[christianw.]

Frei nach Steve Taranovich, Electronic Products

http://www.digikey.com/us/en/techzone/po...dules.html

Zitat:Connecting power modules in series

This design approach is less common than the parallel option but is effective in applications where a designer needs to generate an output voltage not available in the standard product offering. However, be aware that the output current will be limited to that of the stacked module with the lowest current rating. This method can also allow for multiple usage of the same part number to help streamline stocking and reduce costs.

Designers should consider that ramp-up of the input voltage should be sufficiently fast, or usually less than 250 ms, to avoid one module feeding a DC voltage through another module that is offline and inhibiting module start-up.

Designers can avoid this situation by using a pin on the module to hold it in the off state until the input voltage is within the module?s specification. This pin is sometimes labeled INHIBIT, or RC for remote control, and can enable all converters simultaneously to cause the output voltages to rise equally and eliminate the potential problem.

It is sometimes necessary to use a back-biased diode across the output of each power module with dual outputs. To find out, check the manufacturer?s datasheet. (See Figure 2)

[Bild: article-2011august-operation-power-suppl...s-fig2.jpg]