Note - Even though this device can sink 100ma maximum, you must calculate the series shunt resistor so both TL431 and the small resistor do not dissipate more 250mW. At 3:38 when input voltage was 20v, the 330 ohm resistor was dissipating ~1-watt (was OK for quick demonstration). If programming resistors would be used for a 10v reference with 20v input, then TL431 current would need to be limited to no more than 25ma (@10v = 250mW) so shunt resistor would change to maybe 470 or even 560 ohms. It's common to see many TL431 circuits with a transistor output acting as a current buffer. Lots of info and examples on the TI datasheet - it's 83 pages, imagine that for this neat little 10-cent part.. :-)
I got a bag of 100 of these for $10. My question is, if the shunt resistor is that large, wouldn't that increase the output impedance? I suppose, adding another series resistor, leading to a transistor or an op-amp buffer at the output, could help. Thanks.
Thank you for your valuable reply. But I think the power dissipation limit for the TL432 (TO-92) is about 0.7w. There are different limits depending on the package and it can be obtained from the datasheet.
Edited my reply: At 2:30 the calculation is verry correct. Nice work. Thanks for the vid. Before I thought it was wrong, but I can't remember why I thought this now.
Why should it be 22mA? 12-2.5 = 9.5 9.5/330 = 0.0287.....rounded up to 29mA. I'm not being sarcastic, I just would like to know how it's calculated because I'm still learning. Thanks.
@@REVERSE_BIAS OMG! I am so sorry! At the time I was pretty sure and calculated it twice, but now I have no idea anymore what led me to believe what I wrote. I now think 28 is right, I was wrong.
Can someone explain how he got the equation at 4:21 where Vo = 2.5(1+R1/R2). My understanding was that the voltage divider equation is Vo = Vin(R2/(R1+R2))
Late reply, but I think that 2.5(1+R1/R2) is the equation for the Vout of the TL431, not the voltage divider. You're right that voltage dividers by themselves have a different equation.
Giriş direnci TL 431 in üzerinden akacak akimi sınırlamaktadir.Mutlaka kullanılması gerekiyor.Tl431 Max 200 mA akıma dayanabiliyor.Direnc kullanılmaz ise TL431 bozulur.
Hello ! I have a smps with an output voltage of 24 volts. The output part has an opto-coupler and a tl431. I want to make the output voltage 14.5V. By calculating I found R1 = 17.8k and R2 = 3.708k. Vo = (R1 / R2 + 1) * 2.5 = (17.8 / 3.708 + 1) * 2.5 = 14.5 V But there is a problem. The output voltage is not stable and fluctuates between 13.9 and 14.7 volts all the time. How can I solve this problem? Can you help me please?
Can you solve this by adding a small capacitor, in-between shunt resistor and voltage divider and, another capacitor at V-out? Or put the Cap. before shunt and another after divider? Doesn't this smooth out ripple?
Hello, Nice video ! i tried many times to do the same but each time i got different voltages, that divider thing can't get into my mind. The 12v enters in the ref (left PIN when you see it in front of you) or at the third one ? i know the middle one is ground. I would love to see that 2.5v but have something around 7.8v and changing, nothing stable... is my device faulty ?
Great video as always 👍👍 And it made me wondering if this component could be used to regulate the output voltage of a power source in combination with a comparator and a power transistor?
thank you for the informative video 🙏🏼 on page 19 (figure 21) of the TL431 documentation (www.ti.com/lit/ds/symlink/tl431.pdf) the equation for Vka (Vo in your video) is different from what you presented (time 4:00). I am making this note because my circuit with R1=R2=20kΩ (voltage divider) gave me Vka=8.28V instead of the expected 5V. I noticed that with the equation in the documentation the Vka did calculate correctly. Can you explain why is that? 🙏🏼
Note - Even though this device can sink 100ma maximum, you must calculate the series shunt resistor so both TL431 and the small resistor do not dissipate more 250mW. At 3:38 when input voltage was 20v, the 330 ohm resistor was dissipating ~1-watt (was OK for quick demonstration). If programming resistors would be used for a 10v reference with 20v input, then TL431 current would need to be limited to no more than 25ma (@10v = 250mW) so shunt resistor would change to maybe 470 or even 560 ohms. It's common to see many TL431 circuits with a transistor output acting as a current buffer. Lots of info and examples on the TI datasheet - it's 83 pages, imagine that for this neat little 10-cent part.. :-)
Thanks for your input! Its an amzing device indeed
I got a bag of 100 of these for $10. My question is, if the shunt resistor is that large, wouldn't that increase the output impedance? I suppose, adding another series resistor, leading to a transistor or an op-amp buffer at the output, could help. Thanks.
Thank you for your valuable reply. But I think the power dissipation limit for the TL432 (TO-92) is about 0.7w. There are different limits depending on the package and it can be obtained from the datasheet.
