AN3392 datasheet(18/57 Pages) STMICROELECTRONICS

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SPV1020 functions

AN3392

18/57

Doc ID 018749 Rev 1

Figure 16.

PV panels, power vs. voltage and current vs. voltage curves

The voltage-current curve shows all the available working points of the PV panel at a given

solar irradiation. The power-voltage curve is derived by the voltage-current curve, plotting

the product V*I for each voltage applied.

Figure 17 shows the dataflow diagram of the MPPT algorithm implemented by the

SPV1020:

Figure 17.

MPPT data flow diagram

The voltage reference generated by the MPPT algorithm is always limited by the overvoltage

(Vo-max) and voltage regulation (Vo-th) control of the output.

This algorithm is defined as Perturb&Observe because the system is excited (perturbed)

with a certain duty cycle (DC), the power is then monitored (observed), and then perturbed

with a new DC depending on the monitoring result.

The SPV1020 executes the MPPT algorithm with a period equal to 256 times the switching

period. The switching period is 10 µs, therefore the MPPT algorithm period is 2.56 ms. This

time is required for the application to reach the new steady-state (voltage and current) after

Update P(tn-1)

MPPT algorithm

Sign = Inv(Sign)

P(tn) > P(tn-1)

P(t

o (tn)

Output voltage monitoring

ref

Vref =

Vref + Sign * Step

to DAC

Vo-th

Vo-max

AM02604v1

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