Sceadwian
Banned
A half wave rectifier completely ignores half of the AC cycle, so during half of your AC cycle ALL of the power supplied to the regulator is coming from the capacitor. This increases the ripple current on the cap which shortens it's life and makes them more susceptible to voltage dips on the mains line because it can only charge during half of the available AC cycle.
Your diagram also doesn't show any form of isolation, which if your switch mode IC ever fails will expose your circuit (and anything electrically connected to it) to the mains voltage (usually a bad idea) A full wave rectifier will help with voltage dips, not sure if it would completly eliminate your problem or not. But a full wave rectifier would require issolation of mains voltage.
One other thing, there's no bleeder resistor depicted with C4 which means you're trusting the switch mode power supply to drain the capacitor. If you have the switch mode off for some reason the cap C4 will contain 170 volts.
Your diagram also doesn't show any form of isolation, which if your switch mode IC ever fails will expose your circuit (and anything electrically connected to it) to the mains voltage (usually a bad idea) A full wave rectifier will help with voltage dips, not sure if it would completly eliminate your problem or not. But a full wave rectifier would require issolation of mains voltage.
One other thing, there's no bleeder resistor depicted with C4 which means you're trusting the switch mode power supply to drain the capacitor. If you have the switch mode off for some reason the cap C4 will contain 170 volts.