This is a diode bridge. It converts alternating current (AC), into direct current (DC). The circuit is set up so that current is always flowing towards the input of RL, and away from the output. More information about the properties of diode can be found here:’https://tphelectronics.com/2015/09/29/diodes/‘
AC signal output is most commonly just connect to ground (0v).
RL represents the circuit to which you’re applying the DC voltage.
Signal diagram explanation
This shows one full oscillation of the AC signal at the input. Whilst the signal is above the horizontal line, the voltage at the signal input is positive. Whilst the signal is below the horizontal line, the signal input is positive
Flow of current during positive half of the oscillation.
During the section labelled ‘Input is positive’, here’s how the current flows around the circuit:
The reason why the current can’t flow through D4, after passing through RL, is because D4 has already been reverse biased by current flowing from the AC input.
Flow of current during negative half of the oscillation.
During the section labelled ‘Input is negative’, here’s how the current flows around the circuit:
As you can see, regardless of whether the AC input is positive or negative, the current flowing through RL never changes. If we could see what the current looked like at RL, It’d look something like this:
Notes for future.
I’ll add in a diagram and explanation as to how to dampen the rippling effect seen in the graph above.