inverting power supply current issue   - Page 1
Forum section: electronics / projects

author: manjunath
author_rank: Contributor
timestamp: July 24, 2014, 06:10:29 pm
content: 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.....!!!!

author: mariush
author_rank: Super Contributor
timestamp: July 24, 2014, 06:21:50 pm
content: You misread the datasheet. The chip supports a peak switch current of 1.5A, which is not equal to the output current.With 6v input, the best it can probably do is about 0.3A. To get close to 0.5A, you'll need to up the input voltage to 12v or more, or use another inverting regulator.See below, and feel free to download the mc34063 universal calculator from sourceforge to play with numbers

author: manjunath
author_rank: Contributor
timestamp: July 24, 2014, 06:35:58 pm
content: oh..!!!!can i get -5V/1A output voltage and current using mc340063A ..?? or is there any circuit u know ..??Thank you

author: mariush
author_rank: Super Contributor
timestamp: July 24, 2014, 06:56:09 pm
content: Without some "hacks" like using external mosfets, I doubt it.Something similar to mc34063 or mc33063 would be these, with switch current limit from 3A and up ... but even then you can't get -5v @ 1A from 5-6v .. for that you'd need a switcher capable of around 5A switch current, and those are expensive (think 5-10$ a piece):3.4A switch current is enough to do -5v @ 1A if you have at least 9v at the input. 3A would work with 12v and higher.ncp / ncv 3163 (3.4A but hard to solder on pcb) :http://www.digikey.com/product-detail/en/NCP3163BPWG/NCP3163BPWGOS-ND/1434719MC33166D2TG (3a) :http://www.digikey.com/product-detail/en/MC33166D2TG/MC33166D2TG-ND/1479117MC33166TG (3a)http://www.digikey.com/product-detail/en/MC33166TG/MC33166TGOS-ND/919018MC34166TG (3a) :http://www.digikey.com/product-detail/en/MC34166TG/MC34166TGOS-ND/919095MC34166TVG (3a) :http://www.digikey.com/product-detail/en/MC34166TVG/MC34166TVGOS-ND/919096MC34167TG (5A) :http://www.digikey.com/product-detail/en/MC34167TG/MC34167TGOS-ND/919097Note that the internals of these regulators are very similar to the MC34063 or MC33063 so the formulas should be similar as well and not hard to figure out. Pay attention to maximum frequency, pay attention to components... it's VERY IMPORTANT to use proper inductors and diodes (that have the parameters recommended by formulas, or better) and the whole circuit may not work on breadboards, you may have to actually put it on a pcb to work right.

author: manjunath
author_rank: Contributor
timestamp: July 24, 2014, 07:05:01 pm
content: TPS62150RGTRTPS54060AMC33063AMC34063Ai have these IC's from which one can i get -5V /1A current ..??Thank you

author: manjunath
author_rank: Contributor
timestamp: July 24, 2014, 07:07:14 pm
content: what should i have to do to get -5V/1A from mc33064A or mc34063A .... ?? please give some solution for this problem.Thank you,

author: mariush
author_rank: Super Contributor
timestamp: July 24, 2014, 07:54:12 pm
content: Magic, that's what you should have.Please understand that those chips have some limitations, a component inside can only handle that 1.5A of current.To get around that, you would need to use additional components like mosfets for example, but if you can't go and buy one of the regulators I recommended, I doubt you're going to go buy the mosfets required so why should i waste time showing you anything?