CONFIDENTIAL
The Leader in High Temperature
CHT-STROMBOLI
Application Note 15-40_S12-25
High-temperature,Medium-voltage isolated DC-DC Converter
Table of contents
I Introduction ........................................................................................................................ 2
II Block diagram .................................................................................................................... 3
III Detailed Schematics (Figure 2) ......................................................................................... 4
IV Understanding the CHT-STROMBOLI .............................................................................. 7
IV.1 Transformer design .................................................................................................... 7
1. Turn-ratio ....................................................................................................................... 7
2. Primary inductance ........................................................................................................ 7
3. Choice of the transformer core ...................................................................................... 8
IV.2 Input capacitor ......................................................................................................... 12
V The preregulator .............................................................................................................. 14
VI The controller .................................................................................................................. 15
VI.1 Power-good flag ....................................................................................................... 15
VI.2 Switching frequency clock ....................................................................................... 16
VI.3 Current sensing transformer and comparator ......................................................... 17
VI.4 Ramp compensation ................................................................................................ 18
VI.5 Voltage loop ............................................................................................................. 19
VI.6 Output voltage drop dependency vs. Iout ................................................................ 19
VI.7 Current limiting ......................................................................................................... 20
VI.8 Caution on current limiting operation ....................................................................... 20
VI.9 Loop transfer function .............................................................................................. 20
VI.10 Soft start ............................................................................................................... 20
VII Feedback converter ......................................................................................................... 22
VIII Output rectification .......................................................................................................... 24
VIII.1 Current-driven synchronous rectifier ................................................................... 24
VIII.2 Output capacitor .................................................................................................. 27
IX List of figures ................................................................................................................... 28
XI Contact & Ordering .......................................................................................................... 29
XII Disclaimer ........................................................................................................................ 29