Sine wave power inverter

[sougata]

Hi Dayama,

It is possible to reduce the size of the transformer. Looks like a class-d amp solution to me. A simple filter would reconstruct the sinewave and remove the HF component.Did you find anything or anyone having done it on the net. I will also search and probably would like to develop one. But some practical start point is needed.

Regards

Sougata

[psdayama]

Here is the link:They make readymade PWM amplifiers but don't ask cost!!!!!
http://eportal.apexmicrotech.com/mai...m_overview.asp

I asked their reps in Mumbai and they said each IC costs Rs.25,000/-
But one can make PWM output like that and then have just High freq. txr or
direct output with filter.
regards,
Dayama

Hi Dayama,

It is possible to reduce the size of the transformer. Looks like a class-d amp solution to me. A simple filter would reconstruct the sinewave and remove the HF component.Did you find anything or anyone having done it on the net. I will also search and probably would like to develop one. But some practical start point is needed.

Regards

Sougata

[psdayama]

Hello everybody (Saugata,Mel xxxx)
I wonder why there is no activity here since last month!
I have just now made a inverter of Delhi type with sinewave output.
The transformer for 500VA output is whopping 10kg in weight.
You all may be discussing sine wave with PIC but practically
there is no use if such big transformers have to be used and adding
to cost about 60% of the project.
I have hit an idea to circumvate this and will discuss if anybody
is interested.
HAPPY DIWALI!!
dayama

[sougata]

Hi Dayama,

I actually wrote the code for a customer's specific requirement and know any further development is entirely personal and my current schedule does not permit actually working on it. Currently I have a running code with fair sinewave output. However THD measurements and transient response characteristics were not done. Also to use it like a UPS I need to design a fast transfer circuit. The sugar cube relays are fast enough but fails with increasing and mixed type load. I have incorporated an interrupt based AC Fail detection circuit that checks the following:

1. Improper Line Frequency
2. Unhealthy AC-Line Voltage
3. Sudden brown/black out

When I compl



As far as the transformer issue goes I beleive it will take much time and effort which is beyond my scope right now. Also in Kolkata it is very difficult to source good quality ferrite cores.

As I told you previously we need to have a high frequency carrier and modulate it with a 50Hz sine table. (Which I am doing anyway). Use of the high frequency should theoritically be used to drive a ferrite cored transformer (read low cost light weight) so a low pass filter in the secondary should reconstruct the modulating 50Hz.

BTW I am attending the Microchip Masters Seminar at Lonavala on 29th nov. are you?

Thanks for keeping this thread alive and giving me a kick to ponder further.

Regards

Sougata

[psdayama]

Hi Saugata,
Its OK to be late than never. I think U should stop the work on high frequency
as there are more complcations. Instead I suggest that whats Ur code for
current work is alright.
I am planning to make inverter with Half Bridge
output which is direct to Load and not thru transformer. Problem is everybody is inverting at low frequency of 50Hz from battery. And use same
transformer for charging battery when on mains.
If we make high frequency >40 Khz inverter with
square wave and output is rectified and made high voltage DC then with dual supplies (+/-) we can use IGBT/MOSFET half bridge to drive sinwave output
directly without transformer. This will save the output transformer cost and ferrite transformer would cost hardly 100/-. Also for charging battery same type SMPS circuit can be used and its wattage can be max 120W which would cost hardly 200/-.(Old PC SMPS 250W are available for 150/- in market)
I am still designing the circuit. I will post the block diagram here as soon as
it is ready.
When you are working with this type circuit U can have slightly expensive
circuit which doesn't require a relay -sugar cube or any type as U are just switching DC sources with help of diodes and they are very fast!
Basic plan is
MAINS POWER---|----->SMPS WITH CHARGE CONTROL--> BATTERY->-|
|_____>RECTIFIER --->|<RECTIFIER--<SQR.INVERTOR<|
|
50HZ PWM INVERTOR WITH HALF BRIDGE OUTPUT
|
LOAD WITH SMALL FILTER

