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126 Threads found on tl431
if you go to site and download there PI Expert software, it will show you. I am not sure if that chip can be used with an opto.....but if itcan then just use a tl431 with internal reference etc. Otherwise you can set it up to regulate vout via the bias winding.
My question is why we have to connect the TL341 to cathode of optocoupler (input) and connect the reference pin of tl431 to a voltage divider of 2.5Volts Thin of the tl431 as an opamp error amplifier………I appreciate that the feedback goes back to the non inverting input of the tl431, …but remember that there
I see no problem. The tl431 is rated to sink up to 100mA although I would never run one at anything like that current myself. The current it can supply (it isn't fan-out, that refers to digital circuits) is controlled by R11, not the tl431 but as the op-amps input current will be less than 0.2uA each, 11.4K should be fine as long as Vs is high eno
The final schematic (negative voltage regulator) is incorrect, it won't work properly at all. The concept of using a constant current source is it lowers the impedance at the shunt regulator and hence lessens the effect of it's dymanic resistance. Feeding voltage to the output pin of an LM317 and expecting it's input pin to be a constant current s
Maybe there is a problem on the feedback line( at the low voltage between optoccupier and tl431
I thought that tl431's Vref pin is input of opamp. (according to datasheet). So i supposed that it's input impedance is at least few megaohms. But it seems to draw current when i apply voltage to it. And datasheet says the absolute maximum for Vref current is 10mA. So i am supposed to limit it? But how much? If it draws current it will probably
I wonder if there is drawing mistake on the schematic. Something around the opto's cathode return seems strange. I tried to verify with the actual PCB layout, but it is not that easy to follow. Normally, pin 2 will be connected to the cathode of the tl431 as shown below.
Do you agree that equation 35 of page 10 of AN-4137 is incorrect? AN-4137: It surely should say? VFB/Vo1 = - (wi/s) . Do you agree? This is confirmed by equation 3-58 of page 290 of Basso?s book ?switch mode power supplies? (attached)
Hello, Why do the following application notes, both by fairchildsemi, contradict each other about the nearness of the SMPS crossover frequency to the corner frequency of the output LC filter (?post filter?) The text just above fig22, page 12 of the following document by Choi , suggests that tl431/opto feedback can be undertaken with the cross
Would a 10V Zener diode in series to the LED work ? The led has its own turn-on threshold, a few volts probably. Therefore the zener should be 6-7 V. You'll need to experiment with different combinations. If you want convenience in adjusting turn-on threshold, the tl431 (as I'm pretty sure post #2 intends) is an adjustable zener.
Hello, Fig2 ,Page 7 of the attached DER-275 document shows a 3n3 capacitor (C14) across the lower feedback divider resistor of an SMPS. (Page 9 of this document says that this capacitor is there because of noise getting injected into the tl431 reference pin.) Do you agree that this capacitor should not be there? The way to address that noise
You have no capacitor from opto collector to ground, -there should be. -You have no compensation components from cathode to reference of the tl431 -You have an output LC filter which has too high inductance...also, the most of the output capacitance should be upstream of the output inductor...also, the LC resonant frequency of the output filter i
Equation 23, page 14 , of AN57 by power integrations (below) shows a parameter called ?K TL31? which is the gain of the tl431. From the attached tl431 datasheet , does this gain equal ??.which equals 1/0.0014 = 714 tl431 datasheet: AN57 by Power Integr
Use tl431 or similar secondary voltage regulator instead of Z-diode.
Ccm is parasitic capacitance from any part of the flyback to earth ground/case. I found "Design of a tl431-Based Controller for a Flyback Converter", and it does not have an input filter or any capacitor to the case.
hi, Can any one explain the working of the feedback part of the given switching power supply (tl431 and Lm2094 and associated parts).
Hello, We intend to use LNK564 offline flyback controller for a flyback that switches off the 380VDC PFC bus. It will supply a secondary of 5V, 200mA, and will have a 13V bias winding which gives some 100mA to the primary side circuitry. Do you think we can do this via secondary side optopcoupler/tl431 regulation? (The opto transistor would
Hi Guys, I have an isolated power supply which is taking a lower voltage up to 350V DC @ 200W (push-pull topology). At the moment I don't want to rely on a aux winding to power the secondary side circuitry. There isnt a great deal out there with HV isolated feedback to go by, so I thought i'd ask and draw on other peoples experience with this. I
Negative feedback is usually made with a wire (closed loop gain of 1) or with two resistors (any closed loop gain you want). 115142 In the above schematics , please see the highlighted portion, tl431 is acting as an error amplifier , but there is no resistive feedback network , however compensation
tl431 is working as a comparator (with internal 2.5V reference). More details on page 21 of its (from your schematic) should allow a minimum biasing current of 1mA through tl431 cathode (input) for a nor