Voltage doubler? Which component(s) is it?

[yanz]

so that i read this interesting article: Anatomy of Switching PSU (page 2)

but i think the diagram is wrong. what makes the voltage doubler, is it the primary bulk caps? or the bridge rectifier? or is it just a trick in path arrangement?

i live in the country where 220v is used. so i think my (non apfc) psu wont need the voltage doubler . what is the dc voltage applied to the primary bulk caps then? 240v-260v-300v?

shouldn't the right scheme on that diagram is:


Transient Filtering (AC Filter) -> Switch/Voltage selector/Voltage Doubler -> Rectification -> Filtering -> Switcher -> etc...

?

[gonzo0815]

Re: Voltage doubler? Which component(s) is it?

The voltage doubler is existent in most non A PFC PSU`s circuit. it basically consist of the two caps and the corect wirering provided by the 110/220v switch. If the PSU is only sold in 220v locations, the mfk can take only one input cap with 400v rating and halfed capacitance. the other cap would be replaced by a jumper wire.
This is IMHO typicall for ultra cheap psu`s, most branded p PFC psu´s don`t alter that.
The diagram is IMHO correct.

Function: both caps would be independently charged with 110v and then, if they are acting like a power source they would discharged in series, thus there is roughly the doubled voltage.

Therefore it is obviousely, that the voltage doubler can`t be before the rectification.....elektrolytics don`t like AC mutch.

[PeteS in CA]

Re: Voltage doubler? Which component(s) is it?

In the schematic on the page you posted, yanz, it's the switch shown right above the four 1N5406 rectifiers. On P/Ss, it's the voltage selector switch usually located right near the inlet. The voltage doubler is the reason plugging a P/S set for 115VAC into 220VAC results in a loud noise and an unpleasant odor.

[davmax]

Re: Voltage doubler? Which component(s) is it?

Yanz. I tend to agree the block diagram you supplied is not good . Showing the doubler and rectifier seperate. In the circuit diagram you can see that the rectification takes place as part of the doubler. Doubling only occurs with 115v operation, for 230V the rectifier functions as a normal bridge circuit.

[yanz]

Re: Voltage doubler? Which component(s) is it?

Therefore it is obviousely, that the voltage doubler can`t be before the rectification.....elektrolytics don`t like AC mutch.

that is what i'm talking about, gonzo. i think the writer was getting confused with the twin caps of Cy capacitor that he assumed as the main lytics. like you said, it's unlogical to put DC caps in front of bridge rectifier (in this case they are four Diode 1N5406, like Petes has mentioned).



those 470uF 200V lytics that are paired in series would produce 400V (right or wrong?), but that within theirself. i do a real measurement on polarity of bridge rect, it's 268V (between + and -). i measure the voltage after those caps, they are still 268V.

well tell me if im wrong. but imo the 268V comes as a result of conversion of ~270VAC at peak (average/rms 220V) by the bridge rectification diode(s).

the series configuration of main caps aren't intended as voltage doubler, i guess. they are for filtering. on 220v country, a non apfc psu don't have a voltage doubler if it has no switch selector (the red 110v - 220v switch).

so like davemax said, the block diagram on that page is wrong. but not because of the position of voltage doubler, but because it's missing the filtering section.

im not really sure either, i think i have messed something in my understanding....

so far i know, that the voltage doubler is the red switch, but how it works?

[Spyke]

Re: Voltage doubler? Which component(s) is it?

Each lytic gets hit with juice alternately as the AC waveform cycles. The power then from both lytic's in series is the doubled voltage. The bridge rectifier's output is still wired to the main lytics just as if it was set to 220V, but the center common connection between the 2 main lytics is connected to one of the AC mains wires. What the switch does is either connect or disconnect this mains wire connection. It's the simplest of voltage doublers.

Yes, the series configuration of the main lytics is crucial for the voltage doubling.

+160V+(C)-com+(C)-160V = 320V

So yes, the pic is somewhat misleading, you can say the doubling comes after rectification, but a direct AC connection to the main lytics is still required to the circuit after rectification takes place.

[yanz]

Re: Voltage doubler? Which component(s) is it?

thanks, guys. please don't give up on me yet ok, im starting to see things a bit more clearly now. i have some idea for this thread so we can discuss this matter in more imaginative way. spyke, thanks bro for the explanation

[PeteS in CA]

Re: Voltage doubler? Which component(s) is it?

Yer hopeless yanz. Just don't let me near a computer motherboard, .

When the input voltage selector switch is set for 115VAC, it connects one side of the AC line to the center connection between the two lytics. Thus one of the lytics gets charged during the positive half-cycle of the sine wave input voltage and the other lytic gets charged during the negative half cycle of the sine wave input voltage.

[arneson]

Re: Voltage doubler? Which component(s) is it?

First chapter text book quote on the subject.

[gs3]

Re: Voltage doubler? Which component(s) is it?

Sometimes I find that redrawing the circuit I can understand it better and that is what I have done here. Both circuits are equivalent. Now look at the lower one. open the switch and you have a normal four diode bridge with a capacitor (formed by two capacitors in series). Close the switch and you have a voltage doubler circuit where the two diodes to the right are not working. ´hope this helps.