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How to Make a Simple Solar Inverter Circuit

How to Make a Simple Solar Inverter Circuit

In this article we will try to understand the basic concept of a solar inverter and also how to make a simple yet powerful solar inverter circuit.

Solar power is abundantly available to us and is free to use, moreover it’s an unlimited, unending natural source of energy, easily accessible to all of us.

What's so Crucial about Solar Inverters?

The fact is, there's nothing crucial about solar inverters. You can use any normal inverter circuit, hook it up with a solar panel and get the required DC to AC output from the inverter.

Having said that, you may have to select and  configure the specifications correctly, otherwise you may run the risk of damaging your inverter or causing an inefficient power conversion.



Why Solar Inverter

We have already discussed how to use solar panels for generating electricity from solar or sun power, in this article we are going to discuss a simple arrangement which will enable us to use solar energy for operating our household appliances.

A solar panel is able to convert sun rays into direct current at lower potential levels. For example a solar panel may be specified for delivering 36 volts at 8 amps under optimal conditions.

However we cannot use this magnitude of power for operating our domestic appliances, because these appliances can work only at mains potentials or at voltages in the ranges of 120 to 230 V.

Further more the current should be an AC and not DC as normally received from a solar panel.

We have come across a number of inverter circuits posted in this blog and we have studied how they work.

Inverters are used for converting and stepping up low voltage battery power to high voltage AC mains levels.

Therefore inverters can be effectively used for converting the DC from a solar panel into mains outputs that would suitably power our domestic equipment.

Basically in inverters, the conversion from a low potential to a stepped up high mains level becomes feasible because of the high current that’s normally available from the DC inputs such as a battery or a solar panel. The overall wattage remains the same.

Understanding Voltage Current Specifications

For example if we supply an input of 36 volts @ 8 amps to an inverter and get an output of 220 V @ 1.2 Amps would mean that we just modified an input power of 36 × 8 = 288 watts into 220 × 1.2 = 264 watts.

Therefore we can see that it’s no magic, just modifications of the respective parameters.

If the solar panel is able to generate enough current and voltage, its output may be used for directly operating an inverter and the connected household appliances and also simultaneously for charging a battery.

The charged battery may be used for powering the loads via the inverter, during night times when solar energy is not present.

However if the solar panel is smaller in size and unable to generate sufficient power, it may be used just for charging the battery, and becomes useful for operating the inverter only after sunset.

Circuit Operation

Referring to the circuit diagram, we are able to witness a simple set up using a solar panel, an inverter and a battery.

The three units are connected through a solar regulator circuit that distributes the power to the respective units after appropriate regulations of the received power from the solar panel.

Assuming the voltage to be 36 and the current to be 10 amps from the solar panel, the inverter is selected with an input operating voltage of 24 volts @ 6 amps, providing a total power of about 120 watts.

A fraction of the solar panels amp which amounts to about 3 amps is spared for charging a battery, intended to be used after sunset.

We also assume that the solar panel is mounted over a solar tracker so that it is able to deliver the specified requirements as long as the sun is visible over the skies.

The input power of 36 volts is applied to the input of a regulator which trims it down to 24 volts.

The load connected to the output of the inverter is selected such that it does not force the inverter more than 6 amps from the solar panel. From the remaining 4 amps, 2 amps is supplied to the battery for charging it.

The remaining 2 amps are not used for the sake of maintaining better efficiency of the whole system.

The circuits are all those which have been already discussed in my blogs, we can see how these are intelligently configured to each other for implementing the required operations.

A MINI solar inverter circuit with relay changeover is discussed HERE

For complete tutorial please refer to this article: Solar Inverter Tutorial

 

simple solar inverter circuit

Parts List for the LM338 charger section

All resistors are 1/4 watt 5% CFR unless specified.

R1 = 120 ohms

P1 = 10K pot (2K is mistkanly shown)

R4 = replace iit with a link

R3 = 0.6 x 10 / Battery AH

Transistor = BC547 (not BC557, it's mistakenly shown)

Regulator IC = LM338

Parts List for the inverter section

All parts are 1/4 watt unless specified

R1 = 100k pot

R2 = 10K

R3 = 100K

R4, R5 = 1K

T1, T2 = mosfer IRF540

N1---N4 = IC 4093

Remaining few of the parts does not need to be specified and can be copied as shown in the diagram.

For Charging Batteries up to 250 AH

The charger section in the above circuit may be suitably upgraded for enabling the charging of high current batteries in the order of 100 AH to 250 AH.

An outboard transistor TIP36 is appropriately integrated across the IC 338 for facilitating the required high current charging.

