I'm mounting a circuit that operates at 220 V and needs a rectifier diode. I do not have the 1N4007 for 220 V, but only 1N4004 for 117 V (200 V of PIV). Can I connect two in series?
The connection of diodes in series in power supplies is problematic because even though they are of the same type, two diodes do not have exactly the same characteristics. Thus, we can not guarantee that the voltage to be rectified is evenly divided between them. This means that one of the diodes can receive more than the 200 V it supports and the other much less, which would cause the burning of one of them. And, one of them coming in short causes the total tension to appear on the other also causing its burning. There are some devices that can be used as the connection of resistors in parallel with the diodes, but they are not the best solution. In short: avoid connecting diodes in series in power supplies.