This ckt will work like true online UPS still expensive just as much as ordinary
invertors.But U can have Ur DSP alright and also PICs other a/d lines can be used for battery charge management as well!
For cheaper type the Mains rectifier for dual supply can be ommited and
instead sugar cube relay used for switching outputs. Half wave +/- rectifier
requires costly HV elcos.
For good ferrites ask for dealer of Cosmo Ferrites. U check their list on web page. There is another manufacture Hinodaya.
I won't be attending M'Chip Masters course as I am just beginer in this field but not to programming. May be I will attend next time when I hope to get some nuances and I am working on Transformer Ratio test set(comparator
type) and want to use PIC for advanced features.So I think that I will also be
familiar with PICBASIC then.
Wish all the best for conference.My place is abt 2hrs from Lonavala
regards,
psdayama

[sougata]

Hi Dayama,

What you are proposing is a dual conversion design. When you have a battery bank of greater voltage it makes sense other wise for a 12/24 volt system consider this.

1. The Primary current will in the order of 50 AMPs so it is necessary to use copper bands for the primary windings.

2. Frequency has to be kept high (ferrites) consider the switching losses of the primary MOSFETs

3. You have two different switching stage so a single PIC may complicate your programming issues.Of course you can use a ready made SMPS controller like the SG3525 but then this forum may not be the right place to discuss.

4. Microchip has a very good appnote on such type of design.

If you are using PBP then this forum will help you out in solving problems.

One of my laboratory power supplies runs on a PIC for a Buck regulator.

We get only a limited supply (not all models) of cosmo ferrites so it is beyond my scope of experiment. However I would definately like to meet you while I am in Mumbai.Send me a private email if you are interested.

Regards

Sougata

[psdayama]

Dear Saugata,
please read my comments pointwise:

Hi Dayama,

What you are proposing is a dual conversion design. When you have a battery bank of greater voltage it makes sense other wise for a 12/24 volt system consider this.
1. The Primary current will in the order of 50 AMPs so it is necessary to use copper bands for the primary windings.

When one is making Inverter/UPS then the transformer and MOSFETS
have to handle this currents and I have seen atleast 3in parallel to do this.
I think It is OK for 500VA and for 1KVA one has to use 24V battery for same
purpose. Higher rated systems are using batteries 48V or even 110V!!!

2. Frequency has to be kept high (ferrites) consider the switching losses of the primary MOSFETs.

Frequency has been optimised to 40-60KHz for considering this aspect.
I would like to use more than 100Khz if possible but then MOSFETs would be
beyond reach.

3. You have two different switching stage so a single PIC may complicate your programming issues.Of course you can use a ready made SMPS controller like the SG3525 but then this forum may not be the right place to discuss.

My design has 3 switching stages. a)First for conversion to 12V from 230V(SMPS), second a simple Inverter to convert 12Vdc to 300V dc dual supply and lastly the Sinewave converter with half bridge for direct output.
SMPS is based on SG3525 and dc to dc also same but they can have analog
control inputs with additional PWM from Microchip instead of DAC.The last converter is entirely based on Microchip and same chip can used for other indication or control functions. One has to consider the entire system development and how to make optimum use of available resources. It is just
not possible to use one PIC for all functions reqd.

4. Microchip has a very good appnote on such type of design.

Please do send link for that design.

5.If you are using PBP then this forum will help you out in solving problems.

Im not aware of PBP. I am doing programming in Assembly and use a
program to convert it in code.

6.One of my laboratory power supplies runs on a PIC for a Buck regulator.

Im very interested know about it.

7.We get only a limited supply (not all models) of cosmo ferrites so it is beyond my scope of experiment. However I would definately like to meet you while I am in Mumbai.Send me a private email if you are interested.

Regards

Sougata

Please visit cosmo ferrite website. They have dealers all over India and
Kolkata must be having some. If U want some hard to get size then I can
help. But for regular supplies the company will gleadly contact U.
I think I have missed Ur reply due to incorrect setting of intimation. Im
sending U private email for details.
Thanks,
psdayama

[Navneet Vinaik]

Hi Everyone,

I have just started work on sinewave inverter using Metal transformer, using PIC microcontroller.
Can anyone provide me some tips.

