# Voltage regulator?

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I'm expecting to be in a remote area of India with flakey power.
How desirable is it to have a voltage regulator, or does a surge suppressor
suffice? My laptop has a Li Ion battery.

Another question:
How do I determine the required wattage for a surge suppressor or voltage
regulator, given that the laptop can handle 100 - 240 V?
The power cord gives the following input:
100 - 240V ~ 1.8A 50 - 60Hz

## Re: Voltage regulator?

I'd recommend that you get/take a UPS.  You can get an inexpensive UPS
for \$30 or less, something like an APC 350VA model.  In a sense, the
battery is a UPS, and a simple surge supressor would probably protect
the unit, but with low-end UPS' so inexpensive, there's no reason not to
get one.

Wattage is independent of voltage.  Take the DC OUTPUT of the laptop
power supply (typically something between 15 and 19 volts at something
between 3 and 6 amps), multiply that voltage times that current, that
gives the watts used by the laptop.  The charger is less than 100%
efficient, so divide that number by 0.6 (or multiply it by 1.66, same
thing), that gives you the wattage that you need (and it's very
conservative).

michael brooks wrote:

## Re: Voltage regulator?

Padantic point: UPSs are not rated in watts, but in VA (Volt Amps). You
could connect a 50 watt load to a 350VA UPS and still overload it.

## Re: Voltage regulator?

Actually, that's not entirely true.  The manufacturers do promote VA
because it gives a bigger number.  But APC is now putting the wattage
rating on all of their UPS' as well.  The number is lower than the VA
rating, but it's not so much lower that a 50-watt resistive load will
overload any of APC's 300 or 350 VA UPS' (or even come close ... the
wattage rating is typically about 65% of the VA rating).

The Electric Fan Club wrote:

## Re: Voltage regulator?

They may well be doing so for guidance, but it can be nothing more.  The
number that matters is the volt-ampére rating.  All electrical generation
systems are rated this way, because it is the current aspect that causes the
electrical overload*.  Even the large UPSs that we have here are rated at
500 kVA, they don't quote a kW rating at all.  Our rotary frequency
converter is rated a 15 kVA, again there is no kW rating on the tally plate
or in the specification.  A 50 watt resistive load will not overload a 350
VA UPS.  But a a 50 watt load that has a 400 VAr characteristic will (i.e.
highly inductive, highly capacitive or, in the case of switch mode power
supplies, takeing the current in large pulses).  A load that consists
entirely of capacitors can overload the UPS without drawing any power at
all.

The power rating that you quote of about 65% of the VA rating implies loads
with a total Power Factor of 0.65.  This may be reasonable for a mixture of
to bring the power factor up to around 0.8-0.9.  These would allow a higher
power to be drawn.

*Power can mechanically overload a mechanically driven generator, but a UPS
is not mechanically driven, so this does not apply.

## Re: Voltage regulator?

The Electric Fan Club wrote:

On a side note, if your power supply/adapter has a power factor
corrected front end in it you wont need to worry about large spikey
input current waveforms.  A properly designed PFC will essentially
appear as a resistive load and the input current will track the
sinusoidal shape of the input voltage.

(*>

## Re: Voltage regulator?

It doesn't quite appear as a resistive load, but it is better than one that
doesn't have PFC.  The current waveform is still not sinusoidal, and a power
factor of 0.8 to 0.9 can be expected.  To get a perfect sinusoid would
require correction components that would easily rival the size of the
original power supply.

## Re: Voltage regulator?

The Electric Fan Club wrote:

I guess it depends on who designed/built the supply.

All of the designs produced by the company that I work for typically
provide a power factor of 0.98 or better at full load.  For all
reasonable purposes, the load looks resistive.

We are not talking about huge linear power supplies full of passive
components, these are pfc switching front-ends providing bulk voltage
(@400Vdc) to multiple switching outputs.  The pfc function is
incorporated into the control ic for the front-end.  As long as you size
your switching components correctly (inductor/caps) and have the loop
compensated properly you can have amazing power factor without
increasing the size of the supply at all.  These controllers also allow
operation from about 85 - 270VAC when properly applied.

(*>