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NCP1239

Fixed Frequency Current‐Mode Controller for Flyback Converter

ON Semiconductor 

NCP1239

Vbulk

OVP

Vout

.

.

NCP1239

1

8

2

3

6

4

5

NTC

OPP

adjsut.

Figure 1. Application Schematic (OPP Adjustment)

Table 1. PIN FUNCTION DESCRIPTION

Pin No. Pin Name

Description

1

Fault

The controller enters fault mode if the voltage of this pin is pulled above or below the fault thresholds. A

precise pull up current source allows direct interface with an NTC thermistor. Fault detection triggers a latch.

2

FB

Hooking an optocoupler collector to this pin will allow regulation.

3

CS

This pin monitors the primary peak current but also offers an overpower compensation adjustment. When the

CS pin is brought above 1.2 V, the part is permanently latched off.

4

GND

The controller ground.

5

DRV

The driver’s output to an external MOSFET gate.

6

VCC

This pin is connected to an external auxiliary voltage. An OVP comparator monitors this pin and offers a

means to latch the converter in fault conditions.

7

NC

Non-connected for improved creepage distance.

8

HV

Connected to the bulk capacitor or rectified ac line, this pin powers the internal current source to deliver a start-

up current. It is also used to provide the brown-out detection and the HV sensing for the Overpower protection.

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