NCP1398CDR2G データシートの表示（PDF） - ON Semiconductor

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NCP1398CDR2G

High Performance Resonant Mode Controller with Integrated High-Voltage Drivers

ON Semiconductor 

NCP1398B/C

Figure 34. A Typical Start−up Sequence on a LLC

Converter Using NCP1398

Brown−Out Protection

The resonant tank of an LLC converter is always designed

for specific input voltage range. Operation below minimum

designed bulk voltage level would result in current

overstress of converter primary power stage. The NCP1398

offers Brown−Out input (BO) that allows for precise bulk

voltage turn−on and turn−off levels adjustment. The internal

circuitry, depicted by Figure 35, offers a way to observe the

high−voltage (Vbulk) rail. A high−impedance resistive

divider made of Rupper and Rlower, brings a portion of the

Vbulk rail to BO pin. The Current sink (IBO) is active below

the Vbulk turn−on level. Therefore, the turn−on level is

higher than the one given by the division ratio of resistive

divider. To the contrary, when the internal BO_OK signal is

high, i.e. application is running, the IBO sink is disabled.

The Vbulk turn−off level is thus given by BO comparator

reference voltage and resistor divider ratio only. Advantage

of this solution is that the Vbulk turn−off level reaches

minimum error. This error is given only by VBO reference

and resistor divider precisions and is not affected by IBO

hysteresis current tolerance. The NCP1398 thus allows

better resonant tank optimization.

Vbulk

IBO

Rupper

BO

Rlower

+

−

+

VBO

20 s

lter

BO_OK

UVLO

Figure 35. The Internal Brown−out Input Configuration

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