参数资料
型号: NCP1234BD100R2G
厂商: ON Semiconductor
文件页数: 19/33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: 108kHz
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 FB
V FB(fault)
Time
Soft-start ramp
V ILIM
V FB takes
over soft-start
CS Setpoint
V ILIMI
Figure 33. Soft ? Start
t SSTART
Time
Time
P OUT +
@ h @ L p @ F SW @ I p
1 2
Under some conditions, like a winding short ? circuit for
instance, not all the energy stored during the on time is
transferred to the output during the off time, even if the on
time duration is at its minimum (imposed by the propagation
delay of the detector added to the LEB duration). As a result,
the current sense voltage keeps on increasing above V ILIM ,
because the controller is blind during the LEB blanking
time. Dangerously high current can grow in the system if
nothing is done to stop the controller. That’s what the
additional comparator, that senses when the current sense
voltage on CS pin reaches V CS(stop) (= 1.5 x V ILIM ), does:
as soon as this comparator toggles, the controller
Overpower compensation
The power delivered by a flyback power supply is
proportional to the square of the peak current in the
discontinuous conduction mode:
(eq. 1)
2
Unfortunately, due to the inherent propagation delay of
the logic, the actual peak current is higher at high input
voltage than at low input voltage, leading to a significant
difference in the maximum output power delivered by the
power supply.
immediately enters the protection mode (latched or
autorecovery according to the chosen option).
http://onsemi.com
19
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