Mixed mode control for ballast circuit
AssigneeKoninklijke Philips Electronics N.V.
InventorsQiong Li, Ihor Wacyk
Life of this patent
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Abstract
A ballast system in which mixed-mode gate signals are used to control the ballast circuit so as to produce a more straight ballast lines such than only a single solution exists between ballast lines and lamp lines over the whole operating range, whereby a stable of lamp performance is achieved. In a preferred embodiment, symmetric and asymmetric modes are arranged alternatively in every other switching cycle to produce mixed-mode PWM gate signals.
Claims16
A ballast for driving lamps, comprising:
- a ballast circuit having a ballast impedance line for each duty cycle and having at least two switches, said switches being turned on and off in switching cycles by applying respective gate voltages so as to producing a stable driving voltage for said lamps;
- a controller for generating gate signals associated with each of said switches respectively and transmitting said gate signals to said ballast circuit for activating or deactivating said gate voltages for each of said switches;
- and
- wherein said gate signals are of a first mode in some of said switching cycles and are of a second mode in other switching cycles, said first mode causing said ballast circuit to produce concave ballast impedance lines and said second mode causing said ballast circuit to produce convex ballast impedance lines.
A controller for controlling a ballast circuit for driving lamps, said ballast having at least two switches being turned on and off in switching cycles by applying gate voltages thereon for producing a stable driving voltage for said lamps, said controller comprising:
- a generating circuit for generating gate signals for activating and deactivating said gate voltages of said switches;
- means for transmitting said generated gate signals to said ballast circuit;
- wherein said gate signals are of at least two different modes in different switching cycles such that said ballast circuit is caused by said gate signals to have only a single solution between ballast impedance lines and lamp impedance lines for all duty cycles.
A method of controlling a ballast circuit for driving lamps, said ballast circuit having at least two switches being turned on and off in switching cycles, said method comprising steps of:
- generating gate signals of a first mode in some switching cycles and of a second mode in other switching cycles, said first mode causing said ballast circuit to produce concave ballast impedance lines and said second mode causing said ballast circuit to produce convex ballast impedance lines;
- and
- transmitting said gate signals to said ballast circuit for activating and deactivating a gate voltage for turning on or off each of said switches.
Dependencies are inferred from the claim text.