High intensity lamp dimming circuit

Claim 2

In combination with a high intensity gas discharge lamp, a dimmer circuit for controlling the brightness thereof, comprising: ballast means connected to the lamp and connectable to an ac power distribution line; said ballast means including a reactor portion, gated bypass means for providing at least partial bypass of current around said reactor portion of said ballast means; isolation means connected to said gated bypass means; and controllable gas source voltage means operably connected through said isolation means to said gated bypass means for controllably rendering said gated bypass means conductive, and thereby bypassing said reactor portion of said ballast means.

Claim 3

A dimmer circuit as set forth in claim 1, wherein said isolation means includes a transformer.

Claim 4

A dimmer circuit as set forth in claim 1, wherein said controllable gate source voltage means operates at a voltage reduced from the voltage carried by said ac power distribution line.

Claim 5

A dimmer as set forth in claim 1, wherein said ballast means includes a first ballast element in series with said lamp and wherein said reactor portion is a second ballast element in series with said lamp.

Claim 6

A dimmer as set forth in claim 1, wherein said gated bypass means includes a triac and said isolation means includes a transformer, the gate connection of said triac being connected to said transformer through at least two inverse parallel diodes to prevent the inductive voltage buildup from said transformer from falsely firing said triac.

Claim 7

A dimmer as described in claim 1, wherein said controllable gate source voltage means includes switch means operable when a predetermined voltage threshold value thereof is exceeded; and variable source voltage means connected to said switch means for producing an amplitude controllable voltage substantially in phase with the line voltage, the time the amplitude of the controllable voltage reaching the threshold value of said switch means determining the gating on of said bypass means.

Claim 8

A dimmer as described in claim 1, wherein said controllable gate source voltage means includes switch means operable when an applied voltage raises above a predetermined value, the occurrence of said value being set to occur before the voltage across the reactor portion changes polarity with respect to the line current.

Claim 9

A dimmer as described in claim 1, wherein said controllable said source voltage means includes first switch means operable when a predetermined voltage threshold value thereof is exceeded; variable source voltage means connected to said switch means for producing an amplitude controllable voltage substantially in phase with The line voltage, the time the amplitude of the controllable voltage reaching the threshold value of said switch means determining the gating on of said bypass means; and second switch means operably connected to said variable source voltage means and closeably operable when the amplitude of the controllable voltage raises above a predetermined value, the occurrence of said value occurring before the voltage across the reactor portion changes polarity with respect to the line current.

Claim 10

A dimmer as described in claim 1, and including a series resistor and capacitor in parallel with said reactor portion of said ballast means.

Claim 11

A dimmer as set forth in claim 1, wherein said gate source voltage means includes sensing means for detecting the polarity of the current through and the voltage across said reactor portion; control means connected for producing a signal during at least part of each half cycle of said ac power distribution line frequency; and means connected to said sensing means and said control means to produce a gate source voltage when there is a signal from said control means and which renders said bypass means non-conductive when the voltage across said reactor portion is no longer in the same polarity with the current therethrough.

Claim 12

A dimmer as set forth in claim 10, wherein said sensing means includes a voltage sensing means for sensing the voltage across said reactor portion and a current sensing means for sensing the current through said reactor portion.

Claim 13

A dimmer as set forth in claim 10, wherein said control means is normally on and said means for producing the gate source voltage is an inhibiting means.

Claim 14

A dimmer as set forth in claim 10, wherein said control means is normally off and said means for producing the gate source voltage is an enabling means.

Claim 15

A dimmer as set forth in claim 1, wherein said gate source voltage means includes means for deriving a voltage in phase with the voltage supplied by said ac power distribution line, and means for amplitude regulation connected thereto for preventing said gated bypass means from being conductive when the voltage across said reactor portion is no longer in the same polarity with the current therethrough.

Claim 16

A dimmer as set forth in claim 14 wherein said amplitude regulation is provided by a pair of cathode-to-cathode connected zener diodes for shifting the amplitude of the voltage in phase with the power distribution voltage so that it decreases below a predetermined level no matter than the time the voltage across said reactor reverses in polarity.

Claim 17

A dimmer as set forth in claim 14, wherein said amplitude regulation is provided by a detector sensing the zero crossing of the voltage of said ac power distribution line, a one-shot multivibrator activated by said detector, and a semiconductor switch connected to disenable said gate source voltage means when the voltage across said reactor portion is no longer in the same polarity with the current therethrough.

Claim 18

A dimmer as set forth in clailm 14, wherein said amplitude regulation is provided by a detector sensing the peak of the voltage of said ac power distribution line, a one-shot multivibrator activated by said detector, and a semiconductor switch connected to disenable said gate source voltage means when the voltage across said reactor portion is no longer in polarity with the current therethrough.

Claim 19

A dimmer as set forth in clailm 14, wherein said amplitude regulation is provided by a detector sensing the peak of the voltage of said ac power distribution line, a one-shot multivibrator activated by said detector, and a semiconductor switch connected to disenable said gate source voltage means when the voltage across said reactor portion is no longer in polarity with the current therethrough.

