400 Volt Full Wave Voltage Doubler

The goal of this project was to construct a 400 Volt DC supply using the circuit configuration known as a "Full Wave Voltage Doubler". Operation of the circuit is as follows. On the first half cycle of the mains waveform, C2 would be charged through diode D2. On the next half cycle C1 would be charged through diode D1. Assuming 140VAC input, each capacitor would be charged to roughly 200V. Both of these voltages add to ultimately provide 400VDC across the load.


During my construction I used a stove heating element as a test load. I was able to achieve 400VDC with no load, but if the circuit is loaded slightly there is a rather large drop in voltage. At full power it only provided several amps at around 340 volts. The nature of this circuit is also such that it draws current in large pulses from the mains, which leads to poor power factor. This can be helped slighlty by adding a bit of inductance in series with the mains. What this extra inductance does is smooth out the current pulses that occur during the charging of each capacitor.I used the primary of a large transformer to provide this extra inductance. This improves the power factor slightly, but the downside is that the voltage drop under load becomes worse.

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