I'm trying to make a fairly small AC(220V) to DC convertor to power microcontrollers and some actuators. It needs to output a current of 1 amp to the load. I tried looking at using transformers, but all the ones I could find that are rated for 1 Amp output current are too big for my design. So I changed my design to be a capacitor power supply. I'm thinking of using the circuit provided in this website: http://www.circuitsgallery.com/2012/07/transformer-less-ac-to-dc-capacitor-power-supply-circuit2.html
But this one only supports around 150mA, It seems that if I change the X rated capacitor to 11uF from 2.2, I can get an output current of 1 Amp. Does this seem feasible. I am fairly new to electrical design, any help would be very appreciated!
Best Answer
A capacitor input power supply is only appropriate for specific, low current, non-isolated applications, like tickling a SMPS into life, or driving an isolated low power LED bulb, where safety is not an issue, and a constant output current is OK.
As you want to drive microcontrollers and actuators, safety and isolation is paramount, and this is the wrong design to use. In addition, 1A is quite high, and the load will vary, so this type of supply is triply inappropriate.
If an iron transformer based supply is too large for your application, see if you can find a complete SMPS solution, like a USB charger. If they are too big, then you need to rethink your project dimensions.
When you do your own designs, it's often quite easy to get the behaviour you intend, say 1A output. It's more difficult to avoid the behaviour you don't intend, like electrocuting yourself. That's the reason that people buy isolated power supplies rather than build their own, anticipating all the bad things that can happen, then avoiding them, takes a lot of experience. You're unlikely to get it right and safe first time.