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參數資料
| 型號： | NCP1351 |
| 廠商： | ON SEMICONDUCTOR |
| 英文描述： | Variable Off Time PWM Controller |
| 中文描述： | 變關閉時間PWM控制器 |
| 文件頁數： | 11/19頁 |
| 文件大小： | 222K |
| 代理商： | NCP1351 |
NCP1351
http://onsemi.com
11
Figure 12. The OPP is Relatively Easy to Implement and It Does not Waste Power
C
Bulk
+
C3
270p
R1
150k
R
sense
DRV
I
Lp
V
CC
L
P
DRV
CS
R
offset
D2
1N4148
C4
22p
+
R
OPP
100k
CV
CC
L
aux
D
aux
Suppose you would need to reduce the peak current by
15% in highline conditions. The turnratio between the
auxiliary winding and the primary winding is N
aux
. Assume
its value is 0.15. Thus, the voltage on D
aux
cathode swings
negative during the on time to a level of:
Vaux_peak
Vin_maxNaux
375
0.15
56 V
(eq. 7)
If we selected a 3.7 k resistor for R
offset
, then the
maximum sense voltage being developed is:
Vsense
3.7 k
270
1 V
(eq. 8)
The small RC network made of R
1
and C
3
, purposely limits
the voltage excursion on D
2
anode. Assume the primary
inductance value gives an on time of 3
μ
s at highline. The
voltage across C
3
thus swings down to:
tonVaux_peak
R1C3
150 k
Typically, we measured around –4 V on our 50 W prototype.
By calculation, we want to decrease the peak current by
VC3
3
56
270 p
4.2 V
(eq. 9)
15%. Compared to the internal 270 A source, we need to
derive:
Ioffset
0.15
270
40.5 A
(eq. 10)
Thus, from the –4 V excursion, the R
OPP
resistor is
derived by:
4
40.5
ROPP
98 k
(eq. 11)
After experimental measurements, the resistor was
normalized down to 100 k .
Feedback
Unlike other controllers, the feedback in the NCP1351
works in current rather than voltage. Figure 13 details the
internal circuitry of this particular section. The optocoupler
injects a current into the FB pin in relationship with the
input/output conditions.
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相關代理商/技術參數 |
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| NCP1351ADAPGEVB | 功能描述:電源管理IC開發工具 NCP1351 57 W ADAPTER EVB RoHS:否 制造商:Maxim Integrated 產品:Evaluation Kits 類型:Battery Management 工具用于評估:MAX17710GB 輸入電壓: 輸出電壓:1.8 V |
| NCP1351ADR2G | 功能描述:電流型 PWM 控制器 OSPI 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 |
| NCP1351APG | 功能描述:電流型 PWM 控制器 VRIABLE OFF TM CNTRL 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 |
| NCP1351BDR2G | 功能描述:電流型 PWM 控制器 OSPI 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 |
| NCP1351BPG | 功能描述:電流型 PWM 控制器 VRIABLE OFF TM CNTRL 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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