Full bridge on two ir21531

[Dvinchy]

This is a full bridge MOSFET or IGBT with the programable oscillator that made with the help of couple IR21531D. I would wonder if someone make a test on this circuit. I did and it has worked excellently but there is no suitable equipment at home to determine about advantage and disadvantage.

 

[Hero999]

What are you using it for?

An inverter?

 

[Dvinchy]

It is. The circuit works out all the range of frequency from 0.1 Hz up to 100 kHz. In particular it has functioned tip-top during 50 Hz oscillating mode.

 

[Dvinchy]

Also here is a method to get some three phases full oscillating bridge. That is created by the three IR 21531D.

 

[Hero999]

Is there a way to make a modified sinewave just as easily?

Square wave is a very poor choice for powering mains appliances unless there's resistive, in which case you might as well use DC anyway.

 

[Dvinchy]

Is there a way to make a modified sinewave just as easily?

Square wave is a very poor choice for powering mains appliances unless there's resistive, in which case you might as well use DC anyway.

Here is not any modulation frequency like complicated three phases drivers. Here are three phases square pulse in interaction each other. Their phase shift 120 degree as needed to be. The most important condition it is the same kind of Ct capasitors in range 0.1-0.0001µφ and the same range resistors Rt. Frequency depend of them. Three phases have been created by circuit are suitable for three phases AC motor. I has already checked. If the modulation have to be, it would be added from DC supply unit.

 

[Hero999]

That's not what I was asking.

A modified sinewave has a step in it, see the waveform in green below.

**broken link removed**

 

[Dvinchy]

Well known there is no amplitude in that case. All the AC equipment doesn't care what kind of amplitude form the most important only is simmetry. In other words the different half-periods have to be the same by the form and time of duration like reflection.

 

[Hero999]

Well known there is no amplitude in that case. All the AC equipment doesn't care what kind of amplitude form the most important only is simmetry. In other words the different half-periods have to be the same by the form and time of duration like reflection.

Sorry but neither of those statements are true:

1) There is an amplitude, the modified sine wave has the same peak amplitude as a real sine wave.

2) Plenty of appliances prefer a pure sine wave and a modified sine wave is better than a square wave and there are appliances which require a sinewave If this wasn't true, then why are most cheap inverters on the market modified sine wave? And why is it people bother to buy more expensive pure sine wave inverters?

Why is a modified sine wave inverter better?

It can power a greater range of appliances than a square wave inverter.

Some appliances require the same peak voltage as the sinusoidal mains but aren't bothered about the wave shape, e.g. some non-universal switched mode power supplies. These work by rectifying the mains and converting it to DC, the trouble is, the electronics might not work reliably off 230VDC and might require at least 300VDC. A square wave or even a DC voltage could be used to supply these sorts of appliances but the output voltage would need to be √2 times the normal mains voltage so you'd need a 325V suqarewave, if the appliance was designed for a 230V sine wave. The problem is that a 325V square wave will cause resistive loads to overheat and possibly catch fire so it's a bad idea.

A modified sine wave inverter will be able to run both appliances designed for a peak voltage of 325V and resistive loads which require an RMS voltage of 230V, regardless of the wave shape.

A modified sinewave inverter produces less harmonics than a square wave inverter so it causes less interference and heating of iron cores.

Why is a pure sine wave inverter better than a modified sine wave inverter?

Because it can supply any device designed to work from the mains.

Some appliances require a sinusoidal voltage and can be damaged by a squarewave or modified sine wave. This is because the higher frequency harmonics can cause overheating in some transformers and motors. There are also some circuits such as phase controllers (lamp dimmers) and single phase induction motor starters won't work at all from any other wave shape than a sine wave.

 

[Dvinchy]

Thank you. By the way the simple low- frequency transformer works very well and clean which has been connected to circuit's exit that above. The transformer was working as if it has connected to the grid.

 

[Dvinchy]

That method gives us create the full multiphases bridge MOSFET or IGBT. In particular here is a five phases bridge with self-oscillator.

 

[Dvinchy]

Why is a modified sine wave inverter better?
It can power a greater range of appliances than a square wave inverter

I disagree. The most main reason of the modified sine is self-protection power keys like IGBTs or MOSFETs because their switching is in very hard mode.

 

[Hero999]

I disagree. The most main reason of the modified sine is self-protection power keys like IGBTs or MOSFETs because their switching is in very hard mode.

Sorry what do you mean?

It has nothing to do with the MOSFETs and IBGTs and all to do with peak voltage and harmonics.

 

[shortbus=]

Dvinchy- I want to ask a dumb question about this design. How are you synchronizing this to give the correct wave form out put?

According to the ir21531 data sheet they incorporate a basic 555 circuit in each IC. But there is now way to synchronize the wave forms. From what I know about 555 IC's you cant get two of them to out put the same frequency with out playing around with resistor and cap values, just because of manufacturing tolerances on components.

It also calls them a half bridge driver not a h-bridge.

Can you or some one else correct me if I'm wrong on this?

 

[Hero999]

Dvinchy- I want to ask a dumb question about this design. How are you synchronizing this to give the correct wave form out put?

I haven't read the datasheet but going by the schematic it looks like a ring oscillator to me.

See attached, the plots are the voltages across the capacitors, notice how it's three phase?

The same is true for the squarewaves on the outputs of the gates but the capacitor waveforms are easier to see when places on top of each other.

 

[Dvinchy]

Sorry what do you mean?

It has nothing to do with the MOSFETs and IBGTs and all to do with peak voltage and harmonics.

I'd just said about the main reason why should a modified sine be. Take an imagine the situation when the power keys are functioning with out any sub-frequency-modulated they will have been destroyed in a short while. Even though there were a lightly load connected. There is a couple of decisions that is modified sin or increased current's range of transistors. The first one has probably more advantage than second one.

 

[Dvinchy]

Dvinchy- I want to ask a dumb question about this design. How are you synchronizing this to give the correct wave form out put?

According to the ir21531 data sheet they incorporate a basic 555 circuit in each IC. But there is now way to synchronize the wave forms. From what I know about 555 IC's you cant get two of them to out put the same frequency with out playing around with resistor and cap values, just because of manufacturing tolerances on components.

It also calls them a half bridge driver not a h-bridge.

Can you or some one else correct me if I'm wrong on this?

The first two phases circuit is OK it was tested by me and worked tip-top. What about three or more phases i don't exactly know it was not tested with the load like a suitable motor but it has been tested with some resistive loads. As a result of this test all the voltage and amperage between each phases was exactly the same range. That is showing us the normal three phases mode. It is logical becouse three the same capacitors whose charging and discharging is depend each other will have to be taken sinusoidal shift.

 

[Hero999]

I'd just said about the main reason why should a modified sine be. Take an imagine the situation when the power keys are functioning with out any sub-frequency-modulated they will have been destroyed in a short while. Even though there were a lightly load connected. There is a couple of decisions that is modified sin or increased current's range of transistors. The first one has probably more advantage than second one.

What do you mean by: power keys, sub-frequency-modulated?

Sorry but you seem talking nonsense.

 

[Dvinchy]

1.power transistor
2.pulse-duration modulation

 

[shortbus=]

Hero, Dvinchy- I am not nearly a well versed on this stuff as you guys. But as I understand it a inverter should/has to create a wave form that keeps the phases in the normal accepted AC form- whether 1 or 3 phase.

These driver chips have a internal 555 timer type circuit that controls the switching frequency. There is no way, that I can see, to tie one to the next so that a regular AC wave form is produced. The out puts from the FET's would just be random.