AN4144 datasheet(9/28 Pages) STMICROELECTRONICS

Numer części	AN4144

Szczegółowy opis	Voltage mode control operation and parameter optimization

PDF	28 Pages

Scroll/Zoom	100%

Producent	STMICROELECTRONICS [STMicroelectronics]

Strona internetowa	http://www.st.com

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9 / 28 page

DocID023491 Rev 3

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AN4144

Voltage mode driving

The control system generates the phase voltage using a PWM modulation. The outputs

switch between supply voltage VBUS and ground at a fixed frequency. The mean voltage of

the resulting square-wave is adjusted through its duty cycle (on time over square-wave

period ratio) according to Equation 8:

Equation 8

The duty cycle ranges from 0% (the output is always forced to ground) to 100% (the output

is always forced to VBUS).

The BEMF compensation curve is implemented adjusting the PWM duty cycle, so all the

voltage values must be normalized to the supply voltage of the power stage (Figure 3).

Figure 3. BEMF compensation curve

VPH

VBUS

tON

tSW

---------

VBUS DutyCyclePMW



PH /VBUS

Speed

[step/s]

Intersect

speed

Kval

Starting

slope

Final

slope

AM12859v1

AN4144 Arkusz danych(PDF) 9 Page - STMicroelectronics