Electronic ballast with interface circuitry for phase angle dimming control
First Claim
1. A gas discharge lamp ballast for use with a phase angle dimmer, said ballast comprising:
- a pair of mains input terminals for receiving a phase angle controlled AC mains voltage;
ballasting means for providing electrical power to a gas discharge lamp, said ballasting means including (i) a DC input at which a substantially constant DC voltage is received, (ii) a dim input separate from said DC input for receiving a dimming signal and (iii) first control means for controlling the electrical power supplied to the gas discharge lamp at a level corresponding to a characteristic of the dimming signal;
power supply means connected to said mains input terminals for supplying the substantially constant DC voltage to said DC input of said ballasting means; and
dim signal deriving means for deriving the dimming signal from the phase angle controlled AC mains voltage and for supplying the dimming signal to said dim input of said ballasting means, said dimming signal being independent of the DC voltage provided by said power supply means at said DC input of said ballasting means.
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Accused Products
Abstract
A gas discharge lamp dimming ballast has a two wire input for connection to the hot dimmed and neutral leads of a phase control dimmer. The ballast has an improved topology in which a pre-conditioner supplies a substantially constant DC voltage to a ballast stage including an inverter, a resonant tank output and a control circuit. A dimming interface circuit derives a dimming signal having a voltage equal to the average value of the rectified output voltage of a full-bridge rectifier feeding the pre-conditioner circuit. The dim signal is independent of the DC rail voltage and, in combination with the maintenance of a substantially constant DC rail voltage, permits of improved dimming control while providing the ease of installation of a two wire ballast. The response time of the interface circuit relative to the pre-conditioner is selected to avoid power imbalances. The ballast also includes an EMI filter and circuitry to prevent capacitive hold-up by the EMI filter of the rectified voltage to preserve the conduction angle for the interface circuit.
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Citations
28 Claims
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1. A gas discharge lamp ballast for use with a phase angle dimmer, said ballast comprising:
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a pair of mains input terminals for receiving a phase angle controlled AC mains voltage; ballasting means for providing electrical power to a gas discharge lamp, said ballasting means including (i) a DC input at which a substantially constant DC voltage is received, (ii) a dim input separate from said DC input for receiving a dimming signal and (iii) first control means for controlling the electrical power supplied to the gas discharge lamp at a level corresponding to a characteristic of the dimming signal; power supply means connected to said mains input terminals for supplying the substantially constant DC voltage to said DC input of said ballasting means; and dim signal deriving means for deriving the dimming signal from the phase angle controlled AC mains voltage and for supplying the dimming signal to said dim input of said ballasting means, said dimming signal being independent of the DC voltage provided by said power supply means at said DC input of said ballasting means. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A ballast for use with a phase angle dimmer, said ballast comprising:
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mains input terminals for connection to a common line and a hot dimmed line from a phase angle dimmer, the hot dimmed line carrying an AC mains voltage having a conduction phase angle controlled by the phase angle dimmer, said mains voltage having a mains frequency; rectifier means having a rectifier output, said rectifier being connected to said mains input terminals for providing a full wave rectified DC output voltage at said rectifier output, said rectified output voltage including the conduction phase angle of the phase controlled AC mains voltage; filtering means for suppressing high frequency harmonics from entering the mains supply, said filtering means including a filter capacitor charged by said rectified output voltage; power supply means for providing a DC supply voltage, said power supply means including an input receptive of said rectified output voltage, said power supply means including (i) a controllable switching means switchable between a conductive and a non-conductive switching state, one of said switching states providing a discharge path for said filter capacitor, and (ii) control means for controlling the switching state of said switching means, said control means switching said switching state of said switching means at frequencies substantially higher than said mains frequency to control the DC supply voltage; ballasting means for providing electrical power to a gas discharge lamp, said ballasting means including (i) a DC input receptive of the DC output voltage of said power supply means, (ii) a dim input separate from said DC input for receiving a dimming signal and (iii) means for controlling the electrical power supplied to the gas discharge lamp at a level corresponding to a characteristic of the dimming signal; and dim signal deriving means for deriving the dimming signal from the phase controlled rectified DC output voltage and for supplying the dimming signal to said dim input of said ballasting means, said dimming signal being independent of the DC supply voltage provided at said DC inputs of said ballasting means by said power supply means, and wherein said control means of said power supply means includes means for maintaining said high frequency switching of said switching means so as to discharge said filter capacitor when said phase controlled rectified output voltage is at or near zero, thereby to alleviate capacitive hold-up of the rectified output voltage by said filter capacitor. - View Dependent Claims (14, 15, 16, 17, 18)
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19. A ballast for use with a phase angle dimmer, said ballast comprising:
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only two mains input terminals for connection to a common line and a hot dimmed line from a phase angle dimmer, the hot dimmed line carrying an AC mains voltage having a conduction phase angle controlled by the phase angle dimmer; a full bridge rectifier connected to the two mains input terminals for providing a full wave rectified DC output voltage, the rectified DC output voltage including the conduction phase angle of the phase controlled AC mains voltage and having a peak voltage; a pre-conditioner circuit connected to the full-bridge rectifier, said pre-conditioner circuit including an up converter for providing a DC supply voltage at a level higher than the peak voltage of the rectified DC output voltage from said full-bridge rectifier; an inverter circuit receptive of the DC supply voltage from said pre-conditioner circuit, said inverter converting the DC supply voltage from said preconditioner to a high frequency AC voltage having a frequency substantially greater than the frequency of the AC mains supply; a resonant tank output circuit receptive of the high frequency AC inverter output voltage, said output circuit having lamp connection terminals for connection to a gas discharge lamp, said output circuit providing a substantially sinusoidal lamp current to a gas discharge lamp connected at said lamp terminals; a control circuit connected to the inverter for controlling the AC inverter output voltage, said control circuit having (i) means for receiving a dimming signal separate from the DC output of the pre-conditioner circuit, (ii) means for sensing the power supplied to the gas discharge lamp, and (iii) means for adjusting the AC inverter output frequency fed to said resonant tank output circuit to thereby control the electrical power supplied to the gas discharge lamp at a level corresponding to the voltage of the dimming signal; and a dimming interface circuit receptive of the phase-controlled rectified DC output voltage from said full-bridge rectifier, said dimming interface circuit including means for outputting a dimming signal having a voltage substantially equal to the average value of the rectified line voltage. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26, 27, 28)
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Specification