MC34063 DC-DC high current Stepup Converter

S

Sean Lincolne

Guest
Has anyone built a DC-DC Converter using the Motorola MC34063 with
current outputs higher than 1.5A ?

I'm considering building a DC-DC converter for a laptop computer
to boost 12VDC (ie in car) to 20VDC, capable of supplying in excess
of 50 watts (ie 2.5A to 3.0A).

The sample circuits in the application note mention 1.5A.

I'm specifically interested in the MC34063 because it's easy to get
locally (you can buy them over the counter at Jaycar).

Also, can anyone suggest areas to keep an eye on, such as capacitor
selection and inductor construction ?

Thanks,

Sean
 
In article <pan.2003.07.27.11.09.48.45336.1842@seanstoy.com>, usenet01
@seanstoy.com says...
Has anyone built a DC-DC Converter using the Motorola MC34063 with
current outputs higher than 1.5A ?

I'm considering building a DC-DC converter for a laptop computer
to boost 12VDC (ie in car) to 20VDC, capable of supplying in excess
of 50 watts (ie 2.5A to 3.0A).

The sample circuits in the application note mention 1.5A.

I'm specifically interested in the MC34063 because it's easy to get
locally (you can buy them over the counter at Jaycar).

Also, can anyone suggest areas to keep an eye on, such as capacitor
selection and inductor construction ?
Click to expand...
ETI did an inverter a few years ago, 200 watts, just uses common
transistor components - if they are still available (ETI 1509)
 
Havn't used this one, but the app note has the schematic for higher than 1.5A
out. I've used the regs in the 5 pin TO220 package. Just order then from
OnSemi as samples. These can do 3 amps or 6 amp with two in parallel, provided
your inductor dosn't saturate.


Has anyone built a DC-DC Converter using the Motorola MC34063 with
current outputs higher than 1.5A ?

I'm considering building a DC-DC converter for a laptop computer
to boost 12VDC (ie in car) to 20VDC, capable of supplying in excess
of 50 watts (ie 2.5A to 3.0A).

The sample circuits in the application note mention 1.5A.

I'm specifically interested in the MC34063 because it's easy to get
locally (you can buy them over the counter at Jaycar).

Also, can anyone suggest areas to keep an eye on, such as capacitor
selection and inductor construction ?

Thanks,

Sean
Click to expand...
 
On Sun, 27 Jul 2003 11:09:52 +1000, Sean Lincolne
<usenet01@seanstoy.com> wrote:

Has anyone built a DC-DC Converter using the Motorola MC34063 with
current outputs higher than 1.5A ?

I'm considering building a DC-DC converter for a laptop computer
to boost 12VDC (ie in car) to 20VDC, capable of supplying in excess
of 50 watts (ie 2.5A to 3.0A).

The sample circuits in the application note mention 1.5A.

I'm specifically interested in the MC34063 because it's easy to get
locally (you can buy them over the counter at Jaycar).

Also, can anyone suggest areas to keep an eye on, such as capacitor
selection and inductor construction ?
Click to expand...
I did one based largely on the SLA charger design in SC way back. One
problem I have is inordinately high ripple at some load levels. Part
of the problem is that although the "on" pulses are ~30kHz say, the
actual regulation "envelope" is at several hundred Hz or lower. Errk
- that doesn't sound easy to follow, I'll try again.

The oscillator runs at say 30k. The comparator switches the osc to
the output switch at a rate determined by feedback voltage dynamics,
and can be much lower. As a result, filter calcualtions based on the
30khz rate are a nonsense.

My version delivers up to 3A at 18V for a laptop.

If you do follow the SC design, use Schottky diodes instead of the
original fast recovery types - the heat dissipation in both the FET
switch and the diodes will drop dramatically.
 
Hi,
See the article a few months ago in Silicon chip for a step up converter
using the MC34063.
Oatley electronics had a kit using the same chip which they recently changed
to a newer version
(Not sure if it still uses same chip.)
As you go up in power you need higher current Schottky diodes etc which get
harder to get and get expensive.The oatley kit costs only about $20 which is
what two high power schottky diodes cost me when I designed one .....Not
worth building from scratch...try the Oatley kit
Cheers George....

"Sean Lincolne" <usenet01@seanstoy.com> wrote in message
news:pan.2003.07.27.11.09.48.45336.1842@seanstoy.com...
Has anyone built a DC-DC Converter using the Motorola MC34063 with
current outputs higher than 1.5A ?

I'm considering building a DC-DC converter for a laptop computer
to boost 12VDC (ie in car) to 20VDC, capable of supplying in excess
of 50 watts (ie 2.5A to 3.0A).

The sample circuits in the application note mention 1.5A.

I'm specifically interested in the MC34063 because it's easy to get
locally (you can buy them over the counter at Jaycar).

Also, can anyone suggest areas to keep an eye on, such as capacitor
selection and inductor construction ?

Thanks,

Sean
Click to expand...
 
On Sun, 27 Jul 2003 11:09:52 +1000, Sean Lincolne
<usenet01@seanstoy.com> wrote:

Has anyone built a DC-DC Converter using the Motorola MC34063 with
current outputs higher than 1.5A ?

I'm considering building a DC-DC converter for a laptop computer
to boost 12VDC (ie in car) to 20VDC, capable of supplying in excess
of 50 watts (ie 2.5A to 3.0A).

The sample circuits in the application note mention 1.5A.

I'm specifically interested in the MC34063 because it's easy to get
locally (you can buy them over the counter at Jaycar).

Also, can anyone suggest areas to keep an eye on, such as capacitor
selection and inductor construction ?

Thanks,

Sean
Click to expand...

Check out the June 2003 issue of Silicon Chip mag - page 68 - "DC-DC
Converter for cars" - it only goes up to 2A output but you can
increase this to 3.5A (suitable for IBM Laptops) just but doubling up
on the input & output capacitors AND the D1 & D3 power diodes - all
the resst of the circuit remains the same.

HTH.

Oz Rod
 
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