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Having huge voltage drop from 555 timer circuit

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alianaslan

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First of all, hi everyone! I'm new in this community and this is going to be my first design as an Electrical Engineer.

I'm getting perfect 12VAC signal with 1khz from this circuit. But when I try regulating this 12VAC to 6VDC 1Amps, I'm having huge voltage drops and regulator doesnt work. I think transistors current limits are not enough. Would like to hear your thoughts about it.

asd.jpg
 

Hi,

I assume the output signal (unloaded) is a square wave with about +9V / -10V.
For sure it is not abke to prvide +/-1A.

I don't see how you think you "regulate it to 6V DC". Please explain this.
What do you mean with "regulator doesn't work"? Which regulator?

What is the global function of the complete curcuit?

Klaus
 

This circuit is simulating a signal which EV cars generate. What I need is to turn this signal into 6VDC and current up to 1A or 500mA. So I used LM317 after AC DC conversion with following basic regulator circuit. 2.jpg
 

Hi,

BC547 and BC557 have a max. collector current of 200mA. Regulator: I think you need about ~2.6V dropout at 1A. What package 317 are you using? 1A at 6V would mean 6W... hope there's a heatsink and fan included in the design. As per datasheet formula: PD(MAX) = ((TJ(MAX) - TA)/θJA). let's say, for an example, TO-220, PD(MAX) = ((125ºC - 25ºC) / 50ºC) = 2W.

Besides those transistors being small signal transistors which are clearly not appropriate (medium power BJTs are needed), the regulator is possibly going into thermal shutdown, and if it works at all it may be sacrificing regulation to maintain the current, read about how voltage regulators work.
 

R9 is 330 ohms, correct?

Can you calculate the voltage drop across 330 ohms caused by 1 amp current?

Even if you completely remove that resistor, do you understand what voltage drop the 10K pullup resistor R8 will have, even after dividing the 1 amp output current by Q3's hfe?
 

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