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Thanks, ...yes that does happen, but not at or near full load....what you describe happens when its backed off from full load. On or near full load and its pure voltage mode.
..as per page 4 , RHS, bottom diagram...
Hi
Do you agree, that in the attached (LTspice and PNG) boost converter,
the input impedance of the error amplifier is 47k + 17500R_in_parallel_with_2500R?
Thanks, but if you click "watch on youtube" you can watch it there.
The video is on youtbe and is called..
"Easy to Follow Voltage Mode vs Current Mode vs Voltage Mode + Voltage Feedforward Control Methods"
It is by Dr Ali Shirsavar at Biricha.com
Thanks, you are right, if the Ref pin of TL431 is connected to 0V then it does appear that the cathode current sinks down to 1uA (100nA to 1uA).
This is a surprise, since the cathode is actually also the Vcc pin of TL431, so its surprising that it suddenly stops drawing the 0.4-1mA of bias...
Hi,
08:56 of this...
(...ok i dont know what happened, i hope people can get into that link)
..says that you cant do pushpull SMPS in voltage mode.
But surely this is not totally true?
I mean, yes, voltage mode gives the flux walking problem....and cannot be solved by a blocking cap in...
Hi,
The attached is a 60W, 420kHz Buck with a secondary LC filter after the Buck stage.
The Buck had a crossover frequency of 1700Hz before the LC post filter was added.
The post filter is 1uH and 20mF...so a resonant freq of 1130Hz. This is less than the
aforementioned crossover frequency...
The reactive current does cause extra conduction losses in the mains distribution system......so in a way, it could be made into an efficiency type measurement.......but try drawing out the schematic for that...right back to the power station!.......then work out all the wire gauges and lengths...
Thanks thats interesting...i dont know what "off state cathode current" is...but TL431 will always draw 400uA to 1mA of "bias current" when it has more than 2.5V on its cathode.
Hi,
Do you agree, the expression for "wop" at the bottom left of page 10 should not be square routed?
https://site.uottawa.ca/~rhabash/Practical-Feedback-Loop-Design-Buck.pdf
Also at bottom left of page 10, do you agree in expression (30), the numerator should be "1 + s/wezr1"
you cannot use TL431 like this...it draws 1mA bias current and make the Q2 come on regardless...use the ZR431 instead....or maybe the TLV431, but that is only 1.24v ref
Hi,
The following, in Fig 10, suggests that an FFT can be done with limit lines as shown in Fig 11....
https://www.analog.com/en/resources/technical-articles/how-to-get-the-best-results-using-ltspice-part-1.html
So, I can run our Buck simulation in LTspice. Then i can view the FFT for the EMC...
Hi,
Do you know the reverse current of the 4V7 zener (BZX84-C4V7) when it has 2.5V on it?..and at 125degC?
https://assets.nexperia.com/documents/data-sheet/BZX84_SER.pdf
Datasheet ony gives it at 25degC
Hi,
The attach shows the well known input circuit to an SMPS, (here vin = 24V and power is 50W.)
The SMPS controller must stay disabled until the PFET(s) switch has completely turned ON.
The PFET(s) must stay off until the 220R resistor has charged the input capacitor up to VIN.
The comparator...
Hi,
If you have a 6k2 resistor feeding the cathode of a TL431 (as attached),
then supposing the voltage rises up from zero steadily.....obviously the
cathode voltage cannot become 2.5V until the rising voltage has reached 6.2V + 2.5V = 9V
But when this rising voltage is below 9V, do you agree...
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