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audioguru
Nobel Prize Winner
Canada
4218 Posts |
 Posted - Dec 02 2007 : 12:18:01 PM
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A Chinese 12V 1000W inverter is probably rated in Whats. It is probably 1000Watts for less than 30 seconds or 500Watts all day long.
A simple 500W to 1000W inverter can be made with a CD4047 ocillator driving two Mosfets into a center-tapped transformer. The output will be square-waves but many electronic items won't work from it. |
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furquan
New Member
2 Posts |
Posted - Dec 17 2007 : 11:35:27 AM
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please explain the working of 9 volt dc to 120 volt ac inverter
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audioguru
Nobel Prize Winner
Canada
4218 Posts |
Posted - Dec 17 2007 : 11:43:22 AM
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quote:
Originally posted by furquan
please explain the working of 9 volt dc to 120 volt ac inverter
A 50Hz or 60Hz oscillator drives power transistors or power Mosfets to obtain high current at 50Hz or 60Hz. They drive a stepup transformer.
The output of this very simple circuit is square waves which are different to the sine-waves in the mains. |
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tich
New Member
Lebanon
3 Posts |
Posted - Jan 11 2008 : 10:43:57 AM
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| guys if i put a sine wave oscillator in place of the cd4047 i should be able to get a 500W sine wave oscillator right???? |
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audioguru
Nobel Prize Winner
Canada
4218 Posts |
Posted - Jan 11 2008 : 4:11:10 PM
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quote:
Originally posted by tich
guys if i put a sine wave oscillator in place of the cd4047 i should be able to get a 500W sine wave oscillator right????
Nope.
You will get 500W of heat for a moment then the output transistors will melt.
You don't convert a linear power amplifier into an inverter. It wastes as much power as its output. The wasted power makes a lot of heat.
A sine-wave inverter switches its outputs on and off at a high frequency. Then when switched on there is no voltage across the power Mosfets but the current is high. No voltage then no waste as heat. They switch quickly and the voltage of the many steps of the sine-wave is made by controlling the duty-cycle of the switching waveform using pulse-width-modulation.
Class-D power amplifiers work the same way and are very powerful without a lot of wasted heat. |
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tich
New Member
Lebanon
3 Posts |
Posted - Jan 12 2008 : 07:33:22 AM
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| ummm but i can use the obtained circuit as a 500W amplifier right?? i know this is off-topic and all i want is just a small reply. thx |
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audioguru
Nobel Prize Winner
Canada
4218 Posts |
Posted - Jan 12 2008 : 12:58:33 PM
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| Very few 500W audio amplifiers have enough cooling so they can have a continuous output of 500W. If they barely clip audio at 500W then their average power with most music is 50W. A PWM amplifier is much more complicated than a PWM inverter circuit. You can't hear the distortion from an inverter. |
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tich
New Member
Lebanon
3 Posts |
Posted - Jan 13 2008 : 05:51:50 AM
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| ok thank you for your support :D |
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mira
Apprentice
57 Posts |
Posted - Jan 20 2008 : 10:48:57 AM
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hello all,
i don't know whether my question fits within this topic and it is about inverters so i will ask it anyway. thanks for your reply!
i am looking for a way of boosting 100 volts dc to 250 volts dc able to supply 1 amp current.
this case resembles to the 6 volts to 12 volts inverter which is another topic, i decided to post it here nevertheless, since high voltages are involved.
thanks for your advice! |
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audioguru
Nobel Prize Winner
Canada
4218 Posts |
Posted - Jan 20 2008 : 11:26:31 AM
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An oscillator can drive a pair of high voltage switching Mosfets. The Mosfets drive a custom-made 200V center-tapped to 250V transformer. The output of the transformer can be rectified and filtered into DC.
The 100VDC must supply about 2.8A (280W). |
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AliKhan
New Member
1 Posts |
Posted - Jan 20 2008 : 11:19:28 PM
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Now after reading (most of) this forum... I decided to create & run this schematic in multisim.
I used 1N3600 diodes, and the simulation works.
I get a 117Vac, at around 35 watts (of course, that part doesn't quite fill the hole). But it does work.
Has there been anybody here that has reversed the polarity of the caps, substituded the diodes, and gotten this thing to work?
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audioguru
Nobel Prize Winner
Canada
4218 Posts |
Posted - Jan 21 2008 : 12:01:48 AM
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Multisim doesn't know that the transistors experience avalanche breakdown of their emitter-base junctions when a capacitor tries to drive a base to about minus 23V. Its max allowed reverse voltage is only 7V and it acts like a high current zener diode at about minus 8V where a high current flows through the backwards capacitors with the current being forced by the other transistor. Even if the capacitors have their polarity corrected then the very high current pulses would blow them up.
The transistors need diodes added to stop the emitter-base junctions from avalanching.
Calculate the base current of the transistors. It is way too low for the transistors to conduct enough current to be an inverter. The output transistors need driver transistors. Then the output would be about 120W.
Modern high current Mosfets are used in inverters today.
This inverter is a very simple square-wave one. Many electronic products don't work with a square-wave because its peak voltage is too low. A modified sine-wave should be used. It has three voltage steps where the peak voltages are almost the same as a true sine-wave. |
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mira
Apprentice
57 Posts |
Posted - Jan 21 2008 : 07:31:37 AM
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thank you for your reply. your advice is very helpful.
i have another question:
i have one 24 volts battery, i have connected a 5.6 volts zener circuit and i measure 5.6 volts stable on the output of this circuit.
is it possible to connect the outputs of two such zeners circuits in series? in order to obtain 11.2 volts? |
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audioguru
Nobel Prize Winner
Canada
4218 Posts |
Posted - Jan 21 2008 : 12:55:56 PM
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Of course two 5.6V zener diodes can be connected in series to make an 11.2V reference voltage.
They will be better than an 11V zener diode because the 5.6V zener diode has a stable voltage when the temperature changes. An 11V zener diode's voltage increases when it gets hot and decreases when it gets cold. |
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mira
Apprentice
57 Posts |
Posted - Jan 21 2008 : 11:01:28 PM
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thanks again audioguru..
the custom made center tapped transformer you talked about, can it be done by winding twice 10 turns of 24 AWG wire on a toriod as the primary and 30 turns as a secondary?
thanks again |
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Topic |
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12/120V inverter again
