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參數(shù)資料
| 型號： | NCP1212 |
| 廠商： | ON SEMICONDUCTOR |
| 英文描述： | Current Mode PWM Controller for Both Forward and Flyback Converters |
| 中文描述： | 電流模式PWM控制器正向和反激式轉(zhuǎn)換器 |
| 文件頁數(shù)： | 16/22頁 |
| 文件大小： | 200K |
| 代理商： | NCP1212 |
NCP1212
http://onsemi.com
16
APPLICATION INFORMATION AND TYPICAL WAVEFORMS
The NCP1212 is an ideal choice for next generation
isolated fix switching frequency forward mode converters
that only need few external components to complete the
system. Converting your existing application from using
UC384X controllers to NCP1212 is easy and simple. In
below is a description on how to determine external
components value for a typical application example. For the
schematic of the application, please refer to Figure 1 in this
data sheet.
Finding the external component values can be broken
down into several steps as introduced below:
1. Select the maximum Duty Cycle for forward mode
operation and calculate the SoftStart time.
Select the system, operate in forward mode with
82% maximum Duty Cycle. Only a capacitor is
required at SS/DMAX pin and the SoftStart time is
determined by the capacitor, C
SS
. Its value is given
by the equation below:
I
V1
CSS
TSS
V2
where:
I is an 8.0 A constant current source flow out of the
SS/DMAX pin;
T
SS
is the required SoftStart time;
V
1
is the Upper Threshold Voltage in the oscillator
block and which is effectively controlling the PWM
maximum Duty Cycle at gate driver output.
SoftStart block will have no effect to the PWM
operation once SS/DMAX pin voltage reaches this
threshold. This threshold voltage is 2.5 V with 48%
maximum Duty Cycle;
V
2
is about 0.4 V (1.0 V minus one diode drop)
which is the Lower Voltage Threshold for the PWM
operation. There will be no PWM gate driver output
before SS/DMAX pin voltage attains this threshold.
For example, the required SoftStart time is 50 ms,
the timing capacitor, C
SS
can be calculated as:
8 A
50 ms
2.5 V
In this case, a 0.22 F capacitor is used for this
application and the SoftStart time is calculated as
57.75 ms. The charging waveform at SS/DMAX pin
is shown in Figure 40. From the captured waveform,
the charge time from 0 V to 4.0 V is 115.2 ms and for
the voltage charging up to 2.5 V, i.e. hitting the
Upper Threshold Voltage, the elapsed time is about
70 ms that matched with the theoretical calculation
closely.
CSS
0.4 V
0.182 F
Figure 40. SS/DMAX Pin Charging Waveform
115.2 ms
4.0 V
Overload condition is signified by current sense input
voltage hitting the Maximum Current Sense Threshold,
V
CS
. To avoid false trigger that may happen during transient
load change, C
SS
starts to discharge by an internal current
source of 20 A, I
SD
I
SS
and the overload protection will
only be issued until the voltage at SS/DMAX pin falls below
0.5 V. The discharging time, T
DIS
for 0.22 F SoftStart
capacitor is given by:
CSS
(Vref
ISD
TDIS
VD
ISS
VOL)
where:
C
SS
is the SoftStart timing capacitor;
V
ref
is the internal reference voltage, 5.0 V typical;
V
D
is the internal diode forward voltage on between the
reference voltage and SS/DMAX pin in IC internal, is 0.6 V
typical;
V
OL
is the overload threshold voltage. Refer to Figure 39
Overload Detection Block Diagram, the overload threshold
voltage is 0.5 V typical;
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| NCP1212/D | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Current Mode PWM Controller for Both Forward and Flyback Converters |
| NCP1212_05 | 制造商:ONSEMI 制造商全稱:ON Semiconductor 功能描述:Current Mode PWM Controller for Both Forward and Flyback Converters |
| NCP1212DR2 | 功能描述:電流型 PWM 控制器 High Performance RoHS:否 制造商:Texas Instruments 開關(guān)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(shù)量:1 最大工作溫度:+ 105 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TSSOP-14 |
| NCP1212DR2G | 功能描述:電流型 PWM 控制器 High Performance Current Mode PWM RoHS:否 制造商:Texas Instruments 開關(guān)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(shù)量:1 最大工作溫度:+ 105 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TSSOP-14 |
| NCP1212P | 功能描述:交流/直流開關(guān)轉(zhuǎn)換器 High Performance RoHS:否 制造商:STMicroelectronics 輸出電壓:800 V 輸入/電源電壓（最大值）:23.5 V 輸入/電源電壓（最小值）:11.5 V 開關(guān)頻率:115 kHz 電源電流:1.6 mA 工作溫度范圍:- 40 C to + 150 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SSO-10 封裝:Reel |
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