The "not so lowly" TL431

jackinnj · 25th September 2004, 04:08 PM

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 !

wrenchone · 25th September 2004, 05:44 PM

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.

jcarr · 25th September 2004, 08:36 PM

Older thread along similar lines:

4-part Harmony, a 9 watt class A amp using a voltage regulator IC.

regards, jonathan carr

peranders · 25th September 2004, 08:44 PM

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).

jackinnj · 25th September 2004, 09:12 PM

the point -- Ridley goes on to describe the compensation scheme for optimal performance when using optical isolation.

paulb · 26th September 2004, 01:02 AM

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.

jaycee · 27th September 2004, 02:15 AM

I've also seen the TL431 used as a bias servo, look up the Stochino amplifier. He uses it to set bias along with 4 BD139's in diode configuration as a thermal sensor.

25th September 2004, 04:08 PM	#1
jackinnj diyAudio Member Join Date: Apr 2002 Location: Llanddewi Brefi, NJ	The "not so lowly" TL431 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 !

25th September 2004, 08:36 PM	#3
jcarr diyAudio Member Join Date: Jul 2002 Location: Tokyo, Japan	Older thread along similar lines: 4-part Harmony, a 9 watt class A amp using a voltage regulator IC. regards, jonathan carr __________________ http://www.lyraconnoisseur.com/, http://www.lyraaudio.com

25th September 2004, 08:44 PM	#4
peranders Electrons are yellow and more is better! diyAudio Member Join Date: Apr 2002 Location: Göteborg, Sweden Blog Entries: 4	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). __________________ /Per-Anders (my first name) or P-A as my friends call me Tube Buffered Gainclone in work \|Thread

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25th September 2004, 05:44 PM	#2
wrenchone diyAudio Member Join Date: Feb 2004 Location: Silicon Valley	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.

25th September 2004, 09:12 PM	#5
jackinnj diyAudio Member Join Date: Apr 2002 Location: Llanddewi Brefi, NJ	the point -- Ridley goes on to describe the compensation scheme for optimal performance when using optical isolation.

26th September 2004, 01:02 AM	#6
paulb diyAudio Member Join Date: Jun 2001 Location: Calgary	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.

27th September 2004, 02:15 AM	#7
jaycee diyAudio Member Join Date: Apr 2004 Location: Norwich, UK	I've also seen the TL431 used as a bias servo, look up the Stochino amplifier. He uses it to set bias along with 4 BD139's in diode configuration as a thermal sensor.

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