Electricity: motor control systems – Closed loop speed control system for dc motor with commutator
Reexamination Certificate
2000-03-14
2001-11-20
Nappi, Robert E. (Department: 2837)
Electricity: motor control systems
Closed loop speed control system for dc motor with commutator
C388S909000, C318S471000, C713S323000
Reexamination Certificate
active
06321029
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a DC fan and a method for controlling the same, and more particularly, to a DC (direct current) fan having a DC brushless motor and a method for controlling the rotating speed thereof.
BACKGROUND OF THE INVENTION
In these years, need for electrical products has been greatly increased. Auto shutdown functions of the electrical products are very important for reducing the power consumption and for increasing the lives of electrical products. An auto shutdown function can be performed by a power sleep-mode control. For example, the power sleep-mode of a monitor can be set in a personal computer. In this case, the monitor can be switched to the power sleep-mode under the condition that no input signals to the monitor are generated from a keyboard or a mouse during a predetermined period of time set by the user. Therefore, the power consumption can be reduced, and the life of the monitor can be prolonged. Similarly, a hard disk in a computer, a printer, a power supply, or other electrical products can be switched to their power sleep-modes.
A conventional DC brushless motor is usually used for driving a cooling fan in a computer or a workstation. The cooling fan operates when the computer or workstation is switched on till the time when the computer or workstation is switched off or when the fan fails to operate. In general, an operation period of a computer or workstation is very long. When any part or electrical element of a computer is switched to its power sleep-mode, the corresponding cooling fan can reduce its rotating speed or even stop in order to reduce power consumption and prolong its life.
The power sleep-mode has not been utilized in conventional cooling fans for saving power consumption and prolonging their lives.
Conventionally, a pulse width modulation (PWM) method is widely used for controlling the rotating speed of a cooling fan. According to the method, the rotating speed is controlled by modulating the amount of voltage or current inputted to a DC motor of the cooling fan. However, a circuit for carrying out this method is complicated and consumes a lot of electrical power.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide a DC fan having a power sleep-mode control unit in order to save power consumption and to prolong the life of the DC fan.
In accordance with a first aspect of the invention, a DC fan using a power supply and sleep
on-sleep-mode signals for controlling the rotating speed thereof includes a DC brushless motor as a driving source of the DC fan, and a power sleep-mode control unit electrically connected to the DC brushless motor for receiving the power supply and for generating sleep
on-sleep-mode signals, thereby outputting an operating power supply and controlling the rotating speed of the DC brushless motor.
The DC fan can be selectively shifted to its power sleep-mode. Thereby, its power consumption can be reduced and its life can be prolonged.
In accordance with a second aspect of the invention, the DC fan according to the first aspect further includes a sleep
on-sleep-mode signal venerating unit electrically connected to the power sleep-mode control unit for generating sleep
on-sleep-mode signals, and a firmware for generating time ratio control signals inputted to the sleep
on-sleep-mode signal generating unit. The sleep-mode signals and non-sleep-mode signals are alternately and continuously generated from the sleep
on-sleep-mode signal generating unit, and the rotating speed of the DC fan is controlled by a time ratio of the duration of the sleep-mode signals to the duration of the non-sleep-mode signals.
The rotating speed of the DC fan can be controlled according to the time ratio of the duration of the sleep-mode signals to the duration of the non-sleep-mode signals.
In accordance with a third aspect of the invention, the DC fan according to the second aspect further includes a sensor for detecting the ambient temperature of the DC fan, and outputting detection signals to the firmware to control outputs of the firmware.
The rotating speed of the DC fan can be controlled according to the ambient temperature of the DC fan.
In the DC fan according to the second aspect of the invention, the minimum time ratio of the duration of the sleep-mode signals to the duration of the non-sleep-mode signals is set to keep the DC brushless motor from stopping.
In the DC fan according to the third aspect of the invention, the firmware is composed of a computer and the software for use with the computer. The rotating speed of the DC fan can be controlled by the software.
In accordance with the fourth aspect of the invention, a method for controlling the rotating speed of a DC fan, the DC fan includes a DC brushless motor and a power sleep-mode control unit, the method includes the steps of: outputting first signals from an input signal generating unit to a signal control unit and processing the first signals by the signal control unit; outputting second signals from the signal control unit to a central processing unit and processing the second signals by the central processing unit; outputting third signals from the central processing unit to a sleep
on-sleep-mode signal generating unit and processing the third signals by the sleep
on-sleep-mode signal generating unit; and outputting sleep
on-sleep-mode signals from the sleep
on-sleep-mode signal generating unit to the DC brushless motor, and controlling the rotation/stop of the DC brushless motor by the power sleep
on-sleep-mode signals and the power supply. When the input signal generating unit has not generated the first signals for a predetermined period of time, the sleep
on-sleep-mode signal generating unit generates sleep-mode signals to let the DC brushless motor stop. When the input signal generating unit has generated the first signals continuously for the predetermined period of time, the sleep
on-sleep-mode signal generating unit generates non-sleep-mode signals to let the DC brushless motor rotate normally.
In accordance with the fifth aspect of the invention, a method for controlling the rotating speed of a DC fan, which includes a DC brushless motor and a power sleep-mode control unit, includes the steps of: alternately and continuously outputting sleep
on-sleep-mode signals from a sleep
on-sleep-mode signal generating unit to the DC brushless motor; and controlling the rotating speed of the DC fan by the cooperation of a time ratio of the duration of the sleep-mode signals to the duration of the non-sleep-mode signals and the moment of inertia of the DC fan.
The rotation
on-rotation states of the DC fan can be controlled by the method of using the power sleep
on-sleep mode.
In accordance with the sixth aspect of the invention, the method according to the fifth aspect of the invention further includes the steps of: detecting the ambient temperature of the DC fan by a sensor and outputting detection signals; and receiving the detection signals by a firmware and outputting time ratio control signals to the sleep
on-sleep-mode signal generating unit according to the detection signals, the time ratio of the duration of the sleep-mode signals to the duration of the non-sleep-mode signals being controlled according to the time ratio control signals.
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patent: 6182232 (2001-01-01), Klein
Duda Rina I.
Nappi Robert E.
Winson Semiconductor Corporation
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