US Patent 7394627 Frequency converter having an intermediate circuit without any capacitors

A frequency converter includes an intermediate circuit without any capacitors and an electronics which is supplied with power from a power supply device. The power supply device has a buffer capacitor which is disposed on an input side of the power supply device and connected electrically in parallel with the intermediate circuit. Connected to the buffer capacitor is a supply line in which a decoupling diode is disposed. A semiconductor adapted to be switched off is connected electrically back-to-back in parallel with the decoupling diode and has a control output which is connected to an output of an identification device for recognizing a power-line failure.