Can someone suggest me a way to convert the voltage across capacitor C5=15.517n into a current so that i can then give it to a comparator to compare it with a reference.
Also please a ckt that allows to introduce phase shifts of any degree
How to use a differentiator to get the current across the capacitor. Also in this case the voltage is differential and not single endedI have seen this done by installing either:
* a 2-resistor network (one with a high ohm value, the other with a small ohm value) between output and ground
* a single resistor (small ohm value) between the load and ground.
That is the general concept. You'll need to consult datasheets to get the particulars.
How to use a differentiator to get the current across the capacitor. Also in this case the voltage is differential and not single ended
Now I see you asked previously about C5. I believe it does not influence operation very much, because it is in series with R27, which is 20k, a relatively high value. It looks like it could be a snubber network, but I'm not sure a snubber is needed here.
The R and C in parallel with the inductor are according to the Inductor DCR current sensing method.I want to get the average current so that i can compare it with the reference current from the voltage loop(want to implement average current mode control).
The voltage across C5 is same as R28 by matching the time constants(post #63). I want to extract the current now
You can calculate current through C5 by measuring voltage across R27. It will not be the average value. To find the average, you must take a lot of readings, say ten per cycle. Then average them. Or average their absolute amplitudes.
This could be an area where the spec sheet only tells you a few things, but not everything. I suppose you will need to find someone who has done the exact same thing with the same IC. Or else you will need to use your ingenuity.
Is this approach technically correct. The voltage across the capacitor(15.517n) in parallel ti L1 is Il*R28(this is achieved by matching the time constants).
So if the amplifiy this voltage using a differntial amplifier with a gain of 1/R28 i should get the current Il
The 1k resistor to ground will greatly attenuate current coming through the 20k resistor (R27).
I can't say how well an op amp will work with a 2V supply.
My simulation shows that C5 will have less than 1 mA going through it.
The 1k resistor to ground will greatly attenuate current coming through the 20k resistor (R27).
I can't say how well an op amp will work with a 2V supply.
My simulation shows that C5 will have less than 1 mA going through it.
What will be the effect if i convert the differential voltage across C5 into a single ended output ?
Will that give me correct current ?
This is a new circuit that i tried
When i try to tap the differential voltage across C5(capacitor parallel with inductor DCR) the voltage acoss it and DCR no longer remain same. why ?
I tried a current sense amplifier MAX4372F with a gain of 50V i.e my input gets multiplied by that much i think
now i require a the inductor current at the output which is 10A. I tried connecting a resistor at the output of the current sense amplifier and found that the voltage also changes based on the connected resistor which should not happen. Where am i going wrong here ?
converterC5 has current going one way through it and then the other way.
You can try measuring voltage across it but that will not necessarily tell you about current flow through it.
I'm sorry, but I'm not familiar with the MAX4372 IC. The datasheet says it is designed to measure the differential V across a small resistance. I believe it will be more useful if you use it on R28 which is directly in line with the coil.
This is a complicated application of electronics. In order to set up the proper measuring scheme, you will need to get familiar with simpler concepts. Such as to experiment with the MAX4372 on simpler circuits. Use an oscilloscope to find out what goes on with C5.
Question: Do you still have your original goal to build a power converter? Is C5 important in some way that you are aware of?
Yes, I see how it works now. Here is a simulation:
It has only the essential components for a buck converter. Most of the values are from your latest schematic (post #71).
As you stated, the V across C5 is proportional to A through the coil. C5 has the more positive polarity at the left. Only a few mV appears across it. This amount seems rather low for a device to detect.
I find that R27 needs to be tailored to the coil resistance. When I increase coil resistance to .01 ohm, the capacitor waveform is lifted on a DC component. I must then reduce R27 in order to restore proportional action.
I can't predict what will be the real-life resistance of your coil.
Need a operational amplifier with stable gain sligtly above 500Khz for my current sensing purpose
Kindly suggest me one
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