I'm using following circuit for a boost converter using MC34063A IC.
The circuit is designed for 24 V, 250 mA output. The simulation works fine but the actual circuit on a PCB behaves weirdly. In case of no load I get the very high output of 43 V which doesn't change even if I change the value of potentiometer (R45). This is, I think, the no load behavior of a boost converter, we need a minimum load, so this makes sense. So if I put a load of 1 kohm, the output drops to 25-29 volts, over the complete range of potentiometer(R45). Now if use a load of ~150 ohms (160 mA at 24 V), the output drops to ~16.8 V and doesn't change by changing the value of R45. What could be the issue here?
Similarly, I use following circuit for a buck converter, designed for a 3.3 V, 100 mA output. With 7 V input the converter works fine, but with 5 V input the voltage drops to 2.9 V, and doesn't go to 3.3 V at any value of potentiometer.