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Battery DC converter
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Old 28th November 2017, 05:58 PM   #21
mchambin is offline mchambin  France
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Quote:
Originally Posted by miro1360 View Post
first try more diodes in parallel, if datasheet is right, than low current leads to lower temperature and lower voltage drop ... more diodes parallel == less current through one diode
Not a chance it would significantly lower the voltage drop.
Firstly, they will not share current equally.
Secondly, assuming equal share, the drop will be very little because of the V versus I of diodes.
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Old 28th November 2017, 06:39 PM   #22
miro1360 is offline miro1360  Europe
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Quote:
Originally Posted by mchambin View Post
Not a chance it would significantly lower the voltage drop.
Firstly, they will not share current equally.
Secondly, assuming equal share, the drop will be very little because of the V versus I of diodes.
I am also not sure, in simulation diode which I suggested have this behavior:

https://ctrlv.cz/shots/2017/11/28/suw8.png (load 430mA)

as you can see, more parallel theoreticaly leads to decreasing current through one diode and voltage drop is less in result, but yes, reality can be different ... still not 0.2V but is closer

Last edited by miro1360; 28th November 2017 at 06:41 PM.
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Old 28th November 2017, 06:57 PM   #23
mchambin is offline mchambin  France
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Of course it theoretically decreases the voltage drop.
The point is: You can parall tons of diodes the decrease will not be significant.
See it this way: Ten diodes in // is the same as a single diode that has a junction 10 times larger.
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Old 28th November 2017, 07:44 PM   #24
miro1360 is offline miro1360  Europe
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or even better this one:
VS-STPS20L15D-N3 Vishay
https://ctrlv.cz/shots/2017/11/28/tFqx.png
or this
yes, try some for higher current, more parallel decrease also temperature and voltage should be better ...
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Old 28th November 2017, 08:13 PM   #25
Fob69 is offline Fob69  France
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This one : VS-10BQ015HM3-5BT was given to be -0,21V at 1A and i have -0,3V at 450 ma ... I will try tomorrow with 3 or 4 in parrallel

B.
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Old 28th November 2017, 08:26 PM   #26
mchambin is offline mchambin  France
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Ok, now I see.
From the datasheet:
At 1A 125C ....Vf is 0.21V
At 1 25C....Vf is 0.33V

So this 0.2V is misleading.
You have 0.33V, if this is true, it is a good performance for a Shotsky diode.

Look at power Germanium diodes. You should find true below 0.3V.
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Old 28th November 2017, 08:34 PM   #27
Fob69 is offline Fob69  France
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Yes i have.
Gonna buy a used grill on ebay
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Old 29th November 2017, 06:23 AM   #28
mchambin is offline mchambin  France
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For some odd raison I missed why you need diodes.
There might be a solution using ultra caps.
They are capacitors with so huge capacities, they can be used as batteries.
They have less capacity than batteries, but can be quick charged much faster.
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Old 29th November 2017, 06:32 AM   #29
Fob69 is offline Fob69  France
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Quote:
Originally Posted by mchambin View Post
For some odd raison I missed why you need diodes.
There might be a solution using ultra caps.
They are capacitors with so huge capacities, they can be used as batteries.
They have less capacity than batteries, but can be quick charged much faster.
I need diods to adjut lifepo4 output batteries voltage without to loose the vey low impedance.
I use batteries because i want ultra low noise supply and AC isolation for devices upstream my DAC (downsream Delock MFC and Olimex lime player). Lifepo4 batteries is IME from far the best result in SQ.
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Old 29th November 2017, 07:32 AM   #30
mchambin is offline mchambin  France
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You can use LM337 for a ultra low noise supply.
There is no need for huge caps or sophisticated add ons.
Cascading two LM337 will give zero ripple.
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