[karthickefy]

HI sougata

can you please send me the sourcecode for pic 16f72 based inverter. please find the attachment for 16f72 based inverter circuit.
i'm waiting for your valuable reply.

Thanks and regards,
Karthick
[email protected]

[barkerben]

I made a 24v, 250W Quasi sine wave inverter using a basic PIC (can't remember the exact details) a couple of years back.

It used quasi sine rather than full sine - in other words, a square wave with dead time. Having said that, regulation was less than 10% at full load, and efficiency was over 95%. Quite good fun really...

[psdayama]

I made a 24v, 250W Quasi sine wave inverter using a basic PIC (can't remember the exact details) a couple of years back.

It used quasi sine rather than full sine - in other words, a square wave with dead time. Having said that, regulation was less than 10% at full load, and efficiency was over 95%. Quite good fun really...

Quasi SineWave shouldn't require PIC !
Also regulation seems to poor as even 1% easily achievable. May be U have
some special functions so U are welcome to elaborate.
psdayama

[robinjacob]

Hi Sougata,
Have you finally designed the sine wave inverter? I am really interested to see the design. If you can please send me a schematic.

Thanks and Regards
Robin Jacob.

[psdayama]

Hello!
just scroll down and U will find the schematic in jpg format.
I don't know if Saugata will give the code.
Some part he has already explained.

[mincing]

Dear Souhgata,

Thank you for giving so much of info.What was the ratings of UPS you have made.and what were the efficiencies.
Could you please help with Transforner design information.

Also I have seen a round core trnsformer some ............

also if you are using full bridge topology how do you drive the bridge..........

If you could help with LLC filter inductor design and transformer ,that would be really great.

Thanks in advance

[sougata]

Hi Mincing,

I was too busy in a project and really coudn't get the time to reply to the thread.

1. For the driver part I use TLP250 from Toshiba. Get the datasheet and everything should be easy.

2. For the bridge you would be using all N-Channel Mosfet perhaps cause they are readily available and have much lower Rds On compared to P-Channel. However switching the high side MOSFETs are a little tricky. You need to have a charge-pump circuit to switch them on. Try the IR2101 it makes your design much easy.

3. To maintain low distortion in the output use a flux reset method when changing cycle. You do this by turning of the high-side mosfet, then turning on the other low side mosfet (both low side mosfets on) and then turning off the one which is not required for the current cycle and finally starting the high side driver of the corresponding cycle.

4. Please note that keep your high-side MOSFETs turned on during the entire cycle and apply PWM to the low side MOSFET. Initially I tried steering the PWMs to all of the four MOSFETs to make up for the conduction switching loss. But it did not produce satisfactory results.

5. Now for the transformer design. Say you are operating on a 12 volts battery. Now when the battery is full charged it is upto 13.8 volts nominal and before the deep-discharge of at around 10.8 volts. You can reduce the voltage with PWM but cannot increase it with the current scheme (boosting can be done, theoritically using a boost PFC like technique but I failed to do so). So keep your transformer primary at around 7.5 to 8 volts. This accomodates conduction loss, battery low, and so on.

6. Now the problem is that the same transformer is being used for charging and you need to boost the voltage during charging. Well a PFC boost method can be applied. See the attached PDF. Note the high side rectifiers are your high side mosfet's body diode.

I am attaching a few more documents links which can be handy during the design process. Sorry for Rapidshare. The documents are more than the allowed 200kb and a multipart zip/rar would have been around 10 parts.

Here are the document links:

http://rapidshare.com/files/34936881...r_with_PFC.pdf

http://rapidshare.com/files/34936883...ter_Design.pdf

http://rapidshare.com/files/34936882...c-inverter.pdf



I am sorry I may not be able to provide active support on this thread due to time limitation but will always try too within my knowledge and scope. (I am a completely self-taught with little or no academic background, So I might not be accurate all the times and ready to learn from others.)

