Embodiments of negative pressure wound therapy systems and methods are disclosed. In one embodiment, an apparatus includes a driving circuit that supplies a driving signal to a negative pressure source to cause the negative pressure source to provide negative pressure via a fluid flow path to a wound dressing. The apparatus furthers include a controller that adjusts a frequency of the driving signal supplied by the driving circuit according to a comparison of a previous magnitude and a subsequent magnitude of the driving signal while the negative pressure source provides negative pressure. The transfer of power to the negative pressure source can thereby be tuned to maximize an amount of power transferred to the negative pressure source.