6V to 220V Boost UPS Circuit

The post explains a simple boost converter UPS circuit for supplying an uninterruptible power to satellite TV set top boxes so that the offline recording is never allowed to fail during power outages. The idea was requested by Mr. Aniruddha Mukherji.

Technical Specifications

I think you are a fellow bong like me, I am an enthusiast electronic hobbyist person. Though I know only the basics, I am sure you must be getting 100's of emails daily and I am completely betting on my luck if this one gets to your "eyes" 

My requirement:

16 volt 1 amp DC backup for my apartment Tata sky centralized distribution panel.
Issue: My apartment maintenance people do not run backup (generator) during day time, I have a Tata sky DVR which fails to record since there is signal loss due to power failure.


I had thought of a small back up system,I had purchased a small 6 volt 11 watt CFL Ballast circuit thinking as cheap alternate solution, but the same failed to work.

Why I am looking for AC supply instead of DC?I do not want to tamper with their system and get penalized for whatsoever failures which may come to it due to natural course of operation.

Could you please help me with a very simple cost effective circuit that will give me 220 volt 20 watts power from 6 volt 5ah battery. To be precise 220 volts from 6 volt battery, as I have purchased a 6 volt 5 ah battery recently. The output wattage requirement is less than 20 watts, the
adapter ratings are :

Output - 16 volt 1 amp
Input - 240 volt .06 amp

I know you have lot of work, but if you could spare some time and help me with this it would be of great help. thank you


The Design


Since today all electronic systems employ an SMPS power supply, the input does not necessarily need to be an AC for powering these equipment, rather an equivalent DC or pulsed DC also become useful and works as good.

Referring to the diagram above, a couple of sections can be seen, the IC1 configuration enables a 6V DC to be boosted to a much higher 220V pulsed DC through a boost converter topology using the IC 555 in its astable form. The extreme left side battery section ensures an changeover from mains to battery back up every time a power failure is sensed by the circuit.

The idea is pretty simple and does not require much of an elaboration.

How the Circuit Functions

IC1 is configured as an astable oscillator, which drives T1 and consequently L1 at the same frequency.

T1 induces the entire battery current across L1, causing a proportionately boosted voltage to appear across it during the OFF periods of the T1 (induced back EMF from L1).

L1 must be appropriately calculated such that it generates the required magnitude of voltage across the shown terminals.

The indicated 200 turns is tentatively figured out and might need much tweaking for achieving the intended 220V from the input 6V battery source.

T2 is introduced for regulating the output voltage to the desired safe levels, which is 220V here.

Z1 should be therefore a 220V zener, which conducts only when  this limit is exceeded, which forces T2 to conduct and ground pin5 of the IC, stalling the frequency at pin3 to a zero voltage.

The above process continuously readjusts itself rapidly ensuring a constant 220V at the output.

The adapter which can be seen at the extreme left is employed for two reasons, first to ensure that IC1 works continuously and produces the required 220V for the connected load regardless of the mains presence (just as we have in online UPS systems), and also to ensure a charging current for the battery when mains voltage is present.

The associated TIP122 transistor is positioned to generate a regulated 7V DC for the battery and also to restrict over charging of the battery .

Need Help? Please send your queries through Comments for quick replies!


Hi Swagatam, thanks so much! What should be the amp rating of the 12 volt adapter shown in the schematic diagram?
Swagatam said…
thanks Aniruddha, since the TV modem power is 20 watt, the shown 12V adapter should be 2amp rated
Hi Swagatam, thanks again, can I use any readily available transformer in place of L1? like 6 volt
Swagatam said…
Hi Aniruddha, it'll need to be hand wound....on a ferrite rod or ring or any type of ferrite core will also do.
Raymond Michael said…
Hi sir!
I want to make this cool circuit , but I want it to power two sets of flat screen tv (150w) , two sets of dstv decoder and four energy server lamps (60w) , therefore total load will be approx. 300W, i want to use 12dcv lead acid battery insteady of 6dcv,, please tell me what to modify ,exclude charger from it. Please kindly suggest important perqmeter like transiformer turns , kind of power transistor or mosfets ; I am waiting to hear from you first before I make a move.
Notify me via nziku99@gmail.com
My regards
Raymond Michael said…
Another thing sir, is if there will be a way to make it last longer? What am I suppose to do to make it last longer, here i think it should operate even at very extremely low voltage.
Thanks again Sir
Swagatam said…
Hi Raymond, if you are interested to use only the boost circuit for achieving 300 watts, you may do so by upgrading the transistor and the coil.

