inverting power supply current issue

[manju_gowda]

Hi all ,
I am using mc330063A IC to get negative power supply of -5V and also i need 1A of current , the respective circuit that i am using is in attachment , in this circuit i am getting -5V but if i insert any load resistance above below 500 ohms , the -5V getting decreases to -1.2V. Here i need atleast 0.5A of current . According to datasheet it supports upto 1.5A. Can anyone help me out to get 1A of current out of this circuit.


Thank you.....!!!!

 

[alec_t]

According to the equation given there, the output voltage should be -1.25 x (1+0.33) = -1.66. Yet it's shown as -12V . Even if you swap the R1/R2 values there's something not quite right!

 

[manju_gowda]

sorry i forgot to edit some now see image

 

[dr pepper]

Looks as though it shoudl work to me, I suspect that the inductor you are using is going into saturation, the dc current rating of the inductor needs to be at least 2 amps.
Also the type of core you are using needs to be considered, theres no point in using a iron powder core at high freq's.

 

[manju_gowda]

i have used assemble inductor okay i will try by using core inductor and update u soon.

 

[manju_gowda]

thanks bro itz working i tested using core inductor and i can able to get -5V /1A .


Thank you.

 

[dr pepper]

Excellent, glad I helped.

You can if you put a low value resistor in series with the inductor (around 0.1r) use a 'scope to monitor the current with the probe and ground across the resistor, the trace should rise linearly, if it rises linearly but then suddenly increases on the scope then its going into saturation.