Ballast for a discharge lamp

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 at a suitable switching frequency and for a suitable on-period so as to regulate a DC output being applied to drive the discharge lamp;
• a controller which monitors the DC output and varies 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 high pre-starting voltage enabling the lamp to start as well as a low operating voltage for keeping the operation of the lamp;
• wherein said ballast includes:
• an input DC voltage monitor which monitors an input DC voltage supplied from said DC voltage source, and
• said controller varying at least one of the switching frequency and the on-period of said switching element based upon the monitored input DC voltage in order to increase the output voltage to said pre-starting voltage, irrespective of a possible variation in the input DC voltage, in substantially the same time as is done when the input DC voltage is at an available maximum voltage.

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 at a suitable switching frequency and for a suitable on-period so as to regulate a DC output being applied to drive the discharge lamp;
• a controller which monitors the DC output and varies 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 high pre-starting voltage enabling the lamp to start as well as a low operating voltage for keeping the operation of the lamp;
• wherein said ballast includes:
• an input DC voltage monitor which monitors an input DC voltage supplied from said DC voltage source, and
• said controller including a function of varying at least one of the switching frequency and the on-period of said switching element based upon the monitored input DC voltage in a direction of accelerating the increase of the output DC voltage towards said pre-starting voltage.

A method of operating a discharge lamp with the use of a DC-DC converter, said DC-DC converter being adapted to 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 at a suitable switching frequency and for a suitable on-period so as to regulate a DC output being applied to drive the discharge lamp;

• said method comprising the steps of:
• monitoring the DC output and 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 high pre-starting voltage enabling the lamp to start as well as a low operating voltage for keeping the operation of the lamp;
• monitoring an input DC voltage supplied from said DC voltage source;
• and
• varying at least one of the switching frequency and the on-period of said switching element based upon the monitored input DC voltage in a direction of accelerating the increase of the output DC voltage towards said pre-starting voltage.