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G8MNY > TECH 10.09.06 12:41l 112 Lines 5669 Bytes #999 (0) @ WW
BID : 45840_GB7CIP
Read: DL1LCA DL1RX DL8FBH GUEST OE7FMI
Subj: A Common High Current PSU
Path: DB0FHN<DB0FOR<DB0MRW<DK0WUE<I0TVL<LA1SFS<GB7CIP
Sent: 060910/1018Z @:GB7CIP.#32.GBR.EU #:45840 [Caterham] $:45840_GB7CIP
From: G8MNY@GB7CIP.#32.GBR.EU
To : TECH@WW
By G8MNY (Updated Apr 06)
(8 Bit ASCII Graphics use code page 437 or 850)
This is a simple (eg. reliable) common design used on commercial PSU.
eg. TRIO PS30 & ICOM PS55. Component values differ slightly between models.
HOW IT WORKS
The rectifiers charge up C1 to 25V. R3 puts some voltage on the O/P ( >1.5V ),
a fraction of this turns (pot arm) on Q2 (0.5V on Q2 base). This turns on Q1
that drives the 2 large high current power pass Transistors T1 & 2. When the
O/P voltage is >10v the zener conducts turning off Q2 as it pulls up the
emitter voltage compared to Q2's base on the VR1 pot output fraction setting.
ÚÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÂÄ2.2êÄÂÄÄÄÄÂÄÄÄÄÄÄÄÄÄ¿
³ +19-25V ³ 4m7³+ R1 +³C3 4k7 ³/e TIP
_³_ _³_ === === ÃÄÄÄÄÄÄÄ´ Driver
/_\ /_\ C4ÃÄÄÄÄÄÄÙ4m7 ³ Q1³\
³D1 ³D2 ³ +15-25V ³ ³
³ ÉÍÍÍÍ)ÍÍÍËÍÍ)ÍÍÍÑÍÍÍÍÍÍÍ)ÍÍÍÍËÍÍÍÍ)ÍÍÍÍ» 2x TO-3
³ / \ ³ º ³ ³ ³ \³ ³ ³/ Fan Cooled
AC_³_/' B1`\_³AC º ³ R3 ³ T2ÃÄÄÁÄÄ´T1 & Insulated
~ ³ \ / ~ º ³ 56ê ³ e/³ ³\e on Heatsink
³ `\ /'35A º ³ ³ ³ º º
³ º Bridge º ³ ³ ³ R8 R7
L _³_ º º ³ ³ ³ 0.05ê 0.05ê 20A
E \_/ º º ³ ÃÄÄÄÄÄÄÄ)ÄÄÄÄÊÍÍÑÍÍÍÍÍÍÊÍÑÍÍÍÑÍÍo--oÍÍÍ>+13.8V
D ³D2 º 68mF º+ ³ R6 1k8 ÃÄ¿ ³ ³ ³ @ 20A
_³_ º C1 === ³ ³ Q2³/ ³C7 _³_D3 R9 ³
D4\_/ º 25V º ³ 500<ÄÄÄ´ === '/_\10V 220ê ³+
³ º º ³ POT VR1 ³\e ³10n ³Zener ³ ===C5
390ê º º ³ ³ ÀÄÁÄÄÂÄÄÙ ³ ³4m7
³ º º ³ R5 820ê R4 120ê ³ ³
E>ÍÏÍÍÍÍÊÍÍÍÍÍÍÍÍÊÍÍÏÍÍÍÏÍÍÍÍÍÍÍÍÍÍÍÍÏÍÍÍÍÍÍÍÍÍÍÍÏÍÍÍÏÍÍÍÍÍÍÍÍ>-VE
Some of the reference numbers are repeated as components are on different PCBs.
AC
The mains transformer is a conventional (not toroidal) type 17V @ 26A (2x 13A)
for 20A rated PSU. The high pulse current AC wiring to the bridge & to the
reservoir C, are in thick & twisted wire to keep the losses & magnetic pulse
radiation down. A slow blow mains fuse of 6A is used.
PSU FEATURES
This has 2 power rails, this is because bridge rectifier & capacitor losses
under heavy load can give the driver's supply up to 1V higher. This allows for
better peak drive current when it is needed.
The 2R2 limits the drive current when C5 is exhausted allowing for higher peak
currents than the steady rating, but this current limiting is very dependent on
mains voltage! Current "Foldback" is provided with reference zener D3 fed from
the O/P. The started up current from the R3 56ê, & R9 220ê is the minimum
discharge load.
