发明名称 |
Method and apparatus for determining fan speed |
摘要 |
An operating circuit (1) for controlling the speed of a cooling fan motor (3) for computer cabinetry (7), and for determining an under-speed condition in the fan motor (3) comprises a control circuit (15) which controls a variable output signal generator circuit (18) for outputting a pulse width modulated signal corresponding to the desired fan speed for switching a switching circuit (8) in a power supply circuit of the fan motor (3) for pulse width modulating the power supply to the fan motor (3). A monitoring resistor (R1), a capacitor (C1) and a circuit (12) provides a tachometer signal to the operating circuit (1). A gate circuit (22) gates the second and fourth pulses of the tachometer signal to a counter (20) which counts clock pulses from a clock signal generating circuit (19) between the rising edges of the second and fourth pulses which are in turn stored in a register (23) for comparison with a reference count by a comparator (25). The comparator (25) outputs an alert signal in the event of the count in the register (23) exceeding the reference count indicating under-speed of the fan. The control circuit (15) controls the signal generator circuit (18) for holding the pulse width modulated signal outputted to the switching circuit (8) on during a duty cycle between the rising edges of the second and fourth pulses of the tachometer signal so that the tachometer signal remains available until the fan speed has been determined.
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申请公布号 |
US6528987(B1) |
申请公布日期 |
2003.03.04 |
申请号 |
US20000595953 |
申请日期 |
2000.06.19 |
申请人 |
ANALOG DEVICES, INC. |
发明人 |
BLAKE JOHN;HANRAHAN DAVID;YOSHIDA KOHJI |
分类号 |
G01P3/489;G06F1/20;H05K7/20;(IPC1-7):G01P3/489 |
主分类号 |
G01P3/489 |
代理机构 |
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代理人 |
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主权项 |
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地址 |
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