Transformerless Power Suppply

[sayzer]

Upon the discussion with Melanie, attached is the capacitor value table for the current (mA) that your circuit draws.

Table is quite simple to figure out.

Table is for 110V@60Hz and 220V@50Hz.

Example: If your circuit draws 12mA, and your power line is 110V 60Hz, then, you use 0.289uF (290nF) for C2 in the circuit that Melanie posted here.

Of course you will have to adjust D2 and VDR accordingly.

If this table is any help to anyone!


Regards

[Melanie]

Nice table, but if you limited the Capacitor values to those dozen or so X2 values available (eg 10n, 22n, 47n, 100n, 220n etc, etc), you'll be able to pick the one closest to your current requirement. No point in having a 290n value when you can't buy one, and putting heaps in parallel negates the advantages (cost, size and weight) of a transformerless design to start with.

[sayzer]

Yes, of course.

Just as in your design, C2 is 470nF but in the table the nearest value is 477nF.

I am sure 330nF can also be used there although is not a near value.

Similar to this example, one can look at the table and pick a range.

I will try to make this table as an active WEB page so the user can enter the values of Frequency and Current then have an info for the capacitor range that "can" be used.

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[psdayama]

I have seen in many posts that Melanie is asking to use X2 capacitors.
For the requirement of circuit the value posted in tb008 is correctly just
470n 400V type. These are available at half price than X2 types because
X2 are required for special protection function and 'never short' across the
mains requirement.
Also the resistor across this capacitor can be 220k 1/4 W instead of 100K
1Watt. This resistor is for discharging capacitor when ckt is not in use and
not for providing resistive current. Those who are having 110V/60Hz should
double value and save money.
If one is not finding proper value of capacitor then it is not good that
one should have much higher value available. If used then low voltage regulators (zener or series type ) will dissipate much more power and may
burn out. Consider that this ckt is constant current generator and that when no load is there it will be dissipated in zener. It is better that shunt type
voltage regulators are designed with proper wattage rating so that there is
no problem later.
( I had been manufacturing X2 and normal plastic film capacitors for more than 12 years in India)

[Melanie]

There is a reason I specify X2... and you said it yourself... "they (are specified to) never short accross". If in a Transformerless Power Supply the Capacitor DID short accross it would be very bad news!!! If you don't fit X2's, then yes, your costs are very much reduced, but do you want to take the risk?

[psdayama]

There is a reason I specify X2... and you said it yourself... "they (are specified to) never short accross". If in a Transformerless Power Supply the Capacitor DID short accross it would be very bad news!!! If you don't fit X2's, then yes, your costs are very much reduced, but do you want to take the risk?

This whole thread, I think, is on the brink of veering off!
When U are choosing a very low cost alternative there are many conditions
which are subject to be adhered. first being a circuit a "live" it is not to be
used as any run of mill usage like powering something which can get body
contact. Secondly if "safety" being prime concern then why use "transformerless " supply at all? If I have to get 'risk' of capacitor shorting
eliminated I would rather use a double wound txr and add the cost to safety
of supply!!! Some people are just attached to fancy of some components and
don't look at overall concept of a circuit or device.
How nice it will be if everyone should consider to buy a Merc or BMW as
it won't let U down in middle of road like small car?
For Melani's information we men like to live dangerous but do consult
our purse before risking our reputation in hotel or pub !