LNK306 output question

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liel

Joined Jan 19, 2017
2
hey all
i am using LNK306. the datasheet reads its current output could reach 360mA as the top.
i was wondering that:
12V and 120mA were given in my circuit picture which i will upload, how could i increase the output to 5V 300mA ? I am familiar with the voltage adjustment, just wanted to know that if i down the voltage from 12V to 5V, will the output current increase? or should i make some change of any other part to increase the current? (Hope i have made my point clear)
more than thankful.
 

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hp1729

Joined Nov 23, 2015
2,304
hey all
i am using LNK306. the datasheet reads its current output could reach 360mA as the top.
i was wondering that:
12V and 120mA were given in my circuit picture which i will upload, how could i increase the output to 5V 300mA ? I am familiar with the voltage adjustment, just wanted to know that if i down the voltage from 12V to 5V, will the output current increase? or should i make some change of any other part to increase the current? (Hope i have made my point clear)
more than thankful.
I'm no engineer but it looks to me like if you change that 13K resistor to about 4,300 or 4,700 it should bring the output voltage down to about 5 V. How much current depends on which LNK30x chip you have.
With the 13K (and the 2K) it puts the feedback pin to about 1.6 V. So if you bring that 13K down to 4,500 it should set the output to 5 V. But then I'm no engineer.
 

DickCappels

Joined Aug 21, 2008
6,098
Yes, it works like that. Most likely when going to a lower output voltage efficiency will drop a little.

To what use do you plan to put this?
 

eetech00

Joined Jun 8, 2013
1,787
Hi

R2 = 2000, 1%, 0.25w
Vfb = 1.65
Ifb = 49uA
Vout = 5.00
Imin = 0.003A (min load current, use 0.005A for margin)

R1=(Vout-Vfb)/((Vfb/R2)+Ifb) = 3833
Rpl = Vout/Imin = 1000
Rplwatts = Vout*Imin = 0.02500
R1 = Choose 3.83k, 1%, 0.25w
Rpl = Choose 1k, 1%, 0.25w
L1 = 470uH, Rdc=2.0 ohm max, 450ma min
D1 = BYV26C
So...In your schematic, replace R1 with 3.83k, R4 with 1k, L1 with 470uH, D1 with BYV26C

LNK306 should work ok...
 

DickCappels

Joined Aug 21, 2008
6,098
Sorry but this fallsl under the heading of Transformerless Power Supplies, discussion of which are prohibited under the User Agreement. To wit:
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