Good post moderator,
I thought I said those things but maybe I didn't do a good job......
Sorry about that all.....
Chris
I thought I said those things but maybe I didn't do a good job......
Sorry about that all.....
Chris
diode>>
thank you for doing your best, im just a slow understander 🙂
it would probably have made sence to someone a bit more experienced
thank you for doing your best, im just a slow understander 🙂
it would probably have made sence to someone a bit more experienced
Olle Bard:
To really get a feel for how to do all the math on winding the power transformer for a modified SMPS, please, please check oyt George Chryssis' excellent book "High-Frequency Switching Power Supplies". Most recent edition I have seen is 1989, but everything covered is still VERY relevant.
Despite what you may have been cautioned against, designing and prototyping a SMPS need not be that difficult. First, you need to ask yourself some basic questions:
1) How much power do I need from it; 2) What will the output voltages and currents be from it 
; 3) What frequency will I operate it at? Ref: jackinnj's comment on working DX on 20M. The switching frequency chosen can introduce harmonics at certain frequencies, like the HF Ham bands. This is very bad! 😱
This book divides up the different sections of the typical SMPS and devotes a separate chapter to each. The section on designing the power transformer has all you will ever need to to flybacks and forwards like the push-pulls half- and full-bridge topologies.
It shows you how to select the core material (very important as different alloys exhibit different magnetic properties), size and how to calculate the windings for a successful design.
Since you've spoken of modifying an existing unit, and not designing from the ground up, the chapter on the power transformers is still relevant. You will most likely modify only the secondaries on the power transformer, so whatever turns you unwind from the primary, be VERY careful 😱 to rewind them EXACTLY as they were unwound.
The material is most likely a high-permeability ferrite, like Amidon's #77. Amidon has a website www.amidon.com, and a good data sheet with all their core chapes, materials and applications. These two sources, Chryssis' book, and the Amidon datasheet, are two very good tools to get you where you want to go.
Best of Luck, and please let us know how you fare with this.
N-Channel
To really get a feel for how to do all the math on winding the power transformer for a modified SMPS, please, please check oyt George Chryssis' excellent book "High-Frequency Switching Power Supplies". Most recent edition I have seen is 1989, but everything covered is still VERY relevant.
Despite what you may have been cautioned against, designing and prototyping a SMPS need not be that difficult. First, you need to ask yourself some basic questions:
1) How much power do I need from it; 2) What will the output voltages and currents be from it ; 3) What frequency will I operate it at? Ref: jackinnj's comment on working DX on 20M. The switching frequency chosen can introduce harmonics at certain frequencies, like the HF Ham bands. This is very bad! 😱 This book divides up the different sections of the typical SMPS and devotes a separate chapter to each. The section on designing the power transformer has all you will ever need to to flybacks and forwards like the push-pulls half- and full-bridge topologies.
It shows you how to select the core material (very important as different alloys exhibit different magnetic properties), size and how to calculate the windings for a successful design.Since you've spoken of modifying an existing unit, and not designing from the ground up, the chapter on the power transformers is still relevant. You will most likely modify only the secondaries on the power transformer, so whatever turns you unwind from the primary, be VERY careful 😱 to rewind them EXACTLY as they were unwound.
The material is most likely a high-permeability ferrite, like Amidon's #77. Amidon has a website www.amidon.com, and a good data sheet with all their core chapes, materials and applications. These two sources, Chryssis' book, and the Amidon datasheet, are two very good tools to get you where you want to go.
Best of Luck, and please let us know how you fare with this.
N-Channel
I think this is the amidon link
http://www.amidon-inductive.com/index.html
http://www.amidon-inductive.com/index.html
http://www.amidon-inductive.com/index.html
http://www.amidon-inductive.com/index.html
Yes, this is the link. Sorry about the bad post. Amidon's website has changed, nad they have all the stuff you will ever need.
FYI, I have prototyped many switching power supplies and DC-DC converters, and everytime, I have referred to these two sources. Best of luck.
FYI, I have prototyped many switching power supplies and DC-DC converters, and everytime, I have referred to these two sources. Best of luck.
don't forget that International Rectifier has an entire tutorial on flyback transformer theory and design on their website.
jack
jack
My idea of getting higher output voltage from standard computer SMPS
The secondary of the chopper transformer will produce perfect alternating hi-freq square wave, right..? If we tap two wires from the ends of the 12V coil of the transformer and connect it to primary of the external toroid, the secondary of the toroid can be wound to produce any voltages we need at reasonable current levels, provided neither toroid or the chopper-trans not going into saturation.
Since the power is tapped off from the feedback loop, I am not quite sure what implication this will cause to the internal regulation of the computer smps.
If the DC filtering e-caps of the smps are replaced with the one with less capacity units, probably the PWM controlling IC will detect some kind of output voltage drop when external toroid is loaded extensively.
This is just a tought, never been tried so far... Please comment.
The secondary of the chopper transformer will produce perfect alternating hi-freq square wave, right..? If we tap two wires from the ends of the 12V coil of the transformer and connect it to primary of the external toroid, the secondary of the toroid can be wound to produce any voltages we need at reasonable current levels, provided neither toroid or the chopper-trans not going into saturation.
Since the power is tapped off from the feedback loop, I am not quite sure what implication this will cause to the internal regulation of the computer smps.
If the DC filtering e-caps of the smps are replaced with the one with less capacity units, probably the PWM controlling IC will detect some kind of output voltage drop when external toroid is loaded extensively.
This is just a tought, never been tried so far... Please comment.
- Status
- Not open for further replies.