Patent ID: 7253542

Claim:
A computer comprising: a first voltage source for providing a first voltage; a fan having a first power terminal and a second power terminal, said first power terminal coupled to said first voltage source; and a fan driver circuit having an output coupled to said second power terminal of said fan, said fan driver circuit operative to provide a pulsed modulation voltage at said output, said pulsed modulation voltage pulsing between a base voltage and a second voltage, said base voltage being intermediate said first voltage and said second voltage, said fan driver circuit including a pulse width modulation driver having an output coupled to said output of said fan driver circuit, a third voltage source for providing a DC voltage between said base voltage and said second voltage, and a clamp coupled to said output of said fan driver circuit for preventing said output of said fan driver circuit from falling below said base voltage, said clamp comprising at least one diode coupled between said third voltage source and said output of said fan driver circuit.