In this article I have explained a couple of inverter circuits featuring an automatic feedback control for ensuring that the output does not exceed the normal specified AC output level, and also does not exceed the specified overload conditions.
What is Feedback Control in Inverters
A feedback control in inverter is generally incorporated to control the output voltage and output current and prevent it from exceeding beyond dangerous limits.
In this system, the output AC mains voltage is first dropped to a proportionately lower level, and fed to the shut down pin of the control IC. The stepped down feedback voltage now follows the output AC and varies up/down accordingly, in a proportionate manner.
The control ICs shut down circuitry comares and monitors this feedback signal with a fixed ference derived from the battery volatge of the inverter.
In an event that the output voltage tends to rise above the predetermined value, and increase beyond the reference level, it activates the error amplifier, which shuts down the inverter output PWM. Once this happens, the output voltage instantly dips, causing the feedback signal to decrease below the reference value. This situation prompts the shut down feature of the IC to get disabled, and the IC starts working normally again.
If the output yet again tries to rise beyond the unsafe level, the above process is repeated in the identical manner, and this goes on continuously and rapidly, ensuring that the output voltage is never allowed to surpass the specified unsafe level.
Feedback Control in SG2524/SG3524/SG3525 Inverters
The first example circuit belw shows how an automatic feedback control can be added to a SG2524 inverter circuit. The same concept can be also applied to all the other inverter versions, using the IC SG3524, and SG3525.
You can refer to the following two datasheets for exactly knowing how the pinouts of the IC SG2524 IC are designed to function:
The feedback control loop is configured in the following can be understood with the following points:
The 220V AC output is first rectified using a 4 diode bridge rectifier circuit.
The rectified high voltage DC is dropped to a lower DC level, at around 5V to 10V through the voltage divider network built using the 220K resistors and the 10K preset.
The 10K preset is used to adjust the feedback voltage until the output voltage is controlled just at the right level.
The feedback is taken from the 10K preset's center arm and fed to the error amplifier's non-inverting input pin#1 of the IC 2524.
This error amplifier is nothing but an opamp set internal to the IC for controlling the PWM of the output pin#11 and Pin#14.
The inverting or the (+) input pin#2 of the op amp is clamped at a fixed reference level of +2.5V through the couple of voltage divider resistors configured around the pin#2 and pin#16 of the IC. The +5V reference potential is derived from pin#16 of the IC and then dropped to 2.5V using the two voltage divider resisters.
Since the pin#2 of the error amplifier is fixed at 2.5V reference, means that if the pin#1 of the opamp rises above the 2.5V level would instantly trigger the PWM feature of the IC, causing narrowing of the output PWM to the transistors.
The feedback 10k preset is adjusted in a such a way that feedback voltage at pin#1 reaches the 2.6 V mark as soon as the output voltage reaches the specified unsafe high voltage level.
In such situations, when the pin#1 receives a 2.6 V, it will cause the internal error amp to activate, narrowing the output PWMs to the transistors, which will in turn cause the output voltage to reduce to the safe lower levels, appropriately.
Adding Feedback in IC 555 Inverter
You might have already gone through the post which explains how to build simple 555 based inverters.
Although all these inverters are decently designed and will produce the intended 220 V or 120 V from an easy IC 555 set up, these do not have a built-in feedback system for ensuring a constant output voltage.
The following figure shows how an ordinary IC 555 inverter could be transformed into an enhanced inverter through an easy feedback loop control network.
In this circuit also, we find that the 220V output from the transformer is first rectified to a DC level, and then it is stepped down through a resistive network comprising of a 220K resistor and a 10k preset.
The 10k preset center lead is configured with the NPN transistor BC547, whose collector can be seen connected with the pin#5 of the IC which is control input of the IC.
We know that normally when pin#5 is open, the PWM at the output pin#3 of the IC has a maximum PWM, however, as the potential at pin#5 is reduced, the output PWM also gets reduced proportionately.
Grounding the pin#5 causes the output PWM at pin#3 to become very narrow, with almost zero average voltage at this pinout.
