1. A system comprising:a light source;
a converter configured to convert AC voltage to DC operating voltage;
a power backup device coupled to the converter;
a current source coupled to the power backup device, the current source being powered by the converter, the current source being configured to receive the DC operating voltage generated by the converter through the power backup device, and the current source being configured to output a pulse-width modulated (PWM) signal to the light source based on the DC operating voltage; and
a switching device coupled to the power backup device in parallel with the current source, the switching device being configured to couple the light source to the power backup device when the current source is disabled as a result of a supply of AC voltage to the converter being interrupted.