MC34063 Inductor query

Krunal Patel

Prodigy 80 points

Hi everyone here...

I want to design a buck DC/DC converter using MC34063.

My basic required pararmeter are:

Input voltage: 24 Volt

Output Vol: 12 Volt

Maximum Output current : 700mA.

I have refere the application circuit given in the datasheet of Mc34063.

I have a query regarding the design.

If I use 1 Mili Henry Inductor instead of 220 Micro henry value then How does it affect the circuit performance?

And for 700mA current, 1N5819 Diode at output pin will suffice the circuit requirement.?

Thanks n Regards.

Krunal.

over 14 years ago

0 Ron Michallick over 14 years ago

TI__Guru**** 164976 points

Hello Krunal,

The formulas give a minimum inductance. It is acceptable to increase the inductance.
Doing so will decrease the inductive ripple current. The cross over from discontinuous to continuous will occur at a lower current level. Both effects are generally considered good.

The diode is good enough for normal operation, but a output load fault could stress the diode beyond the recemmemded range.

Regards,
Ron Michallick

0 Krunal Patel over 14 years ago in reply to Ron Michallick

Prodigy 80 points

Hi Ron Michallick,

thanks a lot for such a quick response.

I have tried last night with 1Mili Henry inductor and ss14 Diode for output current 250 mA.

It works very well, I think.

Before that trial I had also tried with 220Micro Henry, but 220micro henry Inductor got heated upto certain extent

Both inductor have same physical diemension ,but I think 220Micro Henry inductor would be of lesser current capacity causing the inductor heat up at 250mA output current.

By the way, I am using simple axial type inductor ( like simple DIP resistor).

Regards.

Krunal.