Method and circuit for controlling current in a high pressure discharge lamp

A method for controlling current during run-up of a high pressure discharge lamp, the method comprising the steps of:

• operating a buck converter at a first duty cycle during a first period of time;
• altering the duty cycle of the buck converter at a first predetermined time;
• and
• operating the buck converter at a second duty cycle after the first predetermined period of time, wherein the second duty cycle is different than the first duty cycle.

A method for controlling lamp current during run-up of a high pressure discharge lamp, the method comprising the steps of:

• detecting ignition of the high pressure discharge lamp;
• operating a buck converter at a first duty cycle for a first period of time during run-up to maintain the current in the lamp below a specified maximum value;
• operating the buck converter at a second duty cycle for a second period of time after the first period, wherein the second duty cycle is greater than the first duty cycle;
• and
• altering the duty cycle of the buck converter during a third period of time to reduce the lamp current before steady state operation is reached.