参数资料
型号: NCP1027ATXGEVB
厂商: ON Semiconductor
文件页数: 12/30页
文件大小: 0K
描述: BOARD EVAL NCP1027 10W STANDBY
设计资源: NCP1027ATXGEVB Schematic
NCP1027ATXGEVB Test Procedure
NCP1027ATXGEVB Bill of Materials
标准包装: 1
主要目的: AC/DC,主面
输出及类型: 1,非隔离
功率 - 输出: 10W
输出电压: 5V
电流 - 输出: 2A
输入电压: 85 ~ 265VAC
稳压器拓扑结构: 回扫
频率 - 开关: 65kHz
板类型: 完全填充
已供物品:
已用 IC / 零件: NCP1027
其它名称: NCP1027ATXGEVB-ND
NCP1027ATXGEVBOS
NCP1027
Figure 25. A typical startup sequence showing the V CC capacitor
voltage evolution versus time.
Suppose our power supply takes 10 ms (t startup ) to bring
the output voltage to its target value. We know that the
switcher consumption is around 2.0 mA (I CC1 ). Therefore,
we can calculate the amount of capacitance we need, to
hold V CC above 7.5 V at least for 10 ms while delivering
2.0 mA:
C w
ICC1tstartup
D VCC
or, by replacing with the above values,
C w 2m · 10 m w 20 m F then select a 33 m F for the V CC
1
capacitor.
Fault Condition – Short-Circuit on V CC
In some fault situations, a short-circuit can purposely
occur between V CC and GND. In high line conditions
(V HV = 370 V DC ) the current delivered by the startup
device will seriously increase the junction temperature. For
instance, since IC1 equals 3.0 mA (the min corresponds to
Figure 26. The startup source now features a
dual-level startup current.
the highest T J ), the device would dissipate 370 3m=
1.1 W. To avoid this situation, the controller includes a
novel circuitry made of two startup levels, IC1 and IC2. At
C
The first startup period is calculated by the formula
V=I t, which implies a 33 m 1.3/650 m = 66 ms
powerup, as long as V CC is below a 1.3 V level, the source
delivers IC1 (around 650 m A typical), then, when V CC
reaches 1.3 V, the source smoothly transitions to IC2 and
delivers its nominal value. As a result, in case of
short-circuit between V CC and GND, the power dissipation
will drop to 370 650 m = 240 mW. Figure 26 portrays
this particular behavior.
startup time for the first sequence (t 1 ). The second
sequence (t 2 ) is obtained by toggling the source to 4.0 mA
with a delta V of VCC ON – VCCth = 8.5 – 1.5 = 7.0 V,
which finally leads to a second startup time of
7 33 m /6.0 m = 39 ms. The total startup time becomes
66 m + 39 m = 105 ms as a typical value. Please note that
this calculation is approximated by the presence of the knee
in the vicinity of the transition.
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