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 12/120V inverter again
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JUAN DELA CRUZ
Mad Scientist

Philippines
476 Posts

Posted - Sep 19 2011 :  11:27:19 PM  Show Profile  Reply with Quote
quote:
Originally posted by audioguru

quote:
Originally posted by JUAN DELA CRUZ
Regarding with your idea of using complementary emitter-follower BJTs.. I was wondering if 2N2222 & 2N2907 with a 100-ohms pull-ups will drive Power MOSFETSs very well?

If you use the SG3525A IC then it already has the high current output transistors and it doesn't need pullup resistors. Also the 555 is not needed.




So, the output of the SG3525A can drive the base "directly" (w/out series resistor?) of the complementary emitter-follower BJTs.. then drive the gates of the Power Mosfets with a 10-ohms series resistor each??

juan dela cruz
Penniless INVENTOR
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audioguru
Nobel Prize Winner

Canada
4214 Posts

Posted - Sep 20 2011 :  09:44:31 AM  Show Profile  Reply with Quote
I said that the SG3525A already has the high current output transistors. Then you don't need the complementary transistors.
Yes, use a 10 ohm resistor in series with each Mosfet gate mounted very close to the gate pin.
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JUAN DELA CRUZ
Mad Scientist

Philippines
476 Posts

Posted - Sep 26 2011 :  12:15:55 PM  Show Profile  Reply with Quote
quote:
Originally posted by audioguru

I said that the SG3525A already has the high current output transistors. Then you don't need the complementary transistors.
Yes, use a 10 ohm resistor in series with each Mosfet gate mounted very close to the gate pin.


Thanks audioguru..
I have read some articles regarding power mosfet driver.
And I'd found out that a "fast swithing diode" is needed in the gate of the power mosfet parallel to the gate resistor 10 ohms.

Do you think 1N4148 schottky diode will do?
... and how about its polarity? the anode to the gate of the power mosfet?

juan dela cruz
Penniless INVENTOR

Edited by - JUAN DELA CRUZ on Sep 26 2011 12:17:00 PM
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audioguru
Nobel Prize Winner

Canada
4214 Posts

Posted - Sep 26 2011 :  6:59:19 PM  Show Profile  Reply with Quote
I have never seen a Mosfet driven with a diode parallel with the 10 ohms resistor at its gate.
A diode will not do anything since the 10 ohms will quickly charge the gate capacitance for a fast turn on and the 10 ohms will also quickly discharge the gate capacitance for a fast turn off.

A 1N4148 is an ordinary fairly fast low current silicon signal diode. Its forward voltage is about 0.7V.
A Schottky diode is very fast and has a forward voltage of about 0.3V.
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JUAN DELA CRUZ
Mad Scientist

Philippines
476 Posts

Posted - Sep 27 2011 :  03:23:30 AM  Show Profile  Reply with Quote
quote:
Originally posted by audioguru

I have never seen a Mosfet driven with a diode parallel with the 10 ohms resistor at its gate.
A diode will not do anything since the 10 ohms will quickly charge the gate capacitance for a fast turn on and the 10 ohms will also quickly discharge the gate capacitance for a fast turn off.

A 1N4148 is an ordinary fairly fast low current silicon signal diode. Its forward voltage is about 0.7V.
A Schottky diode is very fast and has a forward voltage of about 0.3V.




Ok, thanks.

How about the "snubber ckt needed" in the primary winding of the transformer to filter out the spikes that might damage the IC?

What will be the value of the resistor and capacitor needed if the power inverter is operating with the frequency of 60Hz?

juan dela cruz
Penniless INVENTOR
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audioguru
Nobel Prize Winner

Canada
4214 Posts

Posted - Sep 27 2011 :  09:01:14 AM  Show Profile  Reply with Quote
We don't know if your transformer will produce voltage spikes. If it does then you must test different snubber parts to reduce the spikes since your transformer has no detailed spec's when it is driven with a square-wave.
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JUAN DELA CRUZ
Mad Scientist

Philippines
476 Posts

Posted - Sep 27 2011 :  1:34:03 PM  Show Profile  Reply with Quote
quote:
Originally posted by audioguru

We don't know if your transformer will produce voltage spikes. If it does then you must test different snubber parts to reduce the spikes since your transformer has no detailed spec's when it is driven with a square-wave.



Ok, so the snubber ckt isnt that essential for the PWM IC protection?

