600/800W 220~230v AC Inverter SMPS from 12v DC

[goldsmith]

i am using yellow/white core to design an inductor with L=300uh, i have wound 57 turns of 18 gauge wire and checked it with indutance meter to get the desired inductance. with 12V and for 190us, i should get a peak current of approx 7.7A, but when i constructed and used the inductance, it gives me only the peak current of 3.4A.

please advice why it is happening?

Thanks in advance

Hi Adeel
In what kind of circuit it should give you that current ? a switch mode circuit ? what frequency ? and what arrangement ? if you don't mention those parameters , how we can help you ? where is your schematic ? how you expect that we help you with these low informations ?
Best Wishes
Goldsmith

 

[adeel abid]

Hi Adeel
In what kind of circuit it should give you that current ? a switch mode circuit ? what frequency ? and what arrangement ? if you don't mention those parameters , how we can help you ? where is your schematic ? how you expect that we help you with these low informations ?
Best Wishes
Goldsmith

thanks for your response. please consider my thread "DC-DC boost converter problem". & let me know for further info .

waiting for response.

thanks in advance

 

[goldsmith]

thanks for your response. please consider my thread "DC-DC boost converter problem". & let me know for further info .

waiting for response.

thanks in advance

I fear
Can you add it's address here , please ? because i can't remember that . and now i'm a bit more busy , hence i don't have any time to search and find your thread .
All the best
Goldsmith

 

[adeel abid]

Dear Goldsmith

here it is. waiting for your response.

thanks
Adeel

 

[goldsmith]

Hi again
Well , now how can i help you ? how you have designed your inductors ? how you have selected cores ? how about capacitor ? all of these parameters are important for judgement about a boost converter .
If you tell me a bit more explanations about your exact , problem , i can help you more .
Best Wishes
Goldsmith

 

[adeel abid]

i am using the cores whose snaps are attached in my previous post (yellow/white & green/blue). i have selected it randomly. i started winding the core with 18 AWG wire until my LCR meter gives 300uH.
Capacitor used is 47uF 400V polar.
My problem is that i theoretically should get the peak inductor current of at least 6.5A but in practice i am getting only about 3.5A. Either there is some parasitic resistance or additional inductance that is limiting the current. i am doubtful about the inductance because it seems to be increased during circuit operation. how could verify it if my doubt is correct or otherwise?

please advice

thanks in advance

 

[goldsmith]

i have selected it randomly

Hi Adeel
A designer won't select a core randomly . it is not named design !
Would you like that i tell you how to select a core ? ( according to the frequency and power and color ? )

meter gives 300uH.
Capacitor used is 47uF 400V polar.

How you have calculated those numbers ? again randomly ?

My problem is that i theoretically should get the peak inductor current of at least 6.5A but in practice i am getting only about 3.5A. Either there is some parasitic resistance or additional inductance that is limiting the current. i am doubtful about the inductance because it seems to be increased during circuit operation. how could verify it if my doubt is correct or otherwise?

please advice

thanks in advance

Can you show me your calculations , please ?

All the best
Goldsmith

 

[adeel abid]

yes please tell me how to select the best core for a particular application. also tell me what is wrong with these cores.

i have measured them & their value is unchanged.

I=V/R*[1-exp(-r*t/L)]
I=12/0.5*[1-exp(-0.5*190u/300u)]
where 0.5 is Rds(on) of IRF740

 

[goldsmith]

Hi again
For core selection and Magnetic element design , take a look below , please :
https://www.edaboard.com/threads/229615/

Now i have to go , because i'm terribly busy . so , tomorrow i'll have more time to help you more .

Until tomorrow , have a nice time !
Goldsmith

 

[adeel abid]

Dear Goldsmith,

i have gone through the thread and i found it very useful but is there any procedure to find out the power and frequency of a randomly selected core through some experiments. also consider this **broken link removed**. what kind of transformer it is? what is its core material? what kind of primary winding and wire gauge it has to support a huge current of greater than 40A? Can you provide me the more detailed technical specs of this transformer so that i can made it by myself? please advice

thanks in advance

- - - Updated - - -

Dear Goldsmith,

i have gone through the thread and i found it very useful but is there any procedure to find out the power and frequency of a randomly selected core through some experiments. also consider this **broken link removed**. what kind of transformer it is? what is its core material? what kind of primary winding and wire gauge it has to support a huge current of greater than 40A? Can you provide me the more detailed technical specs of this transformer so that i can made it by myself? please advice

thanks in advance

 

[goldsmith]

i have gone through the thread and i found it very useful but is there any procedure to find out the power and frequency of a randomly selected core through some experiments. also consider this aritcle. what kind of transformer it is? what is its core material? what kind of primary winding and wire gauge it has to support a huge current of greater than 40A? Can you provide me the more detailed technical specs of this transformer so that i can made it by myself? please advice

thanks in advance

Hi again
As it appears you didn't read , that link carefully . because at end pages of that thread i have added some tables which can handle your aim . why you didn't read that thread carefully ?
Best Wishes
Goldsmith

 

[sam781]

Due to some official and personal work pressure I could not give full concentration in my Inverter making task. It is advancing in very slow motion...
Recently I bought two MOSFET driver IC IRF2110, four IRF3205 and some diodes (1N4007). But for such high frequency operation (50kHz) this diode is not suitable. To complete converter I need to buy some Schottky diode. Now, I've the following question in my mind need comments from you -
1. Do I need Freewheeling diode for MOSFET bridge configuration?
2. If yes, can I use normal diode (1N4007) as freewheeling diode?
3. Which value of recovery time should I use for 50kHz operation? Also refer some part number for this.
4. What will be output waveform after rectification?
5. How can I design filter for this sample case? If I get some idea about filter I'll try to manage required ferrite core when I'll go to market for Schottky diode.

