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Meeting a trouble in my pure sine wave inverter.

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XiDianDongDong

New Member
Recently ,I design a 500w pure sine wave inverter, but there is a problem that unnormal wave of this PCB bord disturb me .Please experts give me some advice. Thank you very much .



I want to ask why After installing the transformer, the SG3525 produce unnormal PWM waveform. :)
Mod edit... To upload images there is an "Upload a file" button bottom right of the posting box..

You can upload jpg's without problems...
 
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cowboybob

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Most Helpful Member
Welcome to ETO, XiDianDongDong!

Please retry uploading your pictures (perhaps in *.jpg or *.bmp format.

The site you sent us to is very difficult to navigate for someone not familiar with Chinese characters (like me :woot:). And the schematics are truncated and incomplete.
 

cowboybob

Well-Known Member
Most Helpful Member
Thanks Ian.

As much as I consider myself "current" in most things tech, I must concede that I am falling behind.

(which is a somewhat more acceptable way of saying that I'm losing my mind...:woot: :banghead: )

PS - gotta love the translation :)
 
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chemelec

Well-Known Member
I Believe the SG3525 Produces Square Waves, Not Sine waves.
Other than adding a Coil and Cap on the output, you won't get Sine Wave out.
And it will only be Somewhat Sine, Not PURE Sine.
 

audioguru

Well-Known Member
Most Helpful Member
The SG3525 is supposed to generate high frequency PWM pulses. The PWM is modulated by a low frequency sinewave. The LC filters at the outputs smooth the PWM pulses so the output is a low frequency sinewave.
 

XiDianDongDong

New Member
Thanks for you help! I think it is necessary in detailed describe the problem again.
This pure sine inverter consists of two parts, the first level is the push-pull booster circuit, after level is a Single phase full bridge inverter circuit.
Now,I'm debugging the first level ,the function of this part is will boost the voltage from 12v to 260v ,but meeting a problem .
The after level needs SPWM driving signal to driver MOSFETs of Single phase full bridge and produces SPWM waveform ,Then through LC filter will get pure sine wareform.
1.Using the SG3525 generates PWM signal to driver push-pull circuit:
the circuit of SG3525 :
3525.jpg
the circuit of push-pull
push-pull.jpg
2.before installing transformer,the PWM waves of SG3525 produced:
3.jpg
3.then after installing transformer ,I don't konw why the PWM waves became unnormal. The Duty of PWM waveform is too small.
4.jpg
I hope to get your advice ,Thank you!
 
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XiDianDongDong

New Member
Welcome to ETO, XiDianDongDong!

Please retry uploading your pictures (perhaps in *.jpg or *.bmp format.

The site you sent us to is very difficult to navigate for someone not familiar with Chinese characters (like me :woot:). And the schematics are truncated and incomplete.
thanks for you advice. I post the problem again.
 

XiDianDongDong

New Member
I Believe the SG3525 Produces Square Waves, Not Sine waves.
Other than adding a Coil and Cap on the output, you won't get Sine Wave out.
And it will only be Somewhat Sine, Not PURE Sine.
Thanks for you answer .The SG 3525 only produce PWM waves,and I want to get sine wave form a singel full-bridge .I post my problem again .
 

XiDianDongDong

New Member
The SG3525 is supposed to generate high frequency PWM pulses. The PWM is modulated by a low frequency sinewave. The LC filters at the outputs smooth the PWM pulses so the output is a low frequency sinewave.
Thanks for you advice . now I post my the detailed question again. Please look again,Thanks.
 

alec_t

Well-Known Member
Most Helpful Member
Just a guess. Perhaps the IC is trying to drive too much current through the FET gates and is shutting down internally? Do you have any current-limiting resistors on the FET gates?
Do you have a connection to external shut-down pin 10 of the SG3525?
 
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mbarazeen

Member
check the second stage MOSFET brifge for any overlapping / instantaniuos short. It may overload the booster and shutdown. make sure you have suffecient dead time between 2nd stage gate pulses.
 

audioguru

Well-Known Member
Most Helpful Member
It looks like the narrow width of the output pulses is the difference of the widths of the alternating pulses.
 

moffy

Member
What does the output look like at the output of the TX and diodes? With the transformer you have closed the feedback loop for the first time through the opto coupler.
 

MrAl

Well-Known Member
Most Helpful Member
Hello,

Who designed the transformer for this thing, or was it purchased ?
 
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