Using a RomanBlack Two Transistor Regulator..

I am thinking of trying Roman Black's "Two Transistor Black Regulator"
to regulate 24VDC input to 5VDC-500mA output.

The website, http://www.romanblack.com/smps.htm , mentions

"
If you want to use the Black Regulator for high voltage circuits I
suggest the following:
* Make sure Vce of Q1 and Q2 are rated 50% higher than input voltage
* D1 must be Vr rated at 50% higher than input voltage that means
a schottky won't do. For efficiency try a 1N4937, 600v 1A fast diode
* Use a Darlington for Q1, so you can use a high value resistor for
R2 to keep R2 dissipation low
* Increase RZ, as Q2 base current is less with a Darlington Q1
* Reduce C1 and C2 as RZ was increased
* A resistor in series with C2 may be needed
* Retuning of the C1:C2 ratio will be needed
* R1 and RZ may need to be 1/5w or 1w types - check
* Use a fuse on circuit input! Failure of Q1 may cause smoke! )
"

The above suggestion is over my head, so I'm thinking of using two
"Black Regulator"s, one to drop from 24V to 12V then another to drop
from 12V to 5V. Would this work?? It sounds like it would still be
much less expensive then to use a switcher..

Steve

 

[snip]

The Black regulator is kind of quirky. You will have better success if
you use a switching PS chip with a couple transistors or power FETs.
See Maxim or Linear for a great chip selection.

 

-I am thinking of trying Roman Black's "Two Transistor Black Regulator"
-to regulate 24VDC input to 5VDC-500mA output.
-
-The website, http://www.romanblack.com/smps.htm , mentions
-
-"
-If you want to use the Black Regulator for high voltage circuits I
-suggest the following:
-* Make sure Vce of Q1 and Q2 are rated 50% higher than input voltage
-* D1 must be Vr rated at 50% higher than input voltage that means
- a schottky won't do. For efficiency try a 1N4937, 600v 1A fast diode
-* Use a Darlington for Q1, so you can use a high value resistor for
- R2 to keep R2 dissipation low
-* Increase RZ, as Q2 base current is less with a Darlington Q1
-* Reduce C1 and C2 as RZ was increased
-* A resistor in series with C2 may be needed
-* Retuning of the C1:C2 ratio will be needed
-* R1 and RZ may need to be 1/5w or 1w types - check
-* Use a fuse on circuit input! Failure of Q1 may cause smoke! )

High voltage in this case is something like dropping 120VDC down to 5VDC.
It'll probably work as advertised for 24VDC in.

-"
-
-The above suggestion is over my head, so I'm thinking of using two
-"Black Regulator"s, one to drop from 24V to 12V then another to drop
-from 12V to 5V. Would this work?? It sounds like it would still be
-much less expensive then to use a switcher..

How many do you need to make. If it's a single, then cost really isn't an
issue and you should simply get something like a LM2574 Simple Switcher
which will work directly.

BAJ