PH not starting at -20C or colder

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I am having problems with the LinkSwitch PH not starting at -20C or colder.  It does start reliably just slightly warmer, around -15C.  At -20C it will flash every few seconds.  It starts easier at higher line voltage input for a given temperature.  Is there anything that can be done?

Hi,

IC operates from -40 based from our evaluation but we need to use parts that operates down to this temperature. 

 

Normally the component that limits the operation are the capacitors.  Make sure you are using capacitors rated down to this level.

 

Regards,

PI-Jono

Components checked for temp. rating and they are.  I was able to improve cold performance by changing resistor connected to pin 1 to 24.9k from 49.9k.  I also tweaked Vmon resistors down a bit.  It now reliably starts at line voltages of 140 to 300 when cold.  If I reduce Vmon resistors values a bit more it will reliably start at 110 volts but then it won't work at all at 260 volts or more.  I need this supply to work over wide range and handle cold.  Anything else I could do?  I don't want to use different resistors for different temperature range and/or voltage applications.  It increases UL testing costs and forces us to stock multiple supplies.

Hi,

We could not duplicate the problem.  Would you mind to send the schematic.

 

Thanks,

PI-Jono