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42 Threads found on edaboard.com: tl431 Feedback
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 (...)
Maybe there is a problem on the feedback line( at the low voltage between optoccupier and tl431
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
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
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
hi, Can any one explain the working of the feedback part of the given switching power supply (tl431 and Lm2094 and associated parts).
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
A reasonable controller design operates the TL494 with PI error amplifier and thus doesn't depend on opto coupler linearity for the static performance. That's how the industry standard tl431 opto isolated feedback works. Opto coupler transfer gain and gain non-linearity still matters for stable loop closure, but as said, this isn't a problem for a
The dominant pole of an opto coupler is associated with the photo transistor, not the LED. (I'm not sure which side you mean with the unusual term "opto diode"). Usual tl431 circuits already achieve a current source characteristic a higher frequencies. A cascode stage can partly improve the frequency characteristic of a resistor loaded poto t
@pplus can u tell what u mean by Vka? is the cathode voltage of tl431 or that of the optocoupler? thanks
If the feedback loop is tl431 based (tl431 is a 3-pin shunt regulator, aka Variable zener) you can change the resistor values to get 30V on the 12V rail. Formula for tl431 voltage is 2.5*(1+ (HIGH_SIDE_RESISTOR/LOW_SIDE_RESISTOR)) values are in Ohms and 2.5 is the tl431 internal reference voltage. For (...)
I would like in switching power supplies controlled TopSwitchJX (flyback) replaced the error amplifier with an external reference.Suggest you consult as compensation network, gain, etc.? Basically my point of replacement tl431, operational amplifier and a fixed reference point I used the DAC to control the output voltage of the source.
With the second scheme, you changed the flyback into a forward converter, not what you want, I guess. Twe too high output voltage in first case isn't a problem of transformer design, it means that the feedback circuit isn't working. Your schematic has a missing ground connection, but there may be other problems too. The tl431 circuit is rather u
it depends on the load type, but usually some type of isolation is necessary to prevent electrical shocks. the simplest yet high performance feedback isolation is opto-coupler which consists of a voltage reference (e.g. tl431) and an error amplifier (opamp or tl431 itself). also compensation could be done in the secondary side. BEST
Hello, I am doing the following DCM Buckboost LED driver?. Schematic: Vin = 9-100VDC Vout = 40 to 72VDC I out = 90mA This converter was extremely difficult to compensate. Would it have been easier if I had used the tl431 instaed of the LT1006 opamp? LT1006 Datasheet: cds.linear.c
what is my fault?is it not the similier circuit to SMPS feedback output? The missing feedback makes the diference. tl431 can either used as a simpled programmable shunt regulator (as in your second circuit). Then the feedback goes directly from pin3 to to pin 1. Or as a building block of a SMPS voltage controller. (...)