Motor drive device including shared converter

A motor drive device comprising:

• one converter which performs power conversion between AC power of an AC power source side and DC power of a DC link which is a DC side;
• a DC link capacitor provided to the DC link;
• at least one inverter connected to the DC link, each switching element being controlled to be turned on/off based on a switching drive signal supplied, to perform power conversion between DC power of the DC link and AC power which is drive power or regenerative power of a motor;
• a DC/DC converter which is connected to the DC link, converts DC power of the DC link to DC power for a control power source, and outputs the same;
• a servo motor control circuit which outputs each switching drive signal for controlling power conversion of the inverter and operates using, as drive power, DC power for the control power source outputted by the DC/DC converter;
• a torque cut-off circuit which allows supply of each switching drive signal to each switching element while receiving a safety signal, and cuts off supply of each switching drive signal to each switching element, to stop power conversion of the inverter when not receiving a safety signal;
• and
• a safety monitor circuit which stops transmission of the safety signal to the torque cut-off circuit when an abnormality of the torque cut-off circuit occurs.