Interesting, in the current issue of "SwitchingPower" magazine, Dr. Riddley has a lengthy article on the popular and cheap (not inexpensive, cheap !!!) TL431 adjustable reference. The conclusion is that it will work quite well as an error amplifier cum reference (and a good low noise reference at that.) Riddley suggests several compensation methods which will result in very good performance.
These parts cost about a dime apiece !
These parts cost about a dime apiece !
This is no great secret - the TL431 (and its earlier incarnation, the TL430) have been used as error amp/references by the power supply industry for over 20 years. Hardly anyone uses them for their original intended application.
Older thread along similar lines:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=12377&highlight=
regards, jonathan carr
http://www.diyaudio.com/forums/showthread.php?s=&threadid=12377&highlight=
regards, jonathan carr
jackinnj, what was your point?
BTW: I have it in a fairly new design with power factor correction and all. It (the LM431) works pretty good as a comparator/voltage level sensing element. Switching frequency 100-200 kHz (don't know exactly).
BTW: I have it in a fairly new design with power factor correction and all. It (the LM431) works pretty good as a comparator/voltage level sensing element. Switching frequency 100-200 kHz (don't know exactly).
the point -- Ridley goes on to describe the compensation scheme for optimal performance when using optical isolation.
There is an elegant design for a soft-start circuit using the TL431 as the only active element in the latest AudioXpress magazine. When the input voltage via an RC exceeds the reference voltage, the output pulls down a relay to ground.
It's also in the TL431 datasheet, Fig. 27.
It's also in the TL431 datasheet, Fig. 27.
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