Zalman ZM500-RS Power Supply Review

Secondary Analysis

This power supply has nine Schottky rectifiers attached to the secondary heatsink. Eight of them are from the model: SBL3040CT (30 A, 15 A per internal diode at 100° C, 0.55 V voltage drop). The ninth rectifier, an SBL1045CT (10 A, 5 A per internal diode at 95° C, 0.55 V voltage drop) is in charge of the +5VSB output.

The maximum theoretical current each 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. Just as an exercise, we can assume a typical duty cycle of 30%.

The +12 V output is produced by four of the rectifiers, giving us a maximum theoretical current of 86 A or 1,029 W.

The +5 V output is produced by two of the rectifiers, giving us a maximum theoretical current of 43 A or 214 W.

The +3.3 V output is produced by the last two rectifiers, giving us a maximum theoretical current of 43 A or 141 W.

All these numbers are theoretical. The real amount of current/power each output can deliver is limited by other components, especially by the coils used on each output.

Figure 13: +12 V, +5 V, +3.3 V and +5VSB rectifiers.

The outputs are monitored by a PS223 integrated circuit, which supports over current (OCP), under voltage (UVP), over voltage (OVP) and over temperature (OTP) protections. Any other protection that this unit may have is implemented outside this integrated circuit.

Figure 14: Monitoring circuit.

Electrolytic capacitors from the secondary are also from Teapo and labeled at 105° C.