Enermax Liberty ECO 500 W Power Supply Review

Secondary Analysis

Liberty ECO 500 W uses four Schottky rectifiers on its secondary.

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%. Of course the maximum current (and thus power) this line can really deliver will depend on other components, especially the coil.

The +12 V output is produced by two 40CPQ060 Schottky rectifiers in parallel, each one supporting up to 40 A (20 A per internal diode at 120° C). This gives us a maximum theoretical current of 57 A [(20 A x 2)/(1 – 0.30)] or 686 W for the +12 V output.

The +5 V output is produced by one STPS30L30CT Schottky rectifier, which is capable of delivering up to 30 A (15 A per internal diode at 140° C). So the maximum theoretical current the +5 V output can deliver is of 21 A [15 A/(1 – 0.30)] or 107 W.

The +3.3 V output is produced by one S30SC4M Schottky rectifier, which is capable of delivering up to 30 A (15 A per internal diode at 126° C). So the maximum theoretical current the +3.3 V output can deliver is of 21 A or 71 W.

Figure 13: +3.3 V rectifier, +5 V rectifier and +12 V rectifier (the other +12 V rectifier is on the opposite side).

This power supply uses a PS223 monitoring integrated circuit, which is in charge of the power supply protections. This integrated circuit provides over current protection (OCP), over voltage protection (OVP), under voltage protection (UVP) and over temperature protection (OTP, not implemented on Liberty ECO series), but not over power protection (OPP). According to Enermax OPP is implemented on the primary side, through the CM6802 integrated circuit.

Figure 14: Monitoring integrated circuit.

The electrolytic capacitors from the secondary are from CEC (manufactured in China) and labeled at 105° C, as usual.