Motor driving device

A motor driving device comprising:

• a speed command voltage which is used to generate a high-voltage side speed command voltage and a low-voltage side speed command voltage;
• two analog-to-digital conversion circuits to which respective ones of the high-voltage side speed command voltage and the low-voltage side speed command voltage are inputted, the high-voltage side speed command voltage and the low-voltage side speed command voltage instructing a rotation speed of a motor;
• a microcomputer configured and programmed to generate a speed command having a pulse width which is changed according to the high-voltage side speed command voltage and the low-voltage side speed command voltage based on output signals of the two analog-to-digital conversion circuits;
• a signal isolator configured to transmit the speed command between an input and an output while providing isolation between the input and the output;
• and
• a drive circuit configured to generate a driving signal in response to the speed command outputted from the signal isolator and to change the rotation speed of the motor.