NCP1377PG 데이터 시트보기 (PDF) - ON Semiconductor

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NCP1377PG

PWM Current−Mode Controller for Free−Running Quasi−Resonant Operation

ON Semiconductor 

Drain

Signal

NCP1377, NCP1377B

Timeout

Signal

Drain

Signal

Demag Restart

Current Sense and Timeout Restart

Timeout

Signal

5 ms

5 ms

Figure 20. When the primary natural ringing becomes too low, the internal TimeOut

together with the sense comparator initiates a new cycle when FB passes the skip level.

Demagnetization Detection

The core reset detection is done by monitoring the

voltage activity on the auxiliary winding. This voltage

features a FLYBACK polarity. The typical detection level

is fixed at 50 mV as exemplified by Figure 21.

7.0

5.0

POSSIBLE

RESTARTS

3.0

1.0

0V

−1.0

50 mV

Figure 21. Core Reset Detection is Done through

a Dedicated Auxiliary Winding Monitoring

An internal timer prevents any restart within 8.0 ms

further to the driver going−low transition for NCP1377,

and 3.0 ms for NCP1377B. This prevents the switching

frequency to exceed (1.0/TON + Tblank) but also avoid false

TO INTERNAL

COMPARATOR

Rint

Resd

2

ESD2

1

1

ESD1

Rdem

5

4

Resd + Rint = 28 k

Figure 22. Internal Pad Implementation

4

Aux

3

leakage inductance tripping at turn−off. In some cases, the

leakage inductance kick is so energetic, that a slight

filtering is necessary.

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