A power supply unit includes a boost converter having an input node and output node. The output node is coupled to a high-side of an H-bridge that is for supplying power to a capacitive load that is coupled to a first node and to a second node of the H-bridge. A first diode is coupled in forward direction between the first node of the H-bridge and the input node of the boost converter. A second diode is coupled in forward direction between the second node of the H-bridge and the input node of the boost converter.