Application of PWM Actuation of Capacitor Capacitance to Stabilize the Output Characteristics of Implants’ Inductive Power Supply System

In order to compensate displacements of the transmitting and receiving inductance coils, a method of changing the capacitor’s capacitance in the transmitting part of the system of inductive power transfer to implantable devices is applied. However, the use of this method does not completely solve the problem of controlled management of a capacitor’s capacitance. In this study, to maintain constant output power in an inductive power transfer system, a method for compensating the displacements of inductance coils is proposed using the pulse-width modulation (PWM) actuation of the circuit’s capacitance by two series capacitors and a switching transistor connected in parallel to one of the capacitors. The effect of the PWM signal’s duty cycle, PWM signal’s frequency, and the intrinsic characteristics of the transistors on the amount of output power in an inductive power transfer system based on the PWM actuation of the capacitance is studied. It is demonstrated that there are many combinations of the capacitances of two capacitors that can achieve the required equivalent capacitance even with an identical duty cycle of the PWM signal. It is established that increasing the frequency of the PWM signal and reducing the switching transistor’s transconductance allow increasing the output power of an inductive power transfer system.