The disclosed invention varies the width of the energy pulses with constant frequencyand constant amplitude to regulate the amount of energy transferred from an energytransmitting device placed outside a patient to an energy receiver inside thepatient. The pulse width is achieved with a modulation technique, PWMT, to controlthe amount of energy transferred from the external energy transmitting coilin the system to the implanted receiver. The PWMT is used to digitally vary theamount of power from the power amplifier that drives the transmitting coil. Comparedto previous analog systems a PWM system is a great deal more efficient and can easilybe controlled from a digital domain system such as a microprocessor.
