At 05:46 AM 7/27/01 -0700, you wrote:

>I would not add a resistor in series with the capacitor (C9) as this will
>vary the effective capacitance reactance which is providing the desirable
>voltage drop and will also dissipate heat.

It is the only thing limiting current when voltage transients appear at
the input (as at turn-on). All production circuits will include this
resistor.
Consider the surge current rating on the metal film capacitor if nothing
else...
the current at switch-on is otherwise limited only by the impedance of
the mains and the connections to the capacitor, which can blow the
thin metalization right off the dielectric, creating holes and eventual
failure ('self healing' notwithstanding). Needless to say, it also
whacks the diodes with a surge, though diodes are fairly tough, I don't
like to see the circuit dependent on external factors (such as whether
the customer has plugged it into an extension cord or not) to be reliable.

>I would not be too concerned with the capacitor (C9) remaining charged as
>the approximate 6 mA current consumption from the voltage regulator will
>quickly discharge the capacitor. UL and TUV stipulate that the voltage
>potential on an unplugged power cord must diminish to 1/3 of the mains
>voltage within 10 seconds. So, If I wanted to increase the rate at which
>the capacitor discharges, I would place a resistor in parallel to (C5) on
>the low voltage side of the circuit.

This will do nothing- the capacitor is in series with the low voltage
side when the plug is removed from the socket and the voltage will remain
too long to meet any kind of safety standards without a parallel resistor.
You won't see an approved design without it, or some equivalent.

>I would want a 1/4 amp fuse between the 220 Vac main and the series
>capacitor (C9).

A flameproof fusible resistor can probably be used to avoid the need for
that...
it has to be a high surge current type anyway (not metal film, but MOF
or wirewound).

>I would also want the series capacitor (C9) rated for 800 V to 1000 V.

Preferably with an AC rating > maximum line voltage.

>If the series capacitor (C9) is getting warm at all, then the voltage
>rating should be increased.

Yes, a film cap should never get warm.

Have you gotten your "several amperes" supplies inspected by any
safety approval agencies?  Are there any power factor specifications
that cause problems?

Best regards,
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