Power Supply frequency
Asrto-
You will know by the timing resistor and cap chosen. What is the controller? TL494? SG3525? UC1846? MC33025? Each of these has their own plug-n-chug formuls for choosing the clock frequency. Also, because this is push-pull (double-ended), remember that the clock frequency will be twice the switching frequency. Most popular switching frequencies are in the 33-36kHz range (clock in the 66-72kHz range).
'73,
de N8XO
Asrto-
You will know by the timing resistor and cap chosen. What is the controller? TL494? SG3525? UC1846? MC33025? Each of these has their own plug-n-chug formuls for choosing the clock frequency. Also, because this is push-pull (double-ended), remember that the clock frequency will be twice the switching frequency. Most popular switching frequencies are in the 33-36kHz range (clock in the 66-72kHz range).
'73,
de N8XO
Astro Power :
Be prepared to learn a lot about SMPS before starting such an ambitious project. There is already a lot of information on that forum so use the search engine
Be prepared to learn a lot about SMPS before starting such an ambitious project. There is already a lot of information on that forum so use the search engine
i only want to add to my pwm a stronger transformer.
and add a more mosfet's to give to the transformer the power is need.
if my core is not good.....so i will go to a transformers store, and buy from them a good transformer and they make for me the turns of the transformer....
tamir.
and add a more mosfet's to give to the transformer the power is need.
if my core is not good.....so i will go to a transformers store, and buy from them a good transformer and they make for me the turns of the transformer....
tamir.
This is not the way to do it and classic transformer stores understand nothing about SMPS ferrite transformers or SMPS design. They just do 50Hz transformers and some of them know how to do audio transformers
The right way to obtain higher powers is to use several small SMPS cells. SMPS circuits and transformers must be kept small, since as size is increased problems increase very quickly
Also, using too much switching devices causes a lot of trouble due to PCB track inductance and gate drive requirements. Those IRFZ44 are quite outdated, check IRFZ48V out, they are cheap and each of them does the job of two or more IRFZ44. There are even better devices from Intersil and others
I would go for something like four 700W cells using four ferrite toroids of 40 to 50mm diameter or four E42/20 EE ferrite cores, two or three pairs of IRFZ48V or better per cell, and a single 19V secondary per transformer connecting all them in series [38+38V] for better current sharing and ease of winding
Finally, have you considered the ultrafast diodes required to rectify the output? You will need new diodes
Be patient, you have still a lot to learn
The right way to obtain higher powers is to use several small SMPS cells. SMPS circuits and transformers must be kept small, since as size is increased problems increase very quickly
Also, using too much switching devices causes a lot of trouble due to PCB track inductance and gate drive requirements. Those IRFZ44 are quite outdated, check IRFZ48V out, they are cheap and each of them does the job of two or more IRFZ44. There are even better devices from Intersil and others
I would go for something like four 700W cells using four ferrite toroids of 40 to 50mm diameter or four E42/20 EE ferrite cores, two or three pairs of IRFZ48V or better per cell, and a single 19V secondary per transformer connecting all them in series [38+38V] for better current sharing and ease of winding
Finally, have you considered the ultrafast diodes required to rectify the output? You will need new diodes
Be patient, you have still a lot to learn
Astro (I got it right that time)-
Eva gives good advice- there is still alot to learn about SMPSs, aven for us veterans. Simple PWM push-pull designs must be done carefully, or else very bad things can happen, especailly at the power levels you're talking about.
May I recommend several books that I've recommended here and on other forums?
1) George Chryssis' book "High Frequency Switching Power Supplies" (c) 1989- most recent edition
2) Abraham Pressman's "Switching Power Supply Design" (c) 1998
3) Marty Brown's book about Switchers from the EDN series. He used to work for Motorola before they spun off the semi group int owhat is now ON Semiconductor. I can't remember the title of his book.
Anyway, Chryssis' book has a chapter devoted entirely to transformer design for both flyback and forward (thre type you're doing). I have taken hisdesign process, and reduced it to a 11-12 step design process that is pretty much cut-n-dried. I have has great results with this.
Eva gives good advice- there is still alot to learn about SMPSs, aven for us veterans. Simple PWM push-pull designs must be done carefully, or else very bad things can happen, especailly at the power levels you're talking about.
May I recommend several books that I've recommended here and on other forums?
1) George Chryssis' book "High Frequency Switching Power Supplies" (c) 1989- most recent edition
2) Abraham Pressman's "Switching Power Supply Design" (c) 1998
3) Marty Brown's book about Switchers from the EDN series. He used to work for Motorola before they spun off the semi group int owhat is now ON Semiconductor. I can't remember the title of his book.
Anyway, Chryssis' book has a chapter devoted entirely to transformer design for both flyback and forward (thre type you're doing). I have taken hisdesign process, and reduced it to a 11-12 step design process that is pretty much cut-n-dried. I have has great results with this.
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