recently i was playing with some regulators and i wanted to parallel 3-4 of them so i can raise the current.. no specific reason, i was just playing...
now.. from what i know i can't parallel many of them, but i don't know why.. can somebody explain to me the reason?
Regulators don't like being paralleled because they all have slightly different output voltages. The one with the highest voltage will power the circuit at low currents, at higher currents its voltage will start to drop and one of the lower voltage regulators will kick in.
This process can result in instability, I've never tried it myself but I imagine that the voltage could drift all over the place and there's a risk of oscillation.
Just out of interest, how many did you parallel before you started having problems?
What sort of problems did you have?
Are you sure that your power sorce can handle the current?
This process can result in instability, I've never tried it myself but I imagine that the voltage could drift all over the place and there's a risk of oscillation.
Just out of interest, how many did you parallel before you started having problems?
What sort of problems did you have?
Are you sure that your power sorce can handle the current?
Regulators can be somewhat successfully paralleled if you add a small-value resistor (of a power rating that can handle the power dissipation at full current, in this case 100mA), maybe less than a few ohms. The result is that there will be a small voltage drop among the regulator outputs and all will do better at sharing the load and won't fight and get frustrated. The down side is that you end up making the overall regulation a bit softer, in that you've increased the source impedance and the percent of regulation will increase. To avoid oscillation in this configuation, try a 0.1µF cap to ground at EACH regulator output (between output and resistor) as will as the final output (common connection of all resistors).
Once you have to parallel more than two 78L05s, you might as well give up the space and use a 7805.
Did you scope it to make sure there were no instabilities? I've seen 78xx series regulators with >1Mhz oscillations even though a multimeter showed the correct output voltage.
Why not use a transistor, or several of them to "up the current"?
an old psu I made a good few years ago used an LM317 (adjustable voltage regulator) but low current I think it was 1A max? not sure it was many years ago
and a bank of 2n2222's to bring the current up to around 20A
I've lost the circuit many years ago, but the attached one gives you a basic idea to work from
... an old psu I made a good few years ago used an LM317 (adjustable voltage regulator) but low current I think it was 1A max? not sure it was many years ago
and a bank of 2n2222's to bring the current up to around 20A
parallelling with 3~4 78L05 is not a good idea to raise the current. May be all the 78l05 not the very same
voltage,may be one is 5.001V ,the other is 5.015V .when I am a sutdent.my teach tell me , We can't parallelling with voltage source with not the same voltage. you can find same other Linear Voltage Regulators at A Datasheet Search Engine for electronic designers.We also provide Pinouts,circuits.Good luck