MS Surface power supply
During normal operation: When the MOSFET in the Connector box switches on (pulls the Blue line low) it prevents the pulses from the "Pulse Gen" from getting to the main power MOSFET (the left side MOSFET), those pulses are effectively shorted out, the main power MOSFET is full on, and the LED pair is also full on, (not blinking).   

For a flaw that might cause it to blink: If the MOSFET in the Connector box went bad, or the Power on Controller went bad, or the resistor or the 3.3v (above that) went bad.  In those cases the LED might be blinking instead of full on.  Possibly even a loose 12v connection (from the battery or connection on the left side) could make it blink.  To be thorough I suppose you could also include the possibility of loose (dirty or worn out) pins in the connector box making it blink too.