Method and apparatus for determining fan speed
US6528987B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Jun 19, 2000 |
| Grant date | Mar 4, 2003 |
| Priority date | — |
| Expiry date | Jun 19, 2020 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06F1/206
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
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 puls…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.