Analog PWM Fan Controller
Published:
Design and simulation ยท No physical build
This circuit explores analog PWM control of a 12 V, four-pin fan using a temperature-related voltage input.
Design targets
- Fan off below a 2.5 V input.
- A 50% PWM duty cycle at 2.5 V, increasing to 100% at 4.5 V.
- PWM frequency near 25 kHz.
Circuit approach
The triangle-wave generator uses a TLV2372IP dual rail-to-rail op-amp: one section as a Schmitt-trigger comparator and the other as a Miller integrator. A divider from the single 12 V supply sets a reference near 3.39 V. An earlier version used LM741 op-amps.
Simulation result
The triangle-wave stage produced approximately 3.08 V peak-to-peak, a 2.60 V DC offset, and a frequency of 25.8 kHz in Multisim. These values describe the simulated oscillator; the complete fan response has not been verified on physical hardware.
Tools: Multisim, op-amp circuit design, analog PWM.