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US 4,663,570 AGranted
High frequency gas discharge lamp dimming ballast
AssigneeLutron Electronics Co., Inc.
InventorsDavid G. Luchaco, Dennis Capewell
Life of this patent
Estimating the term…
Abstract
A high frequency gas discharge lamp dimming ballast with good line power factor is disclosed. The unit is controlled by a current sensing loop which senses control switch current rather than lamp current and employs simple circuitry with sufficiently rapid control response necessary to maintain high line power factor and stable lamp operating characteristics over a very wide range of light output. An isolated output transformer provides protection against most common miswire conditions and accurately regulates lamp energy over a wide range of input and lamp arc voltage conditions. A pulse width modulated control input provides an isolated control input for easier wiring and reduces the susceptibility of the control to noise interference.
Claims27
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, said filter capacitor having a value less than about 30 microfarads;
- a transformer means having primary and secondary windings;
- a gas discharge lamp connected 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 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 primary winding, said single semiconductor switch means and said current sensing means being connected in closed series relation.
10 more elements
An electronic ballast for a gas discharge lamp;
- said electronic ballast being dimmable over a large range;
- said ballast comprising:
- and 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, said filter capacitor having a value less than about 30 microfarads;
- an energy storage element having first and second terminals;
- a gas discharge lamp inductively coupled to said energy storage element;
- 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 close series relation.
11 more elements
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, said filter capacitor having a value less than about 30 microfarads;
- a transformer means having primary and secondary windings;
- a gas discharge lamp connected 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;
- said d-c output terminals, said primary winding, said single semiconductor switch means and said current sensing means being connected in closed series relation.
9 more elements
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, said filter capacitor having a value less than about 30 microfarads;
- an energy storge element having first and second terminals;
- a gas discharge lamp inductively coupled to said energy storage element;
- 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 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.
8 more elements
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 recifier 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 transformer means having primary and secondary windings;
- a gas discharge lamp connected across the terminals of said secondary winding;
- 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;
- said d-c output terminals, said primary winding, said single semiconductor switch means and said current sensing means being connected in closed series relation;
- said ballast further comprising current 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.
15 more elements
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 inductively 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;
- 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 ballast further including current 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 in said series circuit;
- and a zener diode connected between said base of said bipolar transistor and said source of said MOSFET.
14 more elements
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;
- a transformer means having primary and secondary windings;
- a gas discharge lamp connected across the terminals of said secondary winding;
- 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;
- said d-c output terminals, said primary winding, said single semiconductor switch means and said current sensing means being connected in closed series relation;
- said ballast further comprising current 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 in said series circuit;
- and a zener diode connected between said base of said bipolar transistor and said source of said MOSFET.
14 more elements
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 inductively 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;
- 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 closing series relation;
- said ballast further comprising current 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 in said series circuit;
- and a zener diode connected between said base of said bipolar transistor and said source of said MOSFET.
13 more elements
Dependencies are inferred from the claim text.