Input isolated voltage monitor

A fly-back circuit comprising:

• a voltage source;
• a transformer comprising a primary winding electrically coupled to the voltage source and a secondary winding electrically coupled to a load;
• a diode connected between the secondary winding and the load;
• a switch electrically coupled to the primary winding;
• a controller operable to open and close the switch to control energy transfer from the primary winding to the secondary winding;
• and
• wherein a voltage monitor includes a comparator that generates an output signal, the comparator having a first input connected to a node between the secondary winding and the diode and a second input connected to a monitor threshold voltage,
• and wherein the output signal being a toggling output when the voltage source is operating above an input voltage threshold and a constant output when the voltage source is operating below the input voltage threshold.