PWM current control loop

L6258EX

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Figure 9.

Aloop bode plot (compensated)

We can see that the effect of the load pole is cancelled by the zero of the Bx block ; the total

Aloop cross a the 0dB axis with a slope of -20dB/decade, having in this way a stable system

with an high gain at low frequency and a bandwidth of around 8KHz.

To increase the bandwidth of the system, we should increase the gain of the Bx block,

keeping the zero in the same position. In this way the result is a shift of the total Aloop

transfer function up to a greater value.

3.5

Effect of the Bemf on the current control loop stability

In order to evaluate what is the effect of the Bemf voltage of the stepper motor we have to

look at the load block: