Hold Time on Power Supply

[loosy]

How can you increase the hold up time on the power supply from 30msec to 150msec without adding more and bulky capacitance.<br><br>This is in a case when the power is off to the appliances and you need the power supply to hold that power for 150msec to store all the settings.<br><br><br>Thank you

 

[elecmec]

Unfortunately capacitors or batteries can only do the job.&nbsp;&nbsp;Be careful with batteries, you will need control circuits.&nbsp;&nbsp;If the problem was only in the RAM, the power supply could be isolated via a resistor, and a capacitor added at the RAM.&nbsp;&nbsp;This would hold the RAM info longer.&nbsp;&nbsp;A similar schiem could be used with the Processor, but many of the newer processors are low voltage high current, which would require a good strategy.&nbsp;&nbsp;I am not totally familiar with the archatechture every PC, so don't assume anything.&nbsp;&nbsp;Since most PC's have a great deal of room inside ( not the power supply) caps can be added.&nbsp;&nbsp;You will need to know the current draw to calculate the time constant.

 

[eblacker]

Unfortunately you can't get something for nothing.<br>The hold-up time you are dealing with (30msec) is provided by the power supply designer so that you can ride through a missing cycle of the AC mains without disturbing the output voltage. The energy to supply the output has to be stored somewhere, usually capacitors.<br><br>If you need hold up time to store settings, you obviously have the capability of storing the information if you had the 150msec of hold up time. Therefore the solution is in software. save your settings as soon as they are changed or every few seconds, updating as required. If the power fails don't let the settings data be changed by that event and restore the last good settings on power up.<br><br>I hope that helps.