Retrofit fluorescent lamp energy management/dimming system

Claim 3

The method of claim 1 wherein said high frequency component is derived by very rapidly switching on and off said current from said AC source for controlled periods, simultaneously establishing said high frequency component and said duty cycle of said low frequency component.

Claim 4

The method of claim 1 wherein said high frequency component is derived from a high frequency signal modulated to provide a substantially constant peak ballast voltage when added to said low frequency component having a varied duty cycle.

Claim 5

The method of claim 1 wherein said high frequency component is derived from a high frequency signal added to said ballast voltage substantially only during the off periods of said duty cycle.

Claim 6

The method of claim 1 wherein said high frequency component is derived from a high frequency signal modulated by a full-wave rectified signal from said AC source phase shifted by 90°; whereby voltage peaks across said ballast substantially in excess of a predetermined value are avoided.

Claim 7

A dimming circuit connected in an AC line between a low frequency AC source and a fluorescent lighting system, said lighting system including a conventional transformer ballast for supplying voltage to a fluorescent lamp and filaments thereof, said dimming circuit comprising: a power switch in said AC line for selectively coupling said AC source to said ballast; and a control circuit coupled to said power switch, said control circuit providing high frequency switching signals to said power switch to turn said power switch on and off at said high frequency for controlled intervals during each half cycle of said AC source, said control circuit turning on said power switch during the remaining portions of each half cycle, said high frequency being greater than the resonant frequency of said ballast; whereby substantially constant power is supplied to said filaments via high frequency and low frequency components of voltage supplied to said ballast while the power suppled to said lamp via said low frequency component of voltage supplied to said ballast is variably reduced.

Claim 8

A dimming circuit connected in an AC line between a low frequency AC source and a fluorescent lighting system, said lighting system including a conventional transformer ballast for supplying voltage to a fluorescent lamp and filaments thereof, said dimming circuit comprising: a power switch in said AC line for selectively coupling said AC source to said ballast; and a control circuit coupled to said power switch, said control circuit providing high frequency switching signals to said power switch to turn said power switch on and off at said high frequency for controlled intervals during each half cycle of said AC source, said control circuit turning on said power switch during the remaining portions of each half cycle, said high frequency being greater than the resonant frequency of said ballast; whereby substantially constant power is supplied to said filaments via high frequency and low frequency components of voltage supplied to said ballast while the power suppled to said lamp via said low frequency component of voltage supplied to said ballast is variably reduced.

Claim 9

A dimming circuit in accordance with claim 6 wherein said power switch is switched on and off during said controlled intervals at a frequency in the range of 600 hertz and higher.

Claim 10

A dimming circuit in accordance with claim 6 wherein said power switch comprises a semiconductor switching element connected within a bridge circuit.

Claim 11

A dimming circuit in accordance with claim 8 further including a relay connected across said power switch adapted to close during periods of no dimming to reduce bridge conduction losses.

Claim 12

A dimming circuit in accordance with claim 8 wherein said semiconductor switching element comprises an IGT.

Claim 13

A dimming circuit in accordance with claim 6 further including a bilateral trigger device connected across said ballast.

Claim 14

A dimming circuit for connecting in a first AC line between a low frequency AC source and a conventionally ballasted fluorescent lighting system, comprising: a power switch adapted to be connected in said AC line for varying the duty cycle of the voltage of said low frequency AC source supplied to the ballast of said lighting system; high frequency voltage providing means adapted to be connected in said first AC line between said power switch and said ballast for supplying a high frequency component to said ballast, said high frequency component being modulated to provide a substantially constant peak voltage when added to the voltage provided by said power switch; and a high frequency short-circuit adapted to be connected between the junction of said power switch and said high frequency voltage providing means and the other AC line of said low frequency AC source.

Claim 15

A dimming circuit for connecting in a first AC line between a low frequency AC source and a conventionally ballasted fluorescent lighting system, comprising: a power switch adapted to be connected in said AC line for varying the duty cycle of the voltage of said low frequency AC source supplied to the ballast of said lighting system; high frequency voltage providing means adapted to be connected in said first AC line between said power switch and said ballast for supplying a high frequency component to said ballast, said high frequency component being modulated to provide a substantially constant peak voltage when added to the voltage provided by said power switch; and a high frequency short-circuit adapted to be connected between the junction of said power switch and said high frequency voltage providing means and the other AC line of said low frequency AC source.

Claim 16

A dimming circuit in accordance with claim 12 wherein said high frequency component has a frequency in the range of 600 hertz and higher.

Claim 17

A dimming circuit in accordance with claim 12 wherein said power switch comprises a semiconductor switching element connected within a bridge circuit.

Claim 18

A dimming circuit in accordance with claim 14 further including a relay connected across said power switch adapted to close during periods of no dimming in order to reduce bridge conduction losses.

