NCP1392B Datasheet, PDF(17/19 Page) ON Semiconductor – High-Voltage Half-Bridge Driver with Inbuilt Oscillator

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NCP1392B Datasheet, PDF (17/19 Pages) ON Semiconductor – High-Voltage Half-Bridge Driver with Inbuilt Oscillator

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VCC

NCP1392B

Vbulk

Rupper

Rlower

Ihyste

IC1

TLV431

Voltage

Feedback

Rfstart

CSS

VrefEN

VrefBO

0.5ms

Filter

20ms

Filter

to AND gates

To PFC Delay

High Level for 50 ms after VCC ON

NCP1392

GND

Figure 33. Skip Mode Feature Implementation (Better Accuracy)

Figures 31 and 33 shows skip mode feature

implementation using NCP1392 driver. Voltage across

resistor R1 (R4) increases when converter enters light load

conditions. The enable comparator is triggered when

voltage across R1 is higher than Vref EN + Vf(D1) for

connection from Figure 31 (voltage across R4 is higher than

1.24 V for connection from figure 16). IC then prevents

outputs from pulsing until BO terminal voltage decreases

below 1.92 V.

Note that enable comparator serves also as an automatic

overvoltage protection. When bulk voltage is too high, the

enable input is triggered via BO divider.

The HighâVoltage Driver

Figure 34 shows the internal architecture of the

highâvoltage section. The device incorporates an upper

UVLO circuitry that makes sure enough Vgs is available for

the upper side MOSFET. The VCC for floating driver section

is provided by Cboot capacitor that is refilled by external

bootstrap diode.

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