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G8MNY > TECH 31.12.07 00:14l 139 Lines 6450 Bytes #999 (0) @ WW
BID : FCHON0AR_0RC
Read: GUEST
Subj: Reactance controlled SM PSU
Path: IZ3LSV<IW2OAZ<IK2XDE<F5GOV<F1ZNR<ON0AR
Sent: 071215/2315z @:ON0AR.#AN.BEL.EU [BBS Antwerpen] OBcm1.07b3
From: G8MNY @ ON0AR.#AN.BEL.EU
To: TECH @ WW
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R:071210/0016Z @:GB7CIP.#32.GBR.EU #:38727 [Caterham] $:38727_GB7CIP
From: G8MNY@GB7CIP.#32.GBR.EU
To : TECH@WW
By G8MNY (New Dec 07)
(8 Bit ASCII Graphics use code page 437 or 850)
I came across a different type of SMPSU recently. I think it was from a mini
mainframe. it looked quite conventional at first sight until I saw the
independent output regulation per rail! How did it do that?
THE MAINS BIT
This was push pull @ 76kHz to a large ferrite transformer (600W), it had pulse
width control that seemed to just control the overall power available.
_
/~ ~\ ÄÄÄÄÄ ±±HF±± Û Isolated
| 50Hz| | 340V DC ±±±±±± Ü HF square
\_ _/ ÄÄÄÄÄ Ü waves Ú¿_Ú¿
~ _______________________ÚÄÄÄÄÄÄÄ¿
______ ³ ______ ________ ³FERRITEÃÄ
LÄFuseÄ´ ÃÂTRAC´BRIDGEÃÄ´INVERTERÃÄ´ ÃÄ isolated
MAINS ³FILTER³ÀÄRÄÄÙ³& CAPS³ ³ OUTPUTS³ ³OUTPUT ÃÄ secondary
NÄÄÄÄÄÄ´______ÃÄÄÄÄÄÄ´______ÃÄ´________ÃÄ´TRANS- ÃÄ outputs
EÄÄÄÄÄÄÄÄÄ´ 340VDC ÚÄÄÄÄÄÁÄÄÄÄ¿³FORMER ÃÄ
ÄÁÄ ³PW controlô_______ÃÄ
³ TDA1060 ³ _³_
ÀÄÄÄÄÄÄÄÄÄÄÙ
The main soothing caps (2x 1000uF & option for more off board!) are charged up
via the series mains R, & when the output starts up an isolated winding is used
to drive the mains live triac on, to short out the series mains R.
SECONDARY PCBs
There was one of these per output rail a semi-linear 24V 1A PCB, & controlled
reactance regulators for 5-7V @ 40A 2x 10-19V @ 10A, their circuits are very
strange...
ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÂÄÄÄÂÄÄ>+12V
_³_ _³_ ³ ³ 10A
76kHz AC D2 /_\ D5\_/ === ³
50V P-P ³ :::: ³ 470u³ ³
HF ÃÄÄ()))ÄÄÄÄ)ÄÄÄÄÄ´ ³1000u
Transformer _³_ L1 ³ ³ ===
Secondary D1 \_/ 22R ³ ³ D1 & 2 HF 30A types on heatsink.
ù ³ ³ ³ ³ D3 4 & 5 HF 1A types.
ÄÄÂÄÄÂÄÄÄÄÄ()))ÄÄÄÙ ³ ³ ³
_³_ ³ :::: T1 ³ ³ ³ T1 is a 1:1 ferrite ring transformer
\_/ ÀÄ´>ÃÄ()))ÄÄÄÄÄÄÄ56RÄÄÄÄ´ ³ ³ with the lower winding being light
D3³ D4 ù ³/ ³ ³ current, the phase of the windings
³ Control>ÂÄÄÄ´TIP ³ ³ is important. The top coil is rated
³ ³ ³\e NPN ³ ³ about 1/3 of the output current. L1
ÃÄ220RÄÂÄÄÄÂÄ>Op ôÃÄÄÂÁÄÄÄÄÄ´ ³ is another ring ferrite about 2x the
³+ _³_ === amps À100RÙ ³ ³ volume of T1 with the winding rated
=== /_\' ³4u7 0.01R ³ at the full output current.
