AN2025 - APPLICATION NOTE

9/11

The two method of optimization of conventional parts numbers are given in the table below:

In this example, avalanche losses and switching-off losses are negligible in comparison with the forward

losses. The following table gives the forward losses saving for each output.

In this example, the total efficiency improvement on the 3 outputs is equal to 1.9%.

VI. Conclusion

This paper presents the specification tool allowing the admissible avalanche power of Schottky diodes to

be calculated. With this tool and the simple method to estimate the maximum avalanche peak power, one

can easily determine if a given Schottky diode can work in the avalanche area. In SMPS, the efficiency

drop is mainly determined by the rectification diode stage.

In most of cases and according to the converter topology, the use of Schottky diodes in the avalanche

area will allow the converter's efficiency to be improved. Alternatively it can enable the cost to be optimized

by reducing the current rating of the rectification diode.

References:

[1] AN1453: NEW FAMILY OF 150V POWER SCHOTTKY (by F.Gautier)

[2] AN587: TRANSISTOR PROTECTION BY TRANSIL( by B.Rivet)

[3] ANALYSIS AND OPTIMISATION OF HIGH FREQUENCY POWER RECTIFICATION (by J.M.Peter)

Figure 15: SMPS for PC

3.3V

10A

5V

25A

12V

10A

STPS3045CT

STPS6045CW

STPS20H100CT

Part Number

Current solution

Power losses saving sol.

Cost saving solution

3.3 V

STPS3045CT

STPS3030CT

STPS2030CT

5 V

STPS6045CW

STPS6030CW

STPS3030CT

12 V

STPS20H100CT

STPS20L60CT

STPS10L60CT

Output

Part Number

Pfwd (W)

STPS3045CT

4.35

STPS3030CT

3.12

STPS6045CW

12

STPS6030CW

9.1

STPS20H100CT

5.85

STPS20L60CT

4.66