It would be advantageous to reduce weight and size of high voltage power supplies, to increase frequency of pulses of high voltage, and to improve control of magnitude of high voltage. The embodiments of high voltage power supplies described herein can solve these problems. The high voltage power supply can be used with an x-ray tube. The high voltage power supply can comprise an array of planar transformers each defining a stage with an AC input and a DC output. Each stage can comprise a pair of flat, coil windings adjacent one another and including a primary winding electrically-coupled to the AC input and configured to induce a current in a secondary winding. At least two stages can be electrically-coupled together in series with the DC output of one stage electrically-coupled to an input of the other stage such that a voltage is amplified across the stages.