eem2am
Banned
Ticking SMPS
hello,
do you know why my isolated, offline, 10W, 100KHz, one transistor forward converter ticks ?
(ticking as in output voltage jumping wildly at irregular intervals)
This ticking can usually be stopped by grabbing one of the output caps by its case,
or by putting my finger on the positive or negative output rail, or by switching the 390R inrush resistor into the AC input line.
This SMPS has no earth wire, just live and neutral.
I have not yet put an EMC filter at the front end, and i haven't added any Y caps.
I put an RCD snubber across the primary since it otherwise wouldn't work, -the output voltas went mad.
I am wonderign if the leakage inductance of primary is resonating with the RCD snubber cap. RCD is R = 10K in parallel with C = 10nF)
There is just 1.5uF on the DC bus after the diode bridge....so the DC bus varies from 176V to 340V.......when the ticking occurs, the DC bus doesn't drop down with the mains but stays high for say 3 cycles.
The transformer buzzes when ticking happens.
The transformer is wound 81 turn primary, then 71 turn demag winding, then 14 turn secondary.
Any thoughts greatly appreciated.
hello,
do you know why my isolated, offline, 10W, 100KHz, one transistor forward converter ticks ?
(ticking as in output voltage jumping wildly at irregular intervals)
This ticking can usually be stopped by grabbing one of the output caps by its case,
or by putting my finger on the positive or negative output rail, or by switching the 390R inrush resistor into the AC input line.
This SMPS has no earth wire, just live and neutral.
I have not yet put an EMC filter at the front end, and i haven't added any Y caps.
I put an RCD snubber across the primary since it otherwise wouldn't work, -the output voltas went mad.
I am wonderign if the leakage inductance of primary is resonating with the RCD snubber cap. RCD is R = 10K in parallel with C = 10nF)
There is just 1.5uF on the DC bus after the diode bridge....so the DC bus varies from 176V to 340V.......when the ticking occurs, the DC bus doesn't drop down with the mains but stays high for say 3 cycles.
The transformer buzzes when ticking happens.
The transformer is wound 81 turn primary, then 71 turn demag winding, then 14 turn secondary.
Any thoughts greatly appreciated.
