500 Watt Power Inverter (UPS)

[Eshal]

Hello all

I am working on a project. I want a schematic, a working schematic of 500W power inverter or UPS.

I googled but I am not sure if I assemble those schematics on PCB or breadbaord will they work or not. That's why I am posting my problem here.

Regards,
Princess

 

[Audioguru]

Hi Princess,
A digital switching inverter will be about 80 percent efficient if the transformer is good and modern Mosfets are used. Then it draws 625W from a battery. If the battery is 12V then the current is 625W/12V= 52A(!) that cannot be used on a pcb nor on a breadboard.

A very simple inverter has a squarewave output that cannot power many modern products that rely on the smooth waveform and higher peak voltage of a sinewave. I do not think you can buy a squarewave inverter.
Most manufactured inverters use a "modified sinewave" which is actually a modified squarewave.
Expensive very good inverters use a pure sinewave produced with a PWM circuit.

Google has many inverter circuits, some work and others don't. I fixed a "500W" squarewave inverter circuit posted in two forums that had its capacitors polarity backwards so they blew up and the output transistors had avalanche breakdown that wasted most of the battery power.
Here is the schematic of the bad circuit:

 

[Eshal]

First of all thank you and it sounds good that you remember me

I have understood what all you said. But your given diagram is just like google's bad circuit. It is of no use.
I have found many circuits but I am not satisfied from them. :-(

 

[Audioguru]

A good inverter uses a programmed microcontroller to make a high frequency carrier modulated at 50Hz or 60Hz with Pulse-Width-Modulation to make a pure sinewave output. It has negative feedback so that the output voltage does not change when loaded or unloaded and when the battery voltage is dropping as it discharges. It detects when the battery voltage is too low and shuts off. It also has overload protection.

 

[Eshal]

i know sir that the pure sinewave inverter are programmable microcontrollers but i have a shop near my hope and they have a simple inverter which is being driven by a 12V car's battery. it has only two power transformer. and the shopkeeper is running one CFL bulb on it for one year and it is still running good. i have a similar circuit. here is attached. tell me if you see any mistake in this circuit sir.

 

[Audioguru]

Hi Princess,
Your extremely simple squarewave inverter has nothing to control its frequency. Each transformer will produce a different frequency.
The transformer winding with 12V on each side is too low because the transistors have saturation voltage losses then the output voltage will also be too low. A transformer made for 12VAC output when loaded is probably made as a 14V winding that drops to 12V when loaded. If it is used backwards to stepup the voltage then the "12V" winding will produce the proper high voltage output with no load when the battery is 14V and might need 16V when there is a load. You cannot get 16V from a 12V battery when there is saturation voltage losses.
The base winding has a voltage much too low because the datasheet shows at 0.7V then the typical transistor output current is only 0.6A. If the voltage is increased and since nothing limits the base current then the transistors will be destroyed.

I did not bother looking to see if the charger works. It has nothing to limit its voltage or current but I think its voltage will be much too low. If the transformer is changed so that the high voltage loaded output voltage is correct then the charging voltage will be much much too low.

Here is another squarewave inverter I fixed. It is used in The Philippines where a guy on a motorcycle delivers a charged battery and picks up your discharged battery. The transistors have emitter resistors so that they are better matched.
They are driven from a fairly accurate 50Hz or 60Hz oscillator. It has no voltage regulation. The voltage changes with the amount of load and the amount of battery charge. It does not shut off when the battery voltage gets low enough to damage the battery.

 

[Eshal]

It does not shut off when the battery voltage gets low enough to damage the battery.

Then when will it get shut off?

Sorry for late reply and thanks for your interest

 

[Audioguru]

Then when will it get shut off?

The datasheets for the CD4047 and LM358 show that they still work when their supply has dropped to 3V. But the output high of the LM358 is about 1.5V less than its supply. The output transistors, driver transistors and pre-driver transistors each have a base-emitter voltage drop so the total of the voltage drops is 3.6V at low currents. Then the battery voltage will drop to about 3.6V when the load will no longer be be powered but the circuit will still be oscillating. I do not know the minimum allowed voltage for a "deep discharge" 12V lead-acid battery. EDIT: A battery manufacturer says below 10.3V it does not produce much power.

Since the output voltage is not regulated then it will be a little too high with a low power or no load and will continue dropping as the battery voltage runs down. It is a lousy circuit anyway since its output is a squarewave that many modern products cannot use because they rely on the higher peak voltage of a sinewave.

 

[Eshal]

It is a lousy circuit anyway since its output is a squarewave that many modern products cannot use because they rely on the higher peak voltage of a sinewave.

Is it able to run to ceiling fan nearly in good condition with low or no noise?

Since the output voltage is not regulated

Sorry but at the output we are getting sinewave. Do you think we need to regulate it? I mean in AC to DC converter we have a regulator circuit for DC. But here is Sinvewave, do we need regulator?

Finally, which battery should I use and how much Amperes' battery? Does car battery of 12V is enough? But tell me the amperes of the battery so that I could buy.

Thanks,

Princess.

 

[Audioguru]

Is it able to run to ceiling fan nearly in good condition with low or no noise?

