Transformerless Power Supply

[psdayama]

OK, "nothing is impossible!!!" is Adidas ad.
But have U considered the power dissipation in regulator?
Capacitor voltage divider is 'lossless' so there is hardly any dissipation
in dropper.
Anyway we expect Volkov to announce his result.Although his use
of Bipolar instead of MKT is little deviation I think his ckt will work OK.
Best Luck to all who want to use same method. I have constructed
10s of units with such supply and are working OK last 2-3years.

[Luciano]

Hi,

With a current of 25mA the power dissipation will be less than 1 watt.

30V AC - 1.2V (rectifier loss) = 28.8V
28.8V x 1.41 = 40.608V DC
40.608V - 5V = 35.608V
35.608V x 0.025A = 0.8902 W

* * *

Not in this project but maybe one day you will need a voltage
regulator with an input voltage up to 60V.

http://www.national.com/pf/LM/LM317HV.html

Best regards,

Luciano

[psdayama]

Well estimated 1watt loss can heat LM317HV quite a bit.
I think that in the price of that regulator U can buy 2MKT capacitors
easily (Atleast in this part of world )
Please make calculations as follows:
30V ac = 30 x 1.41 = 42.42 volts DC
- 1.2volts drop = 41.22 volts - 5volts output = 36.22V
x .025A = 0.9055 Watts.

One needs big heatsink for this.

The purpose of circuit is to get lower voltage without transformer
and not much regulated voltage is required.

When required I will certainly use HV regulator if called for.
otherwise I will use switching one to make it "cool" !

Thanks a lot for suggestion.

[Luciano]

One needs big heatsink for this.

Your statement is not accurate.

1 Watt of power dissipation without heat sink is possible with a LM317HV/TO220.
Below you can see how to calculate the maximum allowable power dissipation without heat sink.

Best regards,

Luciano

How to calculate the maximum allowable power 
dissipation without heat sink:


PD MAX = TjMAX − TaMAX
         _____________
             Rja

PD MAX = Maximum Power Dissipation (Watt)


TjMAX = maximum junction temperature (°C) 
For the LM317HV the operating junction temperature range is 0°C to +125°C.


TaMAX = maximum ambient air temperature (°C) 
Room temperature or temperature inside enclosure.


Rja= thermal resistance from junction to ambient without heat sink (°C/W) 
For the LM317HV/TO220 is 50 °C/W.


Example ambient air temperature 45°C: 

125°C − 45°C
__________    =  1.6 Watt 
   50°C/W


With an ambient temperature of 45°C, the maximum power dissipation 
of the LM317HV / TO-220 without heat sink is 1.6 Watt.

With an ambient temperature of 75°C, the maximum power dissipation 
of the LM317HV / TO-220 without heat sink is 1 Watt.