Motor driving apparatus

A motor driving apparatus which drives a motor based on a external control signal inputted from outside, the motor driving apparatus comprising:

• a temperature control signal generator which generates a pulse-modulated temperature control signal whose duty ratio changes depending on temperature;
• a signal synthesizer which synthesizes the external control signal and the temperature control signal;
• and
• a drive controller which drives the motor based on output of the signal synthesizer;
• wherein the external control signal is pulse-modulated according to a target frequency of the motor;
• and
• wherein the temperature control signal generator comprises:
• a periodic signal generator which generates a periodic voltage whose frequency is proportional to frequency of the motor;
• a temperature detector which generates a temperature detection voltage that changes depending on temperature;
• a voltage comparator which compares the periodic voltage and the temperature detection voltage;
• and
• a logic circuit which receives an output of the voltage comparator and a periodic signal frequency of which is proportional to the frequency of the actual frequency of the motor, and generates the temperature control signal which has a high level in a period from when the output of the voltage comparator becomes high, to when the periodic signal becomes high;
• wherein the temperature control signal generator generates the temperature control signal based on output of the voltage comparator.