In the IC 555 feedback circuit, when the output voltage tends to rise above the unsafe high voltage threshold, as per the setting of the 10k preset, the base of the BC547 slowly starts getting biased. When this happens, the BC547 begins conducting and causes the pin#5 of the IC to get gradually grounded. The grounding of the pin#5 of the IC causes the output PWM at pin#3 to get narrower, which in turns causes the output voltage to drop to the normal levels.
With over 50,000 comments answered so far, this is the only electronics website dedicated to solving all your circuit-related problems. If you’re stuck on a circuit, please leave your question in the comment box, and I will try to solve it ASAP!
Pic 18f2431 is it better than 16f72 and dsppic30f2010 in its ability to drive the fet/igbt effectively.
Hay its me again, is it possible to add an sg2524 to an ZVS circuit. I have had somewhat of a working ZVS circuit. I am trying to make it more stable. When it works it works well, but some time later it blows up. The best mosfets that have worked for me is the hy3408 only problem is they can handle voltage to 80. The irf260n which the circuit calls for very tempemental and costly. Thanks for your time.
ART
Thanks Art, I think it is possible, however the crucial part is calculating the buck converter section. I am not well versed with ZVS technology, let me investigate more and then I can try to add more explanation…
Hi. I have made this circuit but when i change the preset, the frequency of the ic changes instead of the duty cycle
Hi, In the 555 circuit the frequency might also slightly change when the 100k preset is adjusted.
If you want to change only the PWM, you can replace the 555 stage with the following stage:
i mean sg3524 not 555
If you adjust the feedback 10k preset the frequency cannot change because that preset has no connection with frequency.
When feedback is adjusted the PWM is narrowed or widened, frequency remains the same.
Please measure the frequency across the CT capacitor.
Pls if I connect the feedback circuit to ic4047 as indicated can it still shutdown the inverter on a high load more than the inverter power as some inverter do. Pls I want to know
No, the previous circuit is only for regulating high output voltage, it is not an over load protector…
Can I connect a 12v transformer to the inverter output before going to the bridge rectifier and the 220k, 10k preset for the feedback
If you use a small 12v step-down transformer for the feedback, then the 220k/10k divider will not be required.
Pls how can I add a feedback circuit to my cd4047 inverter that I build pls
you can try the following circuit:
connect the collector of BC547 to the Ct pin of the 4047 IC.
Thanks but what will be the minimum voltage the battery must get to indicate it is a low battery and can I replace the transistor with MOSFET.
A 12V battery may be considered low when its terminal voltage reaches 11V or 10.5V. Yes you can replace the BJTs with MOSFETs
I mean for 6v06v transformers I want to use u said I should used 9v battery max.but at what voltage will 9v battery be low
It will be around 8V…
Can I use a 6v06v to 220v transformer from old ups instead
You can use it but then the battery will need to be around 7V or max 9V.
What if instead of rectifying the output voltage for the feedback you just use a mobile charger that produce 5v for the feedback.pls will work?
No it will not work, because mobile phone will produce a fixed 5V and not a varying voltage.
Ok thanks
Hay me again looking for my last post found this topic on feedback circuit. Well first off the two boost converters work great paralleled I used , 2x. .
0.1 ohm 10-watt resisters one on each positive leg. When I got to about 2000 watts they got very hot. I guess that’s ok since that is why I used 10 watts. I also saw that a diode was used instead of the resister, could you explain the difference and in my case it would have to be a big diode of high current. I also saw your feedback circuit, going to put that to use. Thank you have the best web site, you cover everything, no need to go any place else.
ART
Thanks for updating the results. Glad the idea is working for you.
You last comment was posted under this article:
https://www.homemade-circuits.com/inverter-circuit-with-feedback-control/
Can you please tell me where is the diode placed in your boost converter circuit?
The function of the diodes could be to provide isolation across the outputs of the two boost converters.
You are most welcome, I am always happy to help!
