I'm trying to get 19V / 3.5A supply From 12V battey,
I made a boost converter circuit using mc34063 ic,
The simulation of the circuit was perfect and I got 19V/3.7A as output,
This is my circuit
But the problem was in real time … I made it but i couldn't get more than 600mA,
I think there is two possibilities for that failure
- Maybe R1 value .. Because I couldn't get a small resistance with
value of 0.07ohm so I replaced with a wire - Or the inductor L1 which i used have a considered resistance
Please help me .. What is the problem and how to solve it
Best Answer
If the wire shorting out R1 is less than 0.07 ohms, that defeats the current limit function and should not be the source of the problem described.
The peak current through the inductor would be around 3 times the output current. That would be 10.5A. You need an inductor with saturation current rating higher than that. An undersized inductor could be a source of your problem.
In your schematic, there is nothing at the base Q1 to turn off the transistor. That is definitely an issue. The simplest thing you can put there is a resistor to ground.
I am curious on what do you use to simulate the circuit and where do you get the MC34063 simulation model. Also, I wonder why doesn't the simulation catch the lack of turn off on Q1.
The 180uH 10.5A saturation inductor is quite big. You can try to reduce its size by increasing the switching frequency and therefore reducing the inductance required.