Cougar GX 700 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 four IPP032N06N3 MOSFETs, each one capable of handling up to 120 A at 100° C in continuous mode, or up to 480 A at 25° C in pulse mode, with an RDS(on) of only 2.9 mΩ. In this power supply the +12 V output is also used to generate the +5 V and the +3.3 V outputs, as you know. As an exercise, if we assume that all load was exclusively pulled from the +12 V output, we would have a maximum theoretical current limit of 343 A or 4,114 W.

Figure 14: Transistors in charge of the +12 V rectification (on the far left we have the +5VSB rectifier and on the far right we have the -12 V voltage regulator)

Instead of having only one +12 V coil, this power supply has two. Each pair of transistors are connected to a separate coil, and we guess that they switch out of phase (i.e., while one coil is conducting, the other is charging).

The +5 V and the +3.3 V outputs are generated by two small power supplies available on small daughterboards attached to the +12 V rail. Each of these power supplies is comprised of two APM2510N MOSFETs, two APM2556N MOSFETs (60 A at 25° C or 48 A at 100° C, 7.5 mΩ resistance), and one APW7073 PWM controller. They use solid capacitors.

Figure 15: One of the DC-DC converters

The outputs are monitored by a PS223 integrated circuit that is soldered on the printed circuit board shown in Figure 16. This circuit supports over voltage (OVP), under voltage (UVP) and over current (OCP) protections. This circuit offers four over current protection channels (one for +3.3 V, one for +5 V, and two for +12 V). An LM393 voltage comparator is also present, probably to increase the number of +12 V OCP channels to four in order to match the number of +12 V rails advertised by the manufacturer.

Figure 16: Monitoring circuit

The Cougar GX 700 W uses solid capacitors to filter the +12 V, +5 V and +3.3 V lines, but some regular electrolytic capacitors from Teapo are also used on the +12 V line and on the +5VSB line, and two capacitors from Su’scon are used on the -12 V line.