Secondary Rectifier Diode Overheats
Hello PI,
I have fabricated a SMPS as per attached design derived from PI Expert.
Everything seems to work perfectly except that, secondary rectifier diode BYV32-200 overheats.
At half the rated load, say around 3.5A load current, diode's heatsink's temperature rises to almost 80 degree Celsius within in 5 mins of operation, ambient temperature being 23 to 26 degree Celsius.
With full load, heatsink's temperature rises beyond 110 degree Celsius, under same ambient condition.
I tried changing the diode to MBR20100, no improvement.
Transformer construction is modified a bit, foil is not used, and primary winding is not split.
Care is taken to keep leakage inductance under control.
Transformer heats too but not as much as diode.
Could you kindly suggest any workaround to reduce the heat / power dissipation across the diode.
Proposed SMPS operation is up to 55 degree Celsius ambient. Under current circumstances SMPS, probably will fail in no time.
Thanks and Regards,
RRS
Files
| Attachment | Size |
|---|---|
| PI Expert Design File | 678.5 KB |
Hello,
Based on the very general nature of the information provided regarding transformer used and its construction it is difficult to know the root cause.
It appears that the diode is overheating and this could be due to excess conduction and/or switching loss of the diode.
I suggest you verify the diode voltage waveform and verify if the diode voltage rating is being exceeded. The RC snubber across the diode may have to be adjusted depending on the leakage reactance of the transformer secondary and the trace inductance due to the circuit board traces.
I do not know what sort of heatsink is being used for the diode. The same may have to be made larger or replaced with a more efficient heatsink if this is thermal issue is due to inadequate heatsink efficiency.