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failed (?) brownout experiment

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dlj04(at)josephson.com
Guest

Posted: Thu Sep 26, 2013 10:00 am Post subject: failed (?) brownout experiment

The ebay board looks like it uses an LM2577 regulator. I've built a few 

things with this part and it's sometimes tricky to tame. The 

characteristics of the inductor, diode and compensation capacitor are 

critical, see the TI datasheet. At low currents it will work fine with 

wide variations in components, but once you draw significant current 

even for a short time the circuit can misbehave.



--

David Josephson

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rnewman(at)tcwtech.com
Guest

Posted: Thu Sep 26, 2013 12:02 pm Post subject: failed (?) brownout experiment

I realize that many of those on this list are interested in the educational experience of solving some of these interesting problems we run into with our electrically oriented aircraft.    I totally respect that.   However, I did want to address the issue of brown out protection for some of the critical devices such as efis and engine monitors.   We do sell a line of products specifically for this purpose.   They are purpose built dc:dc converters that take as little as 4 volts in and boost it to a steady 12 volts.  Thereby providing stabilized power to the connected loads.   The product line is known as IPS,   Intelligent Power Stabilizer and is available in 14 and 24 volt models at various output current levels.   Also some of the banter going on regarding the operation at very low voltages  is very much true, recognizing that we came up with a creative solution for which we received a US patent that is implemented I'm these products.    So our IPS units do operate smoothly and properly to 4 volts and below.     All the details are on   

www.Tcwtech.Com 



Thanks 

Bob Newman 

RV-10.  N541RV 



Sent from my iPhone



On Sep 26, 2013, at 1:59 PM, D L Josephson <dlj04(at)josephson.com> wrote:



 	  Quote: 	
		   

 

 The ebay board looks like it uses an LM2577 regulator. I've built a few things with this part and it's sometimes tricky to tame. The characteristics of the inductor, diode and compensation capacitor are critical, see the TI datasheet. At low currents it will work fine with wide variations in components, but once you draw significant current even for a short time the circuit can misbehave.

 

 --

 David Josephson

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edpav8r(at)yahoo.com
Guest

Posted: Thu Sep 26, 2013 8:48 pm Post subject: failed (?) brownout experiment

I'm not so sure...



The description and photos of the board Joe bought show a buck/boost unit, but the LM2577 is a boost/flyback IC.  With the part number obliterated in the eBay photos, we can't really know for sure.  That was probably done because the IC is a black market knockoff, which I believe is common on these kinds of inexpensive boards from China.  How else do they deliver them halfway around the world for the price of the IC alone?



A quick search on Digi-Key revealed a number of adjustable buck/boost ICs from Linear Technologies and ON Semiconductor in the DDPAK/TO-263 package, but none with a 180kHz switching frequency.  Hmmm....



Besides the difficulty David mentioned below (in selecting just the right components to support a switching regulator), there's also their sensitivity to board layout.  If that isn't done right, even the perfect components can't help.



Eric

On Sep 26, 2013, at 10:59 AM, D L Josephson <dlj04(at)josephson.com> wrote:

 	  Quote: 	
		   The ebay board looks like it uses an LM2577 regulator. I've built a few things with this part and it's sometimes tricky to tame. The characteristics of the inductor, diode and compensation capacitor are critical, see the TI datasheet. At low currents it will work fine with wide variations in components, but once you draw significant current even for a short time the circuit can misbehave.

 

 --

 David Josephson

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nuckolls.bob(at)aeroelect
Guest

Posted: Fri Sep 27, 2013 5:17 am Post subject: failed (?) brownout experiment

At 11:47 PM 9/26/2013, you wrote:

 	  Quote: 	
		  



I'm not so sure...



The description and photos of the board Joe bought show a buck/boost 

unit, but the LM2577 is a boost/flyback IC.  With the part number 

obliterated in the eBay photos, we can't really know for sure.  That 

was probably done because the IC is a black market knockoff, which I 

believe is common on these kinds of inexpensive boards from 

China.  How else do they deliver them halfway around the world for 

the price of the IC alone?


	


    The power requirements are simply too

    great for any of the LM2577 class devices

    irrespective of their pedigree.



    I would have tride a converter more along

    these lines . . .



http://tinyurl.com/n7rsteo



    Given the very short and widely spaced

    loading in this application, the heat sink

    would not be necessary . . . but the ability

    to grunt a 50W+ load is critical to preventing

    it from falling out of bed.



   Bob . . .

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