Closed Loop Frequency Control for an Hyperthermia Magnetic Field Applica

M. E. SPINELLI; A. VEIGA; S. A. GONZÁLEZ

Simposio; 8th IEEE Latin American Symposium on Circuits & Systems; 2017

An automatic frequency control for a magnetic field applicator is presented. It operates at a frequency between 100-200 kHz and is intended for a magnetic hyperthermia equipment used in oncology therapy experiments on small animals. The proposed scheme is based on a phase locked loop (PLL) which ensures operation at the natural frequency of a high Q resonant circuit, which includes a coil that produces the magnetic field. An analysis of the different blocks composing the system is presented and also an study of its stability and perturbation rejection features. Preliminary experimental results obtained on a low power prototype allowed to verify the theoretical models assumed for the different transfer functions the circuit involves. It presents a recovery time smaller than 10 ms for variations in the inductance value.