Ballast for a discharge lamp
AssigneeMatsushita Electric Works, Ltd.
InventorsHirofumi Konishi, Toshiaki Nakamura, Takashi Kambara, Miki Kotani, Toshifumi Tanaka
Life of this patent
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Abstract
A ballast for a discharge lamp includes a DC-DC converter which provides a regulated DC output so as to start and keep operating the lamp. A controller is included to give a closed-loop control for regulating the DC output based upon a monitored DC output. The controller also provides an open-loop control which interrupts the closed-loop control for a limited period immediately after the initiation of the lamp discharge in order to supplement a sufficient lamp current which would not expected with the closed-loop control, thereby successfully complementing the lamp start and proceeding to the stable lamp operation.
Claims19
A ballast for a discharge lamp comprising:
- a DC-DC converter adapted to receive an input DC voltage from a DC voltage source, said DC-DC converter including a switching element which is driven to repetitively switch said input DC voltage to provide a variable DC output being applied to drive said discharge lamp;
- a controller which monitors the DC output and provides a closed-loop control of varying the duty of said switching element based upon the monitored DC output in order to regulate the DC output such that the DC-DC converter provides a starting voltage of initiating a discharge of said discharge lamp as well as an operating voltage of keeping the operation of said discharge lamp;
- wherein said controller provides an open-loop control which interrupts said closed-loop control to give a start-assisting period in which the switching element is controlled to turn on and off in a predetermined pattern to give said DC output of a sufficient level for successfully complementing the starting of said discharge lamp,
- said start-assisting period starting upon recognition that the DC output satisfies a first reference indicative that the discharging of said discharge lamp is just started and ending upon recognition of a condition indicative of the completion of the starting of said discharge lamp.
A method of operating a discharge lamp with the use of a DC-DC converter,
- said converter being adapted to be receive an input DC voltage from a DC voltage source and including a switching element which is driven to repetitively switch said input DC voltage to provide a variable DC output being applied to drive said discharge lamp;
- said method comprising the steps of:
- monitoring the DC output and making a closed-loop control of varying the duty of said switching element based upon the monitored DC output in order to regulate the DC output such that the DC-DC converter provides a starting voltage of initiating a discharge of said discharge lamp as well as an operating voltage of keeping the operation of said discharge lamp;
- making an open-loop control which interrupts said closed-loop control to give a start-assisting period in which the switching element is controlled to turn on and off in a predetermined pattern to give the DC output of a sufficient level for successfully complementing the starting of said discharge lamp, and
- starting said start-assisting period upon recognition that the DC output satisfies a first reference indicative that the discharging of said discharge lamp is just started and ending said start-assisting period upon recognition of a condition indicative of the completion of the starting of said discharge lamp.
Dependencies are inferred from the claim text.