Hi senior Swagatam, I’ve been following your post for years. My question is, can a square wave inverter power a submersive pump machine? I’ve made one of your circuit using SG3525 3kv. I recoil the transformer 48 0 48. I used 48v battery. Everything worked fine but the transformer is overheating. The output MOSFETs, I used 6 pairs (12pcs) of irf260n
Thank you so much Barry, for being a dedicated reader of this blog.
An appropriately rated square wave inverter can power a submersive pump motor, but the motor might make a lot of noise and heat up.
So you have to make sure your inverter is at least a modified sine wave inverter with a capacitor filter at the secondary side of the inverter transformer.
Here is an example design which you can effectively employ for the same;
You can change the transformer specifications accordingly to improve power efficiency.
good day boss, please can you share the circuit you used?
Can this circuit withstand refrigerator
That will depend on the transformer, MOSFET and battery capacities.
Please what changes can be done to convert and ordinary square wave inverter to modified sine wave
You will have insert a 40% deadtime to convert the square wave into modified sinewave.
How do I achieve it with sg3525 inverter driver you posted in this forum. Please suggest a schematics to achieve that the pwm ic above.
You can add a deadtime capacitor in the circuit and experiment with its value until a perfect modified waveform is achieved.
Mr Swatagam, thanks for your kind explanations on the two circuits. Please, the inverter circuits with 555 timer ic and 3524ic. How can I replace those transistors with MOSFETs?
I would like to see the diagrams of the two.
Thanks.
You can send it to my mail.
Hi Elisius, I cannot find the circuit that you are referring to, please provide me the link, so that I can check it out.
This is the link. But I later found where you posted.
Thanks.
Please, I have another request. I need these inverter circuit to be configured to have feedback.
You can replace the the BJTs with MOSFETs in the 555 circuit, just make sure to replace the 1K gate resistors with 100 ohms.
For the feedback you can use the same feedback network which is shown for the 555 circuit. The collector of the BC547 must go to the pin#1 of the 4047 IC.
Hi,
I’m a beginner in need of your assistance with a simple PCB design for a Fan powered and ATX Inverter silent
electromagnetic generator proto… I only am left with a picture of the generator in question and electronics professionals may quickly figure out the wiring map of such a picture of the generator. In short, I need help with the schematic layout and can get started in my home workshop asap.
Hi, I wish I could help you, however, sorry, it may be difficult for me to solve your generator wiring problem, because my expertise is restricted to circuit diagrams and schematics only.
Please help me know how to practically build a working igbt welding inverter especially the inverter section and the output section.I understand the theory but how to do it is the problem.Thank you.
IGBT welding circuit is a very complex design, it cannot be explained through comments. You can refer to the following post for a related article:
https://www.homemade-circuits.com/smps-welding-inverter-circuit/
How can I add more mosfet to ag3524 or tip to this inverter sg3524 for more output watts
You can read the following article for more information regarding how to upgrade the power output of an inverter,:
https://www.homemade-circuits.com/upgrading-low-power-inverter-to-high/
Please who can help me with this with this inverter I tried many times and I failed who can guide me to make it work
The above circuit was taken from the datasheet of the IC 3524, so it cannot be wrong.
If you build the circuit without understanding, then you can never succeed. You will have to understand and build the circuit step-wise, only then you can troubleshoot the faults and ultimately succeed, otherwise you will keep struggling.
How many voltage of 100nf and 10nf and 1nf capacitor can I use
All should be 50 V or above….normally nF and pF capacitors are all 50V by default
Can I use SG3524 to replace sg2524
Yes you can…
Can this inverter give me constant output watts
Yes, as long as the battery is not over loaded.
0.001uf =100pf
0.01=10nf is it correct
Use the following calculator:
https://www.digikey.in/en/resources/conversion-calculators/conversion-calculator-capacitance
Sir 0.1uf and 0.01uf and 0.001uf and 0.1ohm is not in market what can I use replace it
These values are actually very standard values, you cannot replace them with other values….
