AN4158 datasheet(12/34 Pages) STMICROELECTRONICS

Part #	AN4158

Description	Peak current control with automatic decay adjustment

PDF	34 Pages

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Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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12 / 34 page

Phase current control in stepper motor driving

AN4158

12/34

DocID023635 Rev 2

Phase current control in stepper motor driving

In order to impose a constant current in the stepper motor phases, a current control

algorithm must be implemented.

The most common control system is shown in Figure 6 and is composed of:



A power H-bridge used to drive the phase



A current sensor (usually a shunt resistor)



A controller driving the power bridge



The motor phase electrical model.

This system is applied to both phases.

The motor phase electrical model is shown in Figure 7 and is made up of:



The equivalent phase resistance RPh



The equivalent phase inductance LPh



The back electromotive force generator VBEMF.

Figure 6. Current control system for each motor phase

BUS

SHUNT

BEMF

Controller

Motor phase equivalent circuit

AM15108v1

AN4158 Datasheet(PDF) 12 Page - STMicroelectronics