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Will this simple smps cct work.

Discussion in 'Electronic Design' started by [email protected], Feb 16, 2005.

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  1. Guest

    Hi to all.
    Does anyone know if this simple cct will actually work. I have
    simulated it in LTSPICE and it seems to run ok , although the collector
    voltage is getting a bit high. I plan on winding the transformer on a
    small powdered iron toroid. I don't have the toroid yet , hence only
    the simulation to go on. As soon as I get what I need , I'll breadboard
    the cct. Just want to know if I'm wasting my time at this early stage
    :0)

    Cheers
    Rob

    Just save the following code as an .asc file and it should open fine.

    Version 4
    SHEET 1 1092 680
    WIRE -368 208 -368 48
    WIRE -368 448 -368 288
    WIRE -144 48 -368 48
    WIRE -144 96 -144 48
    WIRE -144 288 -144 176
    WIRE -16 48 -144 48
    WIRE -16 112 -16 48
    WIRE -16 224 -16 192
    WIRE -16 288 -144 288
    WIRE 112 48 -16 48
    WIRE 112 144 112 112
    WIRE 112 288 -16 288
    WIRE 128 288 112 288
    WIRE 176 48 112 48
    WIRE 176 96 176 48
    WIRE 176 224 112 224
    WIRE 176 224 176 176
    WIRE 176 240 176 224
    WIRE 176 352 176 336
    WIRE 176 448 -368 448
    WIRE 176 448 176 432
    WIRE 176 464 176 448
    WIRE 272 96 272 16
    WIRE 272 272 272 176
    WIRE 416 272 272 272
    WIRE 416 288 416 272
    WIRE 432 16 336 16
    WIRE 432 112 432 16
    WIRE 432 272 416 272
    WIRE 432 272 432 176
    WIRE 528 16 432 16
    WIRE 528 112 528 16
    WIRE 528 272 432 272
    WIRE 528 272 528 192
    FLAG 176 464 0
    FLAG 416 288 0
    SYMBOL npn 112 240 R0
    SYMATTR InstName Q1
    SYMATTR Value 2N2219A
    SYMBOL ind2 160 80 R0
    SYMATTR InstName L1
    SYMATTR Value 100µ
    SYMATTR Type ind
    SYMATTR SpiceLine Rser=0.5
    SYMBOL res -160 80 R0
    SYMATTR InstName R1
    SYMATTR Value 4.7k
    SYMBOL voltage -368 192 R0
    WINDOW 123 0 0 Left 0
    WINDOW 39 0 0 Left 0
    SYMATTR InstName V1
    SYMATTR Value 12
    SYMBOL ind2 0 208 R180
    SYMATTR InstName L2
    SYMATTR Value 2µ
    SYMATTR Type ind
    SYMATTR SpiceLine Rser=0.2
    SYMBOL cap -32 224 R0
    SYMATTR InstName C2
    SYMATTR Value 47n
    SYMBOL ind2 288 80 M0
    WINDOW 0 -34 87 Left 0
    WINDOW 3 -58 53 Left 0
    SYMATTR InstName L3
    SYMATTR Value 220µ
    SYMATTR Type ind
    SYMATTR SpiceLine Rser=0.8
    SYMBOL cap 416 112 R0
    SYMATTR InstName C3
    SYMATTR Value 10µ
    SYMATTR SpiceLine V=25 Irms=0 Rser=0.001 MTBF=0 Lser=0 mfg="TDK"
    pn="C575OX7RIE106M" type="X7R" ppPkg=1
    SYMBOL res 512 96 R0
    SYMATTR InstName R3
    SYMATTR Value 150
    SYMBOL schottky 272 32 R270
    WINDOW 0 32 32 VTop 0
    WINDOW 3 0 32 VBottom 0
    SYMATTR InstName D2
    SYMATTR Value 1N5819
    SYMATTR Description Diode
    SYMATTR Type diode
    SYMBOL res 160 336 R0
    SYMATTR InstName R2
    SYMATTR Value 4.7
    SYMBOL cap 96 48 R0
    SYMATTR InstName C1
    SYMATTR Value 47n
    SYMBOL res 96 128 R0
    SYMATTR InstName R4
    SYMATTR Value 4.7
    TEXT -72 416 Left 0 !.tran 60m startup
    TEXT 112 -16 Left 0 !k l1 l2 l3 1
     
  2. Guest

    Guest Guest

    The simulation shows that you're getting only 54% efficiency. That's
    sure to go down with real-world parts. I'd say you need to work to get the
    efficiency up before heating up your soldering iron.

    Jim
     
  3. legg

    legg Guest

    Try reversing the phase of L3.
    Then reduce C3 to 1N.

    Re-couple L2 to ground, rather than 12V, to remove supply decoupling
    effects from the base drive. Suggest you re-check effects of supply
    voltage, C2 and load.

    However: there's little reason to expect that a simulation,
    particularly of an oscillator, most particularly one using a simple
    magnetic component model, will accurately reflect reality.

    RL
     
  4. Guest

    Hi guys , thanks for the tips.
    Bit more work to do I think :0)
    cheers
     
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