Patent ID: 7612521

Claim:
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.