Sine wave power inverter

[batee]

Hi,

Can anybody provide me schematic diagram of output stage of HalfBridge as could not found application for dual voltage tapping +/- since the gate voltage should not exceed to say 20 V w.r.t. source of lower side Mosfet/IGBT. This can be achieved by using Bridge driver IC, but I could not find any practical application for it, however a separate bridge driver like TLP250 can be used but practically I have not yet used. Is anybody enlight/share on this with their experience.

IR2184 is a high side AND low side driver. It generates the extra 10-15V needed above the bridge supply voltage to turn on the top FET, and gets you dead time protection and logic-level inputs, too. It's good for up to 600V, unlike every other FET bridge driver I saw. Two are needed for full bridge operation. If you need programmable deadtime, use the 21844.

Half-bridge schematic is included in the datasheet.

http://www.irf.com/product-info/data...ata/ir2184.pdf

Good luck,

Bryan A. Thompson
[email protected]

[psdayama]

IR2184 is a high side AND low side driver. It generates the extra 10-15V needed above the bridge supply voltage to turn on the top FET, and gets you dead time protection and logic-level inputs, too. It's good for up to 600V, unlike every other FET bridge driver I saw. Two are needed for full bridge operation. If you need programmable deadtime, use the 21844.

Half-bridge schematic is included in the datasheet.

http://www.irf.com/product-info/data...ata/ir2184.pdf

Good luck,

Bryan A. Thompson
[email protected]

Hi,
thanks but this driver may not be useful as the half bridge ckt we are discussing. I went thru the datasheet and driver ICs Vcc is referenced to
lower mosfet. However in our case the lower mosfet source is - 350 volts so there may be problem. D.K. Nagare has used pulse transformers which are
proper and no headache for driver configuration. He had problem due to voltage rating of Mosfet (600V type used in 700volt ckt). I hope he has found
the circuit working with say atleast 800V rated mosfets. I have suggested a
high value resistor network so that at output of bridge each mosfet has nominally 350V to withstand.
Hope to hear from U again,
psdayama

[batee]

A capacitor pump of +12V referenced to the center of the bridge allows the top FET to turn on. I tried it at +170V top, 0V bottom and it works great, but agree the 700V would exceed its ratings.

Why generate a split source to power the inverter? I've not seen that done before. It seems like the cost of the copper and the extra DC link capacitor outweighs the cost of a couple of extra transistors.

If you're custom-winding a transformer to achieve this, can't you just add a tap at +/- 350V and another at +/- 360V to allow a simple level shifter transistor to turn on top FET?

[batee]

Has anyone looked into using a DDS IC like the AD9833 for an inverter application? What were the results? How did you achieve PWM from the analog output?

Bryan A. Thompson
[email protected]

[psdayama]

Has anyone looked into using a DDS IC like the AD9833 for an inverter application? What were the results? How did you achieve PWM from the analog output?

Bryan A. Thompson
[email protected]

I haven't seen the AD9833 datasheet. In analog it is very simple to make
PWM. What U need is to make a reference sinewave oscillator. This U can find
from Opamps Application note of National Semiconductors. Oscillator uses
weign bridge and JFET to stabilise amplitude. Then U need a trinagular wave
of " carrier " frequency i.e. at which frequency U want PWM. U feed the
triangualar wave and sinewave to good comparator and Uget the PWM in output. If U want -ve side PWM also then U use one inverter for sinewave
and feed that to another comparator. And U get the -ve half signal for pwm.
There is interesting article about this on
url:http://www.drbrushless.com/

[batee]

Yes, I understand the ironless / transformerless concept. I also plan to use no transformers (step-up or step-down) or inductors in my design.

An advantage of DDS is that it is programmed via SPI, so a jumper change or RS232 command could make changes to waveform shape and frequency.

Pulse transformers and driver ICs appear to cost about the same here in Midwest US. I chose the driver ICs because they could be driven with logic level inputs regardless of the FET design.

It looks like more research money is going into 250V and 600V FETs and IGBTs than into any other voltage ratings, so that's where I have chosen to focus my designs.

Do you anticipate problems with running a system like this continuously (for months or years at a time)? Even if the FETs were well heatsinked and stay cool, I would anticipate continuous operation would degrade their lifetime.

Good luck guys.

Bryan

[psdayama]

Hi Everybody!
it seems that nobody is interested in this topic now.
I have found one interesting paper and hope everyone will have a look:

http://eprints.iisc.ernet.in/archive...ass_Of_PWM.pdf

In the 4th example circuit is what exactly I have been searching.
Also don't know where is D.K.nagare now. He said he has already made
prototypes and was doing field trials. Now he is vanished from Forum and
also from Yahoo.
Hope to hear from U soon.

[psdayama]

A capacitor pump of +12V referenced to the center of the bridge allows the top FET to turn on. I tried it at +170V top, 0V bottom and it works great, but agree the 700V would exceed its ratings.

Why generate a split source to power the inverter? I've not seen that done before. It seems like the cost of the copper and the extra DC link capacitor outweighs the cost of a couple of extra transistors.

If you're custom-winding a transformer to achieve this, can't you just add a tap at +/- 350V and another at +/- 360V to allow a simple level shifter transistor to turn on top FET?

Problem is U haven't caught the thread! We are discussing eliminating
bulky 50Hz transformer for Inverter/UPS. Now there are upteen circuits with psudo sinewave output which are not upto mark in many situations like
running fans. What I have been proposing that instead of using PWM for
sinewave generation from battery there should be high frequency DC to DC
converter and the PWM drive the Half Bridge ckt. Now the load can be connected to output of inverter or normal mains supply just by switching
with relay and referenced to Neutral. Also if U don't want to switch then
U just arrange for proper battery charger and keep inverter always on making
online UPS.
I have found that the transformer costs whopping Rs.1200/- and weighs
more than 7kgs for 500VA output. On the other hand whole inverter costs as
much that amount as we use Ferrite txr of small size operating at 40KHz.
Instead of costly driver ICs one should use Pulse transformer as they cost
just Rs.12 and have 2 windings also. I just checked cost of 800V mosfet which is 6-7 times costly than 600V type 6N60. So what I think that in this
case 2 Mosfets in serries in one leg of HalfBridge would work well with pulse
transformer having 2 secondary windings.