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Suresh R
02/14/06 02:20
Read: 580 times

#109924 - followups
Responding to: Kai Klaas's previous message
Kai Klaas said:

Between output pin and adjust pin of LM338 internal circuitry of regulator produces a very stable reference voltage of 1.24V. This voltage drops across R7, so that a current of about 10mA is flowing.

Let the o/p of regulator be for instance 10 V. since this is been fedback to the Adj Terminal through the 120E resistor , will this feedback, don't experience any effect due to R7?

Kai Klaas said:

At turn-on this current flows via emitter collector path of Q4 to ground. The base current, which is needed to allow this current to flow charges up C9. This current is much greater than the current that flows through R8 driven by the Ube of Q4. R8 is needed to fully charge C9, when Ube of Q4 becomes smaller than 0.7V

So how does this lead to a soft start when the device is turned 'ON'.
Is it that the 10mA current is being avoided when the device is turned 'ON'. why is it that C9 should be fully charged with the help of R8 when Vbe of Q4 becomes smaller than .7V.
Kindly explain.

Kai Klaas said:

R12 can be reduced a bit, but not too much. Otherwise regulation performance will suffer.

during plating operation i measured the following.
current set using R17 = 1A
voltage drop accross load = 1.5V
for this condition,
i would like to know what would be the voltage drop accross the resistor R12 which would be appearing in the inverting i/p of U2A. (or) in short, how could i know this is the voltage dropping in R12. how should i calculate it.
Also kindly tell me how to calculate the power dissipated in MJE 3055( Q3 ).

Suresh said:
Is the buck regulator proving main cause of power dissipation?
I would like to know how, more power is being dissipated in the regulators and mje3055 referring to my circuit.

Kai Klaas said:

Don't know what you mean. What do you mean by 'buck regulator' by the way?

i meant the LM 338 i have used as a Buck Regulator. Due to its requirement for high i/p to produce a stable o/p. i have learned that these step down regulators could dissipate power in it for the difference in voltage between its i/p and o/p.

Thanking all,

List of 21 messages in thread
3A constant current source      Suresh R      02/11/06 04:41      
   Where did you find it?      Andy Neil      02/11/06 05:56      
   Ripple      Andy Neil      02/11/06 06:00      
      plating purpose      Suresh R      02/11/06 09:45      
         I got it from a person known to me      Andy Neil      02/11/06 15:04      
            replies      Suresh R      02/12/06 09:24      
               plating circuit      Terry Lingle      02/12/06 11:40      
                  Compliance of source      Steve M. Taylor      02/12/06 13:51      
                     yes      Terry Lingle      02/12/06 16:21      
         Think about that      Neil Kurzman      02/11/06 16:08      
   Component Purposes      Bruce Bailey      02/11/06 12:58      
   This circuit will never work!      Kai Klaas      02/11/06 19:46      
      Could it be?      Neil Kurzman      02/11/06 23:55      
         Function      Kai Klaas      02/12/06 20:08      
            issues      Suresh R      02/13/06 02:42      
                plating quality control.      Terry Lingle      02/13/06 07:29      
               Answers      Kai Klaas      02/13/06 11:36      
                  followups      Suresh R      02/14/06 02:20      
                     Answers II      Kai Klaas      02/14/06 07:01      
                        followups & Back EMF's?      Suresh R      02/15/06 03:59      
                           Floating regulator      Kai Klaas      02/15/06 09:27      

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