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BM2PXX2F
(5) Over Current limiter
BM2PXX2F is built in Over Current limiter per cycle. If the SOURCE pin exceeds a certain voltage, switching is stopped. It is
also built in AC voltage compensation function. This is the function which compensates the maximum power as the AC voltage’
s change by increasing over current limiter with time.
Shown in figure-12, 13, and 14.
Figure 12. No AC voltage compensation function
Figure13. built-in AC compensation voltage
Primary peak current is decided as the formula below.
Primary peak current:
Ipeak = Vcs/Rs + Vdc/Lp*Tdelay
Vcs：Over current limiter voltage internal IC, Rs：Current detection resistance, Vdc input DC voltage, Lp：Primary inductance,
Tdelay：delay time after detection of over current limiter
Figure 14. Over current limiter voltage
(6) L.E.B period
When the driver MOSFET is turned ON, surge current occurs at each capacitor component and drive current.
Therefore, because SOURCE pin voltage rises temporarily, the detection errors may occur in the over current limiter circuit.
To prevent detection errors, DRAIN is switched from high to low and the SOURCE signal is masked for 250 ns by the on-chip
LEB (Leading Edge Blanking) function.
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TSZ02201-0F2F0A200040-1-2
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7. Mar.2017.Rev.007
TSZ22111・15・001
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