LEPA G700-MA Power Supply Review

Primary Analysis

On this page we will take an in-depth look at the primary stage of the LEPA G700-MA. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.

This power supply uses one GBU2006 rectifying bridge on its primary, which is attached to an individual heatsink. This bridge can deliver up to 20 A at 100° C if a heatsink is used, which is the case. At 115 V this unit would be able to pull up to 2,300 W from the power grid; assuming 80% efficiency, the bridge would allow this unit to deliver up to 1,840 W without burning itself out. Of course, we are only talking about this component. The real limit will depend on all other components from the power supply.

Figure 9: Rectifying bridge

On the active PFC
circuit, two TK20J60T power MOSFET transistors are used, each one capable of delivering up to 20 A at 25° C in continuous mode (unfortunately, the manufacturer doesn’t state the limit at 100° C) or up to 40 A at 25° C in pulse mode. These transistors present a resistance of 165 mΩ when turned on, a characteristic called RDS(on). This number indicates the amount of power that is wasted, so the lower this number the better, as less power will be wasted, thus increasing efficiency.

Figure 10: Active PFC transistors and diode

The active PFC circuit is controlled by a CM6502 PFC controller.

Figure 11: Active PFC controller

This power supply uses a Japanese capacitor, from Rubycon, labeled at 85° C to filter the output from the active PFC circuit. For a “Gold” power supply, we expected to see a 105° C capacitor here.

In the switching section, two SiHG20N50C power MOSFET transistors are used. Each of the transistors is capable of delivering up to 20 A at 25° C or 11 A at 100° C in continuous mode or up to 80 A at 25° C in pulse mode, with an RDS(on) of 225 mΩ.

Figure 12: Switching transistors

The switching transistors are connected using a design called LLC resonant, controlled by a CM6901 integrated circuit, which operates under PWM (Pulse Width Modulation) mode when the power supply is operating under light load but under FM (Frequency Modulation) mode under other loads.

Figure 13: Controller

Let’s now take a look at the secondary from this power supply.