c output terminals, said energy storage inductor, said single semiconductor switch means and said current sensing means being connected in closed series relation, said coupling capacitor coupling said ballast to said single semiconductor switch means.

Claim 3

The electronic ballast of claim 1, said gas discharge lamp having filaments and heaters in the filaments and further including transformer means coupled to said d-c output terminals and connected to the heaters of the filaments of said gas discharge lamp.

Claim 4

The electronic ballast of claim 1 wherein at least two series connected gas discharge lamps are connected across the terminals of each of said secondary windings.

Claim 5

The electronic ballast of claim 1 wherein said single semiconductor switching means comprises a bipolar transistor.

Claim 6

The electronic ballast of claim 1 which further includes a dielectrically isolated coupling device for coupling said dimming level set circuit to said control circuit.

Claim 7

An electronic ballast for a gas discharge lamp; said electronic ballast being dimmable over a large range; said ballast comprising: an a-c input circuit; a bridge connected rectifier having a-c terminals connected to said a-c input circuit and having d-c output terminals; a filter capacitor connected in parallel across said d-c output terminals; an energy storage element having first and second terminals; a coupling capacitor; a gas discharge lamp connected in circuit relation to said energy storage element and receiving its energy therefrom; a single semiconductor switching means which comprises a high voltage bipolar transistor and a low voltage power FET connected in cascode relation; and having a control electrode and first and second power terminals; a current sensing means; a control circuit connected to said control electrode and operable to turn said switching means on and off at a controlled duty cycle rate; a dimming level set circuit connected to said control circuit to set said duty cycle to a value related to a given degree of dimming of said lamp; said current sensing means being connected to said control circuit and operable to adjust said duty cycle to a value which maintains the current through said current sensing means at a value related to that called for by said dimming level set circuit; said d-c output terminals, said first and second terminals of said energy storage element, said single semiconductor switch means and said current sensing means being connected in closed series relation, said coupling capacitor coupling said gas discharge lamp to said energy storage inductor.

Claim 8

An electronic ballast for a gas discharge lamp; said electronic ballast being dimmable over a large range; said ballast comprising: an a-c input circuit; a bridge connected rectifier having a-c terminals connected to said a-c input circuit and having d-c output terminals; a filter capacitor connected in parallel across said d-c output terminals; an energy storage element having first and second terminals; a coupling capacitor; a gas discharge lamp connected in circuit relation to said energy storage element and receiving its energy therefrom; a single semiconductor switching means which comprises a high voltage bipolar transistor and a low voltage power FET connected in cascode relation; and having a control electrode and first and second power terminals; a current sensing means; a control circuit connected to said control electrode and operable to turn said switching means on and off at a controlled duty cycle rate; a dimming level set circuit connected to said control circuit to set said duty cycle to a value related to a given degree of dimming of said lamp; said current sensing means being connected to said control circuit and operable to adjust said duty cycle to a value which maintains the current through said current sensing means at a value related to that called for by said dimming level set circuit; said d-c output terminals, said first and second terminals of said energy storage element, said single semiconductor switch means and said current sensing means being connected in closed series relation, said coupling capacitor coupling said gas discharge lamp to said energy storage inductor.

Claim 9

An electronic ballast for a gas discharge lamp; said ballast comprising: an a-c input circuit; a full wave bridge connected rectifier having a-c terminals connected to said a-c input circuit and having d-c output terminals; a filter capacitor connected across said d-c output terminals; circuit means coupling said gas discharge lamp to said d-c output terminals; a single semiconductor switching means having a control electrode and first and second power terminals; a current sensing means; a control circuit connected to said control electrode and operable to turn said switching means on and off at a controlled duty cycle rate; a current level set circuit connected to said control circuit to set said duty cycle to a value related to a given value of current in said lamp; said current sensing means being connected to said control circuit and operable to adjust said duty cycle to a value which maintains the current through said current sensing means at a value related to that called for by said current level set circuit; said d-c output terminals, said energy storage inductor, said single semiconductor switch means and said current sensing means being connected in closed series relation, said couplinq capacitor coupling said ballast to said single semiconductor switch means.

