Constant current source mirror tank dimmable ballast for high impedance lamps
AssigneeUniversal Lighting Technologies, Inc.
InventorsWei Xiong, Thomas Lunn, Christopher Radzinski
Life of this patent
Estimating the term…
Abstract
A constant current source mirror tank dimmable ballast operates multiple high impedance lamps in a stable and balanced manner. The dimmable ballast has an inverter connected to two third-order resonant circuits. These third-order resonant circuits dominate the transfer function of the ballast circuits. Consequently, changes in the impedance of the lamp do not affect the current output to the lamps.
Claims12
A dimming electronic ballast for operating a plurality of two or more high impedance lamps comprising:
- an inverter;
- a first ballast circuit comprising a first lamp output terminal configured to couple a first lamp current from the ballast to a first one of a plurality of two or more high impedance lamps;
- a second ballast circuit comprising a second lamp output terminal configured to couple a second lamp current from the ballast to a second one of a plurality of two or more high impedance lamps;
- the first ballast circuit further comprising a first resonant tank circuit coupled between the inverter and the first lamp output terminal;
- the second ballast circuit further comprising a second resonant tank circuit coupled between the inverter and the second lamp output terminal;
- the first and second ballast circuits are electrically coupled in parallel;
- the inverter further comprising circuitry to cause the ballast to selectably operate in a full power mode and in a dimming power mode;
- each of the first and second resonant circuits comprises a resonant inductor, a resonant capacitor, and a ballast capacitor having respective component values;
- and
- wherein the respective component values for the resonant inductor, resonant capacitor, and ballast capacitor in each of the first and second resonant circuits are selected so that when the ballast is connected to a plurality of two or more high impedance lamps, the ballast is functional
- to provide substantially constant and equal first and second lamp currents when operating in the full power mode, and
- to provide substantially constant and equal first and second lamp currents when operating in the dimming power mode.
A lighting system comprising a dimmable electronic ballast for powering a plurality of gas discharge lamps, the ballast comprising:
- an inverter circuit functional to operate in a normal mode and in a lamp dimming mode;
- three or more lamp terminals configured to provide lamp currents to three or more gas discharge lamps;
- three or more resonant circuits coupled between the inverter and the corresponding three or more lamp terminals;
- each of the three or more resonant circuits comprises a third order resonant circuit having a resonant capacitor, a resonant inductor, and a ballast capacitor;
- each resonant capacitor, resonant inductor, and ballast capacitor have respective component values;
- and
- wherein the respective component values for each resonant inductor, resonant capacitor, and ballast capacitor in each of the three or more resonant circuits are selected so that when the ballast is connected to the three or more gas discharge lamps, the ballast is functional
- to provide substantially constant and equal lamp currents when operating in the normal mode, and
- to provide substantially constant and equal lamp currents when operating in the dimming mode.
Dependencies are inferred from the claim text.