Basic operation
According to the
conventional model of
current flow originally established by
Benjamin Franklin and still followed by most engineers today, current is
assumed to flow through
electrical conductors from the
positive to the
negative pole.
[2] In actuality,
free electrons in a conductor nearly always flow from the
negative to the
positive pole. In the vast majority of applications, however, the
actual direction of current flow is irrelevant. Therefore, in the discussion below the conventional model is retained.
In the diagrams below, when the input connected to the
left corner of the diamond is
positive, and the input connected to the
right corner is
negative, current flows from the
upper supply terminal to the right along the
red (positive) path to the output, and returns to the
lower supply terminal via the
blue (negative) path.
When the input connected to the
left corner is
negative, and the input connected to the
right corner is
positive, current flows from the
upper supply terminal to the right along the
red (positive) path to the output, and returns to the
lower supply terminal via the
blue (negative) path.
[3]
AC,
half-wave and full wave rectified signals.
[4]
In each case, the upper right output remains positive and lower right output negative. Since this is true whether the input is AC or DC, this circuit not only produces a DC output from an AC input, it can also provide what is sometimes called "reverse polarity protection". That is, it permits normal functioning of DC-powered equipment when
batteries have been installed backwards, or when the leads (wires) from a DC power source have been reversed, and protects the equipment from potential damage caused by reverse polarity.
Prior to the availability of
integrated circuits, a bridge rectifier was constructed from "discrete components", i.e., separate diodes. Since about 1950, a single four-terminal component containing the four diodes connected in a bridge configuration became a standard commercial component and is now available with various
voltage and current ratings.