Transformer-voltage regulator problem

Discussion in 'General Electronics Chat' started by hazim, Jun 24, 2009.

  1. hazim

    Thread Starter Active Member

    Jan 3, 2008
    419
    13
    A 220V to 12V x 2 / 0.6A is connected at its output with a rectifier. The required output voltage is +6V -6V and 0V. For this reason I used two voltage regulator, 7806 and 7906...
    For a 6V 0.5A small lamp load, the voltage regulator 7806/or 7906 becomes so hot... I put a heat sink and on the two voltage regulators but their temperature still comes very high...

    What should I do? If I used a transformer with output 9V x 2 / 1A affect positively?


    LM7806 is 1.5A
    LM7906 is 1A
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Part of the problem is that the filtered output from the rectifier is 1.4 times the nominal AC voltage, or almost 17 volts. That is 9 volts more than the regulator needs to supply its output, and shows up as heat.

    A transformer that had outputs of +/- 6 VAC (12 VAC center tapped) would be better.
     
  3. hazim

    Thread Starter Active Member

    Jan 3, 2008
    419
    13
    I first tried a +/-6 VAC 1A transformer but the output voltage dropped to less than 5V DC... I need a +/-6 V DC at 1.5A or 2A...
     
  4. hazim

    Thread Starter Active Member

    Jan 3, 2008
    419
    13
    Any help? I want to build a power supply with regulated output +/-6V DC at 1.5A..
     
  5. bertus

    Administrator

    Apr 5, 2008
    15,646
    2,345
    Hello,

    What size of capacitors do you use afther the rectifier?
    Take a look at the attached PDF on rectifying circuits.
    There is also a part to calculate the capacitor.

    Greetings,
    Bertus
     
  6. gerty

    AAC Fanatic!

    Aug 30, 2007
    1,153
    304
    How much current does the bulb require?
    Sounds like you are trying to draw more current than the transformer can provide
     
  7. hazim

    Thread Starter Active Member

    Jan 3, 2008
    419
    13
    There was bulbs used and dc motors and a solenoid which needs high current to activate...all of these and other parts doesn't work and stop at the same time... they are not related to each other..... anyway I solved the problem and used a 3A +/-9V transformer with 2200uF capacitors in the rectifier.... It worked fine
    Thank you guys
     
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