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

Discharge

Rshift

Rt

Rocp

Cocp

Rss

Rt

Css

FB fault

VDD

C1 R1

To resonant

capacitor D2

D1

R2

OLP

C2

Itimer

Fault

OCP

fault

timer

logic

Vref_fault

OCP

To latch

1 us

Vref_latch

OCP

RC

filter

To DRV logic,

VCO and Vcc

management

VtimerON/

VtimerOFF

GND

Ctimer Ct

Rt

Figure 40. Overload Protection Input Connection NCP1398B

Fault Timer

The NCP1398 implements fault timer with fully

adjustable fault and auto−recovery periods – refer to

Figure 40 in OLP section. External capacitor Ct is used in

combination with internal current source and voltage

comparator to implement this function. Once the fault

condition occurs the Ctimer pin sources current (Itimer)

which charges Ct capacitor. The fault is confirmed and

drivers are disabled once the Ctimer pin voltage exceeds

Vtimer_off threshold. The Itimer current source is then

disabled and Ct capacitor discharges via parallel resistor Rt.

Controller places new try for restart (featuring Soft Start)

once the Ctimer pin voltage drops below Vtimer_ON

threshold. Controller will work in hiccup mode, repeating

fault and auto−recovery sequences, if the fault condition

remains present in the application (overload conditions or

secondary side short circuit). The Fault timer is from the

principle of operation a cumulative type of timer i.e. the

Ctimer pin voltage integrates if there are multiple faults

coming during short time period – refer to Figure 41.

The fault timer can be initiated by several fault sources:

1st – when feedback voltage drops below VFB_fault

threshold. This could happen when the FB loop is opened i.e.

during secondary regulator or optocoupler fail or open FB

pin events. Note that the fault timer is not activated by FB

fault detection circuitry for NCP1398C version.

2nd − when the OLP input voltage exceeds Vref_Fault_OCP

threshold. This situation happens during overload. The fault

timer is activated on both IC versions in this case.

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