Claim 10

An electronic ballast for a gas discharge lamp; said ballast comprising: an a-c input circuit; a full wave bridge connected rectifier having a-c terminals connected to said a-c input circuit and having d-c output terminals; a filter capacitor connected across said d-c output terminals; circuit means coupling said gas discharge lamp to said d-c output terminals; a single semiconductor switching means having a control electrode and first and second power terminals; a current sensing means; a control circuit connected to said control electrode and operable to turn said switching means on and off at a controlled duty cycle rate; a current level set circuit connected to said control circuit to set said duty cycle to a value related to a given value of current in said lamp; said current sensing means being connected to said control circuit and operable to adjust said duty cycle to a value which maintains the current through said current sensing means at a value related to that called for by said current level set circuit; said d-c output terminals, said energy storage inductor, said single semiconductor switch means and said current sensing means being connected in closed series relation, said couplinq capacitor coupling said ballast to said single semiconductor switch means.

Claim 11

The electronic ballast of claim 7 which further includes heater tap sections connected to the heaters of the filaments of said gas discharge lamp and energized from d-c output terminals.

Claim 12

The electronic ballast of claim 7 which further includes a dielectrically isolated coupling device for coupling said current level set circuit to said control circuit.

Claim 13

An electronic ballast for a gas discharge lamp; said ballast comprising: a bridge connected rectifier having a-c terminals connected to said a-c input circuit and having d-c output terminals; a filter capacitor connected in parallel across said d-c output terminals; an energy storage element having first and second terminals; a gas discharge lamp coupled to said energy storage element; across the terminals of said secondary winding; a single semiconductor switching means having a control electrode and first and second power terminals; a current sensing means; a control circuit connected to said control electrode and operable to turn said switching means on and off at a controlled duty cycle rate; a current level set circuit connected to said control circuit to set said duty cycle to a value related to a given value of current in said lamp; said current sensing means being connected to said control circuit and operable to adjust said duty cycle to a value which maintains the current through said current sensing means at a value related to that called for by said current level set circuit; an energy storage inductor and a coupling capacitor; said d-c output terminals, said energy storage inductor, said single semiconductor switch means and said current sensing means being connected in closed series relation, said coupling capacitor coupling said ballast to said single semiconductor switch means.

Claim 14

An electronic ballast for a gas discharge lamp; said ballast comprising: a bridge connected rectifier having a-c terminals connected to said a-c input circuit and having d-c output terminals; a filter capacitor connected in parallel across said d-c output terminals; an energy storage element having first and second terminals; a gas discharge lamp coupled to said energy storage element; across the terminals of said secondary winding; a single semiconductor switching means having a control electrode and first and second power terminals; a current sensing means; a control circuit connected to said control electrode and operable to turn said switching means on and off at a controlled duty cycle rate; a current level set circuit connected to said control circuit to set said duty cycle to a value related to a given value of current in said lamp; said current sensing means being connected to said control circuit and operable to adjust said duty cycle to a value which maintains the current through said current sensing means at a value related to that called for by said current level set circuit; an energy storage inductor and a coupling capacitor; said d-c output terminals, said energy storage inductor, said single semiconductor switch means and said current sensing means being connected in closed series relation, said coupling capacitor coupling said ballast to said single semiconductor switch means.

Claim 15

The electronic ballast of claim 10 which further includes a dielectrically isolated coupling device for coupling said current level set circuit to said control circuit.

Claim 16

The electronic ballast of claim 10 wherein said single semiconductor switching means comprises a transistor.

