On the left of the circuit shown below is a 120V AC current. I know that the diode (D1) rectifies the signal so that only the positive half of the AC signal goes through.
I have seen circuits with a Diode, L1 and EC2, but with EC1 left out that acts as an half-wave rectifier.
So my question is as follows:
- Is the output at node 2 a perfect DC signal?
- What is the voltage of the DC signal if the original AC signal has a voltage of 120V?
- Am I correct that EC2 keeps the voltage supply to node 2 constant and that L1 keeps the current supply to node constant?
- What is the purpose of EC1? If it is the same as EC2, why is it not in parallel with EC2 after the inductor?
Note: This is not a homework question. I am brushing up on my knowledge about circuits and came across this as part of a design of a power PCB.
Best Answer
I'll give a general overview.
1) The output voltage should be ideally constant if you provide perfect filtering (which isn't realistic). Think of \$L_1\$ and \$EC_2\$ as a low pass \$LC\$ filter, that what it is.
2) If your input is a \$120V_{ac}\$ voltage signal, then, after some cycles \$EC_1\$ will get charged up to the peak value of that signal \$V_{peak}=120V(\sqrt2)\approx170V \$. Minus the drop across the diode.
3) Yes. A relatively large inductor keeps current constant (e.g choke inductor) and a relatively large capacitor behaves as a voltage source.
4) Don't think of \$EC_2\$ separately. Along with \$L_1\$, it forms a low pass filter which reduces the ripple on the output signal.