Is those uf the same with 100nf
yes, 100 nF = 0.1 uF
How many watts of resistor can I use
All are 1/4 watt 5% CFR
Can I use 12volt battery 7amp on the first inverter.
Yes you can….
Please can I use UPS transformer
Yes you can…
I am looking for an inverter LED circuit (not an emergency light circuit), curious after seeing Philips Inverter LED bulb 9W or 12W, which glows on mains if power is there, else switches to Li-ion battery mode. Thanks.
I haven’t yet designed it….. I will try to design it if possible and let you know.
is it possible to make a 50hz inverter using atmega8 ic ?? and if possible can you make one???
It is definitely possible, but my Atmega coding knowledge is not good, so I cannot make it.
Sir for the above circuit 2v truck battery is used, will the same circuit with same components work for 12V 35Ah battery
Hi Alwin, yes the circuit can work with 12V also, just make sure to use a 9-0-9V transformer for a 12V operation.
Hello sir ,pls is it safe to connect the output of the bridge rectifier to your circuit directly without the use of a capacitor? As you did not use one in your diagram.
Then, if voltage at transformer tends to increase, does the output voltage of the diode rectified increases too?
Hello Igbinoba, Actually a small value capacitor should be connected with the feedback bridge rectifier. You can add a 10uF/400V capacitor with the bridge outputs. Yes the bridge output will increase when the inverter voltage increases and vice versa.
good day swagatam. I am faced with construction of automatic voltage regulator (stabilizer) please do you have a circuit diagram for that
Hi Hillary, here’s a simple stabilizer circuit which you can try:
https://www.homemade-circuits.com/how-to-make-small-homemade-automatic/
good day swag. thank for your reply and help so far, you are really doing a great work. my question is, the 5k resistors at the voltage divider stage of the opamp, can they be changed to 10k since I can’t get an exact value
Thank you Hillary! You can use 4k7 for all those resistors
Please swagatam, I also a related issue with pic16f716 inverter module, it voltage feedback and as well as the current feedback. Can I get a diagram? Thanks sir
Hi AYODELE,
Since I do not know the shut-down pinout details of the PIC16F, it can be difficult for me to solve your query.
Hi Swagatam. a diagram of the 12-230V inverter 4047 with feedback circuit, please. Thank you.
Hi Alexandru, you can do it in this way:
Connect a bridge rectifier circuit at the output of the inverter.
Create a resistive divider across the positive/negative lines of the bridge rectifier, using a 220K resistor and a 100K preset.
Make sure to connect the 100K preset at the ground or the negative side of the bridge rectifier.
Take a BC547, connect its base with the wiper arm of the 100K preset.
Connect the emitter to the negative output of the bridge rectifier.
Connect the collector of the BC547 with the Ct pin of the IC 4047.
Make sure to connect the negative line of the bridge rectifier with the negative of the battery.
After this, adjust the 100K preset so that the inverter output voltage is unable to rise above a desired threshold such as above 220V etc
thank you Swagatam for the prompt reply.
You are welcome Alexandru!
Pin#1 is the Ct pin of the 4047 IC
thank you, sir
Hi sir
What is the work of latch in pulse with modulation?
Not sure about it! I have not yet studied this concept!
Hi sir
I must thank you for giving beaginers like us a chance to interact based on what we don’t understand.
My question is, what is the voltage value I will get at pin 14 and pin 11 respectively if I use 24v as my vcc
Thnks
Thank you Aminu.
You will get an average voltage of about 11V, and a peak voltage of around 24V on the output pins of the IC SG3535, when 24V is used as the supply input.
Thank you sir
Sir, am an electrical/electronic engineering student. Can you please direct me or help me with circuit diagram for wind turbine inverter, at least that can power 60watts bulb, charge a laptop and a mobile phone. Or maybe 100watt inverter for my
vertical axis wind turbine project
Daniel, you can use any one of the circuits from the following article for your requirement. Just make sure the transformer is rated at 9-0-9V, 8 amp or 10 amp, and the windmill is able to supply around 12V with 7 t 8 amp current.
