DC Fan Speed Control PWM Signal Introduction WayneChen

DC Fan Speed Control PWM Signal Introduction Wayne_Chen ADDA RD Chief Engineer Wayne@adda. com. tw 886 -8 -755 -0579 ext: 326 0

Topical: 1. Speed Control Fan Configuration (old version) 2. What is PWM Signal ? 3. PWM Control Methods Introduction 4. PWM Fan Specification 5. PWM Fan Sample 6. Q & A 1

1. Speed Control Fan Structure (old version) 1 -1. Use ON/OFF control by Transistor Advantage： I. Easy design and control method II. Price cheaper. Disadvantage : I. Power Dissipation is a design issue. II. Not use friendly. 2

2. What is PWM Signal ? • PWM(Pulse Width Modulation): It’s a fixed frequency and pulse modulated for fan speed control. • Whenever change the duty cycle, the fan speed will be changed by system requirement. Ø The Purpose are : 1. The power dissipation will be saving. 2. And the working time will be increasing if the battery could not be charged outside. (especially NB system) Figure : PWM Control Signal 3

3. PWM control Methods introduction 3 -1 Speed Control Fan Structure (old version) Ø Use ON/OFF control by Transistor Advantage： I. Easy design and control method II. Price cheaper. Disadvantage： I. Poor Reliability ( Transistor are On/OFF continuously) II. Error judgment of tachometer signal. 4

Actual Tachometer Signal Waveform PWM input signal Error judgment of tachometer signal 5

3 -2. Regulator Control Fan Configuration (Current version For Notebook <Three Wires>) Advantage： I. The better Reliability II. RPM Stable III. Power efficiency saving. Disadvantage： I. Cost expensive. II. Control Circuit Complex 6

Actual Tachometer Signal Waveform PWM input signal tachometer signal ( normality) 7

3 -3. Control PWM Fan Configuration<Four Wires> System Fan PWM control Configuration 8

3 -4. Next Generation Version PWM Control Fan: Type A 9

3 -5. PWM Control Fan: Type B 10

4 -1. PWM Input Signal Specification (from system) • • PWM Operating Frequency : 25 k. Hz ± 5 k. Hz Maximum Input Low Voltage (VIL-MAX) = 0. 8 V Minimum Input High Voltage (VIH-MIN) = 2. 0 V High Input Impedance (10 K ohms at least ) (Consider Fan-In Issue，Driver Capability) 11

4 -2. PWM Fan Specification • Operation Voltage : 5 V or 12 V ± 10% • Function: Locked Protection and Auto-restart • Apply the Open Collector or Open Drain Tachometer Output Signal • Low Speed setting with 0~17% (or 20%) on Same PRM level (Type B) 12

5. PWM Fan sample 5 -1. Type A( For NB fan suggestion) Fan Stop Duty Cycle Fan Start_up Duty Cycle 13

5. PWM Fan sample 5 -2. Type A( All kind of fan could be used. ) Fan Stop Duty Cycle Fan Start_up Duty Cycle 14

5. PWM Fan sample 5 -3. Type B(For Desktops fan suggestion) It’s same duty cycle curve for fan start_up and stop. 15

6. Question & Answer (The End) 16