An organic light emitting display device includes a DC-DC converter to supply first and second voltages to one or more pixels. The DC-DC converter includes a first voltage supply to convert an input voltage to a first voltage and a second voltage supply to convert the input voltage to a second voltage. The first and second voltages are coupled to opposing ends of the one or more pixels. The first voltage supply includes a first inductor between a first input terminal and first node, a first transistor between the first node and a reference potential, a second transistor between the first node and first output terminal, a first diode between the first node and a second node, a second diode between the second node and first output terminal, and a first switch between the second node and first output terminal.