Do you think I need to use discrete Zener diode (15V) to power the SG3525A IC instead of using 7809 regulator?

juan dela cruz
Penniless INVENTOR
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JUAN DELA CRUZ
Mad Scientist

Philippines
476 Posts

Posted - Sep 27 2011 :  1:40:46 PM  Show Profile  Reply with Quote
In Addition above....

I will be using a 12V from a deep cycle battery.

juan dela cruz
Penniless INVENTOR
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Bearded Blunder
New Member

2 Posts

Posted - Oct 20 2011 :  11:51:14 PM  Show Profile  Reply with Quote
Just for once somone who doesn't want to replace Sizewell B with Arron's circuit and a huge bank of batteries...

At the start of this long long thread I thought I was on to something. What I'm actually after is a simple ideally efficient low power inverter circuit.

The idea is to power a maximum of 30W high power mains voltage LED lighting in an off grid situation, probably solar powered hence "ideally efficient", not wanting to buy an extra half acre of solar panel to offset losses. I think even a "fixed" version of the original circuit is hence ruled out in favour of something with a MOSFET output stage before the transformer.

The expedient & boring bodge would be to uncase one of the many commercial car accessory socket inverters rated around 100W, however most if not all of these use active cooling, and fans won't work too well once the inverter is housed inside a sealed IP65 luminaire along with the lamp.

Given the size of the load the transformer wouldn't appear to be a problem, being relatively light duty, there are numerous suitable off the shelf.

So does anyone have a schematic they could post that would fit my needs?
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pebe
Nobel Prize Winner

United Kingdom
1078 Posts

Posted - Oct 21 2011 :  02:09:40 AM  Show Profile  Reply with Quote
As LEDs are inherently low voltage devices, is there any way you could disassemble the lighting unit and supply the LEDs from low voltage DC?
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Bearded Blunder
New Member

2 Posts

Posted - Oct 21 2011 :  08:50:19 AM  Show Profile  Reply with Quote
It would be a royal PITA to disassemble, modify, and reassemble, a 5 or 6 foot fluorescent tube replacement, plus lots of time cutting pcb tracks & adding series resistors to small groups, it *may be* possible perhaps, but far from easy.
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Kultus
New Member

Australia
1 Posts

Posted - Nov 05 2011 :  12:28:31 AM  Show Profile  Reply with Quote
I have this Circuit up and running with a rewound MOT as my transformer, I live in Australia and we have 240volt AC mains power, I need to know how to modify this to suit 240volts, I have tried to adjust resistors and to wind more and less winds onto the MOT with no luck.. can anyone help me with this ?

Thanks all for any help given

________________________________________________________
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Never give up, it only takes one crazy Idea to go right, and your not so crazy any more - Kultus 2011

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NCC74656
New Member

1 Posts

Posted - Nov 07 2011 :  10:18:47 PM  Show Profile  Send NCC74656 a Yahoo! Message  Reply with Quote
Hello, im not sure if this is still active but I would like some input on what parts to use for an inverter i need. I need to build a 12V to 110V at 45A. This is going to be used to power a 40A air compressor, i added 5A as padding but please tell me if i need more. My trucks alternator puts out 175A or 100A at idle and i have a 1800CA battery. I have done my share of soldering and such but never any DIY projects like this. I am looking for input on things that may go wrong and on what size caps/resistors to use to get this amperage. thanks.
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audioguru
Nobel Prize Winner

Canada
4214 Posts

Posted - Nov 08 2011 :  07:57:54 AM  Show Profile  Reply with Quote
quote:
Originally posted by NCC74656
I need to build a 12V to 110V at 45A. This is going to be used to power a 40A air compressor, i added 5A as padding but please tell me if i need more. My trucks alternator puts out 175A or 100A at idle and i have a 1800CA battery.

You forgot to calculate how much current the inverter will draw.
110V at 45A is 4950W. The inverter will heat with about 1000W so the total power required is 5950W.
The 12V current is 496A. The current in hundreds of transistors and the transformer is also 496A. You might need use train tracks for the 12V wires.

Instead of an inverter you should use a 110V generator powered by a gasoline engine.
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interland
New Member

Lebanon
1 Posts

Posted - Nov 14 2011 :  06:04:31 AM  Show Profile  Click to see interland's MSN Messenger address  Reply with Quote
Somebody can tel me how to decide the cycle at tr output for this design ,50Hz,or 60 Hz
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