US Patent 11377893 Closing speed control in power off

A swing door operator for moving at least one door leaf between a first and a second position includes a motor and a mechanical drive unit connected to and capable of moving the at least one door leaf from the first position to the second position, and a braking circuit connected to the motor. The braking circuit includes a diode circuit arranged to apply a voltage drop to the motor. The motor is adapted to act as a generator and is configured to generate a voltage when the drive unit moves the at least one door leaf, and to brake a movement of the at least one door leaf when the voltage generated by the motor is larger than the voltage drop applied by the diode circuit. The diode circuit includes at least three diodes connected in series.