Inverter Circuit 12V DC to 230VAC Sine Wave
- Thread starter harrychoo
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Hi there everyone 
I have constructed the H-bridge circuits which is control by PWM, the frequency of PWM is about 4900Hz.
Therefore, a single phase PWM sinewave at 220Vrms is generated.
Then, my questions are how can i filter this 220Vrms PWM sinewave into a perfect sinewave?
Should I choose LC or RC low pass filter?
which type of high frequency with high voltage that should i choose for inductor and capacitor component in order to set the cutoff frequency at 50Hz? ???
I have constructed the H-bridge circuits which is control by PWM, the frequency of PWM is about 4900Hz.
Therefore, a single phase PWM sinewave at 220Vrms is generated.
Then, my questions are how can i filter this 220Vrms PWM sinewave into a perfect sinewave?
Should I choose LC or RC low pass filter?
which type of high frequency with high voltage that should i choose for inductor and capacitor component in order to set the cutoff frequency at 50Hz? ???
audioguru2
- Apr 6, 2004
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Hi Grateful,
4.9kHz is very low for PWM. Your transformer will whistle loudly. Usually a frequency higher than 20kHz is used so it is not audible.
An RC filter will waste a lot of power. Use an LC filter like class-D audio amplifiers use.
The cutoff frequency of a circuit is the frequency where the output is -3dB which is half-power. Use a higher cutoff frequency for less loss.
4.9kHz is very low for PWM. Your transformer will whistle loudly. Usually a frequency higher than 20kHz is used so it is not audible.
An RC filter will waste a lot of power. Use an LC filter like class-D audio amplifiers use.
The cutoff frequency of a circuit is the frequency where the output is -3dB which is half-power. Use a higher cutoff frequency for less loss.
Thanks audioguru
Now i have increase the PWM frequency to 19kHz. But my inverter design at the output there is a bit different.
I use ADC to convert a single phase sinewave with peak amplitude of 5V to PWM signals.
Then, the PWM is used to switch or chop the 220Vdc.
The output that i obtain now is a PWM with amplitude of 220Vdc for positive half cycle and the negative half cycle (in accordance with the ADC signal).
Then, my question is how to design the low pass filter circuit (using RC circuit which is easier to control than LC) which able to smoothen this high voltage PWM signals switching at 19kHz?
So, how can i design a RC low pass fiter that able to withstand high power(100W) and high frequency. Then, finally output a perfect 220Vac at 50Hz? ???
Now i have increase the PWM frequency to 19kHz. But my inverter design at the output there is a bit different.
I use ADC to convert a single phase sinewave with peak amplitude of 5V to PWM signals.
Then, the PWM is used to switch or chop the 220Vdc.
The output that i obtain now is a PWM with amplitude of 220Vdc for positive half cycle and the negative half cycle (in accordance with the ADC signal).
Then, my question is how to design the low pass filter circuit (using RC circuit which is easier to control than LC) which able to smoothen this high voltage PWM signals switching at 19kHz?
So, how can i design a RC low pass fiter that able to withstand high power(100W) and high frequency. Then, finally output a perfect 220Vac at 50Hz? ???
audioguru2
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Hi Grateful,
The 220VAC sine-wave should be 622Vp-p, not 440Vp-p.
An RC filter wastes a lot of power and needs a huge capacitor, an LC filter doesn't.
An RC filter filters at only 20dB per decade of frequency, an LC filter filters at 40dB per decade of frequency.
The 220VAC sine-wave should be 622Vp-p, not 440Vp-p.
An RC filter wastes a lot of power and needs a huge capacitor, an LC filter doesn't.
An RC filter filters at only 20dB per decade of frequency, an LC filter filters at 40dB per decade of frequency.
I c....but the reason that i use RC filter is because i used the connected load as R. Rload = R filter.
Assume that i am using LC filter, what will be the low pass cut off frequency that i should set?
is it 50Hz?
If so, i set the C = 1000pF then, the L value will be very large,right?
Assume that i am using LC filter, what will be the low pass cut off frequency that i should set?
is it 50Hz?
If so, i set the C = 1000pF then, the L value will be very large,right?
audioguru2
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If you use the R of an RC filter as the load, then the filter is highpass not lowpass.
The output of any kind of Butterworth filter is -3dB at the cutoff frequency.
So if you set the cutoff frequency at 50Hz then the output will be at half power.
