Transcutaneous transformers in power supply system for an artificial heart

Abstract

The pump in an artificial heart system generally requires a power of 12-35 W to operate. Electrical energy can be transmitted transcutaneously by means of the inductive coupling between the primary coil and secondary coil of the transcutaneous transformer. The primary part of the transcutaneous transformer is located on the skin and the secondary is implanted inside the body. However, the energy transmission efficiency is low because of the large gap (generally 5∼15 mm) between the coils. In this case, the design of the transcutaneous transformer has been one of the key challenges in developing an efficient power supply system. Three types of transcutaneous transformers have been investigated. The first type is ferrite pot core transcutaneous transformer. The second type use amorphous fibers as the cores. The third type is a transcutaneous transformer with a combination core which has a ferrite primary core and an amorphous secondary core. A high frequency series resonant DC-DC converter is presented for a transcutaneous energy transmission system. By simulating with various values of coil geometry, the shape of each type of transcutaneous transformer has been studied with the aim of obtaining maximum output power. For each type of transformer, a power rating of more than 20 W can be delivered from a 12 V power source. This is sufficient for driving the heart pump. Circuit analysis on the transfer gain has also been presented, the simulation results can be. well explained by theoretical calculation. Besides all this, these three types are also compared with each other with a view of the potential for clinical application.