voltage regulator 320VDC to 5VDC transformless

[yassin.kraouch]

Hi,
have you an idea of a voltage regulator which can convert 300VDC to 5VDC, without transformer ( the output current will be less than 10mA),
the 300 V comes from 220VAC, which is rectified, and filtered,
many thanks,

 

[FvM]

If linear regulator (about 3W power dissipation) isn't an option, you need to design a special buck converter. I'm not aware of an IC solution, so you'll need to combine a suitable switched mode controller with a HV transistor and an inductor, provide start-up power supply for the controller, etc.

 

[yassin.kraouch]

i prefer to use a linear regulator, have you an idea of voltage regulator that can do this ?
thanks

 

[Audioguru]

Remember when we used dial up modems?
Recently I bought some very small name-brand mains input to 5VDC/2A adapters for them at a surplus electronics store for only $1.75 each. They are too small and lightweight to have a mains transformer inside. They probably rectify and filter the mains then use a high frequency oscillator and a small ferrite-core transformer that has its output rectified and filtered then it uses feedback for voltage regulation.

 

[yassin.kraouch]

Remember when we used dial up modems?
Recently I bought some very small name-brand mains input to 5VDC/2A adapters for them at a surplus electronics store for only $1.75 each. They are too small and lightweight to have a mains transformer inside. They probably rectify and filter the mains then use a high frequency oscillator and a small ferrite-core transformer that has its output rectified and filtered then it uses feedback for voltage regulation.

i want to design it by my self, not buy ready solution

 

[Audioguru]

i want to design it by my self, not buy ready solution

Where will you find the special parts?
Will you buy one, take it apart then use its parts in your design? Why bother?

 

[FvM]

A transformer (e.g. 230/6 V 0.35 VA) will be considerably smaller than a heatsink required for a linear regulator dissipating 3 W,

 

[KlausST]

Hi,

Look for high drop out voltage regulators.

No - that was a joke.

Take a resistor, a zdiode, a high voltage transistor (BUK..) and a capacitor..

Klaus

 

[kam1787]

Do you have to use DC, or can you use the AC first?

If AC, try a Capacitive AC Voltage Divider Circuit, followed by the rectifier and filter

 

[dick_freebird]

If your current is fixed enough, I'd look at a shunt regulator
and a feed resistor (which will get mmm, toasty no doubt).
Tough or impossible to find integrated linear series regulators
at that high a voltage. Shunt regulator doesn't care about
the source voltage as long as you limit the current. The
problem lies in any need for significant pulse capability,
which you can only get by burning that capability's worth
of current full time.

 

[yassin.kraouch]

i found this regulator from supertex which is useful **broken link removed**

 

[KlausST]

Hi,

Take a resistor, a zdiode, a high voltage transistor (BUK..) and a capacitor..

Sorry, not BUK, but BUL or BUJ,
I used BUL1102E (450V), and BUJ302A (1050V).

Klaus

Edit1: spelling

 

[yassin.kraouch]

Sorry, not BUK, but BUL or BUJ,
I used BUL1102E (450V), and BUJ302A (1050V).

Klaus

Edit1: spelling

can you please help with schematic ?
thanks,

 

[yassin.kraouch]

do you think that simply zener diode can do the job ?

 

[FvM]

For high precison, you'll use a discrete (z-diode + transistor) pre-regulator and a standard 5V-IC regulator.

 

[KlausST]

can you please help with schematic ?
thanks,

Hi,

i just asked google and found this: (that´s what you could do, also)



Scroll down to : "FIGURE 21.2 Pass-transistor regulator."

Klaus

BTW: Yes, a zener could work also, but with more power dissipation ( in R)

The hint from FvM is good, but look for low Iq 5V regulators, to keep power dissipation small.

Good luck
Klaus

 

[yassin.kraouch]

For high precison, you'll use a discrete (z-diode + transistor) pre-regulator and a standard 5V-IC regulator.

i dont need high precision, why i need pre-regulator ?

 

[iamdnpkc]

hi,

where do you want to use ???
whats the application ???
is this for Driving LEDs ??

 

[yassin.kraouch]

no it is not driving LEDs, i have ICs which need to be supplied by 5V

 

[FvM]

i dont need high precision, why i need pre-regulator ?

I probably misunderstood your previous post. Anyhow, the z-diode used in a discrete regulator will involve about +/- 0.3 V initial tolerance, temperature and load effects in addition.

A R + ZD (shunt) regulator without series transistor will involve a certain amount of excess current and constant power dissipation even with no load. Thus I believe, the idea isn't so good for a 300V input/ 10 mA output regulator.