Claim 19

A dimming circuit in accordance with claim 14 wherein said semiconductor switching element comprises an IGT.

Claim 20

A dimming circuit in accordance with claim 12 further including a bilateral trigger device connected across said ballast.

Claim 21

A dimming circuit for connecting in a first AC line between a low frequency AC source and a transformer ballasted fluorescent lighting system comprising: a power switch adapted to be connected in said first AC line for varying the duty cycle of the voltage of said low frequency AC source supplied to the ballast of said lighting system; a high frequency oscillator for providing a voltage having a frequency in the range of 600 hertz and higher; coupling means adapted to couple the output of said oscillator to said first AC line between said power switch and said ballast during periods of said duty cycle when said power switch is nonconductive; and a high frequency short-circuit adapted to be connected between the junction of said power switch and said coupling means and the other AC line of said AC source.

Claim 22

A dimming circuit for connecting in a first AC line between a low frequency AC source and a transformer ballasted fluorescent lighting system comprising: a power switch adapted to be connected in said first AC line for varying the duty cycle of the voltage of said low frequency AC source supplied to the ballast of said lighting system; a high frequency oscillator for providing a voltage having a frequency in the range of 600 hertz and higher; coupling means adapted to couple the output of said oscillator to said first AC line between said power switch and said ballast during periods of said duty cycle when said power switch is nonconductive; and a high frequency short-circuit adapted to be connected between the junction of said power switch and said coupling means and the other AC line of said AC source.

Claim 23

A dimming circuit for connecting in a first AC line between a low frequency AC source and a conventionally ballasted fluorescent lighting system, comprising: a power switch adapted to be connected in said first AC line for varying the duty cycle of the voltage of said low frequency AC source supplied to the ballast of said lighting system; a high frequency oscillator for providing a voltage having a frequency at least 10 times greater than said AC source frequency; means coupled to said oscillator for modulating said voltage from said oscillator inversely as the amplitude of said AC source; circuit means adapted to couple the output of said oscillator to said first AC line between said power switch and said ballast; and a high frequency short-circuit adapted to be connected between the junction of said power switch and said circuit means and the other AC line of said AC source.

Claim 24

A dimming circuit for connecting in a first AC line between a low frequency AC source and a conventionally ballasted fluorescent lighting system, comprising: a power switch adapted to be connected in said first AC line for varying the duty cycle of the voltage of said low frequency AC source supplied to the ballast of said lighting system; a high frequency oscillator for providing a voltage having a frequency at least 10 times greater than said AC source frequency; means coupled to said oscillator for modulating said voltage from said oscillator inversely as the amplitude of said AC source; circuit means adapted to couple the output of said oscillator to said first AC line between said power switch and said ballast; and a high frequency short-circuit adapted to be connected between the junction of said power switch and said circuit means and the other AC line of said AC source.

Claim 25

A dimming circuit for connecting in an AC line between a low frequency AC source and a fluorescent lighting system, said lighting system including a conventional transformer ballast for supplying voltage to a fluorescent lamp and filament thereof, said dimming circuit comprising: a power switch adapted to be connected in said AC line for selectively coupling said AC source to said ballast; and a control circuit coupled to said power switch, said control circuit providing high frequency switching signals to said power switch to turn said power switch on and off at said high frequency for controlled intervals during each half cycle of said AC source, said control circuit turning on said power switch during the remaining portions of each half cycle, said high frequency being greater than the resonant frequency of said ballast; whereby substantially constant power is supplied to said filaments via high frequency and low frequency components of voltage supplied to said ballast while the power supplied to said lamp via said low frequency component of voltage supplied to said ballast is variably reduced when said dimming circuit is connected to said lighting system.

Claim 26

A dimming circuit for connecting in an AC line between a low frequency AC source and a fluorescent lighting system, said lighting system including a conventional transformer ballast for supplying voltage to a fluorescent lamp and filament thereof, said dimming circuit comprising: a power switch adapted to be connected in said AC line for selectively coupling said AC source to said ballast; and a control circuit coupled to said power switch, said control circuit providing high frequency switching signals to said power switch to turn said power switch on and off at said high frequency for controlled intervals during each half cycle of said AC source, said control circuit turning on said power switch during the remaining portions of each half cycle, said high frequency being greater than the resonant frequency of said ballast; whereby substantially constant power is supplied to said filaments via high frequency and low frequency components of voltage supplied to said ballast while the power supplied to said lamp via said low frequency component of voltage supplied to said ballast is variably reduced when said dimming circuit is connected to said lighting system.

Claim 27

A dimming circuit in accordance with claim 20 wherein said power switch comprises a semiconductor switching element connected within a bridge circuit.

Claim 28

A dimming circuit in accordance with claim 20 wherein said semiconductor switching element comprises an IGT.

Claim 29

A dimming circuit in accordance with claim 20 further including a bilateral trigger device connected across said ballast.