Basic Inverter Voltage regulation

Thread Starter

abdullah8391

Joined Sep 6, 2015
103
Hi!
I copied the DC-AC circuit from here, or specifically speaking this image (I didn't used the diodes because I think they are useless in described configuration). However when I observe AC voltage using DMM, I get the following results:
1. 5W LED bulb with capacitor shows voltage 37.4V
2. 5W LED bulb without capacitor shows voltage 46V
3. 9W LED bulb with capacitor shows voltage 65.9V
4. 9W LED bulb without capacitor shows voltage 99.6V
5. 30W LED bulbs without capacitor shows voltage 100V but LEDs start to flash
6. 30W LED bulbs with capacitor shows voltage 65.6V, LEDs don't flash but light is dim.

Operating Voltage (Desired) = 220V
Operating Frequency (Arduino Coded) = 60 Hz

Kindly tell me the reason of this behavior.
Kindly help me how in getting 220V stable AC output?
if there are any pre-built components that I can attach after transformer to stabilize it, kindly let me know about them too!!!

Thanks in advance!
 

Irving

Joined Jan 30, 2016
2,065
The diodes are to ensure MOSFET gate capacitance is fully discharged and minimise heating in MOSFET. The chances are that the drive from the Arduino isn't sufficient to turn the MOSFETs on hard enough. Either do the extra circuitry further down the article, or, easier, replace them with, for example, IRZL44

What transformer are you using?
 

Thread Starter

abdullah8391

Joined Sep 6, 2015
103
The diodes are to ensure MOSFET gate capacitance is fully discharged and minimise heating in MOSFET. The chances are that the drive from the Arduino isn't sufficient to turn the MOSFETs on hard enough. Either do the extra circuitry further down the article, or, easier, replace them with, for example, IRZL44

What transformer are you using?
OK, I will try that.

12V Center tape, 3A.
 

Papabravo

Joined Feb 24, 2006
16,777
Hi!
I copied the DC-AC circuit from here, or specifically speaking this image (I didn't used the diodes because I think they are useless in described configuration). However when I observe AC voltage using DMM, I get the following results:
1. 5W LED bulb with capacitor shows voltage 37.4V
2. 5W LED bulb without capacitor shows voltage 46V
3. 9W LED bulb with capacitor shows voltage 65.9V
4. 9W LED bulb without capacitor shows voltage 99.6V
5. 30W LED bulbs without capacitor shows voltage 100V but LEDs start to flash
6. 30W LED bulbs with capacitor shows voltage 65.6V, LEDs don't flash but light is dim.

Operating Voltage (Desired) = 220V
Operating Frequency (Arduino Coded) = 60 Hz

Kindly tell me the reason of this behavior.
Kindly help me how in getting 220V stable AC output?
if there are any pre-built components that I can attach after transformer to stabilize it, kindly let me know about them too!!!

Thanks in advance!
Of course you decided to do this because of your vast experience and many advanced degrees from reputable institutions of higher learning.
 

djsfantasi

Joined Apr 11, 2010
7,827
The diodes are to ensure MOSFET gate capacitance is fully discharged and minimise heating in MOSFET. The chances are that the drive from the Arduino isn't sufficient to turn the MOSFETs on hard enough. Either do the extra circuitry further down the article, or, easier, replace them with, for example, IRZL44

What transformer are you using?
Or IRL540N MOSFETs. You really need a logic level MOSFET when it is being driven by a microprocessor. The Vgsth range of the one you’re using is 2-4V. Although it appears as if the Arduino could drive the MOSFET, you are at the edge of the specs. Spec addition might result in that schematic not working in all cases. Better to use a MOSFET designed for use with microprocessors. I.e., a logic level MOSFET, such as an IRL540N. The other MOSFET, the IRZ44 IRZL44, has the same Vgsth specs and may not work either.

