heating problem in tiny 280
hello sir
i design 13w CV supply with the help of PI expert design software. my efficiency and other factors r ok. but as soon as i connect it to full load 13v /1A its o/p rectifier diode and P6KE200 heat about 70 degree within 1 min. please give me some solution.here i am summitting my file also if there is anything wrong tell me.
Comments
The diodes are VR1(P6KE200A) and D6(MUR460). After 5 mins they reached equilibrium at 95DegC when the ambient temperature was 30DegC. I think it is too hot. I'll be using this supply in a warm environment. The air temp could go upto 45DegC. So please suggest what to do to achieve a cooler SMPS.
OK
there are few things you can do to reduce the temperature.
One thing to do is to reduce the leakage inductance of the transformer. To do that, split the primary winding in two windings connected in series and place your secondary in the middle.
Taking your transformer document as reference, start your primary winding at pin 2, wind one full layer and finish the winding in one pin that it is not connected to the circuit. Lets say pin3.
Then wind the secondary as shown in the actual design. Now start at pin 3 wind the rest of your primary winding and finish at pin 1. This sandwich arrangement will reduce your transformer leakage inductance and less energy will be dumped in the DRAIN snubber.
Another thing you can do is to change D5 to 3 amps rated ultrafast diode (700V). Add an RC network in parallel to VR1, Let say 80k//1nf network. This RC network will deviate energy fromVR1 and it will be run at lower temperature.
Make sure you are following the PCB design recommended in the transformer document.
Hey Worf, thanks a lot for your advice. I'll definitely try these tips. In case of any other "Ghosts" :D I'll get back to you.
you are welcome
I saw your schematic. I am not sure which diode you are talking about. Is D5, D6 or any of the input rectifiers?
Anyway, any component that gets as hot as 70 Degrees Celsius is not a problem if the ambient temperature is 25 C. If efficiency is ok, then your design is probably ok.
If you leave the supply running for 15 minutes at ambient temperature, how hot is the diode you are talking about?
From the time you power up the supply with minimum input voltage and maximum load, How long does it take for the diode to reach thermal equilibrium? How hot it is when it reaches equilibrium?