LEPA B650 Power Supply Review

Secondary Analysis

The LEPA B650 uses a regular design in its secondary, with Schottky rectifiers.

The maximum theoretical current each line can deliver is given by the formula I / (1 – D) where D is the duty cycle used and I is the maximum current supported by the rectifying diode. As an exercise, we can assume a duty cycle of 30 percent.

The +12 V output uses four SBR40U60CT Schottky rectifiers (40 A, 20 A per internal diode at 25° C, 0.60 V maximum voltage drop). This gives us a maximum theoretical current of 114 A or 1,371 W for the +12 V output.

The +5 V output uses two SBR30U30CT Schottky rectifiers (30 A, 15 A per internal diode at 150° C, 0.54 V maximum voltage drop). This gives us a maximum theoretical current of 43 A or 214 W for the +5 V output.

The +3.3 V output uses one VS-40CPQ060 Schottky rectifier (40 A, 20 A per internal diode at 120° C, 0.68 V maximum voltage drop). This gives us a maximum theoretical current of 29 A or 94 W for the +3.3 V output.

Figure 14: The +12 V, +5 V, and +3.3 V rectifiers

This power supply uses an ST9S429 monitoring integrated circuit, which apparently is a rebranded S3515. This chip supports over voltage (OVP), under voltage (UVP), and over current (OCP) protections. Even though this chip provides two +12 V over current channels, the manufacturer decided to configure this unit as a single-channel model.

Figure 15: Monitoring circuit

The electrolytic capacitors that filter the outputs are from Teapo and Samxon and labeled at 105° C, as usual.