参数资料
型号: NCP1234BD65R2G
厂商: ON Semiconductor
文件页数: 15/33页
文件大小: 0K
描述: IC REG CTRLR FLYBACK PWM 7SOIC
标准包装: 2,500
PWM 型: 电流模式
输出数: 1
频率 - 最大: 70kHz
占空比: 85%
电源电压: 9.5 V ~ 28 V
降压:
升压:
回扫:
反相:
倍增器:
除法器:
Cuk:
隔离:
工作温度: -40°C ~ 125°C
封装/外壳: 8-SOIC(0.154",3.90mm 宽)7 引线
包装: 带卷 (TR)
NCP1234
V HV
V HV(min)
V CC
V CC(on)
V CC(min)
HV
time
V CC(inhibit)
current
source =
I start1
HV
current
source =
I start2
time
DRV
time
Figure 28. Start ? up Timing Diagram
For safety reasons, the start ? up current is lowered when
V CC is below V CC(inhibit) , to reduce the power dissipation in
case the V CC pin is shorted to GND (in case of V CC capacitor
failure, or external pull ? down on V CC to disable the
controller).
There are only two conditions for which the current source
doesn’t turn on when V CC reaches V CC(min) : the voltage on
HV pin is too low (below V HV(min) ), or a thermal shutdown
condition (TSD) has been detected. In all other conditions,
the HV current source will always turn on and off to maintain
V CC between V CC(min) and V CC(on) .
When the application is turned off, the input capacitor
quickly discharges, and the output starts to fall out of
regulation. At the same time, V CC drops, but because there
is no voltage anymore on the HV pin, the DSS isn’t able to
turn on. As a result, V CC drops even more and reach the
V CC(off) threshold, that turns the controller off, and resets the
internal fault timer, to prevent any unwanted latch ? off and
allow a fast restart in case of a short OFF/ON sequence.
As soon as the application is turned back on, the HV
start ? up current source starts to charge the V CC capacitor.
Note that the threshold at which V CC discharges has no
influence on the ability of the controller to restart. The
switching then turns on when V CC reaches V CC(on) , without
additional delay or “hiccup”.The case of a fast OFF/ON
sequence is described at Figure 29.
http://onsemi.com
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