7 Simple Inverter Circuits you can Build at Home
your site is extremely valuable to the DIY community!
Thanks for sharing this information.
I have a question about using a CT 220-110 output transformer for a “split phase” backup power supply for North America.
My question is this. if I use a CT 220v output transformer ie 220v output with 110v between L1 and CT, is it possible to load balance this arrangement?
If I’m not clear in my explanation, I can try and clarify.
Thanks
Doug
Thank you very much and glad you found this site useful.
I think, yes it is possible to load balance the secondary side of the transformer to get two output phases and a single common neutral at the center
Pls why my inverter always give me no feedback, and i try to rectify it most of time but yet same things.
Sir what is the ways out.
Which circuit did you use?
Hello sir swagatam,iam into the full bridge type of inverter cause i use a small transformer for double power output. Please, can you tell how to connect this feedback to any diagram of a full bridge inverter using sg3524 of your choice that had discussed in one of your articles ,i would really appreciate. Show with a diagram for my quick understanding please,thanks.
Hello Evans, for your full bridge inverter also you can apply the same feedback network which has been shown in the above article.
Also pls sir, how can I increase the wattage output
You can read the following post for more info:
Calculate Battery, Transformer, MOSFET in Inverter
Ok , thanks sir, but sir how can I make it a pure sine wave
You will have to create an SPWM circuit as I have explained below, and then integrate it with the transistor bases, or mosfet gates of the inverter
https://www.homemade-circuits.com/how-to-generate-sinewave-pwm/
Also sir what is the output wattage of the inverter diagram above using same ic sg2524. Thank you.
wattage is 70 watts
Pls @ sir swagatam, is the inverter diagram above using sg2425 a pure sine wave or modified sine wave output inverter. Thanks for your reply
Anthony, the circuit is square wave.
HI MR SWAG, THANKS FOR UR PREVIOUS REPLYS I IT REALLY HELPED ME A LOT :
MY QUERY IS, IS IT POSSIBLE TO REDUCE THE VOLTAGE IN A CAPCITOR ,ie, IF I HAVE A CAPACITOR OF 50v 4700uf CAN I USE RESISTOR TO MAKE IT 25v 4700uf .
You are welcome Martins, the capacitor voltage value determines it maximum holding capacity. If you supply 25V then the capacitor will store 25V, so it depends on how much voltage you are feeding to it.
And please do not in write capital letters.
I MEAN IN THE PLACES U WROTE 1K RESISTOR DO U MEAN 100 ohm
In the first diagram everything is correct, the shown 1K are also correct.
HI SIR
THANKS FOR UR PREVIOUS REPLY
PLS AM A BIT CONFUSED ABOUT SOME ELECTRICAL PART PLS WHEN U WROTE 1K RESISTOR DID U MEAN 100ohm
(2)DID U HAVE AN ARTICLE DAT CAN POWER ELECTRIC IRON
Hi Martins, please specify the comment reply which you are referring to?
All inverter circuits can be used for powering an electric iron provided they are upgraded as per the iron wattage..
Hi sir
can i connect 470ohm + 100ohm resistor to use as 560ohm
Sure, you can do that!
GOOD DAY SIR
PLS DO U HV ANY ARTICLE OF AN INVERTER THAT CAN GIVE AN OUTPUT OF 7.5KVA AND HOW CAN INCREASE THE OUTPUT… THANKS IN ADVANCE, WAITING FOR UR REPLY
Hello Ebuka, you can refer to the following articles for learning the procedures:
https://www.homemade-circuits.com/upgrading-low-power-inverter-to-high/
https://www.homemade-circuits.com/how-to-calculate-and-match-inverter/
1-CAN MOSFET IRF3205 BE USED INSTEAD OF TRANSISTOR
2-HOW CAN INCREASE THE WATTAGE OF THE OUTPUT
1) Yes it can be used.
2) Wattage can increased by implementing the steps explained in the following article:
https://www.homemade-circuits.com/upgrading-low-power-inverter-to-high/