Browse Prior Art Database

Temperature-Sensitive Speed Control Circuit for DC Fan Motors

IP.com Disclosure Number: IPCOM000046976D
Original Publication Date: 1983-Sep-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Shakib, J: AUTHOR

Abstract

A speed control circuit for direct current (DC) fan motors is described which is particularly useful for the case where the fan is located inside of an electronic equipment cabinet and is used for purposes of cooling the electronic equipment therein. In such case, the circuit varies the speed of the fan to keep a constant temperature inside the equipment enclosure. Consequently, at lower ambient temperatures, the fan will run at lower than the normal rated speed, hence reducing the acoustical noise generated by the fan. Temperature sensors in the form of thermistors 1, 2 and 3 are used as the controlling elements. These thermistors 1, 2 and 3 are located at various points inside the electronic equipment enclosure.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 74% of the total text.

Page 1 of 2

Temperature-Sensitive Speed Control Circuit for DC Fan Motors

A speed control circuit for direct current (DC) fan motors is described which is particularly useful for the case where the fan is located inside of an electronic equipment cabinet and is used for purposes of cooling the electronic equipment therein. In such case, the circuit varies the speed of the fan to keep a constant temperature inside the equipment enclosure. Consequently, at lower ambient temperatures, the fan will run at lower than the normal rated speed, hence reducing the acoustical noise generated by the fan. Temperature sensors in the form of thermistors 1, 2 and 3 are used as the controlling elements. These thermistors 1, 2 and 3 are located at various points inside the electronic equipment enclosure. The speed of the fan has to be controlled so that the amount of air being moved is adequate to cool the hottest point inside the enclosure. Determination of the hottest point is accomplished by the use of diodes 4, 5 and 6. The highest voltage at the anodes of these diodes 4-6 indicates the highest temperature and this highest voltage value appears at the common circuit point A. Amplifier 7 compares the voltage at point A with a set- point voltage, and the error voltage is amplified to generate the voltage at point
B. The signal at point B is current amplified by transistor 8 and presented at point C. An inexpensive three-terminal voltage regulator 9 is used as the voltage- control device. Th...