SPF 5000 ES Service manual
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3. Working principle of the major functional block
3.1 Switch Power Supply
The switch power supply (SPS) supplies DC power for Inverter/Charger operation. The input voltage of the SPS is
the battery or AC/PV Charger output voltage.
Figure 3.1 basic circuit of power supply
This is the fly-back DC-DC converter, fly-back operation can be easily recognized from the position of the dots on
the transformer primary and secondary(these dots show starts of the winds). When Q40 is ON, the dot ends of all
winds are negative with respect to their no-dot ends. Output rectifier diodes D51, D52, D60 and D63 are
reverse-biased and all the output load currents are supplied from storage filter capacitors C78, C75, C79 and
C116.The primary coil of the transformer acts as an inductor and stored energy.
When Q40 is OFF, the stored energy in the primary coil is delivered to secondary filter capacitors C90, C94, C98
and C111.
As shown in figure 3.1, this circuit may generate several output voltage, such as +12V,-12V, +15V, +5V, HFPW+.
