A local coil for an MRI system includes a signal antenna to receive a magnetic resonance signal and a tuning/detuning circuit to subject the signal antenna part to switch control according to a control signal. The tuning/detuning circuit is connected to the signal antenna part. The tuning/detuning circuit includes a control signal interface, a resonant circuit and an AC/DC conversion circuit. The control signal interface receives the control signal. The resonant circuit includes a diode. The AC/DC conversion circuit converts an alternating current generated by an electromagnetic wave to a direct current. The AC/DC conversion circuit is connected in series with the diode. A small detuning control current may be used, and detuning control circuitry may be reduced.