Fan speed controller with conditioned tachometer signal
AssigneeDell Products L.P.
InventorsNikolai Vyssotski, Christian L. Critz
Life of this patent
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Abstract
The speed of a fan motor is controlled by varying a DC voltage to the fan motor. A series pass transistor is used to vary the DC voltage to the fan motor. A power management controller sets the fan motor speed by outputting pulses to a pulse-to-DC voltage converter that changes the pulses to a proportional DC control voltage for controlling the series pass transistor. A tachometer output amplifier circuit is used to remove DC components and amplify to useful logic levels a low level tachometer output signal from the fan motor. The amplified tachometer signal is used by the power management controller in controlling the rotational speed of the fan motor.
Claims33
An information handling system, comprising:
- a microprocessor for executing instructions stored in a memory coupled thereto;
- a fan for cooling said microprocessor during operation thereof, said fan comprising a fan motor and a fan blade coupled to a shaft of said fan motor, wherein the shaft rotation speed is proportionate to a direct current (DC) voltage level applied to said fan motor, and said fan motor has a tachometer output for indicating the shaft rotation speed;
- a voltage regulator coupled between said fan motor and a first DC power source, said voltage regulator controlling the DC voltage level applied to said fan motor, wherein the DC voltage level applied to said fan motor can be any voltage from about ground to about the first DC power source voltage;
- a power management controller having a speed control pulse output and a tachometer pulse input;
- a pulse-to-DC voltage converter, said pulse-to-DC voltage converter coupled between the speed control pulse output of said power management controller and a control input of said voltage regulator;
- and
- a tachometer pulse amplifier coupled between the tachometer output of said fan motor and the tachometer pulse input of said power management controller, whereby said power management controller controls said fan motor shaft speed.
An apparatus for controlling fan speed, comprising:
- a fan motor having a shaft speed proportionate to a direct current (DC) voltage level applied to said fan motor and a tachometer output;
- a voltage regulator coupled between said fan motor and a first DC power source, said voltage regulator controlling the DC voltage level applied to said fan motor, wherein the DC voltage level can be any voltage from about ground to about the first DC power source voltage;
- a power management controller having a speed control pulse output and a tachometer pulse input;
- a pulse-to-DC voltage converter, said pulse-to-DC voltage converter coupled between the speed control pulse output of said power management controller and a control input of said voltage regulator;
- and
- a tachometer pulse amplifier coupled between the tachometer output of said fan motor and the tachometer pulse input of said power management controller, whereby said power management controller controls said fan motor shaft speed.
A method for controlling a fan motor having a shaft rotation speed dependent upon a direct current (DC) voltage level applied to said fan motor and a tachometer output, said method comprising the steps of:
- generating a plurality of speed determining pulses, wherein a characteristic of the plurality of speed determining pulses represents a desired fan motor shaft rotation speed;
- converting the plurality of speed determining pulses into a DC voltage proportionate to the desired fan motor shaft rotation speed, wherein the DC voltage can be any voltage from about ground to a maximum voltage level;
- applying the DC voltage to the fan motor;
- and
- determining the shaft rotation speed of the fan motor by measuring a plurality of shaft rotation pulses from the fan motor.
Dependencies are inferred from the claim text.