My ceiling fan runs perfectly and quietly from the sinewave mains electricity that has good voltage regulation. I never tried it with an inverter. Which inverter circuit? You posted two circuits and I also posted two circuits. All four circuits produce a squarewave with no voltage regulation.

Sorry but at the output we are getting sinewave.

All four circuits in this thread produce a squarewave, not a sinewave. Maybe without a load the voltage overshoots into something like a sinewave.

Do you think we need to regulate it? I mean in AC to DC converter we have a regulator circuit for DC. But here is Sinvewave, do we need regulator?

Most inverters that are manufactured do not have a squarewave output, they have a sinewave or a modified sinewave and most have output voltage regulation using feedback.

Finally, which battery should I use and how much Amperes' battery? Does car battery of 12V is enough? But tell me the amperes of the battery so that I could buy.

Go to www.batteryuniversity.com and read about lead acid batteries. There is a car starter battery that is designed to produce massive current for a few seconds and there is a deep discharge (deep cycle) battery that is used to provide a moderate amount of current for a long duration used in wheelchairs or to power an inverter. If the output power from an inverter is 500W then it draws about 600W from the battery with the extra 100W heating the inverter, battery and wires. 600W/12V= 50A. A pretty big and expensive battery is rated at about 60Ah then it can produce 3A for 20 hours or produce 60A for maybe 15 minutes.

 

[Eshal]

The one you posted in post#6. Is this capable to run ceiling fan with good or moderate output?

 

[Audioguru]

The squarewave from the inverter in post #6 might cause a fan to buzz. The massive 500W inverter is wasted when it drives a 60W fan. Without any voltage regulation then the output voltage of the inverter with hardly any load might be too high for the fan.
The inverter was designed for parts available in The Philippines to light incandescent and fluorescent lights and for TVs that use a power supply that works from many different voltages. Charged batteries were delivered to homes and discharged batteries were picked up.

 

[iamthegospel]

Most common commercial use 12VDC-230VAC 500W pure sine wave inverter is a china made model.

**broken link removed**

I had a similar project. So, I bought a 500W inverter to decode its design. I reverse engineered its Schematic diagram from the PCB layout. It was a bit difficult because of SMT. *

Otherwise, you can go for 555 or TL494/KA7500BS based inverter circuits.

If you wanna get really involved in the project then go for this:

**broken link removed**

If you wanna go for Microcontroller(atmega16/32) based SPWM generation, I also designed such circuit. But because of unavailability of IR gate drive ICs I had to abandon the circuit. *

Tips :
1- Use mosfets
2- Use rail to rail single supply design.
3- Use 2 pwm controlled (channel opposite to the channel of mosfets used in the bridge)mosfets to provide voltage levels to Gates of High side bridge mosfets (via. gate driver).
4- In case of choosing gate driver, prefer Gate drive transformer instead of IR2xxx series ICs (saves additional bootstrap capacitance).
5- In case of gate drive transformer use same channel Mosfets in bridge. In case of IC gate drivers use alternate channels on high and low side.

*Schematics are in hardcopy. I drew them on paper. i'll upload them as soon as I complete them on some software.

 

[kam1787]

Is it able to run to ceiling fan nearly in good condition with low or no noise?

Finally, which battery should I use and how much Amperes' battery? Does car battery of 12V is enough? But tell me the amperes of the battery so that I could buy.

I don't know why it is so common that members posting questions or asking for help are so parsimonious with the specifics.

If you had said in the beginning you want to run a ceiling fan [we still do not know the wattage of the fan, is it 220VAC??] from a 12V lead-acid battery it would have saved us and you time and effort.

We don't know for long you want to run the fan off a battery. Nor any idea as to your budget Your objectives seem to change;
first a working circuit
then all circuits are bad [whatever that means]
then noise is an issue
and then it appears that battery life is an issue

 

[Eshal]

@Audioguru
The one you posted in post#6. I think it can run 5 to 7 LED bulbs and a fan too. But fan will buzz because output is squarewave. Right?
Sinewave inverters can be designed but they are time consuming and difficult to design. Right?
In all circuits posted in this thread, which one is the most efficient? In my view, post#6's circuit is good all of them. What is yours view?

@iamthegospel
Sorry but you are not the gospel :-o
It would be much difficult to reverse engineered the PCB design. Right?

@kam1787
Please don't criticise. If you don't want to answer then kindly don't exploit the thread.
Every person has it own way of asking things. I will ask when anything disturb me. Audioguru knows me for about 1 year or 1 and half year. He has helped me in many places. He never criticized me for anything instead he helped me a lot.

Thanks all of you.

Regards,
Princess

 

[KlausST]

Hi,

Please don't criticise.

Pleas don´t be angry about criticism, see it as a help.


Klaus

 

[Audioguru]

Most inverters sold have a waveform that is called "modified sinewave" but it is actually a modified squarewave. It has dead spots between the positive and negative peaks. The voltage of the peaks is almost the same as a sinewave and the average power is the same as a sinewave. The waveform is easy to make from a squarewave plus two digital gates.

 

[iamthegospel]

@iamthegospel
Sorry but you are not the gospel :-o
It would be much difficult to reverse engineered the PCB design. Right?

Umm.. yes it was really difficult. Noting down values of each and every component and trying to make out of all the mess. Well, the circuit expanded to 4 pages. I am trying to simulate the circuit.