I may start up a project on high frequency double-conversion sine wave inverter that utilizes Ferrite Core Transformers as PsDayama suggested. However it would be based on the dsPIC 30F2020. I still don't know whether I would be able to take up that project. Cause I have very little time left for myself catering to clients.

Anyways its good to see that the thread is alive again and would refresh my knowledge base.

[Charles Linquis]

Many years ago I made a 400W . 120V *PURE* sine wave inverter using a PIC. The input voltage was 48. I used a normal inverter (with a ferrite transformer) to give me a regulated 185VDC to feed the PIC-based H-bridge sine wave section.

I used high-side drivers and FETS on the "top" two legs of the bridge and ordinary (low side) drivers and FETs on the lower two.

The high-side drivers can't be "PWM-ed". So I alternately turned them on (one for each half-cycle) while using 78Khz PWM on the lower two. Simple CMOS gates prevented "punch-through" by not allowing the upper and lower FETs on the same side to conduct simultaneously. A small (47uH) inductor was in series with the load and a .1uF was across the load. A scope showed the output to be a perfect sine wave with no glitches whatsoever.

The PWM value was from a lookup table (the program was written in assembly).

The switching FETs needed only a small heat sink.

[mincing]

Many years ago I made a 400W . 120V *PURE* sine wave inverter using a PIC. The input voltage was 48. I used a normal inverter (with a ferrite transformer) to give me a regulated 185VDC to feed the PIC-based H-bridge sine wave section.

I used high-side drivers and FETS on the "top" two legs of the bridge and ordinary (low side) drivers and FETs on the lower two.

The high-side drivers can't be "PWM-ed". So I alternately turned them on (one for each half-cycle) while using 78Khz PWM on the lower two. Simple CMOS gates prevented "punch-through" by not allowing the upper and lower FETs on the same side to conduct simultaneously. A small (47uH) inductor was in series with the load and a .1uF was across the load. A scope showed the output to be a perfect sine wave with no glitches whatsoever.

The PWM value was from a lookup table (the program was written in assembly).

The switching FETs needed only a small heat sink.

Can I get to see the schematic.Idea is quite interesting.In your case how big would be the heat sinks on High side FETs.

Also I would like to know how to post block diagram/schematic in to the forum,so that I can put my design to give a clear understanding.

[babalola]

hi guys,

sine lookup table is a vey important issue as far as digital control of inverter is concerned,can any of you expert treat us (we the beginer )in details the basics of creating this important table?.there is a formular used in microchip reference design,

vref= vp* sin(2II*K/N).
my concerns are:

1. What inform the choice of N( no of samples) other than the niquist sampling theorem?
2. how far can we go in the choice of this value?
3. what is the relationship between this no of samples and the total harmonic distortion of the sine wave?
4. is the above formular valid in all cases?

i dont know if this topic has been mentioned in the past, but i believe detail understanding of this important topic will assist greatly who will become a power inverter designer with microcontroller.

regards,
babalola

[sougata]

Hi All,

While I am not being able to keep up with this thread still the following links might help :

1. http://www.dattalo.com/technical/theory/sinewave.html
2. http://www.mathworks.com/products/si...hd_script.html
3. http://www.doulos.com/knowhow/vhdl_d...ave_generator/
4. Motorola AppNote (Check the attachment)

[EMTRON]

Dear sougata, am very grateful and i appreciate you for your help to every one on this forum. am also happy to join this reportable organization to improve my knowledge in electronics and PIC programing field.thanks for acceptance.

[comtrek]

I have benefited from this thread, although it is not alive now, however, I was able to get charging current from 220 to 8 v primary, info from Sougata re. the use of bridgeless PFC booster, really helped. Thanks to Sougata and other members.

[kolleyjay]

thanks for sharing this great design, can some send me the complete file for this pic16f452 inverter

[kolleyjay]

thanks for sharing this great design, can some send me the complete file for this pic16f452 inverter , my email is [email protected]