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參數資料
| 型號： | NCP1217P65G |
| 廠商： | ON SEMICONDUCTOR |
| 元件分類： | 穩壓器 |
| 英文描述： | Enhanced PWM Current−Mode Controller for High−Power Universal Off−Line Supplies |
| 中文描述： | 0.5 A SWITCHING CONTROLLER, 71.5 kHz SWITCHING FREQ-MAX, PDIP8 |
| 封裝： | LEAD FREE, PLASTIC, DIP-8 |
| 文件頁數： | 12/18頁 |
| 文件大小： | 249K |
| 代理商： | NCP1217P65G |
NCP1217, NCP1217A
http://onsemi.com
12
Figure 22. Inserting a Resistor in Series with the Current
Sense Information Brings Ramp Compensation
+
From
Setpoint
L.E.B.
19 k
CS
Rcomp
Rsense
2.9 V
0 V
Duty Cycle Typ = 74%
In the NCP1217, the ramp features a swing of 2.9 V with
a duty cycle max at 74%. Over a 65 kHz frequency, for
instance, it corresponds to a 254 mV/ s ramp. In our
FLYBACK design, let’s suppose that our primary
inductance Lp is 350 H, delivering 12 V with a Np:Ns ratio
of 1:0.1. The OFF time primary current slope is thus given
(Vout
Vf) ·
Ns
Lp
projected over an Rsense of 0.1 , for instance. If we select
75% of the downslope as the required amount of ramp
compensation, then we shall inject 27 mV/ s. Our
internal compensation being of 254 mV/ s, the divider
ratio (
divratio
) between Rcomp and the 19 k is 0.106.
A few lines of algebra to determine Rcomp:
19 k · divratio
(1divratio)
by:
Np
371 mA
s
or
37 mV
s
when
2.26 k
.
Latching Off the NCP1217
Total latched shutdown can easily be implemented
through a simple PNP bipolar transistor as depicted by
Figure 23. When OFF, Q1 is transparent to the operation.
When forward biased, the transistor pulls the Adj pin toward
V
CC
and permanently latchesoff the IC as soon Vadj goes
above the latching level (typical 3.1 V). Figure 23 shows
how to wire the bipolar transistor to activate the latchoff. A
typical candidate for Q1 could be an MMBT3906 from
ON Semiconductor.
Figure 23. A Simple Bipolar Transistor Totally
Disables the IC
CV
CC
8
7
6
5
1
2
3
4
Off
V
CC
Q1
Rlimit
Figure 24. When Vadj is Pulled Above 3.1 V, NCP1217 Permanently LatchesOff the Output Pulses
Default
adj level
Fault brings adj above latching level
Latchedoff
Reset level
The startup current source keeps the
device latched until reset occurs.
V
CC
Time
Time
Time
Driver
Pulses
Drv
Adj
VCC
ON
= 12.8 V
VCC
min
= 7.6 V
VCC
latch
= 5.6 V
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相關代理商/技術參數 |
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| NCP1218 | 制造商:ONSEMI 制造商全稱:ON Semiconductor 功能描述:PWM Controller with Adjustable Skip Level and External Latch Input |
| NCP1218AD65R2G | 功能描述:電流型 PWM 控制器 ANA PWM CONTROLLER RoHS:否 制造商:Texas Instruments 開關頻率:27 KHz 上升時間: 下降時間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數量:1 最大工作溫度:+ 105 C 安裝風格:SMD/SMT 封裝 / 箱體:TSSOP-14 |
| NCP1219 | 制造商:ONSEMI 制造商全稱:ON Semiconductor 功能描述:PWM Controller with Adjustable Skip Level and External Latch Input |
| NCP1219AD100R2G | 功能描述:電流型 PWM 控制器 ANA PWM CONTROLLER RoHS:否 制造商:Texas Instruments 開關頻率:27 KHz 上升時間: 下降時間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數量:1 最大工作溫度:+ 105 C 安裝風格:SMD/SMT 封裝 / 箱體:TSSOP-14 |
| NCP1219AD65R2G | 功能描述:電流型 PWM 控制器 ANA PWM CONTROLLER RoHS:否 制造商:Texas Instruments 開關頻率:27 KHz 上升時間: 下降時間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數量:1 最大工作溫度:+ 105 C 安裝風格:SMD/SMT 封裝 / 箱體:TSSOP-14 |
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