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Auckland, New Zealand

Wang B.,University of Auckland | Hu A.P.,University of Auckland | Budgett D.,University of Auckland | Budgett D.,Telemetry Research Ltd
IEEE Transactions on Biomedical Circuits and Systems | Year: 2012

This paper proposes a new control method for regulating power flow via transcutaneous energy transfer (TET) for implantable heart pumps. Previous work on power flow controller requires a fast feedback loop that needs additional switching devices and resonant capacitors to be added to the primary converter. The proposed power flow controller eliminates these additional components, and it relies solely on a slow feedback loop to directly drive the primary converter to meet the heart pump power demand and ensure zero voltage switching. A controlled change in switching frequency varies the resonant tank shorting period of a current-fed push-pull resonant converter, thus changing the magnitude of the primary resonant voltage, as well as the tuning between primary and secondary resonant tanks. The proposed controller has been implemented successfully using an analogue circuit and has reached an end-to-end power efficiency of 79.6% at 10 W with a switching frequency regulation range of 149.3 kHz to 182.2 kHz. © 2011 IEEE. Source

Chen F.-Y.B.,University of Auckland | Wang B.,University of Auckland | Hu A.P.,University of Auckland | Budgett D.,Telemetry Research Ltd
Proceedings of the IEEE International Conference on Industrial Technology | Year: 2013

This paper proposes a novel zero voltage switching control method for a push-pull primary resonant converter by regulating its primary resonant shorting period. Also, the same inductive power transfer channel is used to establish a low bandwidth communication channel between the primary and secondary circuits based on frequency disturbance and temporary shorting of the power pickup. Practical results show that the system is able to track zero-voltage switching frequency automatically under variations of load, magnetic coupling, and other circuit parameters; and at the same time it can transmit and detect simple low bandwidth ON or OFF signals between the primary and secondary circuits. © 2013 IEEE. Source

Wang B.,University of Auckland | Hu A.P.,University of Auckland | Budgett D.,Telemetry Research Ltd
Proceedings of the IEEE International Conference on Industrial Technology | Year: 2013

In order to reduce the power loss and associated temperature rise in the implanted side of the transcutaneous energy transfer system, the passive Schottky current doubler rectifier is replaced with an autonomous synchronous rectifier. Two options of driving the synchronous rectifier are proposed, passive autonomous operation and active gate drive using a buffer circuit. The synchronous rectifiers are found to have about 1.3% higher end-to-end efficiency compared to the Schottky only current doubler for the rated heart pump operational power of 10W. © 2013 IEEE. Source

Wang B.,University of Auckland | Hu A.P.,University of Auckland | Budget D.M.,University of Auckland | Budget D.M.,Telemetry Research Ltd
Proceedings of the 2010 5th IEEE Conference on Industrial Electronics and Applications, ICIEA 2010 | Year: 2010

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. © 2010 IEEE. Source

Guild S.-J.,University of Auckland | Barrett C.J.,University of Auckland | McBryde F.D.,University of Auckland | Van Vliet B.N.,Memorial University of Newfoundland | And 4 more authors.
Experimental Physiology | Year: 2010

Since the first recording of sympathetic nerve activity (SNA) early last century, numerous methods for presentation of the resulting data have developed. In this paper, we discuss the common ways of describing SNA and their application to chronic recordings. Suggestions on assessing the quality of SNA are made, including the use of arterial pressure wave-triggered averages and nasopharyngeal stimuli. Calculation of the zero level of the SNA signal from recordings during ganglionic blockade, the average level between bursts and the minimum of arterial pressure wave-triggered averages are compared and shown to be equivalent. The use of normalization between zero and maximal SNA levels to allow comparison between groups is discussed. We recommend that measured microvolt levels of integrated SNA be presented (with the zero/noise level subtracted), along with burst amplitude and frequency information whenever possible. We propose that standardization of the quantifying/reporting of SNA will allow better comparison between disease models and between research groups and ultimately allow data to be more reflective of the human situation. © 2010 The Physiological Society. Source

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