Methods and apparatus for heating a substrate in a process chamber are provided herein. In some embodiments, an apparatus for heating a substrate in a process chamber includes a lamp group comprising one or more sets of lamps to provide radiant energy to heat a substrate when disposed in the process chamber, wherein each set of lamps comprises a plurality of lamps wired in series, and wherein each set of lamps is wired in parallel with respect to other sets of the one or more sets of lamps; an alternating current (AC) power source to produce an AC input waveform; and a lamp driver to power the lamp group, the lamp driver including a rectifier coupled to the AC power source to convert the AC input waveform to DC voltage; and a direct current to direct current (DC/DC) converter to reduce voltage of the DC power.