• A Common UA723 PSU

    From G8MNY@21:5/101 to TECH on Tue Jul 2 05:20:05 2019
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    From g8mny%gb7cip.#32.gbr.euro@n2nov.ampr.org Tue Jul 2 04:11:26 2019 Received: from n2nov.ampr.org by n2nov.ampr.org ([JNOS]) with SMTP
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    From: g8mny@gb7cip.#32.gbr.euro
    X-JNOS-User-Port: Circuit (CIPOUT:GB7CIP-13 GB7CIP) -> Sending message

    From: G8MNY@GB7CIP.#32.GBR.EURO
    To : TECH@WW

    By G8MNY (Updated Apr 09)
    (8 Bit ASCII graphics use code page 437 or 850, Terminal Font)

    This is a common design used by several makers both 13V & 27V models etc.

    AC
    The mains is wired straight to the conventional transformer either 17V @ 6A or 30V 3A, for these 2 types.

    13.5V 4A NEC Version ┌─┤<├─┐ F2
    ┌───┬───┬──┬──┬────────────────┬┴┐ D7┌┴┬R11┬──────────o-o──┬───┬──┬─>+VE
    D2│ │D3 │ │ _│_ T1 │/ │ e│ │ │ │ │ │
    _│_ _│_ │ │ \_/D5 ┌─┤ _\_/_ │ │ R9 │ │
    /_\ /_\ │ │ │ │ │\e T2│ │ │ │ │ │
    F1 │ │ +│ │ ├──────┐ │ └───┴─R7┤ │ R8 │ │ ─o-o─)───┤ === │+ │ │ ├──────R4───┤ │ │ │ │
    ~____│ │ C1│ === │ │ │C5┌┤├┐ │ │ ├┤├─┤ │ ~│D1_│_ _│_ │C2│ │ ├──┐ │ │ ├─────)───)───────────┬───┤C10│ │
    │ /_\ /_\ │ │ │ 12│11│10│13│ 4│ │ │ │ │ +│ │
    _│_ │ │D4 │ │ │ ┌┴──┴──┴──┴──┴┐ R5 │ │ │ === │
    \_/ │ │ │ │ +│ │ IC1 │ │ │ │ │ C7│ │
    │D10│ │ │ │ === └┬──┬──┬──┬──┬┘ │ │ │ │ │ _│_
    _│_ │ │ │ │C3│ 6│ 5│ 7│ 2│ 3└─────)───┘ │ R10 │ /_\
    \_/ │ │ │ │ │ │ │ │ │ │ _│_ │ │ │D8
    │LED│ │ │ │ │ R3 │ │ └────────┤ /_\ │ │ │
    │ │ │ │ │ │ └──┤ │ │ │D13│ │ │
    R1 │ │ │ │ │ === │ R6 │ │ │ │
    │ │ │ │ │ │ C4│ │ │ │ │ │ │
    └───┴───┴───┴──┴──┴─────────┴──┴───────────┴───────────────┴───┴───┴──┴─>-VE No Resistor Capacitor Diode Transistor Fuse ICs
    1 1k 2200uF 40V 8A TIP31 6A uA723
    2 2200uF 40V 8A 2N3055 6A
    3 4k7 100uF 40V 8A
    4 1k 0.1uF 16V 8A
    5 680 1nF 1N4001
    6 8k2
    7 100 1N4001
    8 33 8A
    9 4k7 Preset
    10 6k8 1N4001
    11 0.33
    13 1N4147

