METHODS AND APPARATUS FOR A DIMMABLE BALLAST FOR USE WITH LED BASED LIGHT SOURCES
First Claim
1. A lighting ballast comprising:
- a full wave bridge rectifier configured to receive an AC line voltage having a line frequency, and provide a time varying DC voltage comprising a rectified AC line voltage at a first output node and a second output node of said full wave bridge rectifier;
a driver circuit configured to receive a supply voltage derived from said time varying DC voltage, said driver circuit configured to provide a periodic first output signal and a periodic second output signal wherein said first output signal and said second output signal operate at a switching frequency less than 100 kHz;
a first switching element having a first terminal connected to said first output node of said full wave bridge and a second terminal connected to an input of a tank circuit, said first switching element configured to receive said first output signal and in response connect said first terminal to said second terminal thereby providing said time varying DC voltage to said input of said tank circuit; and
a second switching element having a first terminal connected to said input of said tank circuit and a second terminal connected said second output node of said full wave bridge rectifier, said second switching element configured to receive said second output signal and in response connect said first terminal of said second switching element to said second terminal of said second switching element thereby connecting said input of said tank circuit to said second output node of said full wave bridge rectifier;
a non-electrolytic capacitor connected across said first output node and said second output node of said full wave bridge, wherein said non-electrolytic capacitor is configured to at least partially discharge when said first switching element provides said time varying DC voltage to said input of said tank circuit, said non-electrolytic capacitor configured to charge when said first switching element does not connect said time varying DC voltage to the input of said tank circuit,wherein said lighting ballast does not have an electrolytic capacitor having a first terminal connected to said first output node and a second terminal connected to said second output node,wherein said tank circuit is configured to operate at a resonant frequency less than or equal to said switching frequency andsaid tank circuit comprises;
a) a resonant circuit comprising an inductor connected in series with a second capacitor, said resonant circuit configured to generate an alternating voltage,b) a rectifier circuit coupled to said resonant circuit, said rectifier configured to generated a second-DC voltage, andc) one LED or a plurality of LEDs connected in series configured to receive said second time varying DC voltage to generate light.
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Accused Products
Abstract
Methods and apparatus for powering a dimmable ballast operating with LED light source(s) are provided. In one embodiment, the ballast circuit includes sections comprising: power input, full wave bridge rectifier, voltage regulator, integrated circuit driver, switching transistors, bypass capacitor, resonant circuit, rectifier diodes, and an LED light source. The resonant circuit receives energy from the voltage source and the bypass capacitor every switching cycle, and provides current to the rectifier diodes and one or more LEDs for generating light. Further, because the current flowing into the resonant circuit is substantially sinusoidal and in line with the input voltage, the circuit exhibits a desirable power factor. The ballast circuit can also effectively dimmed over a wide range using a phase angle dimmer, allowing further energy savings.
220 Citations
30 Claims
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1. A lighting ballast comprising:
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a full wave bridge rectifier configured to receive an AC line voltage having a line frequency, and provide a time varying DC voltage comprising a rectified AC line voltage at a first output node and a second output node of said full wave bridge rectifier; a driver circuit configured to receive a supply voltage derived from said time varying DC voltage, said driver circuit configured to provide a periodic first output signal and a periodic second output signal wherein said first output signal and said second output signal operate at a switching frequency less than 100 kHz; a first switching element having a first terminal connected to said first output node of said full wave bridge and a second terminal connected to an input of a tank circuit, said first switching element configured to receive said first output signal and in response connect said first terminal to said second terminal thereby providing said time varying DC voltage to said input of said tank circuit; and a second switching element having a first terminal connected to said input of said tank circuit and a second terminal connected said second output node of said full wave bridge rectifier, said second switching element configured to receive said second output signal and in response connect said first terminal of said second switching element to said second terminal of said second switching element thereby connecting said input of said tank circuit to said second output node of said full wave bridge rectifier; a non-electrolytic capacitor connected across said first output node and said second output node of said full wave bridge, wherein said non-electrolytic capacitor is configured to at least partially discharge when said first switching element provides said time varying DC voltage to said input of said tank circuit, said non-electrolytic capacitor configured to charge when said first switching element does not connect said time varying DC voltage to the input of said tank circuit, wherein said lighting ballast does not have an electrolytic capacitor having a first terminal connected to said first output node and a second terminal connected to said second output node, wherein said tank circuit is configured to operate at a resonant frequency less than or equal to said switching frequency and said tank circuit comprises; a) a resonant circuit comprising an inductor connected in series with a second capacitor, said resonant circuit configured to generate an alternating voltage, b) a rectifier circuit coupled to said resonant circuit, said rectifier configured to generated a second-DC voltage, and c) one LED or a plurality of LEDs connected in series configured to receive said second time varying DC voltage to generate light. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A system for providing power to one LED or a plurality of LEDs comprising:
