# Transformer-voltage regulator problem

#### hazim

Joined Jan 3, 2008
419
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

#### beenthere

Joined Apr 20, 2004
15,808
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.

#### hazim

Joined Jan 3, 2008
419
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...

#### hazim

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

#### bertus

Joined Apr 5, 2008
19,947
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

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#### gerty

Joined Aug 30, 2007
1,250
How much current does the bulb require?
Sounds like you are trying to draw more current than the transformer can provide