SilverStone Decathlon 700 W Power Supply Review

Secondary Analysis

As you know by now, SilverStone Decathlon 700 W has two transformers. The first one (T1) and part of the second one (T2) are used to produce the +12 V output, through the use of two Schottky Rectifiers. The +5 V output is produced by the second transformer through the use of one rectifier, while the +3.3 V output is produced by one output from T1 and one output from T2 connected in parallel and using one rectifier. So basically two transformers are used just to replace one big transformer, not bringing any other benefit besides that on the project that is used by this unit.

The +12 V output is produced by two 63CPQ100 Schottky Rectifiers, each one capable of handling up to 60 A at 153° C (30 A per internal diode). 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 30 A diodes in parallel). Just as an exercise, we can assume a typical duty cycle of 30%. This would give us a maximum theoretical current of 86 A or 1,029 W for the +12 V output. The maximum current this line can really deliver will depend on other components, in particular the coil used.

Figure 12: +12 V rectifiers.

The +5 V output is produced by one S60SC4M Schottky Rectifier, which is able to handle up to 60 A at 126° C (30 A per internal diode). The maximum theoretical current the +5 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 one 30 A diode). 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 214 W for the +5 V output. The maximum current this line can really deliver will depend on other components, in particular the coil used.

The +3.3 V output is produced by another S60SC4M Schottky Rectifier. The maximum theoretical current the +3.3 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 30 A diodes in parallel). 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 141 W for the +3.3 V output. The maximum current this line can really deliver will depend on other components, in particular the coil used.

As you can see the rectifiers are clearly overspec’ed, which is always nice to see.

The -12 V output is produced by one LM7912 voltage regulator integrated circuit, which has a current limit of 1.5 A.

On the same heatsink you can also see the rectifier used for the +5VSB output, an SBL1060CT, which is capable of delivering up to 10 A at 95° C (5 A per internal diode), so the maximum theoretical current limit for this output is of 5 A or 25 W.

It is always good to remember that the real current/power limit for each output will depend on other factors, like the coils and the width of the printed circuit board traces.

Figure 13: +5VSB rectifier, +3.3 V rectifier, +5 V rectifier and -12 V voltage regulator.

The outputs are monitored by a PS232 integrated circuit, which supports the following protections: over current (OCP), under voltage (UVP) and over voltage (OVP). Any other protection that this unit may have is implemented outside this integrated c
ircuit.

Figure 14: Monitoring integrated circuit.

As you can see in Figure 13, this unit has two thermal sensors, which is usually implemented when the power supply has over temperature protection (OTP). SilverStone does not list this protection and as mentioned we couldn’t have access to PS232 datasheet.

All the electrolytic capacitors from the secondary are Taiwanese from Teapo and labeled at 105° C as usual.