Thermaltake Toughpower Grand 750 W Power Supply Review

Secondary Analysis

This power supply uses a synchronous design in its secondary, meaning that the Schottky rectifiers were replaced by MOSFET transistors in order to increase efficiency. On top of that, this unit uses a DC-DC design, meaning that this unit is basically a +12 V power supply, with the +5 V and +3.3 V outputs being generated by two small power supplies attached to the +12 V output.

The +12 V output is generated by five IPP034NE7N3 MOSFETs, each one capable of handling up to 100 A at 100° C in continuous mode or up to 400 A at 25° C in pulse mode, with an RDS(on) of only 3.4 mΩ. Three of them are used for the direct rectification, while the other two are used for the “freewheeling” part of the rectification.

Figure 14: +12 V transistors

Like most of the power supplies that use DC-DC converters in the secondary to generate the +5 V and +3.3 V outputs, the Toughpower Grand 750 W has two separate printed circuit boards installed in the secondary, one for each output. Each converter is managed by an APW7073 PWM controller and uses two ME90N03 MOSFETs – 60 A at 25° C or 47 A at 70° C in continuous mode, 240 A at 25° C in pulse mode, 9 mΩ RDS(on) –, and two ME70N03S MOSFETs – 62 A at 25° C or 50 A at 70° C in continuous mode, 100 A at 25° C in pulse mode, 11 mΩ RDS(on).

Figure 15: One of the DC-DC converters

Figure 16: One of the DC-DC converters

The secondary is monitored by a PS223 integrated circuit. This chip supports OCP (over current protection), over voltage protection (OVP), under voltage protection (UVP) and over temperature protection (OTP). The over current protection circuit has four channels (+3.3 V, +5 V and two +12 V), but the manufacturer decided to use only one of the available +12 V channels to make this unit to have a single +12 V rail.

Figure 17: Monitoring circuit

Half of the electrolytic capacitors of the secondary are Japanese, from Chemi-Con, and the other half uses solid capacitors.