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a full wave bridge rectifier providing a rectified AC line voltage; a non-electrolytic capacitor having a first terminal and a second terminal, said capacitor having a reactance of more than 1 ohm at a switching frequency; a first switching element having a first terminal and a second terminal, said first terminal connected to said first terminal of said non-electrolytic capacitor, said first switching element configured to switch said rectified AC line voltage present on said first terminal of said first switching element to said second terminal of said first switching element at the switching frequency; a second switching element having a first terminal connected to said second terminal of said first switching element, said second switching element having a second terminal connected to said second terminal of said non-electrolytic capacitor, said second switching element configured to switch said first terminal of said second switching element to said second terminal of said second switching element at said switching frequency; a resonant circuit comprising an inductor and a first capacitor configured in series, said resonant circuit configured to have an resonant frequency that is less than or equal to said switching frequency, wherein said inductor is configured so as to not saturate at a line frequency of the AC line voltage, wherein said resonant circuit comprises a first input node connected to said second terminal of said first switching element, said resonant circuit having a second input node connected to said second terminal of said non-electrolytic capacitor, wherein an sinusoid or square wave alternating operating voltage and an alternating current is generated in said resonant circuit, and two or more diodes coupled to said resonant circuit to receive said sinusoidal or square wave voltage, said two or more diodes configured to provide a time varying DC voltage across said one LED or a plurality of LEDs, wherein said lighting ballast does not have an electrolytic capacitor having a first terminal connected to said first output node and a second terminal connected to said second output node, wherein said lighting ballast does not have an inductor connected to said full wave bridge, and wherein the ballast is configured to continuously consume no more than 20 watts of power or less. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24)
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25. A method for operating a ballast comprising:
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receiving household line voltage at a line frequency at input terminals of a full wave bridge rectifier; providing a rectified AC voltage comprising a time varying DC voltage having a peak voltage wherein said time varying DC voltage is not filtered from the line frequency, said time varying DC voltage present across a first output terminal and a second output terminal of said full wave bridge rectifier, said time varying DC voltage having a period of twice the line frequency, said time varying DC voltage present across said first output terminal and said second output terminal; connecting said first output terminal to an input node of a resonant circuit for a first time period by a switching element operating at a switching frequency, said first time period defined by the switching frequency, thereby providing said time varying DC voltage to said resonant circuit during said first time period, said resonant circuit comprising an inductor and a capacitor connected in series, said resonant circuit having a resonant frequency less than or equal to said switching frequency, said inductor configured to not saturate when a time varying current passes through said inductor having a frequency twice the line frequency; discharging at least in part a non-electrolytic capacitor into said resonant circuit during said first time period, wherein said non-electrolytic capacitor has a first terminal and a second terminal, wherein said first terminal is connected to said first output terminal of said full wave bridge rectifier and said second terminal is connected to said second output terminal of said full wave bridge rectifier, wherein further said non-electrolytic capacitor allows said time varying DC voltage to drop to a voltage value of no more than 30% of said peak voltage once during a period equal to twice the line frequency; generating an sinusoidal alternating operating voltage in said resonant circuit as a result of switching said switching element; producing a second time varying DC voltage based on rectifying said sinusoidal alternating operating voltage; and providing said second time varying DC voltage to one or more LEDs thereby generating light. - View Dependent Claims (26, 27, 28)
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29. A lighting ballast comprising:
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a full wave bridge rectifier configured to receive an AC line voltage having a line frequency, and provide a time varying DC voltage comprising a rectified AC line voltage at a first output node and a second output node of said full wave bridge rectifier; a driver circuit comprising an integrated circuit configured to receive a continuous supply voltage derived from said time varying DC voltage, said driver circuit configured to continually provide a periodic first output signal and a periodic second output signal wherein said first output signal and said second output signal operate at a switching frequency less than 100 kHz; a first switching element having a first terminal connected to said first output node of said full wave bridge and a second terminal connected to an input of a tank circuit, said first switching element configured to receive said first output signal and in response connect said first terminal to said second terminal thereby providing said time varying DC voltage to said input of said tank circuit; and a second switching element having a first terminal connected to said input of said tank circuit and a second terminal connected said second output node of said full wave bridge rectifier, said second switching element configured to receive said second output signal and in response connect said first terminal of said second switching element to said second terminal of said second switching element thereby connecting said input of said tank circuit to said second output node of said full wave bridge rectifier; a non-electrolytic capacitor connected across said first output node and said second output node of said full wave bridge, wherein said non-electrolytic capacitor is configured to at least partially discharge when said first switching element provides said time varying DC voltage to said input of said tank circuit, said non-electrolytic capacitor configured to charge when said first switching element does not connect said time varying DC voltage to the input of said tank circuit, wherein said lighting ballast does not have an electrolytic capacitor having a first terminal connected to said first output node and a second terminal connected to said second output node, wherein said tank circuit is configured to operate at a resonant frequency less than or equal to said switching frequency, and said tank circuit comprises; a) a resonant circuit comprising an inductor connected in series with a second capacitor, and a third capacitor, said resonant circuit configured to generate an alternating voltage between said inductor and said third capacitor, b) a LED light source parallel loaded to said resonant circuit configured to receive said alternating voltage and generate light. - View Dependent Claims (30)
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Specification