L6563S View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
'L6563S' PDF : 43 Pages View PDF
Application information
L6563S
Figure 40. Tracking boost block
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Figure 41. Tracking output voltage vs Input voltage characteristic with TBO
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6.6
Inductor saturation detection
Boost inductor's hard saturation may be a fatal event for a PFC pre-regulator: the current up-
slope becomes so large (50-100 times steeper, see Figure 42) that during the current sense
propagation delay the current may reach abnormally high values. The voltage drop caused
by this abnormal current on the sense resistor reduces the gate-to-source voltage, so that
the MOSFET may work in the active region and dissipate a huge amount of power, which
leads to a catastrophic failure after few switching cycles.
However, in some applications such as ac-dc adapters, where the PFC pre-regulator is
turned off at light load for energy saving reasons, even a well-designed boost inductor may
30/43
Doc ID 16116 Rev 4
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