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12 V DC to a 220V AC Inverter AMplfier Design


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The designer thought if the cap can work for a 555 it should be good for this as well  :)

Yeah. A 555 has a 200mA output current. An ordinary Cmos logic IC has only about 15mA with a 12V supply. A big difference.

What do you think will happen to the two pairs of 2N3055 transistors that must share 50A when the inverter has a 500W load? Each transistor will conduct 25A.
Their absolute max current is 15A each and they saturate poorly over about 10A.
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dear all,

i think i used the corrected connection for the cd4047 and cd 4001....but i still cant get the require modified sine wave form through it ...is the polarity of the capacitors used affects the result? i hav connected the polarity correctly and use the same value of caps and resistors....my mosfet as source follower? my mosfet in the circuit purposes is just used to drain the current from the batterty through the transformer to ground
so that it will produces a positive voltage on the upper primary windings so do the lower part of the mosfet...if any misconnection pls let me know and any good recommendation for redesign the circuit and to make it works is highly appreciated.....thanks....
i reattach the diagram for u all to view....

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i think i used the corrected connection for the cd4047 and cd 4001

Yes they are fine.

i still cant get the require modified sine wave form through it.

I made your huge schematic smaller and showed where lines cross over and do not join.
Pin 7 of the CD4001 must be connected to ground.
Your CD4047 and CD4001 didn't have +12V.

is the polarity of the capacitors used affects the result?

The two capacitors are non-polarized metalized plastic (Oriental green caps).

my mosfet as source follower? my mosfet in the circuit purposes is just used to drain the current from the battery through the transformer to ground

Your Mosfets are connected properly. Maybe two do not work.
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Hi AN920. I looked at your square wave inverter again. It looks like at 50% duty cycle oscillator, both outputs produce 25% duty cycle. Reducing the duty cycle of the oscillator means that both outputs have even lower duty cycle, and the two waveforms are offset from each other.

Now I am just wondering why there are two mechanisms for lowering the duty cycle. Am I getting your design at all?

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If you read the description you will notice
a) One adjustment to set the output operating frequency for 50 or 60 Hz inverter
b) One adjustment to set the on-time of each device. On-time can't be more than 50% of total inverter cycle time because of push-pull operation. 

If you use the crystal option your output operating frequecy will be fixed at 50 or 60 Hz.

The waveforms I included shows
1. Drive for a normal fixed duty cycle square wave inverter
2. Typical drive for a modified fixed duty cycle square wave inverter
3. Example of small duty cycle available from circuit.

The advantage of having the adjustable duty cycle allows the use of transformers with non standard winding ratio's and a range of power supplies other than 12V. It also allows you to adjust the final output voltage.

Good reading http://powerelectronics.com/mag/608PET21.pdf

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hi au,

The two capacitors are non-polarized metalized plastic (Oriental green caps).

this is means the capacitors can be used is ceramic type?

i think without the resistors infront of the mosfet doesnt affect much if the circuit?

y the capacitor and resistor near the transformer is reduced?
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dear au,

then the 2 capacitors to be used is metalized plastic type? since there are no 0.22uF capacitors in the circuit.

A resistor is needed in series with the gate of a Mosfet to keep it from oscillating at a very high frequency. Usually 47 ohms is used

so 50Hz of frequency doesnt neccessary to put the resistor in front of the mosfet? since the osc frequency in this circuit is just 50Hz....

the capacitors and resistors used in the circuit is just a protection from the current of the transformer or just use for filtering purposes?
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then the 2 capacitors to be used is metalized plastic type? since there are no 0.22uF capacitors in the circuit.

The 220K is 220,000pF which is 220nF or 0.22uF.

so 50Hz of frequency doesnt neccessary to put the resistor in front of the mosfet? since the osc frequency in this circuit is just 50Hz.

No. A Mosfet oscillates at a very high frequency if it doesn't have a resistor in series with its gate. It will overheat if you allow it to oscillate at a very high frequency.

the capacitors and resistors used in the circuit is just a protection from the current of the transformer or just use for filtering purposes?

