Will this simple smps cct work.

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

 

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

 

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

 

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