T
treez
Guest
Hello,
We have an offline 60W Flyback SMPS. The primary clamp resistor is dissipating 450mW.
This resistor is a 3W rated ROX3SJ39K.
The power supply will be at full power 8 hours through a night, in Europe.
The power supply simply turns on/off once per day.
A thermocouple (k type) attached to its body showed a temperature of 100degC, whilst the internal ambient in the power supply enclosure was 50degC. (external temp was 25degc)
Despite the fact that the datasheet appears to show that this is fine, we cannot believe that such a resistor will last for many years.
Do you agree that the part won’t last for years?
I have requested failure rate details from TE connectivity, but didn’t receive any.
Datasheet 1 below shows resistance change data which shows the power being repetitively pulsed on/off in the resistor with a 2 hour period……..does this suggest that rather than the actual resistor temperature, it’s the resistor power cycling (temperature change) that causes the most problems?
ROX3SJ39K datasheet 1
https://www.te.com/commerce/Documen...rtrv&DocNm=1773271&DocType=DS&DocLang=English
ROX3SJ39K datasheet 2
https://www.farnell.com/datasheets/...MI4LOA0c_P3wIVWflRCh2r2A9_EAAYASAAEgJgR_D_BwE
We have an offline 60W Flyback SMPS. The primary clamp resistor is dissipating 450mW.
This resistor is a 3W rated ROX3SJ39K.
The power supply will be at full power 8 hours through a night, in Europe.
The power supply simply turns on/off once per day.
A thermocouple (k type) attached to its body showed a temperature of 100degC, whilst the internal ambient in the power supply enclosure was 50degC. (external temp was 25degc)
Despite the fact that the datasheet appears to show that this is fine, we cannot believe that such a resistor will last for many years.
Do you agree that the part won’t last for years?
I have requested failure rate details from TE connectivity, but didn’t receive any.
Datasheet 1 below shows resistance change data which shows the power being repetitively pulsed on/off in the resistor with a 2 hour period……..does this suggest that rather than the actual resistor temperature, it’s the resistor power cycling (temperature change) that causes the most problems?
ROX3SJ39K datasheet 1
https://www.te.com/commerce/Documen...rtrv&DocNm=1773271&DocType=DS&DocLang=English
ROX3SJ39K datasheet 2
https://www.farnell.com/datasheets/...MI4LOA0c_P3wIVWflRCh2r2A9_EAAYASAAEgJgR_D_BwE