Huntkey X7 900 W Power Supply Review

Secondary Analysis

The Huntkey X7 900 W uses a synchronous design in its secondary, meaning that the diodes were replaced with transistors in order to increase efficiency. While the +12 V output uses a fully synchronous design, the +5 V and +3.3 V outputs use a half-synchronous design, where only the diodes in charge of the direct rectification were replaced with MOSFETs. The “freewheeling” part of the rectification continues to use Schottky diodes.

The +12 V output is rectified using four IRFB3206PbF MOSFETs, each one capable of handling up to 210 A at 25° C or 150 A at 100° C in continuous mode, or up to 840 A at 25° C in pulse mode, with an RDS(on) of only 2.4 mΩ.

The +5 V output uses an IRF1404 MOSFET for its direct rectification, a component that is capable of handling up to 202 A at 25° C or 143 A at 100° C in continuous mode, or up to 808 A at 25° C in pulse mode, with an RDS(on) of only 4 mΩ. For the “freewheeling” part of the rectification, one STPS3045CT Schottky rectifier is used. This rectifier supports up to 30 A (15 A per internal diode at 155° C), with a maximum voltage drop of 0.84 V.

The +3.3 V output uses another IRF1404 MOSFET and STPS3045CT Schottky rectifier. The specifications for these components were already discussed above.

Figure 17: The +5 V transistor, two of the +12 V transistors, and the +3.3 V rectifier

Figure 18: The +3.3 V transistor, two of the +12 V transistors, and the +5 V rectifier

The secondary transistors are monitored by a WT751002 chip, which only supports over voltage (OVP) and under voltage (UVP) protections. However, over current protection (OCP) is present, as we could test it, and is implemented using two LM339 voltage comparators.

Figure 19: Monitoring circuit

The electrolytic capacitors used in the secondary are from KSC, Teapo, and Fcon, and labeled at 105° C, as usual.