Claim 20

A dimmer as described in claim 1, wherein said isolation means includes a first transformer for reducing the voltage from the voltage carried by said ac power distribution line, and wherein said controllable gate source voltage means includes a second transformer connected across the ac power distribution line to provide a reduced ac voltage; a full wave bridge rectifier for rectifying the reduced voltage to dc voltage; a pair of cathode-to-cathode connected zener diodes for shifting the amplitude of the reduced ac voltage in phase with the power distribution voltaGe so that it goes to zero no later than the time the voltage across said reactor goes to zero; a triac connected in series with said zener diodes conducting when the gate voltage applied thereto exceeds the reduced voltage from said first transformer and the zener diode voltage; and programmable unijunction transistor means connected to said rectifier and to said triac for determining the amplitude and timing of the gate voltage applied to said triac.

Claim 21

A dimmer as described in claim 18, wherein said programmable unijunction transistor means includes a unijunction transistor; the cathode of which is connected to said triac; first variable resistor means operably connected to the dc terminals of said rectifier for controlling the voltage applied to the anode of said unijunction transistor, said first variable resistor means including a resistance divider connected to said rectifier, a diode connected to the output of said divider, and a time constant network; and second variable resistor means operably connected to the dc terminals of said rectifier for controlling the voltage level on the gate of said unijunction transistor.

Claim 22

The dimmer as described in claim 18, wherein said programmable unijunction transistor means includes reset means for rendering said unijunction transistor conductive when the anode-to-gate voltage does not cause conduction and for rendering said unijunction transistor non-conductive following polarity reversals of said ac power distribution line voltage.

Claim 23

A dimmer as described in claim 20, wherein said reset means includes a capacitor connected to the gate of said unijunction transistor and to said full wave bridge rectifier; and a diode connected to said anode of said unijunction transistor and to said full wave bridge rectifier.

Claim 24

In combination with at least three high intensity gas discharge lamps, a dimmer circuit for controlling the brightnesses thereof, comprising a separate ballast means connected respectively to each of the lamps and connectable to an ac power distribution system, each of said ballast means including a reactor portion, separate gated bypass means for respectively providing bypass current around said reactor portion of each of said plurality of ballast means; separate isolation means connected to each of said gated bypass means; and commonly controllable gate source voltage means operably connected through said isolation means to each of said gated bypass means for controllably rendering said gated bypass means conductive, and thereby bypassing said reactor portion of each of said ballasts through a time range when the current through said reactor portions and the voltages thereacross are respectively of the same polarity.

Claim 25

In combination with at least three high intensity gas discharge lamps, a dimmer circuit for controlling the brightnesses thereof, comprising a separate ballast means connected respectively to each of the lamps and connectable to an ac power distribution system, each of said ballast means including a reactor portion, separate gated bypass means for respectively providing bypass current around said reactor portion of each of said plurality of ballast means; separate isolation means connected to each of said gated bypass means; and commonly controllable gate source voltage means operably connected through said isolation means to each of said gated bypass means for controllably rendering said gated bypass means conductive, and thereby bypassing said reactor portion of each of said ballasts through a time range when the current through said reactor portions and the voltages thereacross are respectively of the same polarity.

Claim 26

A dimmer circuit as set forth in claim 22, wherein said separate ballast means are connected respectively to different phases of said ac power distribution system.

Claim 27

A dimmer circuit as set forth in claim 22, wherein said separate ballast means are connected to the same phase of said ac power distribution system.

Claim 28

A dimmer as described in claim 22, and including a series resistor and capacitor in parallel with said respective reactor portions of said separate ballast means.

Claim 29

The dimmer circuit as described in claim 22, wherein each of said isolation means includes a first transformer for reducing the voltage from the voltage carried by said ac power distribution line, and wherein said controllable gate source voltage means includes a second transformer connected across each phase of the ac power distribution line to provide a reduced ac voltage for each phase; a separate full wave bridge rectifier for rectifying each of the reduced voltages to dc voltage; a separate pair of cathode-to-cathode connected zener diodes for shifting the amplitude of each reduced ac voltage in phase with the power distribution voltage so that it goes to zero no later than the timE the voltage across said respective reactor goes to zero; a triac connected in series with each pair of said zener diodes conducting when the gate voltage applied thereto exceeds reduced voltage from said first transformer and the zener diode voltage; and programmable unijunction transistor means connected to each of said bridge rectifiers and to said triac for determining the timing and amplitude of the gate voltage applied to said respective triacs.

Claim 30

The dimmer circuit as described in claim 26, wherein each of said programmable unijunction transistor means includes a unijunction transistor, the cathode of which is connected to said triac; first variable resistor means operably connected to the dc terminals of said rectifier for controlling the voltage applied to the anode of said unijunction transistor, said first variable resistor means including a resistance divider connected to said rectifier, a diode connected to the output of said divider, and a time constant network; and second variable resistor means operably connected to the dc terminals of said rectifier for controlling the voltage level on the gate of said unijunction transistor.

Claim 31

The dimmer as described in claim 26, wherein said programmable unijunction transistor means includes reset means for rendering said unijunction transistor conductive when the anode-to-gate voltage does not cause conduction and for rendering said unijunction transistor non-conductive following polarity reversals of said ac power distribution line voltage.

Claim 32

A dimmer as described in claim 28, wherein each of said reset means includes a capacitor connected to the gate of said unijunction transistor and to said full wave bridge rectifier; and a diode connected to said anode of said unijunction transistor and to said full wave bridge rectifier.