A DC-DC converter and an organic light emitting display using the DC-DC converter are provided. The DC-DC converter can generate a first voltage and a second voltage lower than the first voltage, where the DC-DC converter includes a first voltage generator for generating the first voltage by switching an input voltage and accumulating energy in a first coil, a second voltage generator for generating the second voltage by switching an input voltage and accumulating energy in a second coil, a pulse width modulation (PWM) controller for controlling switching times of the first and second voltage generators in accordance with a control signal, and a voltage adjuster for generating the control signal to vary a voltage level of the second voltage and control a time of change of the second voltage.