³4u7 ³10v³ shunt³ ³
ÀÄÄÄÄÄÄÁÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÁÄÄÄÁÄÄ>-
Negative input swings go through T1 & D1 to L1. These tend to saturate T1 &
apply a charging current into L1. On reversal L1 discharges the stored energy
via D2 to the output capacitors, increasing the output voltage. Applying load
current increases the saturation of T1 & increases the drive to L1.
Positive input swings via D4 & T1s lower control winding & 56R are applied to
the TIP transistor's collector. So turning on the NPN will produce some current
in T1 in opposition to the saturation, e.g. de-saturating it. This allows far
more voltage to appear across T1 & thus there is less output.
This means that 2W of control power controls 200W of DC output & all done with
ferrite rings & diodes @ 76kHz.
OP AMP CONTROL
This is straight forward...
_+Output
³ Volts
³
Preset
5k Voltage Control +10V Current Limiter
³ ÚÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
3k3 1k ³ Preset
³ ³ ³\³ TIP /³ 5k
ÃÄÄÄ)ÄÄ1kÄÄÄÄ´+ \ NPN / +ÃÄ1kÄÄ¿ ³
³ ³ LF³358>ÄÄÄÂÄ1kÄÂÄ´>ÃÄÁÄ´<ÃÄ1kÄÂÄ<358³ ³ 1k
³ ÃÄÄ1kÄÂÄÄ´- / ³ ³ ³ \ -ÃÄÄÂÄÄ)Ä1kÄ´
³ _³_ === ³/³ ³ u1 ³ ³ \³ === ³ ³
3k3 /_\' u1ÀÄÄÄÄ)Ä560RÁÄ´ÃÄÙ À560RÄÄÄÄÙu1³ 150R Current
³ ³5V ³ ³ ÀÄÄ>Shunt -
ÁÄÄÄÁÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄ>0V
Voltage control is done with a sample of the output compared to a 5V reference
zener. The op amp is slowed down with CR output to -ve input to avoid HF QRM &
loop instability, but some speed up is applied to the output feed to the TI
NPN. Note that op amp high, means output low!
Current limiting is almost a mirror image using the 0V input feature of the
LF358 op amp. The more negative shunt input is taken to the negative op amp
into to produce a positive output to stop the current. The limit is set up by
applying current to the series 150R to give a small offset voltage, that equals
shunts voltage drop at the limit current.
For diagram simplicity remote sense options are not shown, but they use 100R
to extra terminals for remote sense leads, & these are connected to the
relevant voltage reference points of the circuit not the shown local output
terminals.
On the 5V one the current diode D2 is doubled up & on a larger heatsink. As 5V
is used for logic chips, there is also an overvoltage SCR crowbar.
SEMI LINEAR REGULATOR
It used a swing choke L (ferrite pot core) & RF efficient diode D2 in the
input. This reduces the voltage & increases the current available.
D1 L 28-34V _____
ÄÄÄÂÄÄÄ´>ÃÄÄÂÄÄ()))ÄÄÂÄÄÂÄÄÄÄÂÄÄÄ´78uicÃÄÂÄÄÄÂÄÄ>+24V
³ ³ :::: ³ ³ ³ ÀÄÂÄÄÂÙ ³ ³
À´ÃÄ100RÄ´ +³ ³ 1k ³ ³ 18k ³+
90V ÚÄÄÄ´ === ³ _³_ ³ ³ ³ === 47u
P-P === _³_ 100u³ ³ /_\' ³ ÀÄÄ´ ³
AC ³ /_\ 50V³ \³__³ Z1 ³ 4k7 ³
78kHz 100R ³ D2 ³ e/³ ³ ³ ³
³ ³ ³ ³ T1 ³ ³ ³
ÄÄÄÄÄÄÄÄÁÄÄÄÁÄÄÄÄÄÄÄÄÁÄÄÁÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÁÄÄÄÁÄÄÄ>0
Due to the off load peak of the choke input a shunt regulator Z1 & T1 adds a
load from 33V. The adjustable 78 regulator has inbuilt current limiting at 1A.
EFFICIENCY
Although this SMPSU seem very complex, it all runs quite cold, so I guess it is
quite efficient really.
Why don't U send an interesting bul?
73 de John G8MNY @ GB7CIP
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