On 29 March 2015 at 22:46, embedded systems wrote: > Yes indeed. Maybe fig.31 on page 26 with something similar: > http://www.ti.com/lit/ds/symlink/tl431.pdf Yes But see fig 34 on the following page. Because it works by "shunting to ground" current which is not needed at the time, a shunt regulator must always draw at least the maximum current which it can ever supply without dropping out of regulation. A series regulator draws Iout_actual + Icontrol. In the example in Fig 34 Icontrol is at least about - 0.4 mA (fig 4 page 14) for the TL431 (or about 80 uA min for a TLV431) to keep the TL431 "in regulation) plus - another 0.1 mA via the reference setting resistors. Atr low load currents Icontrol for that circuit is << the steady current that a shunt regulator must always draw. Russell > > > On Sun, Mar 29, 2015 at 9:48 AM, Richard Prosser > wrote: > > > A better way is to use a zener with a voltage ~0.6V lower and use a > > transistor to absorb the power. Connect the collector & the cathode of > the > > zener together. Anode of zener to the base and the emitter of the > > transistor to ground. > > > > RP > > > > On 29 March 2015 at 18:54, embedded systems wrote: > > > > > Not recommended. However if you like hobby electronics, you may pair > some > > > zeners. This will not be easy. Try to use 5V7, 6V2, 6V8 if possible. > They > > > are at the boundary between positive and negative thermal coefficient= .. > > > > > > Vasile > > > > > > On Sun, Mar 29, 2015 at 8:45 AM, Ryan O'Connor > > wrote: > > > > > > > Hmm ok, so it's not recommended at all? > > > > > > > > On 29 March 2015 at 18:29, James Cameron wrote: > > > > > On Sun, Mar 29, 2015 at 06:17:46PM +1300, Ryan O'Connor wrote: > > > > >> Just a quick question, can I use two identical reversed zeners i= n > > > > >> parallel to achieve the same voltage drop as one, but with > increased > > > > >> current capacity? > > > > > > > > > > Nothing is identical? > > > > > > > > > > The voltage drop will be that of the diode with the lower voltage= , > > and > > > > > more current will pass through that diode than the other. > > > > > > > > > > The closer you get to identical, the closer the currents will be. > > > > > > > > > > If you have a zener with more negative temperature coefficient of > > > > > voltage than the other, then it will heat and steal the show. > > > > > > > > > > -- > > > > > James Cameron > > > > > http://quozl.linux.org.au/ > > > > > -- > > > > > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > > > > > View/change your membership options at > > > > > http://mailman.mit.edu/mailman/listinfo/piclist > > > > -- > > > > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > > > > View/change your membership options at > > > > http://mailman.mit.edu/mailman/listinfo/piclist > > > > > > > -- > > > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > > > View/change your membership options at > > > http://mailman.mit.edu/mailman/listinfo/piclist > > > > > -- > > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > > View/change your membership options at > > http://mailman.mit.edu/mailman/listinfo/piclist > > > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .