Another INVERTER we can talk about..

[audioguru2]

Hi Sasi,
How much continuous power output?
Square-wave or modified sine-wave output?

 

[faizanbrohi]

Hello everyone . I found a circuit to generate a modified sine wave. Can it be used with the inverter as an oscillator .

THe Opamp just filters the modified digital sine wave . so if you dis regard the opamp it gives a approximation sine wave or a modified sine wave , digital sine wave , whatever.

Both outputs are shown , with and without op amp

View attachment 39419

View attachment 39420

 

[faizanbrohi]

But the idea is you cannot use pure sinewave in a Inverter , it will heat up the transistors and mosfets very much

 

[audioguru2]

Hello everyone . I found a circuit to generate a modified sine wave.

No. It isn't a modified sine-wave for an inverter, it is just a linear sine-wave with steps in it.

A modified sine-wave allows the output transistors to switch fully-on so there is not any voltage across them, or fully-off so there isn't any current in them. Therefore the power dissipation in the transistors is very low for good efficiency.
With many pulses per wave, Pulse-Width-Modulation is used like in a class-D amplifier to reduce power dissipation in the output transistors.View attachment 39421

 

[audioguru2]

Now its your duty to explain it to all.

Hi Sasi,
I asked about the circuit you attached because you have made many more inverters and power supply circuits than me. Your circuits use that IC frequently but I have never seen that IC.

At 1st glance, I think the inverter has a square-wave output. But it might have a modified sine-wave with its voltage too low if the IC's "dead-time" can be long enough.

 

[faizanbrohi]

Can the SG3525 PWM IC Produce a Modified SIne Wave

 

[audioguru2]

Can the SG3525 PWM IC Produce a Modified SIne Wave?

No. It is designed to make high frequency PWM, not a low frequency square-wave with a step in it.

 

[ante1]

Hi Sasi,

Nice compact circuit!

I’m not an expert but I believe the “dead time” here is very short and the only purpose is to prevent the output transistors from conducting simultaneous and explode! The modified sine wave inverters I have seen does not use the three level method described earlier but a multiple step ramp-up ramp-down output.

 

[faizanbrohi]

How is this circuit for a modified sine wave . see the comparison in the circuit diagram and wave shape. it is zero for some moment as you described in the Diagram

View attachment 39424

 

[audioguru2]

How is this circuit for a modified sine wave

Yes, it is a square-wave with a single step in it. Some electronic equipment will work fine with it as their mains, and others won't.
Now all that is needed is a way to make it drive a push-pull pair of Mosfets that conduct through a center-tapped transformer. Don't forget that the peak voltage must be higher than if a square-wave is used.

 

[faizanbrohi]

How about implementing Sasi's circuit with the osillator i posted above .

 

[audioguru2]

How about implementing Sasi's circuit with the osillator i posted above.

Your circuit and Sasi's circuit are completely different.
Sasi's circuit appears to be a square-wave inverter with a very small "dead-time". Your circuit needs a way to drive output Mosfets.

 

[faizanbrohi]

How do i drive mosfets for a modified sine wave .

 

[audioguru2]

Your circuit has a positive voltage shift and very high resistor values. Mosfets need their inputs to be zero volts when off and low resistance values to switch quickly.
Use a counter with gates instead of resistors to make the signals that feed the Mosfets.

 

[faizanbrohi]

I have found a way , why not use a Class D amplifier after generating a modified sine wave or a linear sine wave . We can use LM4652 and LM4651 to make a Class D amplifier. Here is a schematic for it . IF it has 125W efficiency 86% , it can be used for sine wave generation also .

View attachment 39463

 

[audioguru2]

I don't think the LM4651 is still being made. The National site says, "Lifetime Buy" instead of "Full Production".
A couple years ago I was going to design a pure sine-wave inverter using it when I found out it was being cancelled.

Texas Instruments and other semiconductor manufacturers make power class-D amplifiers that can be used to make a pure sine-wave inverter, not just a simple modified sine-wave one. The high efficiency is due to the PWM used to make it class-D so a pure sine-wave output also has high efficiency.

The class-D amplifiers operate on a supply voltage much higher than a car battery, and a big output stepup transformer needs to be used to make an inverter.

 

[faizanbrohi]

Who says it is out of production . IT is in full production , look at the picture attached . ANd farnell also has it . But the problem is that the PWM IC LM4651 is out of production , can you tell me about the IC number of the Texas Instruments CLass D Amplifier IC. thnx

View attachment 39465

 

[audioguru2]

Here is their most powerful class-D outut stage. Believe it or not it is tiny and is surface mount:

View attachment 39466

 

[faizanbrohi]

I have ordered 5 samples of TAS5152 , TI has shipped it to FedEx , it will be here on 3 august 2006 , but i think it will be delayed because of rainy weather in my country.

 

[faizanbrohi]

Here are the schematics any ideas about where is the input and ouput , because first i want to try out the 125W audio amplifier and see if it works. THe problem is that the TAS5152 side is easy to tackle and understand but i donot understand the PWM Section of where is the Input signal and how to implement it ... ??

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