Claim 17

An electronic ballast for a gas discharge lamp; said electronic ballast being dimmable over a large range; said ballast comprising: an a-c input circuit; a rectifier having a-c terminals connected to said a-c input circuit and having d-c output terminals; a filter capacitor connected across said d-c output terminals; circuit means coupling said gas discharge lamp to said d-c output terminals; a single semiconductor switching means which comprises a high voltage bipolar transistor and a low voltage power MOSFET connected in cascode relation, said switching means having a control electrode and first and second power terminals; a current sensing means; a control circuit connected to said control electrode and operable to turn said switching means on and off at a controlled duty cycle rate; a dimming level set circuit connected to said control circuit to set said duty cycle to a value related to a given degree of dimming of said lamp; said current sensing means being connected to said control circuit and operable to adjust said duty cycle to a value which maintains the current through said current sensing means at a value related to that called for by said dimming level set circuit; an energy storage inductor and a coupling capacitor; said d-c output terminals, said energy storage inductor, said single semiconductor switch means and said current sensing means being connected in closed series relation, said coupling capacitor coupling said ballast to said single semiconductor switch means; said ballast further comprising transformer means having a tap terminal means and end terminals; said end terminals connected to the base of said bipolar transistor and the drain of said MOSFET, respectively; said tap terminal connected to one of the emitter and collector of said bipolar transistor; the source of said MOSFET and one of the emitter and collector of said bipolar transistor which is not connected to said tap terminal being connected in said series circuit; and a Zener diode connected between said base of said bipolar transistor and said source of said MOSFET.

Claim 18

An electronic ballast for a gas discharge lamp; said electronic ballast being dimmable over a large range; said ballast comprising: an a-c input circuit; a rectifier having a-c terminals connected to said a-c input circuit and having d-c output terminals; a filter capacitor connected across said d-c output terminals; circuit means coupling said gas discharge lamp to said d-c output terminals; a single semiconductor switching means which comprises a high voltage bipolar transistor and a low voltage power MOSFET connected in cascode relation, said switching means having a control electrode and first and second power terminals; a current sensing means; a control circuit connected to said control electrode and operable to turn said switching means on and off at a controlled duty cycle rate; a dimming level set circuit connected to said control circuit to set said duty cycle to a value related to a given degree of dimming of said lamp; said current sensing means being connected to said control circuit and operable to adjust said duty cycle to a value which maintains the current through said current sensing means at a value related to that called for by said dimming level set circuit; an energy storage inductor and a coupling capacitor; said d-c output terminals, said energy storage inductor, said single semiconductor switch means and said current sensing means being connected in closed series relation, said coupling capacitor coupling said ballast to said single semiconductor switch means; said ballast further comprising transformer means having a tap terminal means and end terminals; said end terminals connected to the base of said bipolar transistor and the drain of said MOSFET, respectively; said tap terminal connected to one of the emitter and collector of said bipolar transistor; the source of said MOSFET and one of the emitter and collector of said bipolar transistor which is not connected to said tap terminal being connected in said series circuit; and a Zener diode connected between said base of said bipolar transistor and said source of said MOSFET.

Claim 19

An electronic ballast for a gas discharge lamp; said electronic ballast being dimmable over a large range; said ballast comprising: an a-c input circuit; a bridge connected rectifier having a-c terminals connected to said a-c input circuit and having d-c output terminals; a filter capacitor connected across said d-c output terminals; an energy storage element having first and second terminals; a gas discharge lamp coupled to said energy storage element; a single semiconductor switching means which comprises a high voltage bipolar transistor and a low voltage power MOSFET connected in cascode relation, said switching means having a control electrode and first and second power terminals; a current sensing means; a control circuit connected to said control electrode and operable to turn said switching means on and off at a controlled duty cycle rate; a dimming level set circuit connected to said control circuit to set said duty cycle to a value related to a given degree of dimming of said lamp; said current sensing means being connected to said control circuit and operable to adjust said duty cycle to a value which maintains the current through said current sensing means at a value related to that called for by said dimming level set circuit; an energy storage inductor and a coupling capacitor; said d-c output terminals, said energy storage inductor, said single semiconductor switch means and said current sensing means being connected in closed series relation, said coupling capacitor coupling said ballast to said single semiconductor switch means; said ballast further including transformer means having a tap terminal means and end terminals; said end terminals connected to the base of said bipolar transistor and the drain of said MOSFET, respectively; said tap terminal connected to the emitter of said bipolar transistor; the source of said MOSFET and the collector of said bipolar transistor connected to said series circuit; and a Zener diode connected between said base of said bipolar transistor and said source of said MOSFET.

