A power supply includes power modules. Each of the power modules includes an input stage configured to convert an input voltage into an intermediate voltage, and an output stage configured to output a DC supply voltage according to the intermediate voltage. Input terminals of the input stages in the plurality of power modules are electrically connected in series, and the input stages are configured to be controlled with at least one first common control signal having a common duty cycle. Output terminals of the output stages in the plurality of power modules are electrically connected in parallel, and the output stages are configured to be controlled with at least one second common control signal having a common duty cycle. A method of supplying power is also disclosed herein.