 

[goldsmith]

1. Do I need Freewheeling diode for MOSFET bridge configuration?

Most of the switching mosfets have internally anti parallel diodes . ( unless some types of them )

2. If yes, can I use normal diode (1N4007) as freewheeling diode?

Of course not ! do you know about Trr ? you'd better to take a look at concept of Trr .

4. What will be output waveform after rectification?

What ? what kind of rectifier ? which section of your circuit ?

5. How can I design filter for this sample case? If I get some idea about filter I'll try to manage required ferrite core when I'll go to market for Schottky diode.

FIlter of what section ? first section or 2nd section ? ( both are 2nd order LC filters ) but latest stage , needs more attention .
Good luck
Goldsmith

 

[sam781]

As IRF3205 has anti parallel diode, I do not need anymore diode for freewheeling purposes. Diode having Trr lower is better. Could you suggest some part number which I can use?

For now, I wanted to design filter for the first stage i.e, converter stage. 400-450v 50kHz square wave will be rectified with a bridge rectifier.

 

[goldsmith]

Hi Sam

. Could you suggest some part number which I can use?

Yes , of course . if you need diodes , you should mention your power rating ( that diode should be able to handle ) but , these are some usual good points ! ( from low power up to high power ) . 1n4148/
FR104 /UF4007 /SB1020 op to 10100/ MUR1560 /DSSk48 / MUR1060CT or ... etc

For now, I wanted to design filter for the first stage i.e, converter stage. 400-450v 50kHz square wave will be rectified with a bridge rectifier.

Humm i think you're referring to the DC voltage increasing stage , well , are you familiar with formulas of an H bridge filter design ? if no , i can give you two formula , one for , out put capacitor and the other one is for inductor .
All the best
Goldsmith

 

[sam781]

Thanks Goldsmith,
For 50kHz 400v with 350-400w output, 1A-2A current ratting of Schottky diode should be okay.

i can give you two formula , one for , out put capacitor and the other one is for inductor .

Yes, please give me the formula.

 

[Tahmid]

If you haven't already, going through this design may help clear some of your doubts:
**broken link removed**

 

[goldsmith]

Yes, please give me the formula.

L=0.5vo*t/Ion

C=(80*10^-6 )*di/Vr
By the way , i agree with Tahmid , you'd better to take a look at his literature .
Good luck
GOldsmith

 

[sam781]

Converter spec -

Battery=12v (let, operating voltage range 11v to 13.8v)
Desired power=300w

Converter frequency=50kHz (time period 20us)

Nominal input voltage, Vin= 12v
Output voltage, Vout= 325v (needed to make 230v ac rms)

Max primary current, Ip=375/11=34Amp
Secondary current, Is=Ip/N=34/33=1.03=1Amp

Turns ratio, N2/N1=N=33
Max duty cycle 90%. So, max on time, Ton=20us*.9/2=9us

According to the formula given in the ST doc shared by Tahmid [ Lmin=(Vin*N2/N1-Vout)*ton/dI ]
Ripple current, dI=15% of Iout=0.15A
So, L=(12*33-325)*9us/0.15=4.26mH

I cannot understand this formula - L=0.5vo*t/Ion
So, cannot verify the result. Could you please check and explain this simple formula and help me to verify the result?

- - - Updated - - -

For capacitance measurement the formula is C=1/8(dI/dVo)*Ts
Switching time, Ts=20us for 50kHz frequency (not sure whether it is right or wrong)
dVo=0.1%of Vo=325*0.001=0.325v

So, C=1/8(0.15/.325)*20=1.15uF
Is it okay?

 

[goldsmith]

According to the formula given in the ST doc shared by Tahmid [ Lmin=(Vin*N2/N1-Vout)*ton/dI ]
Ripple current, dI=15% of Iout=0.15A
So, L=(12*33-325)*9us/0.15=4.26mH

I cannot understand this formula - L=0.5vo*t/Ion
So, cannot verify the result. Could you please check and explain this simple formula and help me to verify the result?

- - - Updated - - -

For capacitance measurement the formula is C=1/8(dI/dVo)*Ts
Switching time, Ts=20us for 50kHz frequency (not sure whether it is right or wrong)
dVo=0.1%of Vo=325*0.001=0.325v

So, C=1/8(0.15/.325)*20=1.15uF
Is it okay?

Hi Sam
To prevent such high values , you can increase frequency of operation of this stage up to 200KHZ , as well ! ( because a 630V or 400 V capacitor , with low ESR and low ESL with value of 1uf seems a bit expensive and large )
Good luck
Goldsmith

- - - Updated - - -

Switching time, Ts=20us for 50kHz frequency (not sure whether it is right or wrong)

BTW : why you have doubt about it ? TS means switching frequency . so 1/50*10^3 =20usec .
so it's true .