AVR-Chat

Try an MC34063A, UA3843A, or an LM3425A will all do what you want and do 
it very economically.  The first two come in an 8 pin DIP and the last 
one is a 16 pin DIP.  All are easy to use, which to use depends upon the 
application.


REB


James Wagner wrote:
> Shervin -
>
> Yes, you probably could, but the 555 only represents a small part of  
> what would go into a switch-mode power supply. Further, the 555 is  
> really designed to vary its  duty cycle or pulse width based on  
> external resistors and not voltages. This makes it harder to use for  
> this kind of application than one would really like. IF you REALLY  
> want to experiment and learn what the challenges are for making a  
> SMPS, then charge on. However, since you are posting on an AVR list, I  
> would assume that your goal is to power an AVR or peripheral circuits.  
> If that is the case, then you will be spending a LOT of time on  
> something that really is secondary to your end goal.
>
> I can understand, if you are in a part of the world where electronic  
> components are hard to get and you may only have access to 555s and  
> 741 op amps and such. There are some switcher "cores" that have been  
> around for a LONG time and are very low cost and widely available.   
> Unfortunately, I can't find any references to what I remember, but I  
> do know that they are out there. Unfortunately, if your problem is  
> finding modern components, you will also have problems getting  
> Schottky diodes and power inductors you really need for such a supply.
>
> Jim Wagner
>
> On Mar 21, 2008, at 9:03 AM, Dennis Clark wrote:
>
>   
>> Maybe I've lost the spirit of discovery, but I see no reason to  
>> design a
>> new power supply when there are dedicated switching controllers out
>> there for a song (low cost).
>>
>> Is there a reason you want to do this the hard way?
>>
>> DLC
>>
>>     
>>> hi friends
>>> have u ever worked at any switching circuits? i want
>>> to design a DC power supply.may i use 555 Ic's??
>>> is there any sites to help me.your ideas could help
>>> me.
>>> let me know if u have designed a switching power
>>> supply
>>>
>>> thank u
>>> have a nice spring holidays
>>>
>>> Shervin
>>>
>>>
>>> __________________________________________________________
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>>>       
>> -- 
>> Dennis Clark
>> TTT Enterprises
>>
>>
>>
>>     
>
>
>
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>
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