multiple SMPS Voltages

[muhammadali_16]

Triangle WAVE????? i didnt understand.

the most used IC and avaible IC is sg3525 and i il also use it?

did current have any relation with frequency for BOOST circuit?

 

[goldsmith]

Muhammad , are you familiar with SPWM and link inverters ? do you know the difference between SPWM and PWM ? and in the other hand , are you familiar with class D amplifier basics ? Yes , triangle wave ! but not for first stage ! for 2nd stage .

 

[muhammadali_16]

i m not familier with it. i hv only worked with PWM controller(sg3525) which is used to draw gate of the IRF540 and then transformer stuff. i hv heard this first time

 

[goldsmith]

hummmmmm !!!! no problem ! for understanding meaning behind SPWM and PWM see my blogs please , after that if you didn't understand , i can simplify it for you .

 

[muhammadali_16]

i think its for 50Hz pulse. i was asking frequency for BOOST section (12VDC - 350VDC). what frequency should i use to do this

 

[goldsmith]

See post #60

 

[muhammadali_16]

u mean to say for 12vdc-350vdc, i should use nearly 100KHz and for 50Hz inverter, i should use 50KHz carrier Freq

Rite?

 

[goldsmith]

Yes, it was my meaning .

 

[muhammadali_16]

can u tell me the procedure for SPWM, i mean related to hardware, IC etc

 

[goldsmith]

What do you mean by that ? would you like to know how to create SPWM for your purpose ? or you just need the name of components ?

 

[muhammadali_16]

both...... i il implement it

 

[goldsmith]

As you probably know , SPWM , got from Pulse Width Modulation and SPWM is Sinusoidal Pulse Width Modulation .
For SPWM , we will have many ways to create ! but the best way that you can choose is this :
Comparison between a pure sine wave and a triangular wave which has higher frequency . ( in practice we have to select Ftri=10Fsin ) ( at least ! if you select more than this , it will be better .)
you should use a comparator such as LM311 or LM339 or LM319 or ...... etc to do comparing between your triangle wave and sine wave !
And don't forget to create enough dead time for Between your SPWM and SPWM' . each SPWM consists a high frequency spectrum and a low frequency spectrum . if you use an LPF after your SPWM , you'll have your message signal ( sine wave )
I hope you got the idea.

 

[muhammadali_16]

the whole idea is great but the implementation of such things are not so simple. i got the whole idea of SPWM didnt know how to maintain deadband and other parameter related to hardware (MOSFET problems, inductors etc). becz i have to select the components which match woth others

i il try to research this first

 

[goldsmith]

It is pretty simple , but you need to earn some experiences , that i think you haven't now , but you should try , if you can do this project , you'll learn many things from it . for dead time: it is very simple. you can use an schmitt trigger not gate and an RCD network . try , to research about it , if you can't earn success , be sure that i'll help you .
Wish you the best
Goldsmith

 

[pol]

i had use the snubber, but there is still the noise....

 

[pol]

my ferrit tafo is hot,
and still therre is a noise like a clock walk tough i had use the snubber.....

 

[goldsmith]

Dear Pol
Hi again
If your ferrite is going to be warm , it means that it's size isn't enough , or perhaps it didn't design for this range of frequency .
And about noise , did you see me previous suggestions ? creating enough gap space and use , some glue .
Best Luck
Goldsmith

 

[pol]

my ferrit trafo size is ac= 1 cm², aw=1,44cm²

dont you think its good to generated 13,8 v, i=0,5 A with vin = 25 v,using sg 3524 to generated pwm 20 khz

n1=60, n2= 50

 

[goldsmith]

hummmm ! it shouldn't be worm . are you sure that the current through it is just 0.5 A? be sure about it .

 

[pol]

yes 0,5 A,the output is not stabil its, around 12,8 till 15,2 volt..

i want my output stabil 13,8 v,with the current 0,5 a...

in the sg3524, to make the output stabil that we want its there a formula....
i hav did it, but the output there is not stabil and still generated a noise like a clock walk...