But we are really interested on the secondary part of the power supply. It uses the expected configuration for a power supply using a two-transistor forward configuration, but what is odd about this power supply is that the "freewheeling" diodes (diodes that force the coil to deliver the energy it has stored when the rectifying diode is not conducting) have specs far higher than the rectifying diodes. Usually they are identical.
For the +12 V line a STPS30L60CT Schottky rectifier is used as the rectifying diode (30 A total at 130º C) and a S60SC6M Schottky rectifier is used as the freewheeling diode (60 A total at 118º C). For our calculations we need to consider the side with the lower limit. The maximum theoretical current the +12 V line can deliver is given by the formula I / (1 - D) where D is the duty cycle used and I is the maximum current supported by the rectifying diode (which in this case is made by two 15 A diodes in parallel, 30 A total). Just as an exercise, we can assume a typical duty cycle of 30%. This would give us a maximum theoretical current of 43 A or 514 W for the +12 V output. The maximum current this line can really deliver will depend on other components, in particular the coil used.
The +5 V and +3.3 V lines use a STPD2045CT Schottky rectifier as the rectifying diode (20 A total at 125º C) and a S40SC4C Schottky rectifier as the freewheeling diode (40 A total). For our calculations we need to consider the side with the lower limit. Using the same math as above, we have a maximum theoretical current of 29 A for each output or 143 W for the +5 V output and 94 W for the +3.3 V output.
We removed the rectifiers from the power supply and on Figure 15 you can see four of the seven power rectifiers used, the first is used by the +5VSB output and the other three are used as the rectifying diode (marked as D1). On Figure 16 you can see the three power rectifiers used as the freewheeling diodes (marked as D2).
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Figure 15: iGreen Power 430 W rectifiers.
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Figure 16: iGreen Power 430 W rectifiers.
For the +5VSB line a STPS20H100CT Schottky rectifier is used. This part has a maximum current of 10 A for each internal diode (20 A total).
All electrolytic capacitors used on iGreen Power 430 W were manufactured by Ltec, from Taiwan.
