Page 7 - Catalogue

F. SPEED CONTROL MODE
There are two types of speed regula on: one is the fan terminal voltage speed regula on; the other is

Speed control by PWM or Vsp signal .

1.Terminal voltage speed regula on mode: regulate the fan power supply voltage. this kind of
speed regula on is simple, linear or low-cost, However, there are some defects in this type of speed
regula on mode, that is, when the terminal voltage is too low ,It will a?ect the normal opera on of
the fan (no start, stop or abnormal opera on), because the DC fan has Minimum star ng torque and
minimum opera ng voltage of the circuit. Therefore, if you need to adjust the speed to a very low
speed , this kind of speed regula on mode is not applicable.

R B

Terminal voltage

Note: It's risk when the speed adjusted is very low.

2. Adjust the speed by signal:the fan is designed with a speed control port, and the speed control
signal is generally PWM signal or VSP signal.

Adjust speed by PWM mode：Adjust the duty of PWM signal wave to exchange the speed.

Vpp=5vdc f=20±5 Khz
Vpp
System Fan Full speed

PWM

Duty
100%

Adjust speed by Vsp mode：Adjust the value of vsp sinal wave to exchange the speed.

Vpp=5 vdc

Vpp Full speed
System Fan
Vsp

Vsp
5v

At the low speed end, the star ng performance of the fan will not be a?ected, and the normal
opera on of the low speed end can be guaranteed. The PWM control mode is more stable, not easy to
be disturbed.

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