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G8MNY  > TECH     16.02.19 12:00l 76 Lines 3334 Bytes #4 (0) @ WW
BID : 59333_GB7CIP
Read: GUEST
Subj: Palstar PS06 6A PSU
Path: ED1ZAC<ED1ZAC<GB7CIP
Sent: 190216/1048Z @:GB7CIP.#32.GBR.EURO #:59333 [Caterham Surrey GBR]
From: G8MNY@GB7CIP.#32.GBR.EURO
To  : TECH@WW

By G8MNY                                 (Updated May 13)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)

This is a simple design, used on this commercial PSU. It has no overvoltage or
fuse protection other than a 1A slow blow mains fuse. It does include current
limit & output foldback.

HOW IT WORKS
The bridge rectifier charges up C1 & C2 to 23V. R1 & R2 via hum decoupling C3,
puts current into Tab transistor Q3. This drives the two outputs Q6 & Q7.

The output going high powers the zener diode D2 & LED via R5. When the voltage
sample via R6, R8 & VR2 is 0.5V higher than the zener voltage Q1 turns on
removing the drive to Q3. (note a broken lead to the LED means +23V output!)

When too much current flows, Q2 will turn on as the voltage across R13 & R14
exceeds the voltage set up across R3 by current from VR1. Q2 turning on via D1
remove the drive to Q3. When the output voltage falls below the zener reference
output foldback occurs, to maintain a safe output current of about 1 amps into
a short circuit load.

      ┌───────┬───┬───┬───────────────┬───┬────┐
     / \      │   │  R1             │/    │    │
AC_/'BR1`\_AC │   │   ├─R2┬────┬────┤Q3   │    │Insulated
A~ \     / ~B │   │   │   │    │    │\e │/Q6 │/ on Heatsink
 On `\ /'     │  +│   │   │   _│_     ├─┼────┤ Q7
Heat- │       │+ ===  │   │   \_/     │ │\e  │\e
sink  │      ===  │C2 │   │  D1│     R3   │    │
      │    C1 │   │   │   │     \│    │   │    │
      │       │   │   │   │   Q2 ├────┤  R13  R14
      │       │   │   │   │    e/│    │   │    │
      │       │   │   │   │C4  └┬──┬──)───┴────┴──────┬──┬──┬─>+13.8V```
      │       │   │   │   ├┤├─┐ │  │  │         I rd E│  │  │
      │       │   │   │   │   │ R5 R6 │               │  │  │
      │       │   │   │    \│ │ │  │  │               │  │  │  Car
      │       │   │   │  Q1 ├─┴─)──┤  │               │  │ (0) Point
      │       │   │ C3│+  e/│   │  │  │               │  │ └┐
      │       │   │  ===  ├─────┘  │  │               │  │  │
      │       │   │   │  _│_       │  │               │C5│  │ @ 6A
      │       │   │   │  /_\D2    R4  R7              │ === │
      │       │   │   │  N│rd      │  │            C6 │+ │  │
      │       │   │   │  _│_       │  │              === │  │
      │       │   │   │  \_/­LED  VR2 VR1             │  │  │
      │       │   │   │  D│bk      │  │        J bk F │  │  │
      └───────┴───┴───┴───┴────────┴──┴───────────────┴──┴──┴─>0V
                      M A I N   P C B                 TERMINAL PCB

No    R          C        Q        D     VR     BR
1    680     3m3 25V   2SC1815  1N4148  10k    10A
2     1k     2m2 25V   2SC1815   6.1V    2k
3    470    100u 35V   2SD440
4    470     10n
5    1k5    220u 25V   ------
6    330     10n
7    Link
8    2k7
13   0.51
14   0.51

MODIFICATIONS
I have modified mine..
1/ Added more smoothing off PCB, 10,000uF 25V across C1.
2/ Changed C5 for a 1000uF 16V.
3/ Added a 1N4005 diode across output to protect against reverse voltage.
4/ Added a 1N4005 diode from output to input to protect against +load voltages.
5/ Changed very HOT R13 & R14 for 0.22 2.5W & readjusted VR1 for 6A max.
   Note as R7 is a 0 ohms link, so do not take VR1 to Zero ohms!


Why Don't U send an interesting bul?

73 De John, G8MNY @ GB7CIP


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