AN3151

Firmware implementation

Doc ID 17051 Rev 1

19/34

/*Configure the ADC2 external trigger */

ADC2_ExternalTriggerConfig(ADC2_EXTTRIG_TIM, ENABLE);

ADC2_Cmd(ENABLE);

5.3

PI regulator overview and firmware implementation

The general formula for an analog PI regulator is:

Equation 8

where:

●

µ(t) is the driving signal

●

e (t) is the error signal, the difference between the actual value and the target value

●

In the case of digital regulators, the above equation becomes:

Equation 9

where:

●

µ (n) is the driving signal sampled at the instant nT

●

e (n) is the error signal sampled at the instant nT

●

●

T is the sampling time

The following can also be written:

Equation 10

and, subtracting Equation 10 from Equation 9:

Equation 11

The equation shows the variation of the duty cycle

Δµ(n) at the instant nT due to the current

error in the same instant (term e(n)) and to its variation at the instants nT and (n-1)T (terms

Δe(n) and

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