The value of the capacitor is too low and the value of the resistor is too high to make a filter. They reduce high voltage spikes a little.
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dear au,
i have use the same connection which the updated by you...but still no avail, but i tried the cd4047 output from both pin 11, and and 10 and the output is inverted...but when fed into the CD4001...the output seems to be havin a square wave....how could this possible ? i still cant figure it what is wrong with the circuit....mayb is the frequency prob? and i also have taken out the resistor since is not needed.....and can i use the ceramic capacitor which has value of 221k?
thanks for your reply

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dear Au,

if the voltage from the mosfet is lower than the primary winding of the transformer for example....the voltage from the mosfet is approximately 5V then the rating of the transformer is 8V....will it have enough power to power the transformer? or it depends on the rating of the mosfet?

can i put different grounding where the mosfets have different ground than ground together with the ic? becoz i afraid that the high current drain from the mosfet will affect the ic and burn it.... :-\ :-\
thanks for your precious opinion

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if the voltage from the mosfet is lower than the primary winding of the transformer for example....the voltage from the mosfet is approximately 5V then the rating of the transformer is 8V....will it have enough power to power the transformer? or it depends on the rating of the mosfet?

The Mosfet is just a switch. It doesn't have voltage, the transformer has the voltage and the Mosfet shorts it to ground when it turns on.

can i put different grounding where the mosfets have different ground than ground together with the ic? becoz i afraid that the high current drain from the mosfet will affect the ic and burn it.

The pcb traces should be planned so that the very high current through the ground path from the Mosfets doesn't affect the ICs.
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dear au,

do i still need to add on the series resistor to the mosfet? or shouldnt i?
thanks...if yes then i need to drill holes on my pcb board go lab to retry
thanks

As I said before, the gate of a Mosfet needs to have a resistor in series to stop it from oscillating at a very high frequency which wastes power and makes it get hot. 47 ohms or 100 ohms is fine.
Your schematic showed 1k resistors but 47 ohms or 100 ohms will make them switch quicker.
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dear au,

about the grounding...can i separate the grounding as showed in the schematic.... i mean the mosfets has its own grounding and the ic's has it own groundin....or both mosfet and ic need to hav same grounding...i means is connected to same  ground...just wan to confirm b4 i burns everything out... ;D ;D

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about the grounding...can i separate the grounding as showed in the schematic.... i mean the mosfets has its own grounding and the ic's has it own grounding.

Have heavy wires from the Mosfets to the battery connection, then separate wires from the pcb where the ICs are to the battery connection. Then the Mosfets have separate wires for their high current and the ICs also have separate wires for their low current.
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dear au,

yes i have separated the ic wires to the battery connection and the heavy wires from mosfet to the ground and the to battery....but the problem is the ic need to be connected to the mosfet which acts as a wave generator to switch on and off for the mosfet....then ground of the mosfet also separated from the ic ground but the drain of the mosfet are using pcb to heavy wires then to transformer... i will take attach the pic along for you to see.....and 1 more prob which could not be solved...whcih the the waveform....i still cant get the desired waveform from cd 4001 and cd 4047....
i tried the cd 4047 output pin osc, pin Q and pin Q' all is the same in the datasheet...bt when connected to the cd 4001 it will become a square wave....which each of the output from the cd 4001 will have a phase different only not inverted waveform....when add together it will superimpose but not generating modified sine wave..... :'( :'( :'( at 1st, can generated the desired current and voltage but after awhile it will burn the CD4047 ic ...need help thanks

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dear AU , yup i know...but the osc result doesnt have the required result....i tried many times....at last i will get the same square wave form....but this is ok... the main things is the ic burn many times....although i have use diff grounding and bigger size wire....can u recommend me a regulator which suit to the ic? i think this is the most efficient way....can i voltage regulator to regulate current? as i know regulator is to regulate voltage only

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Hi Kachew,
Which IC is burning?
What is the DC supply voltage?

If the supply is from a car then it has many voltage spikes. Connect a 16V 5% 1W zener diode and a 0.1uF ceramic disc capacitor across the supply pins of the ICs and feed the positive supply voltage through a series 47 ohms resistor to them. The positive supply voltage can be connected directly to the transformer's center-tap.
Connect 100 ohm resistors in series with the gate of each Mosfet.

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hi au,

the CD 4047 ic is burning at 1st it can be used for generating pulse but later when i turn off the power supply from the lab...it seems burn and i use OSC to check the waveform and there is only noise no longer have any square wave in it...the DC supply in is 12 volt but after i connected to the inverter circuit and transformer for amplification the reading on the power supply drop to 5V and the current goes high...

is this is the modification u meant?

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You disconnected the ICs from the positive power. You are supposed to connect a 47 ohm resistor from the positive power to the ICs in series, then connect a zener diode and capacitor across the ICs.

An inverter is supposed to be powered by a big car battery, not a lab power supply that doesn't have enough power.

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