EBL having a feedback circuit and a method for ensuring low temperature lamp operation at low dimming levels
First Claim
1. A dimmable ballast lamp, including:
- a lamp;
a ballast circuit including an inverter coupled to and for powering the lamp and having in response to a dimming control signal at least one adjustable operational characteristic selected from the group of duty cycle and switching frequency;
a dimming circuit coupled to the inverter for producing said dimming control signal in response to a control input signal which is based when avoiding a shutoff condition of said lamp on a first precontrol input signal being raised by addition thereto of a second precontrol input signal;
a dimming control interface for producing said first precontrol input signal based on a selected brightness level; and
a feedback control circuit for detecting the shutoff condition of said lamp and for producing said second precontrol input signal in response to detection of said shutoff condition, said dimming circuit being responsive to said first precontrol input signal and to said second precontrol input signal for adjusting the brightness of said lamp to a higher brightness level than said selected brightness level independent of the ballast circuit impedance to thereby avoid the shutoff condition of said lamp.
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Accused Products
Abstract
A dimming ballast lamp includes a lamp, a ballast circuit for converting AC input power to AC output power, a dimming interface circuit for generating a dimming control signal having a voltage level indicative of a selected dimming level of the lamp and a dimming circuit responsive to the dimming control signal for controlling operation of the ballast circuit. A feedback control circuit detects the lamp voltage and produces a feedback control signal in response to the lamp voltage exceeding a perscribed threshold voltage level. The dimming circuit, responsive to the feedback control signal, controls operation of the ballast circuit so as to increase lamp current thereby increasing the dimming level of the lamp, ensuring low temperature ignition of the lamp and protecting against lamp shutdown.
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Citations
20 Claims
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1. A dimmable ballast lamp, including:
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a lamp; a ballast circuit including an inverter coupled to and for powering the lamp and having in response to a dimming control signal at least one adjustable operational characteristic selected from the group of duty cycle and switching frequency; a dimming circuit coupled to the inverter for producing said dimming control signal in response to a control input signal which is based when avoiding a shutoff condition of said lamp on a first precontrol input signal being raised by addition thereto of a second precontrol input signal; a dimming control interface for producing said first precontrol input signal based on a selected brightness level; and a feedback control circuit for detecting the shutoff condition of said lamp and for producing said second precontrol input signal in response to detection of said shutoff condition, said dimming circuit being responsive to said first precontrol input signal and to said second precontrol input signal for adjusting the brightness of said lamp to a higher brightness level than said selected brightness level independent of the ballast circuit impedance to thereby avoid the shutoff condition of said lamp. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A dimmable ballast lamp, including:
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a lamp; a ballast circuit for converting AC input power to AC output power and for delivering said AC output power to said lamp to produce a lamp voltage and a lamp current; a dimming dimming interface circuit for generating a dimming control signal having a voltage level indicative of a selected dimming level of said lamp; a dimming circuit responsive to said dimming control signal for controlling operation of said ballast circuit in such a manner as to adjust said lamp current to a level proporational to the voltage level of said dimming control signal, to thereby drive said lamp to said selected dimming level; a feedback control circuit for detecting said lamp voltage and for producing a feedback control signal in response to said lamp voltage exceeding a perscribed threshold voltage level, said feedback control signal having a voltage exceeds said perscribed threshold voltage level; and
,wherein said dimming circuit is responsive to said dimming control signal being raised by addition thereto of said feedback control signal for controlling operation of said ballast circuit in such a manner as to increase said lamp current, to thereby increase the dimming level of said lamp. - View Dependent Claims (13, 14, 15, 16)
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17. A method for operating a dimmable ballast lamp in such a manner as to protect against shutoff of the lamp, comprising the steps of:
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generating a dim signal representing a desired brightness; detecting a shutoff condition of the lamp; producing a control signal in response to detection of said shutoff condition; and
,using said control signal to increase the level of the dim signal such that the desired brightness of the lamp is increased to a higher level and the shutoff condition is avoided. - View Dependent Claims (18, 19, 20)
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Specification