A new line of pulse-width-modulated (PWM) thermal-cooling fans performs at low noise levels by eliminating the power-switching noise of the fan, whose coils switch at 20 kHz. An external PWM signal controls fan speed. The fans ramp up linearly from a 20% duty cycle to the maximum rated speed. A soft-start circuit limits inrush currents during high duty cycles. These PWM fans are available in sizes of 70 by 15 mm, 70 by 25 mm, 80 by 25 mm, 92 by 25 mm, 120 by 25 mm, and 120 by 38 mm. Additionally, the PWM motor drive also is implemented in the company's 97- by 33-mm blower design. Prices range from $4 to $15 each, depending on fan size, features, and quantities ordered.
JMC Productswww.jmcproducts.com(866) 776-3267