NCP1288(2010) 데이터 시트보기 (PDF) - ON Semiconductor

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NCP1288
(Rev.:2010)

Fixed Frequency Current Mode Controller for Flyback Converters

ON Semiconductor 

NCP1288

At startup, the current source turns on when the voltage on

the HV pin is higher than VHV(min), and turns off when VCC

reaches VCC(on). It turns on again when VCC reaches

VCC(min). This sequence repeats until the input voltage is

high enough to ensure a proper startup, i.e. when VHV

reaches VHV(start). The switching actually starts the next

VHV

time VCC reaches VCC(on), as shown in Figure 5. The current

source is then turned off, saving additional power when the

VCC is supplied externally.

Once the controller has started, if VCC reaches VCC(min)

the switching stops and the protection mode is activated: the

controller must be supplied by an external voltage source.

VHV(start)

VHV(min)

VCC

VCC(on)

VCC(min)

VCC(inhibit)

DRV

HV

current

source =

Istart1

Waits

next

VCC(on)

before

starting

time

HV

current

source =

Istart2

time

Figure 5. Startup Timing Diagram

time

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