Convert 220VAC to 110VDC without transformer

Status
Not open for further replies.
D

diepvu1805

Member level 2
Joined
Jun 20, 2011
Messages
46
Helped
4
Reputation
8
Reaction score
4
Trophy points
1,288
designmicroelectronics.blogspot.com
Activity points
1,595
Hi all,
I want to convert from 220VAC/50Hz to 110VDC without transformer. I also don't want to use the voltage divider capacitor, resistor circuitry.
parametter as follow:
Vin: ~220VAC/50Hz
Vout: 110VDC
Iout: 12 - 20mA.
Non-isolated
Pls, suggest the good solution to me,
thank in advance,
 

Probably the simplest approach would be a rectifier/cap, followed by a 110V zener driving an emitter follower. Not efficient, but cheap!
(And a ~5W heater at maximum Iout
 

Bridge rectify to DC and use a resistor and 110V zener
 

You can use a transistor along with the diode-zener suggestions above to make the transistor dissipate the power rather than the resistor. You'll dissipate about 4W of power. Just use a decent sized heatsink. Or, you could just use a large power resistor capable of handling >> 4W power. Select a resistor such that the heat doesn't become too big an issue. You could "mount" the resistor on a heatsink as well, but if you're gonna do this anyways, I recommend using the transistor.

Hope this helps.
Tahmid.
 

I know you said you didn't want to use this approach - but it is the most robust:

680nF capacitor (275Vac or 400VDC) a surge limiting resistor, say 100R 10W, then a bridge rectifier, say, 4 x 1N4007, then a limiting zener string, 39V zener, 5W, 3 in series to give you 117vDc max, zeners will dissipate 117 x 0.02 = 2,34 watt total (0.8 W each) at no load, less when you have a load.

This will give you your 110VDC at up to 20mA that you seek but will NOT be isolated from the mains.

p.s. a 50V/63V 1000uF cap across each zener will give you a smoother o/p, increase the 680nF mains cap for more o/p current.

The alternative is a small switchmode circuit using a TNY_switch device from Power integrations, they have some good circuits for buck converter implementations that will achieve what you want in a small space (with a small choke - not a transformer)

Regards, Orson.
 
Last edited:



Exactly, Capasitive drop instead of resistive drop was in my mind. but you have to take care that surge voltages need to be handled properly.

also , use proper current limit resistor for surge , use a well calculated wattage of Zener diode. keep in mind a well calculated zener can work perfect as surge protector.
 


 

Attachments

  • FRM025.pdf
    146.2 KB · Views: 191

I like the above solution, however the triac would need to have a very low holding current to keep it on for the light currents required by the original poster, at 110VDC, this could perhaps be overcome with the bridge rectifier and large-ish choke input filter, and a volt feedback system to vary the ON time of the triac.
 
A small switcher (flyback) would seem to be the most practical way, i.e. something from power integrations, a small flyback circuit where you can tie the neg o/p back to the neutral to give you a regulated 110VDC over the mains range you require, all other solutions will likely be quite bulky - and remember there is a limit of 5mA DC that you can draw from the AC supply, a switcher eliminates this problem by full wave rectifying the mains before processing, so that no net DC is drawn.
 
The circuit sketched in post #7 could be build with a half-wave rectifier, a shunt diode and double the capacitor value.
 

Status
Not open for further replies.

Similar threads

Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…