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.
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)
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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.
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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