Application Notes
DN-56A Single Switch Flyback Circuit Converts + 5 V to +/- 12 V for RS-232/422
Texas Instruments

Published : 05 Sep 99
Description
A bipolar 12V supply from a single +5V input can be developed using a number of conventional approaches. A boost converter is the most logical for the +12V output; however it cannot be used in some interface-circuit applications. One significant drawback of the boost topology is that even with the boost converter off the output voltage approaches the input voltage and does not go to zero. This