DI-124 Temperature tests

Posted by: npatel on 08/15/2012

I have a prototypes made for DI-124 with universal input and 12vDC 0.250A output. At 480V Ac input, circuit components' (like transformer, MOSFET and LNK304PN) temperature rises to 92-95F when ambient temperature was around 75F. This happens at just 50 mA load and the temperature rises even more for higher loads. What shoud be the normal temperature of these components at low loads? Do you have themal test results of this circuit?

Please suggest any changes so that the temperature does not rises.

Thanks.

Comments

However, I found some thermal data at 230Vac and 57Vac, and they are pasted as follows. Hpefully it can help.

Item	Temperature (°C)
Item	57 VAC	230 VAC	480 VAC
Ambient	25	25
Input Capacitor (C8)	31	28.3
Transformer (T1)	33	30.3
Output Capacitor (C2)	33	30.8
MOSFET (Q1)	36.3	32
*LINKSwitch* (U1)	51.6	43

You can see two data for each component, the first one is tested at low input and the second one is tested with 230Vac.

Thanks for test results.

As it can be seen from the test results, with higher input voltage, the temperature is lower. In my case, I am applying 480Vac and still the transformer and other componets have higher temperature.

I am using EE16 transformer, is it the cause of it? Please suggest me methods to reduce the temperature.

Thanks.

Are these results for full load current? I have just 50 mA load current and still the temperature is higher.

As you know, at 57Vac, the conduction loss/copper loss will be much higher than conduction/copper loss at 230V. So it makes sense that 230Vac thermal is better than 57V. However at 480Vac, the switching loss/core loss will be much higher than 480Vac, and thus it is very possible that your test result is true. You can test thermal at 57Vac and 230vac, to see if the data can match with data from PI. If data can match, that tells your test board is good, and then you have to figure out thermal solutions.