although the exact parameters are not known to me, approximately speaking you can upgrade the coil by winding 5 parallel strands of 25 SWG wire over any ferrite ring or an EE core assembly.

the number of turns could be approximately equal to the voltage required at the output...and the frequency should be around 20 to 50kHz.

the shown transistor could be replaced with a IRF840 mosfet
Swagatam said…
you mean at a considerably low battery voltage?

you can tweak the coil turns so that it generates a voltage that's considerably higher than the required voltage at the output...and next set the zener diode value such that this high voltage gets regulated to the load specs at the output.

once this is done you'll find the output sustaining a constant voltage even with a considerable drop in the battery voltage.

however discharging the battery beyond a certain minimum level can be fatal for the battery.
Raymond Michael said…
I love it, i love this site, quick reply like nowhere,, keep it up bro!!!
Can i place more than one mosfet for this,it happen I have a lot of IRFP 054N here ;can i use them?
Will it manage to power even tube tv, ( which uses cathode ray tube )?
My regards
Swagatam said…
thanks Raymond, mosfets ca be put in parallel, however for 300 watt you probably wouldn't require mosfets, there are many 500V/300 watt rated mosfets available to choose from..

most DC appliances can be powered with the discussed circuit.
VIJAY AJ said…
Si can I able to convert 6v supply into a 12.5v by using this circuit. If its possible please say the components that I need to change for working this circuit to 12.5v boost from 6v.

I have one more doubt sir. For pwm we need reference voltage and carrier frequency how this single 555ic produces both frequency and reference voltagE.whether this circuit automatically boost up the voltage even my input value less than 6v and greater than 6v
Swagatam said…
Vijay, use 24 to 30 turns for L1, use TIP122 for T1, and 15V 1/2 watt for zener, rest all can be as is....

ordinary pwm does not require reference or carrier...sine wave PWM needs these parameters

boost voltage will depend on the number of turns of L1, and the zener diode value
VIJAY AJ said…
How can I vary the duty cycle by this circuit. You mentioned it as ferrite rod wound with wire will act as a magnet. Please say where I get a ferrite rod. Can I use the core of a transformer as ferrite rod
Swagatam said…
use a 100k pot for R2, it can be used for varying PWM.

you can use any ferrite based core...the shape is not crucial but use the one that can accommodate at least 30 turns of 27 SWG thick wire
VIJAY AJ said…
What happen if I change the value of capacitor from 640pf to c 104 capacitor. Shall I use รง104 instead of it
VIJAY AJ said…
Sir. Thanks for your reply . our project is based on getting a power while riding the bike with the help of small DC motor rated at 12v as per the data we collected it generates up to 6v with more than 0.6A but we used 12v battery for charging so we need to boost up the voltage for charging my 12v battery.we need a circuit that should produce more than 12.5v even if my input voltage is 6v and greater than 6v because we didn't get constantvoltage while riding the bike it has some variation depends upon speed.shall I use this circuit for our application or suggest some other circuit based on our application. If we can use this circuit say what all are the changes we want to do on the circuit for our application. Please help me sir..I am waiting for your reply
Swagatam said…
Vijay, with 0.6amps input, the boosted voltage will yield around 100 to 200mA at 12.5V....so your 12V battery should be not more than 2AH rated....moreover to operate the motor your bike engine will have to do that much extra effort and spend extra fuel on it...
Swagatam said…
the frequency needs to be above 20kHz for a ferrite trafo...so a 104 might not be correct
VIJAY AJ said…
OK sir please say what all are the changes I need to do for my application.what all are the values I need to change
Swagatam said…
No changes would be required, you can use the circuit exactly as shown in the above article, just remove the adapter stage and use the input from the desired source....use 24 to 30 turns for L1 using a moderately thin super enameled copper wire.....27SWG will do

you can wind it over a ferrite rod as shown below:

