A negative pressure wound therapy apparatus that can include a wound dressing, a fluid collection device, a vacuum pump comprising a pump motor, and tubing can be powered by auxiliary power sources such as high efficiency batteries, photovoltaic panels or cells, fuel cells, combustion generators, human powered generators, or other mechanical, electrical, or chemical power sources such as hand operated dynamos or wound springs, or any combination of the foregoing. Additionally, the apparatus can include a high efficiency pressure controller for controlling the output of the vacuum pump. In some embodiments, the pressure controller can control the pump without using a processor, and can have other features such as an intermittent delay function and an anti-stall mechanism to reduce the energy consumption of the apparatus.