Antec TruePower New 750 W (TP-750) Power Supply Review

Secondary Analysis

This power supply uses three Schottky rectifiers on its secondary, all in charge of the +12 V output. The +5 V and +3.3 V outputs are produced by two small power supplies that convert +12 V into +5 V or +3.3 V. As mentioned this design is also used by other power supply series like Signature also from Antec, M12D from Seasonic, UCP from Cooler Master and HX (750 W and above) from Corsair.

The rectifiers used are SBR40U45CT, each one capable of delivering up to 40 A (20 A per internal diode at 150° C with a maximum voltage drop of 0.52 V). 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. Just as an exercise, we can assume a typical duty cycle of 30%.

From the six diodes available (two per component), two are used for the direct rectification and four are used for the “freewheeling” part (i.e., to discharge the +12 V coil). Thus for our math we need to consider the path with the lower current limit, which is the direct rectification path. This gives us a maximum theoretical current of 57 A (20 A x 2/0.70). This limit is for all outputs since the +5 V and +3.3 V outputs are generated from the +12 V output, as explained. If all this current was pulled from the +12 V output alone, this would give us a maximum theoretical power of 686 W. This is less than the labeled capacity from the power supply, but this is not necessarily bad, as the “freewheeling” part is more powerful (114 A) and compensates that.

Figure 13: +12 V rectifiers.

On Figures 14 and 15 you can see the small printed circuit board where the DC-DC converters for the +5 V and +3.3 V outputs are located. As you can see, they use solid aluminum caps. Each converter is based on an APW7073 controller, with seven APM2556N MOSFETs, which present a maximum RDS(on) of only 7.2 mΩ.

Figure 14: DC-DC converter in charge of generating +5 V and +3.3 V outputs from the +12 V output.

Figure 15: DC-DC converter in charge of generating +5 V and +3.3 V outputs from the +12 V output.

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 circuit.

Figure 16: Monitoring integrated circuit.

All electrolytic capacitors from the secondary are Japanese from Chemi-Con. This power supply has five capacitors on the modular cabling system printed circuit board, which is great.