power supply schematic - Page 1
Forum section: electronics / beginners

author: glinjik
author_rank: Regular Contributor
timestamp: March 21, 2022, 10:05:29 am
content: hi was wondering on thoughts of this power supply i dont see any big filter caps on the input or output will this give massive ripple? and replacing the bc transistors with either 2n series or c945/a733

author: Gyro
author_rank: Super Contributor
timestamp: March 21, 2022, 10:28:20 am
content: The schematic doesn't include the transformer, bridge rectifier etc,... and substantial input reservoir capacitor. I recognise the style of the schematic as being from an old Elektor magazine. With a bit of detective work, you should be able to track down the original article from the WorldRadioHistory archive...https://worldradiohistory.com/Elektor.htm

author: glinjik
author_rank: Regular Contributor
timestamp: March 21, 2022, 10:44:36 am
content: it seems that site along with a host of others is blocked to me at the moment

author: Zero999
author_rank: Super Contributor
timestamp: March 21, 2022, 11:43:49 am
content: Quote from: glinjik on March 21, 2022, 10:44:36 amIt's pathetic. Use a proxy server to access it.Regarding the original schematic: it looks reasonable. T5 & T6 aren't matched, so don't expect great regulation/ripple rejection.

author: strawberry
author_rank: Super Contributor
timestamp: March 21, 2022, 12:07:53 pm
content: R7 : replace with current source to reduce ripple

author: Zero999
author_rank: Super Contributor
timestamp: March 21, 2022, 10:31:17 pm
content: You can improve the circuit by using a matched pair, such as the DMMT5401 for T5 & T6.https://www.diodes.com/assets/Datasheets/ds30437.pdf

author: not1xor1
author_rank: Frequent Contributor
timestamp: March 22, 2022, 07:30:35 am
content: Quote from: Zero999 on March 21, 2022, 11:43:49 amIt isn't reasonable at all. C2 makes transient response just ludicrous. That schematic diagram was discussed here several years ago.I don't remember the details and haven't got time to re-read the old thread at the moment.In any case here it is (just scroll down):https://www.eevblog.com/forum/beginners/discrete-regulated-power-supply/

author: m3vuv
author_rank: Super Contributor
timestamp: March 22, 2022, 10:47:10 am
content: better use an lm 723 design if you ask me,loads around!.

author: MathWizard
author_rank: Super Contributor
timestamp: March 24, 2022, 03:54:13 pm
content: OP what did u plan on using it for ? There's lot's of stuff a little circuit like this could be fine for, and if something goes wrong, it's easy to see and fix.

author: BeBuLamar
author_rank: Super Contributor
timestamp: March 24, 2022, 05:40:46 pm
content: It appears that the schematic is for the regulation circuit only and it assumes that you already have a non regulated power supply with sufficient filter capacitor which can supply a nominal 40VDC.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: March 25, 2022, 12:21:09 am
content: I really liked the L200.Very much like the LM317, but with some extra pins for an adjustable current limit.Elektor has also once shown a schematic for the L200 in which the voltage over the current shunt was amplified before feedback, which made it easy to make the current limit adjustable with a potentiometer. Unfortunately it never became very popular and is therefore relatively expensive (around EUR 4).The good ol' 723 is also still something to consider.Discrete circuits like this are more like a curiosity, and to learn how transistors work (either with spice, analyzing in your head, or building it for real and measuring)