a little help with capacitive power supply values

[Dennis]

Hi All

This is turning out to be a very interesting discussion..(well at least for me anyway!)
If you look right the way back to the start of this thread I as asking for a little help regarding the calculations mentioned in the Microchip appnote 954.Plenty have been referenced and suggested since then, and thanks to all who have contributed!

To tie things up I wonder if we could start from scratch again and take a close look at (and discuss) the circuit as we build the circuit up in 3 stages.
Hopefully we could get to a circuit which is able to supply a PIC in the correct way and be as safe as an UNSAFE and DANGEROUS circuit could be.

And the stages are :
1. The mains supply stage up to where it becomes DC
2. The circuit-load stage (where we use the 'DC' portion to power the circuit
(a possible zero crossing detector here and LED and pushbutton)
3. The output-load stage (where a load is switched either by means of a relay or a triac.

To start the ball rolling I would like to draw your attention to the attached diagram which depicts the basic types of transformer-less AC to DC power supply.

Each has its own unique chartacteristics (see AC circuit theory study notes or Google them). Understand that there may be phase shifting to consider as well as the zero crossing (these two will not be discussed yet)

SOMETIMES you may need to power a low voltage circuit such as a

microcontroller with HV AC line current.

The basic steps would be to :

1. Use a reactance to limit the current,

2. Rectify the voltage with a diode (half-wave rectification or bridge
rectifier for full-wave rectification),

3. Regulate the voltage with a zener,

4. Add a large electrolytic capacitor to filter out the ripples.

Transformerless supplies don't offer isolation from the HIGH VOLTAGE

line and present a MAJOR SAFETY ISSUE. I will put all of the possible safety tips together in point form and outline the reasons why each one is used or practiced.

I would like to be using a transformer-less CAPACITIVE circuit with common NEUTRAL (although we still have not discussed the effect on the PIC pin and the triac when there is no load!!)

I have not drawn a fuse in the diagrams yet although it is generally agreed that it is a best practice to place the fuse on the LIVE line not NEUTRAL and also not have a second fuse for example one fuse on LIVE and one on NEUTRAL!

With this in mind please could you confirm the following calculations for 220VAC and 50Hz, max current would be +-30mA.
(check the appnote and posts #14 and #16 for the calculations(Thanks Amgen and Melanie))

Calculations as per Microchip Application Note 954 :
(Please note .. Microchip are using a COMMON LIVE example - I am still not 100% sure why)

NOTE - VOLTAGE is either 230V and 240V (RMS) see appnote for 120V


VRMS 230 240
VZ 5 5.1
C1 0.00000047
R1 100
Freq 49.5 50.1

Equation 4
IIN-Min 0.018482937 Amps 18.48 ma
IIN-Max 0.029218819 Amps 29.22 ma

Equation 6
PR1 0.199702245 Watts 0.399404491 Double Watt

Equation 7
PD1 0.217302793 Watts 0.434605585 Double Watt

Equation 8
PD2 0.020453173 Watts 0.040906347 Double Watt

Please feel free to check my values and comment back.

So at this stage all I would like is some consensus on the values calculated and the different types of circuit.

Can we all agree on this so far ?

Kind regards
Dennis