VIJAY AJ said…
OK sir. From where I can get a ferrite rod weather its available in local shop or shall I use air core inductor with 20 turns. Sir shall I use tip122 instead of t1 and 12v zener instead of z1.please help me sir. I need to clarify my doubts before purchasing the components
Swagatam said…
ferrite rod can salvaged from any old MW transistor's antenna coil

yes tip122, and a 15V zener will be OK...
VIJAY AJ said…
If it is in radio?? Say some electrical appliances like radio,TV,grinder uses ferrite rod for their operation.if u mentioned any application I will take it from old machine and use it. Sir what is the material used in transformer core.shall I use transformer core
Swagatam said…
radio is an easier option....you can see the image below


any other ferrite core will also work, though
VIJAY AJ said…
Thank you very much sir . I purchased all other components except ferrite rod soon I will get it from old radio after that I will implement it please help me sir if I have any doubt while working
Swagatam said…
sure Vijay...wish you all the best!
VIJAY AJ said…
Sir I get a ferrite rod from a old radio.now I winded a 26swg wire on a ferrite rod and I use this as inductor on a above circuit but I will get an voltage of about 0.5v as output when my input is 8v.what is the reason for that sir??. Whether my inductor works. This is the image of my inductor.
Swagatam said…
Vijay, your pic is not in the sharing mode, toggle the share button so that I can see it.

first verify that your 555 is oscillating or not.

remove the coil, and first make simple 555 flasher using an LED at pin3 as shown below,


if the LED flashes then it would confirm that your 555 is oscillating, after that you may replace the capacitor to the lower value (for increasing the frequency), and connect the coil as before and check the response again:
VIJAY AJ said…
OK sir. I will try it later.please say your email Id to share the photo with you. When I press a share button it asks the person email I'd to access the photo.
VIJAY AJ said…
Shall I use 0.01 farad capacitor in led flashing circuit
Swagatam said…
no, it will cause the flashing to be too fast and the LED will appear to be constantly glowing.... use above 1uF
Swagatam said…
it's given in the "contact" page...see at the top
ningrat_edan said…
whether this series has been tested and works fine? and whether this circuit can be used for induction motor equipment such as fans and other similar equipment
Swagatam said…
Ningrat, it is a tested design but practically it will require a lot of tweaking and optimization in order to obtain the intended results.
It can be used for any kind of load provided the parameters are correctly and optimally calculated
ningrat_edan said…
Thank you very much sir,
I think it would replace the supply 6vDC be 12VDC and add a charger automatic standby circuit this circuit will turn on when the power goes out, what do you think?
Swagatam said…
yes you can do that, it is designed to work exactly in that way
Tun said…
sir , I'm having a little problem with the above circuit. 1) after pluging in 7.5v dc battery, I only get 9.5v at the output. 2) i made use of polyester cap.(1uf=680nf) and (0.01uf), UF3003 diode inplace of BA159. Besides, I need u to show me how to replace motorola transitor with mosfet cuz i want to be sure of what i just did . 3) my inductor was made 25 SWG magnetic wire wound on a ferrite core( 332 wounds). pls sir i need u to reply me as fast as u can sir.
Swagatam said…
Tun, you must check the voltage without any load at the output.

you will also need to adjust R1, and R2 to correctly optimize the boost voltage.

initially do not connect the BC547 feedback loop until the circuit is confirmed.

