Power consumption at different voltage input
I'm using a bare-bones TNY277 flyback switcher design. Secondary power consumption under load measures ~2.4W at 12Vdc. The primary line side power consumption measures ~7.8W at 120Vac and ~11.2W at 208Vac.
Questions:
1. Is a 3X difference in input/output power consumption delta reasonable to expect? The PI Expert design tool design was used, the components selected accordingly, but the design results do not suggest such a loss should occur.
2. Why does the power consumption rise at higher line voltage? I'd expect it to stay nearly the same.
Comments
For issue #2, would a change to the diode/zenor snubber selection lead to a less switching loss?
Using RCDZ snubber instead of normal RCD snubber reduces the power loss at light load. Becasue whatever snubber we use, the maximum Vds should be same. The same maximum Vds means same Voltage at full load across the snubber capacitor, but the current through Zenner/TVS is more sensitive to the voltage, and thus the dissipation of RCDZ snubber should be lower at light load..
1.I guess all the 2.4w dissipated on the output diode, not include any loss on transformer at all. How to handle the transformer loss results in the difference between your calacualtion/measurement and PI expert.
2 The higher loss at high line is mainly caused bu higher switching loss. DCM at high line and CCM at low line causes some difference in conduction loss too.
Regards