Lighting ballast having boost converter with on/off control and method of ballast operation

A ballast for driving a gas discharge lamp, comprising:

• an input stage operable to receive an alternating current (AC) input voltage having a peak voltage level and to provide a direct current (DC) bus voltage having a boosted voltage level that is greater than the peak voltage level of the AC input voltage;
• an output stage for converting the DC bus voltage into a high-frequency AC output voltage for driving the lamp;
• further wherein the input stage has a control input;
• further comprising:
• a control stage responsive to a desired light level signal and having an output coupled to the control input of the input stage for sending an input stage control signal representative of a desired input stage mode of operation;
• wherein the input stage changes the DC bus voltage between the boosted voltage level and a reduced voltage level based on the input stage control signal.

A method for reducing the power consumption of a ballast for driving a gas discharge lamp comprising the steps of:

• receiving an alternating current input voltage having a peak voltage level and providing a direct current output voltage having a boosted voltage level that is greater than the peak voltage level;
• converting the direct current output voltage into a high-frequency alternating current voltage in an output stage for driving the lamp;
• receiving a desired light level signal corresponding to a desired light level of the lamp and controlling the light level of the lamp based on the desired light level;
• and
• reducing the direct current output voltage from the boosted voltage level to a reduced voltage level when the desired light level signal is below a first predetermined desired light level.