Motor control device and electric power steering device

A motor control device comprising:

• a control circuit that has a signal output device that outputs a motor control signal by executing current control;
• a driving circuit that is operated upon reception of the motor control signal to supply driving electric power to a motor;
• a first voltage detector that detects a first power supply voltage supplied through an electric power line to apply voltage to the driving circuit;
• and
• a second voltage detector that detects a second power supply voltage supplied to the control circuit through a control line independent of the electric power line, wherein
• the signal output device limits a current command value computed in the current control to a value at or below a predetermined limiting value, and reduces the limiting value in accordance with an increase in motor speed, and
• the signal output device reduces the limiting value in accordance with a decrease in the first power supply voltage, and computes a difference between the second power supply voltage and the first power supply voltage and then reduces the limiting value by a larger amount as the difference increases.