Edited my reply: At 2:30 the calculation is verry correct. Nice work. Thanks for the vid. Before I thought it was wrong, but I can't remember why I thought this now.
Why should it be 22mA?
12-2.5 = 9.5
9.5/330 = 0.0287.....rounded up to 29mA.
I'm not being sarcastic, I just would like to know how it's calculated because I'm still learning. Thanks.
@@REVERSE_BIAS OMG! I am so sorry! At the time I was pretty sure and calculated it twice, but now I have no idea anymore what led me to believe what I wrote. I now think 28 is right, I was wrong.
@@dreamtreater Hey thanks for the reply and I also must says "hats off to ya" for being humble enough to admit an easy mistake. Thanks once again!
Lovely explained ❤
Excellent tutorial !...cheers.
cheers
Can someone explain how he got the equation at 4:21 where Vo = 2.5(1+R1/R2). My understanding was that the voltage divider equation is Vo = Vin(R2/(R1+R2))
Late reply, but I think that 2.5(1+R1/R2) is the equation for the Vout of the TL431, not the voltage divider. You're right that voltage dividers by themselves have a different equation.
nicely explained
Thanks for the very clear explanation ..
3:55 Can you eliminate the input resistor when you have two reference resistors?
Giriş direnci TL 431 in üzerinden akacak akimi sınırlamaktadir.Mutlaka kullanılması gerekiyor.Tl431 Max 200 mA akıma dayanabiliyor.Direnc kullanılmaz ise TL431 bozulur.
Excellent my friend, ty needed this info.
2:32 Can you put resistor on reference pin, instead of in path of load?
saudações do Brasil a todos. não conhecia este componente. é muito bom saber. muito bom. parabéns por seus ensinamentos. sucesso.
Great video...Well explained...Thanks for sharing...!
Very good explanation thank you
Thanks for great explaination
Great explanation. Thanks.
thanks for your video. you are a wizard to explain easily.
Very nice sir
Hello !
I have a smps with an output voltage of 24 volts. The output part has an opto-coupler and a tl431. I want to make the output voltage 14.5V. By calculating I found R1 = 17.8k and R2 = 3.708k.
Vo = (R1 / R2 + 1) * 2.5 = (17.8 / 3.708 + 1) * 2.5 = 14.5 V
But there is a problem. The output voltage is not stable and fluctuates between 13.9 and 14.7 volts all the time. How can I solve this problem?
Can you help me please?
Can you solve this by adding a small capacitor, in-between shunt resistor and voltage divider and, another capacitor at V-out?
Or put the Cap. before shunt and another after divider? Doesn't this smooth out ripple?
can u tell me the exact way how to determine the rs value please?
How can I add autocopler to it sir thank you
Excellent thank you. Even I understood it!
Very nice
Thanks you
thank you sir .very informative
Thank you sir
Can you make a negative diode, or get Vo smaller than 2.5V, with a bipolar supply?
Tl431 use to Feedback signal PWM power supply with optocoupler .
how to get 2 amp of current at output?
Thank you
Useful!
Well explained...
Hello, Nice video ! i tried many times to do the same but each time i got different voltages, that divider thing can't get into my mind. The 12v enters in the ref (left PIN when you see it in front of you) or at the third one ? i know the middle one is ground. I would love to see that 2.5v but have something around 7.8v and changing, nothing stable... is my device faulty ?
supperb, Sir.
Thank you for the class. I will tri to reply.
Great!
It's 12volt for 330ohm if you vary input voltage the resistance value have to change but you vary voltage level to 20volt but it's still working
Great video as always 👍👍 And it made me wondering if this component could be used to regulate the output voltage of a power source in combination with a comparator and a power transistor?
можно
muito bom
Awesome...
Thank you now i,know how battery full charger indicator and cutoff how to work
VERY GOOD THANKS!!!!!!!
thanks
بسیار عالی
Thanks
You eventually burned the 330Ω series resistor at the end of the video!
Right tanks
Basic knowledge but pretty useful.
I'm liking the virrdeo
Hay quá
So you can use a zener diode to step down voltage.? Same like step down transformer.
basic is the great
nice bosq,,,,
Best Dilivery
From Pakistan
five volts sinner
thank you for the informative video 🙏🏼
on page 19 (figure 21) of the TL431 documentation (www.ti.com/lit/ds/symlink/tl431.pdf) the equation for Vka (Vo in your video) is different from what you presented (time 4:00).
I am making this note because my circuit with R1=R2=20kΩ (voltage divider) gave me Vka=8.28V instead of the expected 5V. I noticed that with the equation in the documentation the Vka did calculate correctly. Can you explain why is that? 🙏🏼
Thanks
Thanks