Claim 20

An electronic ballast for a gas discharge lamp; said electronic ballast being dimmable over a large range; said ballast comprising: an a-c input circuit; a bridge connected rectifier having a-c terminals connected to said a-c input circuit and having d-c output terminals; a filter capacitor connected across said d-c output terminals; an energy storage element having first and second terminals; a gas discharge lamp coupled to said energy storage element; a single semiconductor switching means which comprises a high voltage bipolar transistor and a low voltage power MOSFET connected in cascode relation, said switching means having a control electrode and first and second power terminals; a current sensing means; a control circuit connected to said control electrode and operable to turn said switching means on and off at a controlled duty cycle rate; a dimming level set circuit connected to said control circuit to set said duty cycle to a value related to a given degree of dimming of said lamp; said current sensing means being connected to said control circuit and operable to adjust said duty cycle to a value which maintains the current through said current sensing means at a value related to that called for by said dimming level set circuit; an energy storage inductor and a coupling capacitor; said d-c output terminals, said energy storage inductor, said single semiconductor switch means and said current sensing means being connected in closed series relation, said coupling capacitor coupling said ballast to said single semiconductor switch means; said ballast further including transformer means having a tap terminal means and end terminals; said end terminals connected to the base of said bipolar transistor and the drain of said MOSFET, respectively; said tap terminal connected to the emitter of said bipolar transistor; the source of said MOSFET and the collector of said bipolar transistor connected to said series circuit; and a Zener diode connected between said base of said bipolar transistor and said source of said MOSFET.

Claim 21

An electronic ballast for a gas discharge lamp; said ballast comprising: a bridge connected rectifier having a-c terminals connected to said a-c input circuit and having d-c output terminals; a filter capacitor connected across said d-c output terminals; an energy storage element having first and second terminals; a gas discharge lamp coupled to said energy storage element; a single semiconductor switching means which comprises a high voltage bipolar transistor and a low voltage power MOSFET connected in cascode relation, said switching means having a control electrode and first and second power terminals; a current sensing means; a control circuit connected to said control electrode and operable to turn said switching means on and off at a controlled duty cycle rate; a current level set circuit connected to said control circuit to set said duty cycle to a value related to a given value of current in said lamp; said current sensing means being connected to said control circuit and operable to adjust said duty cycle to a value which maintains the current through said current sensing means at a value related to that called for by said current level set circuit; an energy storage inductor and a coupling capacitor; said d-c output terminals, said energy storage inductor, said single semiconductor switch means and said current sensing means being connected in closed series relation, said coupling capacitor coupling said ballast to said single semiconductor switch means; said ballast further comprising transformer means having a tap terminal means and end terminals; said end terminals connected to the base of said bipolar transistor and the drain of said MOSFET, respectively; said tap terminal connected to the emitter of said bipolar transistor; the source of said MOSFET and the collector of said bipolar transistor connected to said series circuit; and a Zener diode connected between said base of said bipolar transistor and said source of said MOSFET.

