I have trouble with SMPS who is used to provide 5V, 10A and 12V, 1A device which is mounted in outdoor environment. Device is closed, not sealed but there is no possibility to water come in.
Everything working nice on temperatures above 0C but SMPS fail to start on temperatures below 0C to -3C. There is some fluo lights in device and they are working properly but SMPS not produce 5V and 12V.
If device is turned on positive temperature and leaved to work 24/7 everything working good even when outside temperature drop to -10C.
So, my question is: what is lower temperature limit to SMPS work properly and which components of SMPS are possible cause of mailfunction of SMPS?
Everything working nice on temperatures above 0C but SMPS fail to start on temperatures below 0C to -3C. There is some fluo lights in device and they are working properly but SMPS not produce 5V and 12V.
If device is turned on positive temperature and leaved to work 24/7 everything working good even when outside temperature drop to -10C.
So, my question is: what is lower temperature limit to SMPS work properly and which components of SMPS are possible cause of mailfunction of SMPS?
Must be a self-oscillating circuit. You'll probably have to post it if you want much help, even if the analysis proves to be beyond me.
Gain of semiconductors reduces at low temperature.
How is it started ? start up resistors. Perhaps there isn't enough foward bias in the switching transistor when it's cold... sounds funny that 🙂 you know what I mean.
How is it started ? start up resistors. Perhaps there isn't enough foward bias in the switching transistor when it's cold... sounds funny that 🙂 you know what I mean.
Everything that i know about this SMPS: very nice (in temperature range 5C to 50C) factory made half-bridge SMPS. Works fine and stable, used to supply MCU systems, different types of electronic devices, some step DC motor and a lot more of devices.
But, there is a problem with cold start.
It make sense that NTC is a problematic component.....
But, there is a problem with cold start.
It make sense that NTC is a problematic component.....
What about use a power resistor as a heater and use a relay to disconnect it when the power supply starts up?
Is that SMPS selfoscillating or some PWM controller based ? PWM controllers are usually characterized for operation from 0C to 70C ( celsius degrees ).
We need to see a circuit... many SMPS use a high value resistor from the base of chopper to +VCC in the 220 to 470 k range for self starting. If the chopper was low gain when cold then I could see it not starting.
Why not use freezer on the chopper and see if it fails to start ?
Why not use freezer on the chopper and see if it fails to start ?
I do not have schematic for this SMPS, i buy it as factory assembled product. I think that IC controller is 7500B, it have NTC on input stage ( in front of rectifier), half-bridge topology, and have ferrite transformer to drive BJT or MOSFET (power switches of primary of main transformer).
That is all that i have see trough the case grid of SMPS.
Freezer tryout have to wait to buy another SMPS because this one is already in use.
About low gain, if i increase gain in low temperatures it may be unstable on normal temperatures.....
I think i will try different type of SMPS or classic transformer and linear regulator approach, because i think that SMPS are for "indor use only" (i dont know is there special, wide temperature range SMPS).
That is all that i have see trough the case grid of SMPS.
Freezer tryout have to wait to buy another SMPS because this one is already in use.
About low gain, if i increase gain in low temperatures it may be unstable on normal temperatures.....
I think i will try different type of SMPS or classic transformer and linear regulator approach, because i think that SMPS are for "indor use only" (i dont know is there special, wide temperature range SMPS).
KA7500B datasheet say that operating temperature range is 0-70C.
Temperature in our city this day goes to -5C and that is problem.
Temperature in our city this day goes to -5C and that is problem.
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