Transistor

transistors in parallel

I would strongly advise against this particular design as this design has no protection or decent regulation and the output waveform is going to be terrible and may potentially damage electrical equipment you connect it to (this is not a practical circuit you should ever use).

In fact I know the circuit would simply self-destruct if you tried to put anything close to a 500W load on the output as the TIP35C transistors are only rated up to 15A (which would give a rough circuit power rating of 180W NOT 500W with a 12V supply).

Additionally the fact that it produces dangerous voltages should not be under estimated.

Perhaps you should buy a proper inverter and try making a circuit a little less dangerous and a little more practical.

how i can convert the o/p of this ckt to sine wave form. is that possible.

No you cannot with this simple circuit design.

or send to me simple invertor ckt having capacity o/p 220vac sine wave 50Hz 500watt and i/p 12vdc

You are better off buying one, the circuit complexity and cost is just too high to build one yourself at this power level. Sine wave inverter circuits that are simple and do work are available on the web, but at much lower power levels.

Additionally you may find some simple designs available through major chip supplier websites (eg- Maxon, Texas Instruments, etc) who do their own line of integrated inverter control chips.

Usually, when paralleling transistors like the TIP35C, there is a problem of equal sharing of current and a risk of overloading one transistor to destruction. Particularly, because the hottest transistor will draw more base current and increase in current gain as it gets hotter - tending to a "thermal run-away" where it gets hotter, till it fails.

Possibly, someone worked out that with six in parallel ( about 10 amps each to get 60 amps) N.B. 60 amps x 10 volts = 600W to get 500W out, allowing transistor and transfo voltage drops etc) this will not occur.

But the Motorola TIP35C data sheet indicates the minimum current gain is about 20 at 10 amps and the 22 ohm resistor has a maximum voltage of 4.7 to keep below 1 watt rating, which gives a base drive of 0.2amp [OK, its 50%duty cycle, so make it 0.3 amp].

0.3 amp x 20 gain = 6 amps - which is far short of 60 amps.

So this looks a dodgy design.........

Unless someone left out a foot-note that each TIP35 needs its own D313 driver and resistors and you get the TIP35Cs from manufacturer xxxx, who always makes them to much better than minimum gain.

And I agree with all of JackofAllTrades comments.

So this looks a dodgy design.........

It looks like something someone designed in a computer circuit simulator class. Nothing about the circuit is practical if you tried to actually build it (and as you mention, transistor load sharing seems to have been ignored). I am not sure what is more worrying, the fact its stated rating is 500W or the fact it is called a UPS.

It can get a bit confusing for hobbyists when these impractical circuits get mixed in with practical circuits on hobby circuit websites.

Better to buy an inverter than try to build one. look here for 12vdc-220ac50hz inverters.

This person looks like there trying to build a solar power system. They have asked this similar question in another post.

hello,

you can easily connect the 6 transistor in parallel by connecting all the 6 collector and all the 6 emitter together and base terminal of all transistor is to connected common or according to your need.

by connecting transistor in parallel basically you can increase the current capability or form basically a transistor with higher current capacity because current is divided into all the transistor and current capacity is going to increase

you can easily connect the 6 transistor in parallel by connecting all the 6 collector and all the 6 emitter together and base terminal of all transistor is to connected common or according to your need.

It isn't that easy as transistors by their very nature are active devices with differing gains and characteristics and they will not share the current equally without careful attention to the current sharing and balancing circuitry that has to be included in such a design (even with carefully matched transistor batch sets).

Even then it may not work (I have heard of good theoretical designs carefully planned out on paper failing when they were put into use in actual products).

Think of it as trying to power a load by connecting multiple 12V batteries in parallel.

Wherever possible I try and limit my product designs to a single large transistor, MOSFET, SCR or similar rather than multiple small ones. Keep it simple, keep it reliable, keep the customer happy.

Heed the warning by "Jack of All Trades" or will apply. Did you read post #3 ????

you can simply connect transistor like this all collector are common and all the emitter are common and rectangle is the load which where you want to connect