Is there a minimum output capacitance for LinkSwitch-TN?
Hello,
The datasheet and app notes default to 100uF. I can't use electrolytic capacitors (because of heat and MTBF) and there is not much space. Is there a lower limit?
It's a conversion from 100-250VDC (and some day up to 500V) to 12VDC at about 250mA max load. Most of the time the load will be less than 150mA, sometimes only 10mA. Ripple is unimportant because we'll be driving non-critical loads and for sensitive stuff there will be a post-regulator.
I'd like to go as low as 10uF ceramic X7R or comparable. I am aware that the pulse skipping scheme these chips use will cause a ton of ripple. The input will be rectified 115VAC/60Hz and we'll only have a single diode with a 2uF cap there.
Regards,
Joerg
Comments
Thanks, Worf. It will be run as a buck so the max drain voltage should not be a problem.
Is there a SPICE model for the LNK306? A behavioral model would be fine, it can greatly help with the design of such converters.
Regards,
Joerg
At this moment we do not provide any Power integrations models. I am sorry
we do not have any design with such low capacitance design. Because your load is very low, the discharge of the cap will be very low too. My impression is that the design should work with such low capacitance. The only way to find is to build a prototype.
About your input voltage (500 V) I think it may be an issue because the device MAXIMUM DRAIN VOLTAGE is 700 V. But because you have very low output current, the voltage spike due to the transformer leakage inductance would be very low too. Then you may meet the DRAIN MAX VOLTAGE. Once you have your prototype running you must check for DRAIN MAX VOLTAGE under all conditions to meet the device's limit. Extreme conditions includes transient load, output overload, output short circuit, start up at 500VDC.