Dynex 400 W Power Supply Review

Secondary Analysis

On this page we will take an in-depth look at the primary stage of Dynex 400 W. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.
This power supply uses one RS806 rectifying bridge in its primary, capable of delivering up to 8 A at 100° C. The Green Star 450 W sample we reviewed used a different bridge, D15XB80, which is capable of providing only up to 3.2 A at 25° C if no heatsink is used (installing a heatsink its current limit grows to 15 A). An 8 A bridge is more than enough for a 400 W power supply. The reason why is that at 115 V this unit would be able to pull up to 920 W from the power grid; assuming 80% efficiency, the bridge would allow this unit to deliver up to 736 W without burning this component. Of course we are only talking about this component and the real limit will depend on all other components from the power supply.

Figure 9: Rectifying bridge.

The switching section from Green Star 450 W and from Green Star 400 W (aka Dynex 400 W) is identical. Both are based on the half-bridge design, which is the design usually used when the power supply does not feature active PFC circuit, using regular power NPN transistors instead of MOSFET components. Here two FJP13009 NPN power transistors are used. They can deliver up to 12 A continuous mode or up to 24 A in pulse mode, which is the case. Both values are given at 25° C.

Figure 10: Switching transistors (the second transistor is on the other side of the heatsink).

The switching transistors are controlled by a DM0265R integrated circuit (PWM controller).

Figure 11: PWM controller.

The two electrolytic capacitors used on the voltage doubler are Chinese from Jianghai and rated at 85° C. The capacitors from the Green Star 450 W sample we reviewed were from Teapo, a Taiwanese company.