How to reduce the Temperature of output capactors witch appling for TNY278
Hello Everybody! I have done a power which using TNY278, which spec is 5V@1A AND 15V@150mA.after measuring the design. I am not satisfied whit the temperature of the output capacitor.It rise to 55 celsius degree( ambient temperature is 20). Rising temperature over 30 need to be pay attention as the datasheet mention.
Spec of two output capacitor is 1000uF/16v (Rubycon)
Transformer: EI-22: Primary ---- 68 : 463uH 5V ---- 3 15v ---- 7
The heating will reduce the lifespan of the capacitor,It have to operating for more than two years!
Does anyone who have the same experences on solving such problem?Anyways, Thanks very much!
Comments
Tks, PI-Worf
Acctually, I used PI EXPERT program calculate the Transformer's Spec. Output caps are low ESR and designing for Switching power supply.Which ESR is 0.028ohm @100K ,rated ripple current is 1760mA
I done another transformer which spec as below
primary side: 90 turns
secondary : 8 turns
the temperature of output capacitor reduce to normal. Comparing the result between the software and experiment,
I suspect the program can not meet the massproduced requirment.
why the gap between theoretical disgn and experiment result is so large?
Many Tks.
Glad you got it working!
I am assuming your output caps are low ESR. if not, you need to change them for low ESR type.
What you need to do is to reduce your RMS current trough the capacitor. Design your transformer with the lowest ripple current for the capacitor. You can use PI EXPERT program. It tells you the approximated value of this current and gives you recommendations for output capacitor. If you are unable to reduce the ripple current, use larger size can capacitor. Larger can will have lower ESR for lowering the heart dissipated by the capacitor. When you design your PCB layout connect the capacitors as close as possible to the output rectifier. Larges traces between the output rectifier and the capacitors will introduce undesirable parasitic components that affect the performance of your power supply.