Could some electronics guru provide some insight into the following ? One can use a Villard multiplier to step-up voltage and a capacitive divider to step-down voltage. However, most power supplies still use a transformer for voltage step-up/down. What is the inherent deficiency of a Villard circuit that prevents it from being used for these purposes. Thanks in advance for your feedback.
villard aka cockroft walton no isolation, terrible regulation, and in most cases illegal.
NT
"Daku"
** No isolation from the AC supply.Means there is an inherent electrocution hazard in most applications.
... Phil
For step-down you can't get inexpensive efficient durable safe switches. (eg for safety isolation of the output) for step up, it is used (eg in CRT supplies)
-- ?? 100% natural --- Posted via news://freenews.netfront.net/ - Complaints to news@netfront.net
vibrating switches are prone to going oc, commutating rotating switches are prone to shorting due to carbon buildup.
NT
Thee Villard/Cockroft-Walton scheme for stepping up from low V
(1) costs energy every time current goes through another diode, so efficiency suffers
(2) costs money proportional to output current and number of stages, because large capacitors are more expensive than small ones. These capacitors' impedances are in SERIES, so they don't add up like capacitors in parallel. The capacitance doesn't add, the cost does.
(3) Isn't completely happy when mated with squarewave inverter power sections, either. Sinewave or trianglewave input power is better, squarewave drive makes for high harmonic content in the current.
"whitless imbecile"
** Puke.** Get all this from Google did you ?
It's crap.
** Huh ?? "completely happy " is hardly a technical term.Square wave drive of such multipliers is very common.
Mainly for low power apps.
Which is mostly the case with high voltages anyhow.
.... Phil
Voltage multipliers do see wide usage in some applications. They are especially suited where you need high voltage, low current and you have a high frequency source to take it from.
At 50/60 cycles the capacitors needed restrict the current you can pull from them - but they are still nice for ion generators, lamp starting circuits, and things of that ilk.
We had some ultrasonic baths at the place I worked that were transformerless and used a doubler to supply the plate voltage for the push-pull transducer driver. A few hundred milliamps for vacuum toobs (that did a double duty of heating the bath by mounting them underneath the stainless steel vessel, as well as supplying high frequency, high voltage and high power)
They did find a lot of application in AC/DC radios and TV's in the
50-60's. I'm using one to light a vacuum fluorescent display that required 35 volts from a 12 volt transformer.I use capacitive reactance to drop 120 VAC to the 12 volts needed for lighting some series connected LEDs in night light applications. ~.5 uf and full wave bridge rectifier works well for a few 20 milliamp leds. No danger of shock since it is all potted in one piece of plastic.
This deserves more explanation, I see. If you use (for instance) a '555 at a kilohertz to drive a capacitor-diode assembly, the diodes conduct during the risetime (0.5 uS) and falltime (0.5 us), and not during the no-slew times (the other 99.9% of the period). So, to make some +15 V 20 mA op amp power, you'd be pumping regular surges of 20A through the '555 output stage and through the diodes. And, from whatever powers your '555. Until something breaks.
If, instead of the '555 square waves, your input were triangle or sine, the diode conduction is at a much higher duty cycle, and peak current to average current gets much less stratospheric.
No danger of shock or burn out until you can a spike in your line which results as a low XL and thus sents a surge of current to your little LEDS!
Jamie
Let me correct that, "CAN" = "GET"
Hard day at the bench..
Jamie
Well the first leds needed replacement in ~5 years because they were dimmer after ~50,000 hours. In that time, my modem died twice due to nearby lightening strikes... and the phone line runs underground with a surge suppressor on the line bonded to the power service entrance.
There's a 100 ohm 1/4 W limiter that may be absorbing the spikes and initial capacitor inrush when power is restored.
When playing with the idea I had it open on the bench and accidentally shorted the cap. The resistor opened but there wasn't even a singed covering, and all three leds shorted...
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