Zetex - AN23 - Zetex SPICE models - understanding ... - Diodes, Inc.
Zetex - AN23 - Zetex SPICE models - understanding ... - Diodes, Inc.
Zetex - AN23 - Zetex SPICE models - understanding ... - Diodes, Inc.
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<strong>AN23</strong> - 16<br />
Application Note 23<br />
Issue 2 March 1996<br />
Figure 13<br />
DC-DC Step-Down Converter using ZTX788B with Active Turn-Off Topology in a 12V to<br />
5V Circuit operating at 100kHz. (Note 1).<br />
An alternative is to consider changing<br />
the passive turn-off (achieved by resistor<br />
R1) to an active turn-off method. Figure<br />
13 shows one option of providing active<br />
turn-off to the base of the Bipolar<br />
transistor, and although this has<br />
resulted in the addition of a few<br />
components, this implementation is<br />
more cost effective than would be the<br />
case with a TO220 MOSFET based<br />
design. The effect of the modification is<br />
apparent in Figure 14, which shows a<br />
combined storage and fall time of 40ns -<br />
comparable with MOSFETs, and also<br />
producing minimal switching loss.
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