US Patent 7449912 Fault detection circuit

Power supplies are disclosed herein. One embodiment of a power supply comprises a first input and a second input, wherein the first input and the second input are connectable to a pulse width modulation controller and wherein a pulse width modulation signal is outputable from the pulse width modulation controller. A power stage connected to the first input and the second input. A first comparator having a first comparator first input is connected to the first input and a first comparator second input connected to the output of the power stage. A change of voltage at the output of the first comparator constitutes a difference in phase between the first input and the output of the power stage.