Two level lighting ballast

A ballast comprising:

• a self-oscillating inverter circuit having an inverter input to receive direct current (DC) voltage and an inverter output to selectively provide an alternating current (AC) lamp current to energize one or more lamps, the self-oscillating inverter circuit comprising:
• a switching circuit, wherein the switching circuit operates at a switching frequency;
• a feedback transformer connected to the inverter output to drive the switching circuit as a function of the lamp current at the inverter output;
• and
• an impedance component connected in parallel with the feedback transformer between the inverter input and the feedback transformer;
• the switching circuit operating such that, when the impedance component is enabled, the switching circuit operates at a switching frequency in a first frequency range and a first lamp current is provided to the one or more lamps;
• the switching circuit operating such that, when the impedance component is disabled, the switching circuit operates at a switching frequency in a second frequency range and a second lamp current is provided to the one or more lamps, wherein the first frequency range is lower than the second frequency range and the first lamp current is greater than the second lamp current;
• and
• a control circuit connected to the impedance component of the inverter circuit, wherein the control circuit selectively operates the impedance component between a first state, in which the impedance component is enabled, and a second state, in which the impedance component is disabled;
• wherein the control circuit comprises a first transistor and a second transistor, wherein the first transistor is selectively connected and disconnected to an AC power supply, and the second transistor is connected to the first transistor and to the impedance component, wherein when the first transistor is connected to the AC power supply, the first transistor is conductive, the second transistor is nonconductive, and the impedance component is disabled, and when the first transistor is disconnected from the AC power supply, the first transistor is nonconductive, the second transistor is conductive, and the impedance component is enabled.