Update: Corrected typo
 
Last edited:

Thread Starter

abdullah8391

Joined Sep 6, 2015
103
Or IRL540N MOSFETs. You really need a logic level MOSFET when it is being driven by a microprocessor. The Vgsth range of the one you’re using is 2-4V. Although it appears as if the Arduino could drive the MOSFET, you are at the edge of the specs. Spec addition might result in that schematic not working in all cases. Better to use a MOSFET designed for use with microprocessors. I.e., a logic level MOSFET, such as an IRL540N. The other MOSFET, the IRZ44, has the same Vgsth specs and may not work either.
Thanks dear, didn't knew it.
Will also change it and will update soon.
 

Irving

Joined Jan 30, 2016
2,065
The other MOSFET, the IRZ44, has the same Vgsth specs and may not work either.
Don't confuse IRZ44 or IRFZ44 with the device I spec'd which is IRLZ44 - that's a logic level MOSFET (LH chart), and is marginally better than the IRL540N (RH chart) though either is good enough for this application.

1618247952008.png1618247974418.png
 

BobTPH

Joined Jun 5, 2013
3,655
Um... That would be a 24V center tapped transformer or a 12-0-12 as another notation. A 12V center tapped transformer would have only 6V from each side to the center tap.

Bob
 

Irving

Joined Jan 30, 2016
2,065
The transformer you use has a significant effect on the output. Do you have a specific part # for that transformer? Or can you measure resistances/inductances for the part you're using?

Here is a LTSpice simulation of that setup... using similar MOSFETs to the ones you have and details of a transformer I happen to have here. The simulation gives an average power output over the cycle of 6.6W. Note also the peaky nature of the output. It looks nothing like a sine wave so AC voltage measurements are meaningless.

1618315513185.png
 

Ian0

Joined Aug 7, 2020
3,221
The leakage inductance is the important part. Most inverters have transformers specifically designed with a suitable amount of leakage inductance to form a 2nd order filter in conjunction with C1.
 

Irving

Joined Jan 30, 2016
2,065
The leakage inductance is the important part. Most inverters have transformers specifically designed with a suitable amount of leakage inductance to form a 2nd order filter in conjunction with C1.
Yes, well a standard mains transformer used backwards is a poor substitute...
 

Thread Starter

abdullah8391

Joined Sep 6, 2015
103
Update from my end:
I couldn't find IRL540, so I used 2n2222 with 12v Supply to trigger gate. I checked the voltages by providing 5v signal and circuit is working Ok. I then further attached transformer and measured voltages (without load), I got the following readings:
1. Without capacitor the output voltage is 133V.
2. With capacitor the output voltage is 37V
Is it because of what Irvings said about the disformed waves? How can I avoid it?

As for the forum:
Thanks a lot for the ideas, I didn't know much about it but your wisdom is helping me a lot!
Hopping for more help in future too!!:)
 

Thread Starter

abdullah8391

Joined Sep 6, 2015
103
The transformer you use has a significant effect on the output. Do you have a specific part # for that transformer? Or can you measure resistances/inductances for the part you're using?

Here is a LTSpice simulation of that setup... using similar MOSFETs to the ones you have and details of a transformer I happen to have here. The simulation gives an average power output over the cycle of 6.6W. Note also the peaky nature of the output. It looks nothing like a sine wave so AC voltage measurements are meaningless.

View attachment 235234
Thanks a lot for the effort, since I don't have any RLC meter, I can't measure it.
As for the abnormal waves, is there any way to minimize this abnormality to make it close to sine?
 

Ian0

Joined Aug 7, 2020
3,221
Thanks for the suggestion but split bobbin transformer aren't available in my area. Any other suggestions please?
Surprised about that - especially for 230V, because it saves having to insulate between the two windings.


1618392770807.png
1618392770807.png
I've added the photo of a split-bobbin transformer so that there is no confusion.
If you can't add output inductance in the transformer (where it's free) then you need an inductor on the output, probably several mH.

I couldn't find IRL540, so I used 2n2222 with 12v Supply to trigger gate.
Could you please redraw the circuit you have now.
 
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