Stall detection

AN4241

14/18

Doc ID 024193 Rev 1

4

Stall detection

The L6470 also includes a sensorless stall detection system. This feature allows the device

to detect the stall condition of the motor measuring the increase of phase current caused by

the sudden cancellation of the back electromotive force.

The voltage mode control applies a sinusoidal voltage to the motor phases obtaining a

sinusoidal current. The amplitude of the voltage sinewave increases according to the speed

in order to compensate the back electromotive force effect and keep the amplitude of the

phase current constant. If the motor stalls (i.e. stops its rotation) the back electromotive

force becomes null, but the voltage applied to the phase is still increased to face its effect. In

this condition the phase current results higher than the nominal one and the stall condition

can be easily detected.

The stall detection threshold must be set above the nominal peak current.

Figure 9.

Stall detection threshold

Stall threshold

Stall threshold

Normal conditionsStall conditions

Iph

Iph

AM16595v1