Figure 2-33 Over
Current Protection (OCP) Protection
Figure 2-34 High
Side Switch Current Extraction from ISNS Signal
Resonant current is reconstructed as ISNS voltage using a differentiator
connected to the resonant capacitor.
OCP1 (OCP1Th: 4 V) is for output
short circuit protection; it checks the magnitude of the resonant current.
OCP2 (OCP2Th: 0.6 V) is for
over-load protection; it checks the average DC input current. The time the
average input current needs to stay above OCP2 threshold before OCP2 is
triggered is 2 ms.
OCP3 (OCP3Th: 0.43 V) is also for
over-load protection but it has lower threshold value compared to OCP2, OCP1; it
checks the average DC input current. The time the average input current needs to
stay above OCP3 threshold before OCP3 is triggered is 50 ms.
DC input current is reconstructed
by capturing the current flowing through high side MOSFET.
Internally, ISNS voltage is
truncated when HO is high and then filtered to get the average dc value.