Note that S1 and S4 should not be closed at the same time, nor should S2 and S3.
Otherwise, a short circuit would exist across the dc source. Real switches do
not turn on or off instantaneously, as was discussed in Chap. 6. Therefore,
switching transition times must be accommodated in the control of the switches.
Overlap of switch “on” times will result in a short circuit, sometimes called a
shoot-through fault, across the dc voltage source. The time allowed for switching
is called blanking time.