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Load regulation in SMPS

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abhishek.2138

abhishek.2138

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For 24V, 0.5A flyback SMPS ,transformer is designed as--

IC used is NCP 1014, core is E19/8/5, Frequency= 65 KHz, Duty cycle min. = 50%

N1 = (VinDCmin * Tonmin) / (ΔB * Ae)
= (275 * 7.7 µs) / (0.23 * 22.5 mm²)
= 410 Turns (primary)

N2 = N1*V2/VinDCmin = 36 Turns (secondary)

No Auxiliary winding needed.

Is this correct calculation??? or Should I increase flux density ΔB to 0.3??? Are there any other calculations for transformer designing???

When I connect load of around 100mA, output voltage drops by 2.5V. I am getting poor load regulation. 24V Zener diode with optocoupler is used for feedback & regulation.

Diagram is as per datasheet attached (page 19, Fig. 30)
Please help...
 

Attachments

  • NCP1010-D.PDF
    383.9 KB · Views: 62

Fig 30 is a diagram for a 6.5W supply.

For a ((24*0.5)=12)W supply, apart from transformer calculations, you'll have to consider charging and discharging times for output capacitors and, thus, a suitably sized output capacitor. You'll also have to do calculations for components in the feedback loop.
 

Akanimo said:
Fig 30 is a diagram for a 6.5W supply.

For a ((24*0.5)=12)W supply, apart from transformer calculations, you'll have to consider charging and discharging times for output capacitors and, thus, a suitably sized output capacitor. You'll also have to do calculations for components in the feedback loop.
Click to expand...



Ok.

But, I want to verify that transformer calculations are correct or NOT??

Also, transformer core air gap = (µr*Np²*Ae ) / Lp

where, µr =4π*10^-7;
Np= Primary turns
Lp= Primary Inductance

So, please let me know my CALCULATIONS ARE CORRECT OR NOT???
 

Please search for this material on the internet: "magnetics design 5 - inductor and flyback transformer design"

I hope it helps.
 

Hello Abhishek.2138,

I have done the Flyback SMPS design (24V,0.5A from VAC in = 100 to 265VAC) for you here. I chose a DCM design.
I used the E 19/8/5 Core like you requested. …

Core datasheet…
https://ferroxcube.home.pl/prod/assets/e1985.pdf

As usual, the available wire sizes and the dimensions of the pre-gapped core and former end up governing the turns ratios etc.
I took VAC input as being 100VAC to 265VAC.
I chose the ferroxcube ready gapped 3C90 E19/8/5 core….it is gapped to an AL value of 63 ( it says the gap for this is 650um).
I chose a split primary of 76 turns of 35SWG wire (Enamelled copper wire [ECW0.2]). This is 2 layers which “sandwich” the secondary. Lp = 364uH
I chose a 32 turn secondary of 7/0.1mm TEX-ELZ triple insulated wire. This is in two layers which are wound one over the other. Ls = 64.5uH
The NS/NP = 0.42
The peak current in primary was about 1.1A…and the saturation current is 1.38A…so you have good margin.
Attached is the schematic and LTspice simulation of it….also the excel design document for the power stage and transformer.

TEX-ELZ wire
https://www.furukawa.co.jp/makisen/eng/product/texelz.htm
Enamelled copper wire:
https://www.farnell.com/datasheets/...9.1019522641.1501332265-1679746183.1489787856

- - - Updated - - -

If you do run the sim, maybe change the solver to "Normal 1".....(hammer icon..SPICE)
 

Attachments

  • Flyback 24V 0A5.TXT
    6.1 KB · Views: 45
  • Flyback 24V 0A5 SCHEM.pdf
    16.6 KB · Views: 82
  • FLYBACK 24V 0A5.zip
    11.8 KB · Views: 49
treez said:
Hello Abhishek.2138,

I have done the Flyback SMPS design (24V,0.5A from VAC in = 100 to 265VAC) for you here. I chose a DCM design.
I used the E 19/8/5 Core like you requested. …

Core datasheet…
https://ferroxcube.home.pl/prod/assets/e1985.pdf

As usual, the available wire sizes and the dimensions of the pre-gapped core and former end up governing the turns ratios etc.
I took VAC input as being 100VAC to 265VAC.
I chose the ferroxcube ready gapped 3C90 E19/8/5 core….it is gapped to an AL value of 63 ( it says the gap for this is 650um).
I chose a split primary of 76 turns of 35SWG wire (Enamelled copper wire [ECW0.2]). This is 2 layers which “sandwich” the secondary. Lp = 364uH
I chose a 32 turn secondary of 7/0.1mm TEX-ELZ triple insulated wire. This is in two layers which are wound one over the other. Ls = 64.5uH
The NS/NP = 0.42
The peak current in primary was about 1.1A…and the saturation current is 1.38A…so you have good margin.
Attached is the schematic and LTspice simulation of it….also the excel design document for the power stage and transformer.

TEX-ELZ wire
https://www.furukawa.co.jp/makisen/eng/product/texelz.htm
Enamelled copper wire:
https://www.farnell.com/datasheets/...9.1019522641.1501332265-1679746183.1489787856

- - - Updated - - -

If you do run the sim, maybe change the solver to "Normal 1".....(hammer icon..SPICE)
Click to expand...



How u do these turn calculations??? Did you use Faradays law?? or Volt-Seconds rule????????

- - - Updated - - -

In the pdf schematic I think there should be Y capacitor between L1 & L2...
 

Yes the schem is just for basic illustration.
I will send you the math doc...contains within it the math you need

- - - Updated - - -

basically you are wanting i(sat) = [B(sat).A.N]/L

Also, AL = [L(nH)]/(N^2)

- - - Updated - - -

Flux = B.A is also useful.

- - - Updated - - -

If you want to calc the gap length then you need to do it by the reluctance.....but to be truthful, the fringin flux always makes the calc inaccurate, so your best to download the TDK design tool for transformer cores and get the AL value for a given gap like that.
Its called MDT....magnetic design tool...it was from epcos.

- - - Updated - - -

You dont need to calc the gap anyway...because the core comes pre-gapped and the datasheet gives you the AL value.
AL is kind of a word for "allowance", and its kind of the oposite of reluctance.
 

Attachments

  • Core Mathematics and Equations for SMPS design.doc
    195.5 KB · Views: 49

treez said:
Yes the schem is just for basic illustration.
I will send you the math doc...contains within it the math you need

- - - Updated - - -

basically you are wanting i(sat) = [B(sat).A.N]/L

Also, AL = [L(nH)]/(N^2)

- - - Updated - - -

Flux = B.A is also useful.

- - - Updated - - -

If you want to calc the gap length then you need to do it by the reluctance.....but to be truthful, the fringin flux always makes the calc inaccurate, so your best to download the TDK design tool for transformer cores and get the AL value for a given gap like that.
Its called MDT....magnetic design tool...it was from epcos.

- - - Updated - - -

You dont need to calc the gap anyway...because the core comes pre-gapped and the datasheet gives you the AL value.
AL is kind of a word for "allowance", and its kind of the oposite of reluctance.
Click to expand...


Thanks a lot for help... Please send/upload the maths document...
 

i put it in the post #8

one useful one is v = Ldi/dt and V = Nd(phi)/dt

The laws of Lenz and Faraday

then equate the right hand sides giving L.di/dt = Nd(phi)/dt
..rearranging..
L.di = Nd(phi)

phi = L.i/N

A.B. = L.i/N

i = B.A.N/L

...This is for i(sat) = B(sat).A.N/L

...and tells you what is saturation current for B(sat)
 
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