Claim 22

An electronic ballast for a gas discharge lamp; said ballast comprising: a bridge connected rectifier having a-c terminals connected to said a-c input circuit and having d-c output terminals; a filter capacitor connected across said d-c output terminals; an energy storage element having first and second terminals; a gas discharge lamp coupled to said energy storage element; a single semiconductor switching means which comprises a high voltage bipolar transistor and a low voltage power MOSFET connected in cascode relation, said switching means having a control electrode and first and second power terminals; a current sensing means; a control circuit connected to said control electrode and operable to turn said switching means on and off at a controlled duty cycle rate; a current level set circuit connected to said control circuit to set said duty cycle to a value related to a given value of current in said lamp; said current sensing means being connected to said control circuit and operable to adjust said duty cycle to a value which maintains the current through said current sensing means at a value related to that called for by said current level set circuit; an energy storage inductor and a coupling capacitor; said d-c output terminals, said energy storage inductor, said single semiconductor switch means and said current sensing means being connected in closed series relation, said coupling capacitor coupling said ballast to said single semiconductor switch means; said ballast further comprising transformer means having a tap terminal means and end terminals; said end terminals connected to the base of said bipolar transistor and the drain of said MOSFET, respectively; said tap terminal connected to the emitter of said bipolar transistor; the source of said MOSFET and the collector of said bipolar transistor connected to said series circuit; and a Zener diode connected between said base of said bipolar transistor and said source of said MOSFET.

Claim 23

A dimmable gas discharge lamp ballast, comprising, in combination: a pair of leads connectable to a d-c power source; a high speed power switching device connected in series with said pair of leads; a switching device current sensor connected in circuit relation with said power switching device for measuring the current carried by said high speed switching device and producing an output related thereto; a pair of gas discharge lamp terminals for connection in series with a gas discharge lamp means; said pair of lamp terminals connected in series with said pair of leads; a lamp current sensor coupled to and producing an output related to the current flow through a lamp means connected to said pair of gas discharge lamp terminals; a control circuit for controlling the conduction of said high speed power switching device in response to input signals derived from said switching device current sensor and said lamp current sensor to controllably change the power applied to a gas discharge lamp means connected to said terminals and cause predetermined dimming thereof from a full output light condition; said output of said lamp current sensor significantly controlling dimming when lamp current is less than about 10% of its value of said full output light condition; said output of said switching device current sensor significantly controlling dimming when said lamp current is greater than about said 10% of its value at said full output light condition.

Claim 24

A dimmable gas discharge lamp ballast, comprising, in combination: a pair of leads connectable to a d-c power source; a high speed power switching device connected in series with said pair of leads; a switching device current sensor connected in circuit relation with said power switching device for measuring the current carried by said high speed switching device and producing an output related thereto; a pair of gas discharge lamp terminals for connection in series with a gas discharge lamp means; said pair of lamp terminals connected in series with said pair of leads; a lamp current sensor coupled to and producing an output related to the current flow through a lamp means connected to said pair of gas discharge lamp terminals; a control circuit for controlling the conduction of said high speed power switching device in response to input signals derived from said switching device current sensor and said lamp current sensor to controllably change the power applied to a gas discharge lamp means connected to said terminals and cause predetermined dimming thereof from a full output light condition; said output of said lamp current sensor significantly controlling dimming when lamp current is less than about 10% of its value of said full output light condition; said output of said switching device current sensor significantly controlling dimming when said lamp current is greater than about said 10% of its value at said full output light condition.

Claim 25

The ballast of claim 16, wherein said high speed power switching device is a power semiconductor device.

Claim 26

The ballast of claim 16, wherein said switching device current sensor is a resistor.

Claim 27

The ballast of claim 16, which further includes a two winding transformer coupled between and inductively coupling said power switching device and said lamp terminals.

Claim 28

The ballast of claim 19, wherein said switching device current sensor is a resistor.

Claim 29

The ballast of claim 16, wherein said lamp current sensor is a current transformer.

Claim 30

The ballast of claim 20, wherein said lamp current sensor is a current transformer.

Claim 31

The ballast of claim 2, which further includes a second circuit sensing means connected in circuit relation with said gas discharge lamp and producing an output related to the current through said lamp; and circuit means connecting said output means to said control circuit for controlling the dimming of said lamp when lamp current is less than about 10% of its value at full light output of said lamp.

Claim 32

The ballast of claim 23 wherein at least two series connected gas discharge lamps are connected across the terminals of each of said secondary windings.

Claim 33

The ballast of claim 23 wherein said single semiconductor switching means comprises a bipolar transistor.