Hi
I never wanted to go low on capacitance, so I have never tryed it. Why I didn't go for lower C, now 3x1000uF for each rail... well because if you have HB Damp you will have so called pumping effect, in other words, at low freq. from amp, low load (resistance of it)... you will get higher voltage on caps that supply is set to, so having higher C lowers this voltage raising
I never wanted to go low on capacitance, so I have never tryed it. Why I didn't go for lower C, now 3x1000uF for each rail... well because if you have HB Damp you will have so called pumping effect, in other words, at low freq. from amp, low load (resistance of it)... you will get higher voltage on caps that supply is set to, so having higher C lowers this voltage raising
classd amps
Luka
I am aware that the HB classd amp presents this problem and there have been a few solutions suggested for this. I would like to offer the link to a website that covers classd and SMPS that has help me and contains a wealth of info from a person who has done alot of work in this area. Keith , I think is a member of this forum as well as the yahoo group for LTspice. I really don't have a solution for these problems.
chas1
http://www.genomerics.talktalk.net/
Luka
I am aware that the HB classd amp presents this problem and there have been a few solutions suggested for this. I would like to offer the link to a website that covers classd and SMPS that has help me and contains a wealth of info from a person who has done alot of work in this area. Keith , I think is a member of this forum as well as the yahoo group for LTspice. I really don't have a solution for these problems.
chas1
http://www.genomerics.talktalk.net/
Halfbridge,Two Switch Forward Conveters
I am posting three zip files which with the help and advice from others and a small part of mine will allow the simulation and I hope the design of a working supply. It does use models from Christophe P. Basso's Switch-Mode Power Supply Spice Cookbook, a book you should add to your reading list . You will also need the LTspice software which is free on the web. These files should be used with knowledge that I am not expert in design or spice simulations I am a DIY like many of you and will respond to suggestions or questions about these offerings along those lines. If you are a professional and can improve these in any form I am sure the members of this forum will be delighted. One of the supplies has be built based on these simulations and is very close to the results. Also you should visit Keith's website at the url mention in a previous post.
Remember spice simulation alone will not kill you but in actual contruction you will be exposed to lethal voltages and situations and should not attempt any conrtruction or attempts to constuct supplies based on others schematic's or work unless you know and follow the safety guidelines offered by others on this forum. With that in mind proceed with caution .
chas1
http://www.genomerics.talktalk.net
I am posting three zip files which with the help and advice from others and a small part of mine will allow the simulation and I hope the design of a working supply. It does use models from Christophe P. Basso's Switch-Mode Power Supply Spice Cookbook, a book you should add to your reading list . You will also need the LTspice software which is free on the web. These files should be used with knowledge that I am not expert in design or spice simulations I am a DIY like many of you and will respond to suggestions or questions about these offerings along those lines. If you are a professional and can improve these in any form I am sure the members of this forum will be delighted. One of the supplies has be built based on these simulations and is very close to the results. Also you should visit Keith's website at the url mention in a previous post.
Remember spice simulation alone will not kill you but in actual contruction you will be exposed to lethal voltages and situations and should not attempt any conrtruction or attempts to constuct supplies based on others schematic's or work unless you know and follow the safety guidelines offered by others on this forum. With that in mind proceed with caution .
chas1
http://www.genomerics.talktalk.net
Parts for construction of smps
The file set is for simulation only but you can get a idea of how it will work with with your requirements as far as parts I suggest you read this thread throughly paying attention to the safety tips as well as pitfalls of contruction. You will find many good ideas about the design of these type power supplies. Once you have the basic idea construct a simple buck regulator using a battery for Vin (12V) and see if you can come up with PWM that will give you 6volts @ 1amp stable output. you can use any of the topologies push-pull, two switch forward, halfbridge and etc. this way you will gain experience in winding transformers, inductors and selecting all your parts. You can scope the supply safely and it can be breadboarded if you keep the frequency about 20kHz to 50kHz. You will also learn how to apply compensation correctly. This should get you up to speed and enable you to construct a supply of your choosing. Don't rush..... this is all about DIY and I will help in any way I can. Sorry, but I don't design supplies except for my need and experimentation. I have posted one supply in this thread and with the improvements I made thru trail and error it works great with my amp. A source of parts is an old pc supply but please don't use it offline just be safe remove the parts and change them as necessary to construct the supply mentioned above.
chas1
The file set is for simulation only but you can get a idea of how it will work with with your requirements as far as parts I suggest you read this thread throughly paying attention to the safety tips as well as pitfalls of contruction. You will find many good ideas about the design of these type power supplies. Once you have the basic idea construct a simple buck regulator using a battery for Vin (12V) and see if you can come up with PWM that will give you 6volts @ 1amp stable output. you can use any of the topologies push-pull, two switch forward, halfbridge and etc. this way you will gain experience in winding transformers, inductors and selecting all your parts. You can scope the supply safely and it can be breadboarded if you keep the frequency about 20kHz to 50kHz. You will also learn how to apply compensation correctly. This should get you up to speed and enable you to construct a supply of your choosing. Don't rush..... this is all about DIY and I will help in any way I can. Sorry, but I don't design supplies except for my need and experimentation. I have posted one supply in this thread and with the improvements I made thru trail and error it works great with my amp. A source of parts is an old pc supply but please don't use it offline just be safe remove the parts and change them as necessary to construct the supply mentioned above.
chas1
This a bit off topic, but I was wondering if anyone knows of any design resources for smps pcb design. I have made a board design very similar to luka's but I do not know if it is suitable. (The schematic is the same as this one). Also, is this a 100kHz smps? I haven't been able to locate this in the thread.
PM650 said:
The field emitted is proportional to the area of the loop enclosed. Keep all conductors of high frequency short, and parallel to the conductor carrying the current in the opposite direction. The trace for the gate of your IGBT/MOSFET should be perpendicular to the trace for the Drain/Source/Collector/Emitter.
The secondary has more current, so it's more important to keep the area of the loop small. If you're using axial rectifiers in the secondary it can create a large loop if they are stood off with the maximum lead length. TO-220 devices are much better at reducing this.
clock frequency or Xfmr frequency
A question are we talking about clock frequency or transformer frequency this will decide the board layout, pay close attention to the tracks around the controller IC and make sure leads are kept as short as possible at the clock pin and bypass caps are close to IC part. In some cases you might have a copper pour under the IC as a ground plane. This is where most of the noise that will effect your design should be dealt with. Good analog as well as digital layout is necessary here. What helps are small components 1/8 watt resistors or small footprint if larger wattage is required. Proper bypassing is critical at hi frequencies and fast rising clocks and pulses can look ugly at circuit nodes if overlooked.
chas1
A question are we talking about clock frequency or transformer frequency this will decide the board layout, pay close attention to the tracks around the controller IC and make sure leads are kept as short as possible at the clock pin and bypass caps are close to IC part. In some cases you might have a copper pour under the IC as a ground plane. This is where most of the noise that will effect your design should be dealt with. Good analog as well as digital layout is necessary here. What helps are small components 1/8 watt resistors or small footprint if larger wattage is required. Proper bypassing is critical at hi frequencies and fast rising clocks and pulses can look ugly at circuit nodes if overlooked.
chas1