The emitter resistor of TIP36 must be calculated appropriately otherwise the transistor might just blow off, do it by trial and error method, start with 1 ohm initially, then gradually go on reducing it until the required amount of current becomes achievable at the output.

solar inverter with high power battery charging

 

Adding a PWM Feature

For ensuring a fixed 220V or 120V output a PWM control could added to the above designs as shown in the following diagram. AS can be seen the gate N1 which is basically configured as a 50 or 60Hz oscillator, is enhanced with diodes and a pot for enabling a variable duty cycle option.

By adjusting this pot we can force the oscillator to create frequencies with different ON/OFF periods which will in turn enable the mosfets to turn ON and OFF with the the same rate.

By adjusting the mosfet ON/OFF timing we can proportionately vary the current induction in the transformer, which will eventually allow us to adjust the output RMS voltage of the inverter.

Once the output RMS is fixed, the inverter will be able to produce a constant output regardless f the solar voltage variations, until of course the voltage drops below the voltage specification of the transformer primary winding.

 

solar inverter with pwm control circuit

SHARING IS CARING!


About the Author

I am an electronic engineer (dipIETE ), hobbyist, inventor, schematic/PCB designer, manufacturer. I am also the founder of the website: https://www.homemade-circuits.com/, where I love sharing my innovative circuit ideas and tutorials. If you have any circuit related query, you may interact through comments, I'll be most happy to help!



96 thoughts on “How to Make a Simple Solar Inverter Circuit”


  1. Howdy, Friend! Interested to Learn Circuit Designing? Let's Start Discussing below!
  2. hi sir great work are doing. i have follow up some of your diagram. please sir if i put together this circuit the it show. will it work perfect. thanks

  3. hi sir great work
    i am making a hybrid energy system my dc wind is 50watt and solar is 30watt 2amp . and battery is 12v and 10 amp.
    and we are are using load 40watt bulb. can you please recommend me which solar inverter i should made ?? and solar inverter power etc
    thnaks

  4. hi sir, if i want using this kind of inverter to operate the inductive load what component should i add or which part should i change?

  5. hi sir, if voltage supply from solar panel is more than 36v and feed into L7812cv what will happen for the invert part and the L7812CV

    • Hi Tommy, If it is within 40V the 7812 will handle it somehow, but above 40V it can be a problem to the IC.

      For the inverter/battery section, the LM338 will drop it to the required level, but again LM338 so also rated at 40V max…so make sure your panel voltage never exceeds the 40V mark

    • mosfet is used for switching the transformer with battery current.
      7812 for supplying constant voltage to the IC
      and 4093 for creating the required oscillations and buffering for mosfet switching.

    • Tommy, check the output with a load connected, such as a 40 watt bulb.
      try increasing capacitor value slightly and check the response again

      I did not understand what you meant by “no AC?” please clarify if possible.

    • Tommy, either you can increase the value of R1 by adjusting the 100K preset or increase the value of C1 appropriately, to reduce the frequency to 50Hz

    • It is IRF540, it is a mosfet, max voltage will depend on the transformer input winding rating and the PWM or the duty cycle from the N1 pot setting

  6. Hi, Swagatam. I try to built the circuit but I am using 10-0-10V x’mer and I get the output only with 88 VAC max with adjusted R1 = 88 Ohms. Here, my question why I cannot 240VAC output is that because I am not using 24-0-24V x’mer?

    • Hi Tommy, by default the N1 stage will produce a fixed 50% duty cycle which implies that the output will get 50% less in voltage, to correct this you may have to use 6-0-6V trafo with a 12V battery meaning the trafo input V specs should 50% less of the battery V spec

      the other option is to modify the N1 circuit with an adjustable PWM circuit, possibly I’ll try to modify it, and publish the modified version soon.

  7. Hi Swagatam,

    My name is tommy from Malaysia. I wish you could help me to design a power inverter that use in rural area and the incomming source is from solar panel
    and not expensive

  8. yes you can go ahead with a 12-0-12 trafo also….in that case you won't require the 7812 IC for stepping down the voltage to the IC.

    R4 can be eliminated, it's actually not required…and R3 = 0.6/charging current

    charging current must be 1/10th of the battery AH rating

    • Hellu Lufono, it will be approximately equivalent to the transformer wattage…. provided the battery is able to supply the specified amount of current and voltage to the trafo.

  9. Sir, I am going to make HERIC Inverter in lab and i am facing a problem to choose SPWM and driver of MOSFETs. Inverter rating is 300W and 230V output. How to make SPWM. Please suggest me.

