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Bridge rectifier running at 103degC junction tamp..how long will it last?

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Flyback

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We are using the DBLS209G bridge rectifier in a 60W offline flyback LED driver. It operates 8 hrs a night, 365 days a year. It dissipates 1.2W. Its case temperature is 85degC. Its junction temperature will be 103 degrees Centigrade.
Datasheet says maximum operating temp is 150degC....but this seems awful hot.

For how many years will this part last?

DBLS209G datasheet:
http://www.farnell.com/datasheets/2...MI1K7DzdKS3wIVgoXVCh35Wgz3EAAYASAAEgIiH_D_BwE
 

JimB

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To adapt a well known phrase:

"There are lies, damned lies and MTBF figures"

JimB
 

Flyback

Well-Known Member
When i worked in the electric drives industry, we though nothing of running FETs rated for 150degC junction at 140degC junction...but our drives were cheap and if they failed after a year then that was fine...we just replaced them.
 

crutschow

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For that information you would need to contact the manufacturer.
 

BusyBee

New Member
I see the from the current handling / ambient temperature curve that there is significant dropoff beyond 40 deg. It may be a problem, dependant on the actual current flow as, in some circumstances, there may be runaway.

Not something I have recent experience with, but what is the degredation of current solder (if any) with regard to operation at elevated temperature. In years past large wirewound resistors were soldered using higher melting point solder, and I often found joints had become dry over extended periods.

Tracy
 

kubeek

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What is the air temperature inside the case now, and is the outside of the case at 25°C?
What temperatures on the outside of the light do you expect?
 

Flyback

Well-Known Member
Thats 103 degrees junction is the hottest it gets...it refers to operation in summer nights in the early evening phase , where ambient is 23 degc hottest.
 

kubeek

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Thats 103 degrees junction is the hottest it gets...it refers to operation in summer nights in the early evening phase , where ambient is 23 degc hottest.
Is that somewhere around the polar circle? The case of the light could be say 40°C or more before the sun goes down, and if the light gets turned on early you will have a problem.
 

Flyback

Well-Known Member
the power supply is in a plastic case which is indeed inside an aluminium casing...but we think shortly after sun-down, the aluminium case would be at the ambient air temperature whcih would be 23degC max.?
 

JonSea

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the power supply is in a plastic case which is indeed inside an aluminium casing...but we think shortly after sun-down, the aluminium case would be at the ambient air temperature whcih would be 23degC max.?
Not if it's been baking in the sun all day. How hot does your car get when parked in the sun? Hint: much hotter than ambient temperature.
 

ronsimpson

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How hot does your car get when parked in the sun?
I designed part of a police car computer years ago. For the temperature test they got a black car, on a summer day they faced it south and turned the heat to high. (Texas USA) The computer worked all day. The plastic case milted down on to the PC boards.

The computer needed to work at -40 and it did. Next year we learned that in Canada it worded at -60 but it would not start up colder then -40. I changed one resistor and fixed that.
 

dknguyen

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I designed part of a police car computer years ago. For the temperature test they got a black car, on a summer day they faced it south and turned the heat to high. (Texas USA) The computer worked all day. The plastic case milted down on to the PC boards.

The computer needed to work at -40 and it did. Next year we learned that in Canada it worded at -60 but it would not start up colder then -40. I changed one resistor and fixed that.
How'd you know it was the resistor?
 

BusyBee

New Member
I designed part of a police car computer years ago. For the temperature test they got a black car, on a summer day they faced it south and turned the heat to high. (Texas USA) The computer worked all day. The plastic case milted down on to the PC boards.

The computer needed to work at -40 and it did. Next year we learned that in Canada it worded at -60 but it would not start up colder then -40. I changed one resistor and fixed that.
My car, like most these days, has lots of electronics. I have found on a couple of occasions over the years, that the smart key (or more correctly the receiver or control unit) has failed to work when the car has been in the sun on a really hot summer's day. This is in the UK so not Texas temperatures. On cooling with the door open for a few minutes (luckily a key is provided) everything was Ok. Obviously it may be just with my car, but I suspect it is not uncommon. I do seem to remember my previous one (this was a US Chrysler) was similarly a bit iffy if it got really hot too.

Tracy
 
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