prabhueng did you already design the oscillator to obtain you desired frequency. please let me know.

 

Most of the world has reliable electricity so we don't use inverters.

If you connect your Bubba sine-wave oscillator to a 500W power amplifier then the amplifier will get extremely hot trying to dissipate 400W! The 12V battery will have a current of 75A. The output transformer will be huge, expensive and heavy.

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Uncle $crooge

 

audio guru, i dont think this he was thinking of connecting the bubba oscillator directly to the power amplifiers. i am thinking that htis is the first step of the overall project. so hence i think you jumped the bat on that one unless i missed something in this forum. thanks audioguru you expertise is always appreciated.

 

Now there are two people in this thread who are designing a pure sine-wazve inverter wirh the Bubba sine-wave generator circuit.
ISmith is the one who is making a heater because he said, "my overall project is to build an inverter and so i decided to use the bubba oscillator as it give me greatest stability with the least distortion given the low frequency output required. i next want to amplify the wave to 120V eventually." The amplifier is the heater.

Cheap Chinese pure sine-wave inverters use a small high frequency stepup DC-DC converter using a small lightweight ferrite transformer. Then they switch the high DC voltage with PWM to make a stepped sine-wave that has its high frequency edges tremoved with a small lightweight ferrite LC filter.
One guy opened one and found Mosfets and two PWM ICs by Texas Instruments.

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Uncle $crooge

 

That showed me i guess! thank you for pointing out that little detail. in any effect i have a request. is there any circuit available that uses a transformer and transistors as switching mechanisms to produce a square wave output of 120 give a 12 DC input. simplicity would be preferred.

 

The simplest square-wave inverter uses a CD4047 as its push-pull oscillator and it drives two Mosfets that drive a center-tapped transformer.

Many electronic products will not work properly from a square-wave and the simple inverter's voltage will drop with a heavy load and will drop as the battery voltage drops as it runs down. It also needs a low voltage detector to turn off the inverter when the battery voltage gets low.

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Uncle $crooge

 

by the way. you should know that the input current is limited to 2 amps. not much power is required for load so a low power will still be good.

 

i know i am asking too many questions without any having any of them answers but this question is specifically for audioguru. I looked at your revised circuit with the cd4047 chipset and i was wondering if i could use this for my purpose. I need to know whether i can use another chip as i have non available to simulate. also i was wondering whether this circuit could be manipulated so that the input dc voltage be 12V and 2A. if so what changes do i have to make to the circuit and what do you think and approximated output power might be. also, what are the part numbers for the diodes. attached is your inverter for reference.

Attached Thumbnails

 

 

What is your current-limiting circuit?

You can make your own CD4047 with about 10 other Cmos logic ICs.

Usually a simple inverter like this is driven from a lead-acid battery that has hundreds of Amps of current available. It uses a fuse for overload protection.

My schematic shows 100W max continuous output power. The battery will need to provide 120W (10A). I am just guessing since nobody has built it.
If you limit the battery current to only 2A somehow then the battery power is 24W and the max output power is only about 19W.

The diodes are shown as 2A (or more) diodes. Their voltage rating is 30V or more.

Why bother simulating it? The sim program probably will not show how poor is its performance.

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Uncle $crooge

 

audioguru as always thank you for your speedy response. I always appreciate it. after much considering i figured out that i dont really need the current to be two amp so 10amps would be just fine. i think i want to construct this circuit i would just need some explanation as to how it works, if not could you point to as to where to look so i could better understand the operations of this circuit. also i am looking fo the data sheet for the cd4047 so i could try to construct it in multisim. any suggestions concerning this would be greatly appreciated.

 

i was looking at the data sheet of the cd4047 and it looks like quite a task to construct such a diagram. do you by any chance have somehind i can use other than or do you already have a constructed one.

 

Hi audioguru, thanks for your suggestion. You are correct i we use straightly use the sine wave bubba oscillator to drive the mosfets or igbt means it will be like an heater. and also we need the huge transformers.

If i am not wrong, that they are two approches for designing the inverters

1. Convert the low voltage DC to high voltage DC, then make this HV DC in to HV sine wave AC.

2. Using the high power mosfets or igbt that will oscillate at 50 hz in the primary of the larger transormer to produce the 230V.

I think the first approach the best and efficient. Because there is no need of large transformers and also we using the PWM techniques which is more efficient.

So my approach is the first one.

The overall project splitted into two main blocks

1. DC -> DC converter
2. DC -> AC converter

1. DC -> DC converter blocks
a. PWM control
b. Half bridge driver

2. DC -> AC converter blocks
a. Sinusoidal PWM control
b. Full-bridge driver
c. Low pass filter

So welcome all of your suggestions for implementation, design and analysis of the above said blocks.

 

So first we need to design is the PWM control for the DC->DC converter.

Points to consider is the
1. How to generate the PWM signal. By using the uC or the PWM chips.
2. What is the frequency of the PWM signal.
3. How to design feedback control to vary the duty cycle or the frequency of the PWM.
4. What is the duty cycle of the PWM.

 

without cutting you short prabhueng but let me ask you a question. i got the circuit that you designed online with the monostable vibrator the cd4047. what is it used for the the circuit, is it just the switch the voltages on and off at a desired frequency?

 

We don't see the circuit.
The CD4047 is usually used as the oscillator in a square-wave inverter since it has two opposing perfect square-wave outputs. Its mono-stable function is not used. The opposing outputs drive push-pull power transistors or Mosfets that drive a center-tapped transformer.

A TL494 or other PWM IC is used for a sine-wave inverter.

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Uncle $crooge