Development of a push-pull current doubler synchronous rectifier for powering heart pumps

A transcutaneous energy transfer system has been developed to provide the power required to drive an implanted heart pump. This will eliminate the risk of infection associated with the existing power transfer method - passing a wire through the skin. For implanted devices, particularly heart pumps which need large amount of power to operate, reducing heat generation is always of interest, and this paper proposes the use of a synchronous rectifier topology. A push-pull current doubler topology has been used due to its simple topology with only two low side MOSFETs to drive. The control circuitry has three stages, including voltage detection, controller and gate driver, to ensure the synchronous MOSFETs bypass the parallel Schottky diodes, and can operate at a high frequency (180kHz) with zero voltage switching. Practical efficiency measurements have shown that the main circuit of the current doubler synchronous rectifier has lower power losses than its Schottky only counterpart, however there is a need to further reduce the power loss of the control circuitry to realise the full potential of the proposed synchronous rectifier.