AN3971

Optimizing the energy from the panel

Doc ID 022119 Rev 2

7/28

This algorithm approach is defined as perturb & observe because the system is excited

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

a new duty cycle depending on the monitoring result.

The SPV1020 IC executes the MPPT algorithm with a fixed period (equal to 256 times the

switching period), required for the application to stabilize its behavior (voltages and currents)

with the new duty cycle.

The duty cycle increase or decrease depends on the update done in the previous step and

by the direction of the input power.

in the previous step (Ptn-1).

If power is increasing then the update is done in the same direction as in the previous step.

Otherwise the update is swapped in the opposite direction (from increasing to decreasing or

vice-versa).

Figure 5 shows the sampling/working points (red circles) set by the SPV1020 and how they

change (red arrows) during normal operating mode.

Figure 5.

MPPT perturb & observe tracking

The input voltage is sampled by an external resistive partitioning, while the input current is

sampled internally in order to reduce the external component. Here follows a simple

schematic of the input voltage sensing circuitry (see the SPV1020 datasheet).