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G8MNY > TECH 26.05.07 19:24l 95 Lines 4237 Bytes #999 (0) @ WW
BID : 16134_GB7CIP
Read: GUEST OE7FMI
Subj: 12V Switch Mode Adaptors
Path: DB0FHN<DB0MRW<DK0WUE<SV1CMG<F6KMO<ON0AR<GB7CIP
Sent: 070526/1745Z @:GB7CIP.#32.GBR.EU #:16134 [Caterham] $:16134_GB7CIP
From: G8MNY@GB7CIP.#32.GBR.EU
To : TECH@WW
By G8MNY (New Feb 07)
(8 Bit ASCII Graphics use code page 437 or 850)
12V adapters for your Walkman, Mobile Phone, PDA, Digital Camera etc. are often
based on the many versions of the 1.5A 34063 8 pin DIL switch mode regulator IC
in this circuit using several PCB layouts in different sized plugs adaptors..
12V Fuse
CarÄÄÄo-oÄÂÄÄÄÄÄÄÄÄÄÂÄÄ¿ ÚÄÄÄÄÄÄÄÄÂÄÄÄÄÂÄÄÄÄÂÄÄÄÄÄ>+ to gadget
Plug ³+ R1 ³ R2 ||C ³ ³
C1=== ³ ³ ³ ||C L1 ³ _³_
47uF³ ÚÄÄÄÂÄÄ´ ³ ÃÄÄÄ¿ ||C ³ \_/==
³ ³ 8ÚÁÄÄÁÄÄÁÄÄÁ¿5 R3 ³ ³+ ³LED
³ ³ ³ K34063 ³ ³ ³ === ³
³ ³ 1ÀÂÄÄÂÄÄÂÄÄÂÙ4 ³ ³ ³C3 ³
³ ÀÄÄÄÙ ÀÄÄ)ÄÄ)ÄÄÄ>ÄÄÄÄ´ ³ R4
³ ³ ³ ³ _³_ ³ ³
³ C2=== ³ ³ /_\D1 ³ ³
gnd ³ ³ ³ ³ ³ ³ ³
gndÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÄÁÄÄÁÄÄÄÁÄÄÄÄÁÄÄÄÄÁÄÄÄÄÁÄÄÄÄÄ>- to gadget
Typical values
R C D Fuse IC PIN Function
1 2 - 4.7R 47uF 1N4001 2A 178 Current drain & sence-
2 1 - 4k7 n47 - 1n 2 Switched Output
3 560 - 1k 4u7 - 220u 3 Osc Timing C
4 560 - 1k 4 Gound
5 Voltage NFB
6 Current limit +ref
R2/3 sets the output voltage.
R1 sets the switching current limit.
Output cap C3 has ripple on it due to pulse currents. These give this sort of
spiky ripple..
³ ³
³_ ³_ Due to the small capacitor value. its self inductance & ESR
³ ~-_³ ~-_ you always get this waveform with the sharp rise QRM edge.
Problems with this simple circuit are:-
1/ no output over voltage protection. (important on costly gadgets!)
2/ no input idiot diode.
3/ high output ripple & QRM?
4/ high input ripple & QRM?
5/ direct QRM radiation from L1 if bobbin type.
6/ too high a fuse rating?
7/ only 1 ground spring connected in car plug.
IMPROVEMENTS
If you have space in the plug in, try some of these embellishments...
12V Fuse __
CarÄÄo-oÄÂÄccccÄÄÄÂÄÄÄÄÄÄÄÄÂÄÄ¿ ÚÄÄÄÄÄÄÄÂÄÄÄÂÄÄÄÂÄÄcccccÄÂÄÄÂÄÄÄÄ>+ to gadget
Plug ³ ==== ³+ R1 ³ R2 ||C ³ ³ ==== ³ ³ ~~
³ L2 === ³ ³ ³ ||CL1 ³ _³_ L3 ³ ³ FB
³ C1³ ÚÄÄÂÄÄ´ ³ ÃÄÄÄ¿ ||C ³ \_/== ³ ³
_³_ ³ ³8ÚÁÄÄÁÄÄÁÄÄÁ¿5 R3 ³ ³+ ³LED +³ ³
/_\ ³ ³ ³ K34063 ³ ³ ³ === ³ C4=== ³
D2³ ³ ³1ÀÂÄÄÂÄÄÂÄÄÂÙ4 ³ ³ C3³ ³ ³ ³D3
³ ³ ÀÄÄÙ ÀÄÄ)ÄÄ)ÄÄÄ>ÄÄÄ´ ³ R4 ³ _³_
³ ³ ³ ³ ³ _³_ ³ ³ ³ /_\'
³ ³ C2=== ³ ³ /_\ ³ ³ ³ ³ FB
gndÄÄ¿ ³ ³ ³ ³ ³ ³ ³ ³ ³ ³ __
gndÄÄÁÄÄÄÁÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÁÄÄÁÄÄÄÁÄÄÄÁÄÄÄÁÄÄÄÁÄÄÄÄÄÄÄÄÁÄÄÁÄÄÄÄ>- to gadget
~~
Typical values
No. R C D Fuse
1 1R8 - 4R7 47uF 1N4001 1A
2 1 - 4k7 n47 - 1n 1N4001
3 560 - 1k 220uF Zener
4 560 - 1k 100uF
MODS
1/ Add an output zener just a bit higher than the no load voltage.
2/ Add input idiot & back EMF diode D2.
3a/ Add series L3 of a few turns on a ferrite 6mm bead feeding new C4.
3b/ Add 2 ferrite beads on the output leads.
4/ Add series input L2, several turns on a 6mm ferrite bead.
5/ If L1 is bobbin, try a ferrite ring & listern to MW QRM for comparison.
6/ Change the fuse to one just higher than the maximum drain.
7/ Tin & wire up the 2nd plug earth spring.
After you have done these mods, & carefully put it back together, tested it
(not on your gadget at first!). If it is working OK, you should find the
adaptor is much safer than before on your precious gadget. And any nearby QRM
is much reduced, as is the possibility of malfunction in an RFI environment.
Why don't U send an interesting bul?
73 de John G8MNY @ GB7CIP
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