Universal input, 16Vx0.9A isolated output, Epoxi filled adapter.
Dear engineer:
I'm using a TNY-280 with auxiliary winding as per your paper RDR-91.
Only the zener VR3 and the transformer was modified according.
It's working fine, giving a 81% eff. from 90 to 265Vac input.
Duty circles are from 47% to 13.4% respectively.
Regulation with load variations is abt 2.5%. With input only 1.5%.
Would you please explain me why the switching frequency is 70kHz?
Conducted noises are very low.
Thanks in advance,
Manoel M. Pereira
Phone: +55-21-2253-1079 (Rio de Janeiro, Brazil)
Email: mmpereira@hotmail.com
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Dear Dr. Spock:
Thanks for your reply. I was not measuring the average frequency.
The skip cycles are working as specified but the period of each cycle is close
to 45usec considering the little projected jitter.
The BP/M pin capacitor is 0.1 uF.
Considering the great performance of the assembled 5 units (3.6 cuin per Watt) nothing to complain but the low frequency (abt half of the specs) make me worried.
Hope you give me a green ligth to go ahead. Thanks again. Manoel.
Note: this was my first time in a forum so my choice for email answers. Please use your most confortable choice to send your coments.
Sorry also for my bad english.
What is the on time of the pulses? In your previous post you said frequency is 70 kHz, 45 us period corresponds to 22 kHz frequency...
Do you have a scope waveform that can show me the switching? Either a drain current or drain to source voltage waveform will do. Capture about 3 switching cycle events.
The wrong time was due a mistyping. The correct time should read 14.5 usec.
Attached are 2 scope waveforms from bias secondary. The first at 90Vac and second 220Vac, both at full load.
At 100 VAC you can see that the time between 2 successive switching cycles is 7.5 us (132 kHz. To maintian regulation every now and then it skips a cycle.
At 200 VAc it delivers more energy per switching cycle (higher KP) so it compensates by skipping more cycles.
The operation looks perfectly ok to me.
Dear Dr. Spock, many thanks for your help. I wish a lot of success to you in your life and professionally. Manoel Pereira.
Tinyswitch is a on off control based device. This means that it will skip switching cycles entirely as necessary to maintain the output within regulation. Thus, depending upon the line voltage and the load, the converter will skip cycles in order to maintain regulation. during each cycle the TionySwitch will conduct until it reaches its internal current limit and then determine based on the output voltage if it will switching or skip the next switching cycle.
Thus on average the switching frequency at low line will be higher than the average switchiing frequency at high line.