Medical implant system including base station and medical implant

A closed-loop control circuit for a base station for transmitting energy to a receiver by means of an electrical resonant circuit, comprising:

• the electrical resonant circuit;
• an evaluation device which is designed to compare energy transmitted to a receiver resonant circuit of the receiver with a target energy value,
• wherein the closed-loop control circuit is designed to cause a changed energy input into a receiver resonant circuit of the receiver by changing a resonant frequency of the electrical resonant circuit on the basis of a result of the comparison,
• wherein the evaluation device is designed to determine the transmitted energy on the basis of a modulation property of a feedback signal that couples to the electrical resonant circuit,
• wherein the closed-loop control circuit is designed to at least partially counteract a change in a coupling of the electrical resonant circuit to the receiver resonant circuit by changing the resonant frequency of the electrical resonant circuit,
• wherein the closed-loop control circuit is designed to move the resonant frequency of the electrical resonant circuit away from a natural frequency of the receiver resonant circuit if the transmitted energy is greater than the target energy value,
• characterized in that the closed-loop control circuit comprises a resistive element which is coupled to the resonant circuit, has a temporally variable resistivity and comprises an open-loop control connection for receiving an open-loop control signal for changing the resistivity.