T
treez
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woops , sorry I read your post #2 as lp="37mH" instead of "1.37mH"Your turns ratio is 38.4:1 ..??
My secondary turns are:5
My Pri Turns are :51
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woops , sorry I read your post #2 as lp="37mH" instead of "1.37mH"Your turns ratio is 38.4:1 ..??
My secondary turns are:5
My Pri Turns are :51
Please find the attached schematicsYou need, 1k gate to source..! AND 22 ohm resistor to the gate, this will limit the VHF oscillations on the gate,,,!
At 12V (13.8) and 10A out, try a 4.7 ohm 3W resistor and 200V 10nF cap (low loss film type)
Hi Smijesh:
Hello c_Mitra,
I am using gate driver of 4 Ampere of silabs.
What is Turn on Hard n how to achieved..?
Why my Gate resistor Burnt.??
Bjtpower:-
In post #11 you say NP=51, NS = 5
But in post #2, you say LP=1.37mH , LS=25uH
…this doesn’t add up.
NS/NP = SQRT(LS/LP)
So by your inductance measurements, your NP/NS = 7.4
what are your latest inductance figures>?, (at 100khz)
The inductances you have so far given don't add up to the ns/np = sqrt(ls/lp) equation
Here is an LTspice simulation of your flyback, as well as an excel spreadsheet which shows calculation of the rms currents etc….(attached)
I considered your spec is…
VIN=180-240VDC
VOUT=12V
IOUT=10A
FSW=100KHZ
LP=1.37mH
LS=25uH
k(transformer)=0.99
you can change the spreadsheet yourself if you wish, the one I sent you a few posts back
Most of you high current is in the secondary, so therefore you want the "secondary duty cycle" to be relatively larger than the primary duty cycle, so you do not want a duty cycle of 48%
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again your above ns/np and ls/lp values don't correspond
You need, 1k gate to source..! AND 22 ohm resistor to the gate, this will limit the VHF oscillations on the gate,,,!
A smaller value for Lpri (bigger core gap) will get you closer to DCM, discontinuous operation, which is better for the o/p diode and for generating RFI....!
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plugging in the values for just DCM operation (@180VDC in min, 130W) gives L opt = 200uH, Ipk = 3.6A, 100kHz, Ton = 4uS (max).
Using these will give you best operation. For Iout = 10A average, Ipk = 40A, so large high quality electrolytics needed to soak up the current peak & ripple... say 5 x 470uF at a minimum.
what inductance did you measure?Are the inductance values are collect
LP:122uH With N87 Material?
Kindly send your calculation at max duty cycle will be 48%
For ETD49, 212mm^2 core area, for 51T on the primary and 200uH Lpri, and 3.6A pk, 100kHz:
the core gap required is 3.64mm (centre only), or 1.8mm in each core leg (3 of) this will give you ~200uH (for 51 turns) and a lot more than 3.6A peak current capability. Flux will be only 0.07 Tesla peak, as you have more turns than you need for this core size.
You will find the performance of your converter will improve markedly under these conditions (large snubbers still required..!)
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Your previous posts of Lp = 1.37mH imply not much gap in the core, which implies a saturating Tx core which implies very high turn off currents (>10A) - giving the big turn off spikes and ringing you have observed...!
For ETD49, 212mm^2 core area, for 51T on the primary and 200uH Lpri, and 3.6A pk, 100kHz:
the core gap required is 3.64mm (centre only), or 1.8mm in each core leg (3 of) this will give you ~200uH (for 51 turns) and a lot more than 3.6A peak current capability. Flux will be only 0.07 Tesla peak, as you have more turns than you need for this core size.
You will find the performance of your converter will improve markedly under these conditions (large snubbers still required..!)
- - - Updated - - -
Your previous posts of Lp = 1.37mH imply not much gap in the core, which implies a saturating Tx core which implies very high turn off currents (>10A) - giving the big turn off spikes and ringing you have observed...!
I have simulate the circuit in Psim and got to know that i can work on the 1.37 mh of inductance.
but i am not able to understand the Core saturation.