    • Gaurav, SPWM can be made by feeding a fast triangle wave at 200Hz and a slow triangle wave at 50Hz across the two inputs of an opamp.

      the triangle waves could be extracted from the R/C junction of a 555IC astable circuit

  10. if you use the solar panel to operate both battery and the inverter then you might require a high power panel, in the order of 10 to 15amps and you must use the last circuit where a transistor is connected with the IC for boosting current.

    R3 will depend on the load current….initially don't use anything keep the points shorted and see the response.

  11. hello sir thank you for you posting. but i have to ask one question than can we implement a circuit which automatically closed the input when the battery is fully charged? if yes than how?
    please reply me soon i have to work on this

  12. hi sir,
    why the battery positive is connected with transformer neutral? and what will happen if I disconnect it? is that possible to use ordinary transformer instead of center tap?

    • Hi rishi,

      what is transformer neutral? I did not understand your question.

      the positive is connected with the center tap of a 9-0-9V transformer

      center is a must here

  13. sir i am trying to build a 50 watt sine wave inverter to be included in my clg major project .
    can u please direct me towards appropriate designs .
    i would really appreciate if u could help me.

  14. sir, i am elect elect engr, i have been into inverter and ups more than 10 years but i want to have more idea on SOLAR SYSTEM, PLEASE CAN I GO ABOUT THIS? to be an installer, designer.etc

  15. sir, for 250ah battery what resistor value and watts for r3 and emiter resistor? thank you very much sir and god bless you sir

  16. I have used LM338 to step down the voltage, but it's not the efficient way of doing it, you can use a buck converter instead.

  17. hai swagatam ,
    i need to convert dc 700 volt to ac and reduce it to low voltage for battery charging ,because i have panels connected series for agri 5 hp solor pumpset which is run by solor vfd ,so i dont want to disturb the connection and i want to keep changeover switch inbetween dc bus voltage from panels and use it to home by ups when not in agri us

  18. Hi Swagatam,

    My name is Benjamin from Malaysia. I wish you could help me to design a power pack with the 230V AC input with less than 5AMPs and output 9.6V dc.

  19. Sir i want to know can i iuse 12-0-12 transformer in the circuit i am using a battery of 12v& 7.2A. also sir i want to know each and every component and how it works

  20. sir i want to ask what isthe valiue of resistors used some of them are not specifeid ,also i want to know can lm 317 be used in place of lm338

    • Shantanu, are you referring to the LM338 R3/R4 resistors? these must be calculated using the following formula:

      R3 = (0.6×10)/batteryAH

      R4 = 2 x R3

      R3 at the top can be simply a 10k resistor

      if your battery AH is less than 10AH then 317 will do.

  21. Hi,
    what rating solar panels will be required to run a 215 Ltrs (5 star rated) refrigerator, also the tell the rating of supporting inverter.

  22. Hi Swagatam, I wanted to seek your opinion about Solar power usage –
    Scenario is: I want to install 10Kv Solar system at my place without using any batteries, it should work when the day starts and entire load should switch over to Solar power, once its dusk the system should fall back to normal electricity supply, the problem I can think off is that entire 10Kv may not be produced/used always and sometimes I might just use about 1-2 kv only and rest might be passed over to grid which can cause damage to lineman working (as they might think lines are off), can you please suggest a solution to this problem or a circuit that best fulfills my problem.

    • Hi Gopal,

      I think you can keep the inverter power isolated from the home grid line using a DPDT relay.

      This relay may be controlled through the solar panel voltage itself or a simple light activated switch.

      So, as long as the solar panel receives the require sunlight, the relay stays activated keeping the inverter isolated from grid and your home wiring connected with the inverter, while during night when the solar panel shuts off, the relay connects your home wiring back to grid mains.

  23. I am designing a boost converter for my solar project (24V to 230V,20A) please can u suggest a circuit with proper values

  24. sir,
    this is kumaran, previous i request "circuit of 500watt (125wattX4 panel) solar panel controller circuit with 150ah tall tubular lead acid battery charger"

    I mentioned my solar panel details,

    *max. power -Pmax-125wp
    *Voltage @ max. power -Vmax-17.7v
    *current @max. power -imax – 7.06A
    *Open circuit voltage-Vocv -21.4v
    *short circuit current – i scv – 7.98A
    *tolerance – T – +- 5%
    *Max. system voltage -v – 1000V

    regards

    kumaran

  25. hello sir,
    i am kumaran, i need a circuit of 500watt (125wattX4 panel) solar panel controller circuit with 150ah lead acid battery charger

    thanking you
    regards
    Kumaran

  26. I have all these circuits published in my blog separately which can be added here, however if we add everything the design will become too complicated for small hobbyists, therefore the external ad-ons can be integrated as per individual preferences.

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