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參數(shù)資料
| 型號(hào)： | 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)： | 11/22頁 |
| 文件大小： | 200K |
| 代理商： | NCP1212 |
NCP1212
http://onsemi.com
11
DETAILED OPERATING DESCRIPTIONS
INTRODUCTION
The NCP1212 implements a standard current mode
architecture where the switchoff time is dictated by the
peak current setpoint. This device represents an ideal
candidate where low external partcount is the key system
requirement. Additionally, the device provides extensive
valueadded functions, SoftStart, Brownout Detect, etc.,
that can be applied to lowcost ACDC adaptor
applications. The NCP1212 incorporates all the necessary
functions normally needed in UC384X based power supply
systems: Oscillator section, PWM Latch section, Current
Sense section, Brownout Detect protection, SoftStart and
Maximum Duty Cycle Selection. With all those functions,
this device becomes a good alternative to UC384X that can
help to improve both performance and system cost. Also, the
innovative Maximum Duty Cycle Selection feature allows
the device applied to both forward and flyback mode
configurations. Detailed functions of individual internal
blocks are described in below and a simplified functional
block diagram is shown in Figure 2.
Oscillator Section
The oscillator frequency is programmed by the capacitor
connected to C
T
pin. The capacitor is charged by a constant
current source to 3.8 V and 2.5 V for 82% and 48%
maximum Duty Cycle condition respectively. Once the
selected voltage is reached, C
T
is then discharged by another
constant current source down to 1.0 V and this charging and
discharging action will carry on perpetually. Desirable
switching frequency can be selected by choosing proper
value of timing capacitor, C
T
. The C
T
pin waveform is
shown in Figure 32.
Figure 32. C
T
Pin Waveform for Oscillator
3.8 V
2.5 V
1.0 V
48%
48%
82%
PWM Latch Section
NCP1212 works in current mode. The power switch
current is converted to a positive voltage by inserting a
sensing resistor R
sense
between the power switch source and
the ground. The power switch peak current is compared with
the level shifted control input voltage on a cyclebycycle
basis. Figure 27 illustrated the internal blocks of the
function. The PWM latch is initialized by the Oscillator set
signal and is terminated by the current sense comparator
when the current exceeds the value dictated by the control
input or current limit level. The current sense Comparator
Latch configuration used ensures that only a single pulse
appears at the output during any given oscillator cycle.
Figure 33. PWM Latch Function
FB
+5 V
3 R
R
9 K
300 ns
LEB
S
Q
Q
Current
Limit
+
Output
+
Output
+
1 V
Oscillator
Reset
Set
R
F/F
DRV
CS
1
2
3
4
Rsense
PWM Control
Totem Pole Driver
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| NCP1212PG | Current Mode PWM Controller for Both Forward and Flyback Converters |
| NCP1212DR2 | Current Mode PWM Controller for Both Forward and Flyback Converters |
| NCP1212P | Current Mode PWM Controller for Both Forward and Flyback Converters |
| NCP1215(中文) | Low Cost Variable OFF Time Switched Mode Power Supply Controller(低成本可變關(guān)閉時(shí)間開關(guān)模式電源控制器) |
| NCP1215ADR2 | Low Cost Variable OFF Time Switched Mode Power Supply Controller |
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(shí)間: 下降時(shí)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(shí)間: 下降時(shí)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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