for a ferrite core inductor, the frequency should be tested in between 20 and 100kHz

make sure you follow all these instructions to succeed with the design

you can also try with a lower number of turns initially and then gradually increase it and simultaneously check the output response.
Sachin said…
Sir, I have wind turbine(may be 500w to 20kw) whose output is pulsating dc, inorder to make it as a CONSTANT DC. I want SMPS BUCKBOOST converter circuit.
Please help me.
Swag said…
Please ignore my previous comment, it was accidentally sent to you... here's a link you can try out

ningrat said…
Hello, sir
the best hope for you
many circuits shared by this group really helped me, thank you very much sir, but there are some things that still bother me that i want to make a mini cfl inverter using input 3.7-5volt i really hope you can help me
Swag said…
Thank you ningrat,

CFL is now outdated, and we have much easier and efficient alternative in the form of LED, so trying a CFL circuit may not be a useful idea.

Still for your interest here's a couple of designs you can modify as per your requirement.


ningrat said…
You're right, sir, CFLs are now out of date
well if so you have a recommendation for the circuit to turn on the LED lights using a 3.7 volt voltage supply with a long flame duration
maybe a DC circuit of 3.7v to 220v AC
Swag said…
Please specify the power of the LED that you wish to use, to be precise you can simply connect 1 watt 3.3V LEDs in parallel an hook them up with 3.7V cell...that's all is needed, and yes a current control stage in the middle will also be required.
ningrat said…
I need a 3.7V mini-inverter circuit to 220v to turn on a led light bulb
Swag said…
You will need a flyback converter for this, sorry presently I do not have the design.
ningrat said…
( You will need a flyback converter for this, sorry presently I do not have the design ) it's OK Sir
Sir, can you build a circuit that reduces the voltage of 3.7 volts to 1.5 volts?
Swag said…
you can use 4 diodes in series with the 3.7V, the output will be reduced to around 1.5V.
ningrat said…
greetings sir,
I just read this article, I want to ask you a few things:
1. can I change the 6V batery input to 3.7V
2. Can I convert transistors 2n2907 to S9012 and TIP3055 to TIP41c
3. by replacing all transistors if the resistor value needs to be replaced
4. can I replace the small ferrite transformer so I make the 15 coil coil coil 0.5mm and 0.3mm 300 secondary coil (because I want to put the module in the CFL lamp to replace the damaged module)
Swag said…
Hi Ningrat, it seems like it is a tested circuit however I cannot suggest regarding its details since I have not yet gone through the design practically
ningrat said…
Thank you sir,
I will try to make the circuit by changing some components and I will share the results later
Swag said…
You are most welcome ningrat, I'll appreciate that very much
ningrat said…
I have tested this circuit, sir, by making some changes:
1. replace R 18k with trimpot
2. 3.7 volt input
3. replace transistor 2n907 with s9012 and transistor TIP3055 with TIP41c
3. 180 rounds 0.3 mm and 18 rounds 0.5 mm
with the results I got, namely: the 20watt cfl flame was not bright and the ferrite transformer sounded
maybe I will get maximum results if I add the number of primary turns because I tried a small ferrite transformer, then how to deal with the ferrite transformer that sounds
Swag said…
That's great ningrat, yes it could be due to lower number of turns across the secondary, however make sure to add a 1K fixed resistor in series with the 18 trimpot otherwise you may burn the transistors if anytime the pot adjustment accidentally reaches the extreme ground end.
ningrat said…
Hello, sir, I hope you are happy
what do you think about this circuit pack? can the ne555 ic timer work with the input voltage below 5volt?
Swag said…
Hello Ningrat, IC 555 will not work properly at 3V, unless it is a 7(555) CMOS version, it is better to go with joule thief concept for 3V operations
ningrat said…
if so can the ic ne555 be supplied using a 1.5volt to 5volt joule thief circuit?
Swag said…
that's possible, but would be an overkill...

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