PSU: Switch Current Boost On/Off???

Discussion in 'The Projects Forum' started by Still Learning, Nov 7, 2010.

  1. Still Learning

    Thread Starter New Member

    Jul 19, 2010
    25
    0
    Made a PSU recently then figured out if I use a NPN TIP2955 Transistor, I could possibly boost the current towards 4 or 5 Amp instead of around 1.5A.

    1. Is the below schematic the correct way to wire this thing?

    2. Where marked, would there be a certain toggle switch capable of turning the boost on/off?

    3. What type of switch? I've been looking at DPDT or SPDT and cant figure out for the life of me where to send each poles output... I thought a DPDT with the second output to run nowhere, would work?

    4. Do I need to disconnect Base also and not just C + E?

    It's been a long day..!
     
    Last edited: Nov 7, 2010
  2. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    You don't know anything about electricity.
    1) A load draws only as much current as it needs so you don't need to switch the current boost circuit off. It provides more current only if the load needs more current. For example, with no load then the current boost circuit does nothing. If the load needs up to 1.5A then again the current boost circuit does nothing. If the load needs more current than 1.5A then the current boost circuit provides as much current that is needed until it smokes.
    2) Your switch shorts the input of the LM317 regulator to its output which makes the output voltage too high. Then the output current will also probably be too high.
     
  3. Still Learning

    Thread Starter New Member

    Jul 19, 2010
    25
    0
    I do understand the ideas of the draw of current, it was a late night idea of adding a switch so not to require the bypass all the time in an already operating PSU. Not required I know..!

    Thanks for being so blunt, but yes you are correct about the short circuit - thanks for the extra pair of eyes
     
Loading...