1000pF if useless at 100Hz or 200Hz. You need a much higher value.
Without a load then the LC will be series resonant and a very low impedance. You don't want the resonant frequency anywhere near your PWM frequency.
Sorry, I don't know the rules for a suitable LC filter.
The output of any kind of Butterworth filter is -3dB at the cutoff frequency.
So if you set the cutoff frequency at 50Hz then the output will be at half power.
1000pF if useless at 100Hz or 200Hz. You need a much higher value.
Without a load then the LC will be series resonant and a very low impedance. You don't want the resonant frequency anywhere near your PWM frequency.
Sorry, I don't know the rules for a suitable LC filter.
audioguru2
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Hi WildSwan,
Which circuit did you build? The defective original circuit, the defective "recently corrected" circuit by MP or the one corrected by me two and a half years ago?
This is a square-wave inverter, a sine-wave circuit is much more complicated and more expensive. If your fan has a speed controller then the square-wave will probably upset it, the same for light dimmers. My corrected circuit has been reported to continuously supply 720W so maybe yours has the pins on a transistor or more connected backwards.
Which circuit did you build? The defective original circuit, the defective "recently corrected" circuit by MP or the one corrected by me two and a half years ago?
This is a square-wave inverter, a sine-wave circuit is much more complicated and more expensive. If your fan has a speed controller then the square-wave will probably upset it, the same for light dimmers. My corrected circuit has been reported to continuously supply 720W so maybe yours has the pins on a transistor or more connected backwards.
I built the original and never returned here again. I was busy trying to figure out why do the Inverter keeps on burning Electric Fans.
Tha fan I used was the common type, one with the 0, 1, 2, 3 mechanical control, not electronics like a light dimmer.
Now that I am out of aces, I returned here and surprised that the circuit has evolved.
Now which circuit will not damage electric fans? I managed to destroy some numbers of electric fans over the years.
I tend to beleive Ante... maybe the inverter are not for Inductive Loads.
Tha fan I used was the common type, one with the 0, 1, 2, 3 mechanical control, not electronics like a light dimmer.
Now that I am out of aces, I returned here and surprised that the circuit has evolved.
Now which circuit will not damage electric fans? I managed to destroy some numbers of electric fans over the years.
I tend to beleive Ante... maybe the inverter are not for Inductive Loads.
audioguru2
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Hi Wild Swan,WildSwan said:
Our original 500W inverter had errors so it didn't work. I helped correct the errors two and a half years ago. My corrected circuit recently was deleted from the project. Which circuit did you make?
What happens to its output when it is loaded with more than only 50W?
Do you have a fully charged car battery powering it through very heavy wires?
Maybe its frequency is wrong.
audioguru2
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Then your fans and 60Hz transformer will be overloaded with a load more than about 400W. It is easy to fix. Change the 47k resistor at the CD4047 oscillator to 39k.WildSwan said:
Did you use a 12V-0-12V 50A transformer? It should be 600VA.
audioguru2
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Hi Ired,ired said:
Welcome to our forum. ;D
A discussion about the calculations for this 500W square-wave inverter is here:
http://www.electronics-lab.com/forum/index.php?topic=8609.0
It is an inverter, not a UPS.
hi guyz,
just wants to ask u guyz how to increase the voltage if i'm using mosfet and center tap tranformer to make the modified sine wave inverter? cos currently i notice that my transformer needed is too bulky....i need to make the inverter portable...thanks for u guyz help....
just wants to ask u guyz how to increase the voltage if i'm using mosfet and center tap tranformer to make the modified sine wave inverter? cos currently i notice that my transformer needed is too bulky....i need to make the inverter portable...thanks for u guyz help....
hi guyz,
just wants to ask u guyz how to increase the voltage if i'm using mosfet and center tap tranformer to make the modified sine wave inverter? cos currently i notice that my transformer needed is too bulky....i need to make the inverter portable...thanks for u guyz help....
just wants to ask u guyz how to increase the voltage if i'm using mosfet and center tap tranformer to make the modified sine wave inverter? cos currently i notice that my transformer needed is too bulky....i need to make the inverter portable...thanks for u guyz help....
audioguru2
- Apr 6, 2004
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The transformer needs to be big for it to have a high power rating because the mains frequency is very low.
The turns ratio between the primary and secondary determines the output voltage.
The turns ratio between the primary and secondary determines the output voltage.
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