A quiet thermally switched DC cylinder fan comes in when the @ heatsink is at a
scalding 60øC.
On the ICOM, the mains is remotely switched on the rig with the same lead as
the high current DC O/P. Polarity of the lead is VERY CRITICAL, as if it is
forced to accidentally connect upside down, (not easy to do) live mains will
flow to the DC side of your Rig! (it may be safer to remotely switch neutral as
that current would be light!)
OTHER LIMITATIONS
There is no rig protection from a shorts of T1/2 pass transistors & 25V O/P
will damage your rig!
There in no mains input adjustment, & 240V is the MINIMUM needed for 20A peak
O/P.
MODIFICATIONS
I have modified mine..
1/ Heatsink added to Q1 & bolted flat to PCB location provided.
2/ Blackened main T1 & T2 heatsink so the thermal controlled fan runs less.
3/ Fused added on T1 & T2 emitters on PCB tags (13A soldered in).
4/ Proper current limiting (15A/transistor) with 2 extra PNP Transistors Q5&6.
These will also shut the PSU down if 1 of the 13A fuses blows.
Removed the 2R2 the old current limiting method, to gain more O/P current.
5/ Added an O/P overvoltage protection zener (like an SCR Crowbar).
6/ Larger O/P Cap (10mF 16V) wired across PCB O/P tags.
7/ Mains Transformer tuned (PF=1) for /P work with 1uF 250VAC.
8/ Added a fused low current O/P.
ÚÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÂÄÄÄÂÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ +18-25V ³ 4m7³+ +³4m7 4k7 ³/e TIP Driver
_³_ _³_ === === ÃÄÄÄÄÄÄÄÄÄÄÄÄÄÄ´ on a Heatsink
/_\ /_\ C4ÃÄÄÄÙC5 ³ Q1³\.
³D1 ³D2 ³ +15-25V ³ ³ 2x TO-3
³ ÉÍÍÍÍ)ÍÍÍËÍÍ)ÍÍÑÍÍÍÍÍÍÍ)ÍÍÍÍÍËÍÍÍÍÍÍÍÍÍÍ)ÍÍÍÍÍÍÍÍÍ» Mounted on
³ / \ ³ º ³ ³ ³ `\³ ³ T2³/' Blackened Fan
AC_³_/' B1`\_³AC º ³ R3 ³ T1ÃÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄ´ Cooled Heatsink
~ ³ \ / ~ º ³ 56ê ³ e/³ 1n 1n ³\e
³ `\ /'35A º ³ ³ ³ ÇÄÄÄÂÄÄÄÄ¿ ÚÄÄÄÄÂÄĶ
³ º Bridge º ³ ³ ³ º e³ === === ³e º 2A
³ º º ³ ³ ³ Fuse `\³ ³ ³ ³/' Fuse Úo-oÄÄ>+13.8V
³ º º ³ ³ ³ º Q3ÃÄÄ´ ÃÄÄ´Q4 º ³ @2A
L _³_ º º ³ ³ ³ 0.05ê ./³ 1k5 1k5 ³\. 0.05ê ³ 20A
E \_/ º º ³ ÃÄÄÄÄÄÄÄ)ÄÄÄÄÄÊÑÍÍ)ÍÍÍÍÏÍÍÍÏÍÑÍÍ)ÍÑÊÍÍÑÍÍÍÑÏÍo-oÍ>+13.8V
D ³ º 68mF º+ ³ 1k8 ÃÄ¿ ³ ³ ³ ³ ³ ³ ³+ @20A
_³_ º C1 === ³ ³ Q2³/' ³ _³_ ÀÄÄÄÄÄÄÂÄÄÄ)ÄÄÙ ³ _³_ ===
D4\_/ º 25V º ³ 500<ÄÄÄ´ === '/_\ 10v ³ ³ +³ '/_\ ³10mF
³ º º ³ POT ³\e ³10n ³ ³ R9 === ³17V³ 16V
390ê º º ³ ³ ÀÄÁÄÂÄÄÁÄÄÄÄÄÄÄÄÄÙ 220ê ³C5 ³75A³ ÚÄÄ>Earth
³ º º ³ 820ê 120ê ³ ³4mF³ ³ ³
E>ÍÏÍÍÍÍÊÍÍÍÍÍÍÍÍÊÍÍÏÍÍÏÍÍÍÍÍÍÍÍÍÍÍÏÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÏÍÍÍÍÏÍÍÍÏÍÍÍÏÍÍÍÏÍÍ>-VE
Why Don't U send an interesting bul?
73 De John, G8MNY @ GB7CIP
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