Dear sir,
1)I found this circuit on web, TIP36C and TIP35C is going to do current boosting. Whether the 0.1 ohm /5W resistance should be in collector or emitter terminal?(to share equal current in all transistor)
2) D2 and D3 are 1 amp diode but RPS supplies up to 10 amps of current. Is it correct to use 1AMP diode?
3) Whether current limiting function of LM317 will happen when current drawn by base of TIP35C's exceed at 2.2Amps?
Thank you
To understand how this circuit works and answer those questions it would help a lot to do a simulation that's what simulators are made for. They help understand what happens and what could happen when things vary during the actual operation of the circuit.
Without doing a simulation here are some ideas.
[1] It's a little difficult to say if the 0.1 Ohm resistors would work better in the emitters than in the collectors, but there does seem to be a strong possibility that idea would make the circuit work better. For one, the collectors act more like constant currents which means the resistors will not do as much, and also if moved to the emitters a little more voltage drop in the emitter circuits may allow the smaller transistor to work better for limiting the total output current because that would loosen up the saturation voltage requirement of the smaller transistor.
A more easily noticed problem though is the rating of the 0.06 Ohm resistors. 5 watts isnt enough because at some point they could be working too close to that power level. 10 watts (or even higher) would be better, and with free air flow all around.
[2]
Yes, I would say those two diodes should be at least of the 1N5400 series which are 3 amp diodes not 1 amp diodes. The higher the rating the better as they are for reverse polarity protection against an external active load like a battery. With the 1N5400 series, the protection relies partly on the behavior of the diode when it blows out. They are banking on it shorting out. If it happens to open up, the protection is lost.
There are better ways to do this too but they are more complicated. For example, the higher power diodes plus a series fuse. If a reversed active load is connected to the output and the diode conducts, the fuse blows, and the load is disconnected.
[3]
The current to the base of the larger transistors is hard to predict exactly, but if we estimate using a minimum beta of 10 and with the LM317 drawing 1 amp, that means each base current is about 0.3 amps, ideally. The problem then seems to be that R1 is not the right value if the goal is to get 10 amps out of the output of this circuit. With the emitters drawing 1 amp and the LM317 drawing 1 amp, we would want about 1.4 volts drop, which would mean we would need a resistor of about 0.7 Ohms. This wouldn't be too much different if the LM317 was drawing 1.5 amps as then the emitters would be drawing less, but the total current might be around 2 amps again. Obviously 2 amps through a 2 Ohm resistor is 4 volts, so the current limit would kick in too soon and limit the current to less than 10 amps, probably a lot less.
This means R1 value would have to be decreased. If it was 0.7 Ohms and with 2 amps through it, the power would be 2.8 watts, so a minimum of 5 watts would be a good starting point for the power rating of that resistor, with free air flow.
These ideas should be verified with a simulation. This circuit isn't too complicated so it's not hard to use with a simulator. I might try this myself if I get a chance later today or tomorrow morning. I'll update with any additional info I might find out.
However, because of the more obvious problems lurking here and there in this circuit, I would study it out carefully before building a prototype. A simulator would help a lot, followed by a bench test. One of the things to pay attention to is the power dissipation in the transistors as well as the resistors. I'd check every resistor power rating to make sure it can handle the required power. I do not see any way around using somewhat larger heatsinks either for the transistors, and one for each LM3xx device.
Linear power supplies are great for use for short term testing of other circuits and devices. Not as good for long term use as they eat up too much energy in most cases.
This idea should be studied in more depth with a simulation.