Patent ID: 7495400

Claim:
A temperature control apparatus, comprising: a fan, including: a field winding; a speed controller for providing a speed control signal to said field winding responsive to a first control signal to control a rotating speed of said fan; first and second inputs for enabling operating power to be provided to said field winding and said speed controller, at least one of said first and second inputs being operatively coupled to a first voltage source; and a third input for providing said first control signal to said speed controller, said third input being operatively coupled to a second voltage source; temperature measuring means for measuring a temperature and providing a temperature indicating signal indicating said measured temperature; processing means for providing a second control signal responsive to said temperature indicating signal; pulse generating means for generating pulses responsive to said second control signal; first switching means for switching on and off responsive to said pulses to provide an output signal corresponding to said first control signal via a first conducting terminal, said first switching means having a second conducting terminal operatively coupled to said pulse generating means for receiving said pulses and a third conducting terminal operatively coupled to ground; a first resistor having a first terminal operatively coupled to said first conduction terminal of said first switching means and a second terminal operatively coupled to the third input of said fan; and a second resistor having a first terminal operatively coupled to ground and a second terminal operatively coupled to said second terminal of said first resistor, wherein said first control signal is a current signal, and a circuit formed by the second voltage source and the second resistor provides a predefined current signal to the third input terminal to control said rotating speed to a predefined speed corresponding to a minimal speed.