    27V 2A RS Version ┌─┤<├─┐ F2
    ┌───┬───┬──┬──┬────────────────┬┴┐ D7┌┴┬R11┬────┬───┬─o-o──┬───┬──┬─>+VE
    D2│ │D3 │ │ _│_ T1 │/ │ e│ │ │ │ R12 │ │ │
    _│_ _│_ │ │ \_/D5 ┌─┤ _\_/_ │ │ e\│ │ R9 │ │
    /_\ /_\ │ │ ├──R17─┐ │ │\e T2│ │ │ T3├─┤ │ │ │
    F1 │ │ +│ │ │ │/ │ └───┴─R7┤ │ /│ │ R8 │ │ ─o-o─)───┤ === │+ ├R2┬─┤T4 ├──────R4───┤ │ │ │ │ │ │
    ~____│ │ C1│ === │ │ │\e │C5┌┤├┐ │ │ │ │ ├┤├─┤ │ ~│D1_│_ _│_ │C2│ │ │ ├──┐ │ │ ├─────)───)────)───)──┬───┤C10│ │
    │ /_\ /_\ │ │ │ │ 12│11│10│13│ 4│ │ │ │ │ │ │ +│ │
    _│_ │ │D4 │ │ │ │ ┌┴──┴──┴──┴──┴┐ R5 │ │ R13 │ │ === │
    \_/ │ │ │ │ +│ │ │ IC1 │ │ │ R14 │ │ │ C7│ │
    │D10│ │ │ │ === │ └┬──┬──┬──┬──┬┘ │ │ │ _│_ │ │ │ _│_
    _│_ │ │ │ │C3│ │ 6│ 5│ 7│ 2│ 3└─────)───┤ │ '/_\ │ R10 │ /_\
    \_/ │ │ │ │ │ │ │ │ │ │ │ _│_ │ D9│ _│_ │ │ │D8
    │LED│ │ │ │ │ _│_ R3 │ │ └────────┤ \_/CR1│ │ /_\ │ │ │
    │ │ │ │ │ │'/_\ └──┤ │ │ │\___│ │ │D13│ │ │
    R1 │ │ │ │ │ │D11 === │ R6 │+│C9│ │ │ │ │ │
    │ │ │ │ │ │ │ C4│ │ │ │=== R15 │ │ │ │ │
    └───┴───┴───┴──┴──┴──┴──────┴──┴───────────┴───┴─┴──┴───┴──┴───┴───┴──┴─>-VE No Resistor Capacitor Diode Transistor Fuse ICs CR
    1 2k2 1000uF 63V 8A TIP31 3A uA723 TAB SCR
    2 2k2 1000uF 63V 8A 2N3055 3A
    3 3k9 47uF 63V 8A PNP
    4 1k 0.1uF 16V 8A NPN
    5 680 1nF 1N4001
    6 15k
    7 100 47uF 40V
    8 6k2 8A
    9 4k7 Preset 47uF 30V Zener
    10 3k3 1N4001
    11 0.68 36V Zener
    12 1k
    13 1k 1N4147
    14 1k
    15 1k
    17 100

    HOW THEY WORKS
    The 4 rectifiers D1-4 charge up C1/2. D5 puts voltage onto the IC (via 36V reg D11/T4 on 27V model). The attenuated R8/R9/R10 output voltage on pin 4 is compared to the internal 7V reference pin 6, fed back into pin 5, & drive on pin 10 turns on T1 & heatsinked T2. Output current is the voltage across R11 & the control loop goes into current limit mode when this is greater than the DC set up across R5 by R6.
    Diode D7 ensures the output voltage is not higher than the input, Diode D8 protects the circuit from reverse current.
    On the higher voltage model also has crowbar where if a 30V is exceeded T3 is turned on firing the SCR to short the PSU.

    PSU FAILINGS
    There is a high overhead needed in this design of about 3V! This is partly overcome by making the 2nd power rail D5/C3 for the IC that holds up from the peaks when the main high current one badly sags due to the small smoothing Cs.

    Volts
    26V ┤~─--│~─--│~─-- · · IC Rail
    │ \ │ \ │ \
    │ \ │ \ │ \ . . Un-regulated Rail
    17V__│ \│ \│ \
    │ 3V min drop out
    13.8V ┤────-────-──── · · Output @ 5A
    │ ^ Ripple



    0V ┴──────────────>Time

    This results in quite a lot of heat at full output.

    The Ua723 is prone to having the current input opamp damaged due to direct connection to the current sample resistor R11. Series R of 1k in pin 3 is recommended if you find this failure when there is no current limit working.


    Why Don't U send an interesting bul?

    73 De John, G8MNY @ GB7CIP



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