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LM3578 slow start up

Thomas Fernando
Prodigy 20 points
Other Parts Discussed in Thread: TPS61175

Hello,

I am using a LM3578  as a boost converter to get 12V (150mA) from a 6V battery (4x1.5V AA).

The problem I am facing is that during power on ,the battery voltage dips to about 1.5V and the output is about 2V.After about 5~10 seconds the output jumps to 12V and the battery voltage recovers to about 5.2V ( 5.6V NL voltage).Suppose I switch on again with some voltage (about 3V) left in the output capacitor it works immediately.

I am using the same circuit as the datasheet for the boost converter,except that the inductor is 470uH wound on a drum core and the switcher is LM3578.I am doing some further experiments,but can anyone suggest some usual suspects ?

Thomas

  • 0
    Prodigy 90 points
    Hello Thomas
    I also meet the same problem when I use TPS61175 as a boost converter to get 24V(8200mA) from 12V(3A). During power on, the 12V power output is about 3A ,after 3~5 seconds the output jump to 24v and the 12V power recovers to 12V about 2A.
    Have you solve the problem ?
  • 0 in reply to carry
    Prodigy 20 points

    Hello Carry

    I could not solve the problem exactly,but I was able to workaround it.I used a 9V battery instead of the 4x1.5.This worked without any glitches,since the startup current is now lower due to the higher input voltage.

    During power on, the 12V power output is about 3A ,

    What is the input voltage dipping to?

    If you are allowed to,is it possible for you to series 3x6V = 18V?This could solve your problem and also give you more storage capacity (just an idea).

    Thomas

  • 0 in reply to Thomas Fernando
    Prodigy 90 points
    Hello Thomas

    Thank you for your advise.But the input voltage is 12V fixed.

    During power on, the input voltage dips to 5V and the output is about 2.8A.

    When using WENBENCH to simulation, I find a peak in input current during power on.

    I sorry that i can't find ways to insert picture. if you interested in simulation of it,you can tell me you E-mail.

    CARRY