Design of a transcutaneous power regulator for artificial hearts

Recently, a high efficiency transcutaneous power regulator for artificial heart with PWM-PLL control has been proposed in the literature. In this paper, a new method of sensing the output voltage inside the human body utilizing the same power transcutaneous transformer as signal transmission media is introduced. The feedback signal is modulated in the secondary at a frequency band above the PWM-PLL cut-off frequency and below the converter switching frequency. In this way, the feedback signal can be demodulated from the primary current measured. A SPICE macromodel for the resonant converter is developed to help designing the control loop and the selection of modulation-demodulation frequency banks. Hardware prototype using single-chip DSP together with analog filters was built and control software was implemented as DSP program codes. PLL switching frequency locking function is done by using on-chip analog comparator, it saves extra hardware for PLL control. The voltage loop control algorithm uses a modified PI controller with input voltage feed-forward and output loading estimation.