- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄374166 > CS51221ED16 (ZF Electronics Corporation) Enhanced Voltage Mode PWM Controller PDF資料下載
參數(shù)資料
| 型號(hào)： | CS51221ED16 |
| 廠商： | ZF Electronics Corporation |
| 英文描述： | Enhanced Voltage Mode PWM Controller |
| 中文描述： | 增強(qiáng)的電壓模式PWM控制器 |
| 文件頁(yè)數(shù)： | 7/12頁(yè) |
| 文件大?。?/td> | 164K |
| 代理商： | CS51221ED16 |
C
TypicApplication Information
7
Feed Forward V oltage Mode Control
In conventional voltage mode control, the ramp signal has
fixed rising and falling slope. The feedback signal is
derived solely from the output voltage. Consequently,
voltage mode control has inferior line regulation and audio
susceptibility.
Feed forward voltage mode control derives the ramp sig-
nal from the input line, as shown in Fig.1. Therefore, the
ramp of the slope varies with the input voltage. At the start
of each switch cycle, the capacitor connected to the FF pin
is charged through a resistor connected to the input volt-
age. Meanwhile, the Gate output is turned on to drive an
external power switching device. When the FF pin voltage
reaches the error amplifier output V
COMP
, the PWM com-
parator turns off the Gate, which in turn opens the external
switch. Simultaneously, the FF capacitor is quickly dis-
charged to 0.3V.
Overall, the dynamics of the duty cycle are controlled by
both input and output voltages. As illustrated in Fig. 2,
with a fixed input voltage the output voltage is regulated
solely by the error amplifier. For example, an elevated
output voltage reduces V
COMP
which in turn causes duty
cycle to decrease. However, if the input voltage varies, the
slope of the ramp signal will react immediately which pro-
vides a much improved line transient response. As an
example shown in Fig.3, when the input voltage goes up,
the rising edge of the ramp signal increases which reduces
duty cycle to counteract the change.
Figure 1: Feed Forward V oltage Mode Control.
The feed forward feature can also be employed to provide
a volt-second clamp, which limits the maximum product
of input voltage and turn on time. This clamp is used in
circuits, such as Forward and Flyback converter, to prevent
the transformer from saturating. Calculations used in the
design of the volt-second clamp are presented in the
Design Guidelines section.
Figure 2: Pulse Width Modulated by Output Current with Constant
Input V oltage.
Figure 3: Pulse Width modulated by Input V oltage with constant
Output Current.
Powering the IC & UV L
The Under Voltage Lockout (UVL) comparator has two
voltage references; the start and stop thresholds. During
power-up, the UVL comparator disables V
REF
(which in-
turn disables the entire IC) until the controller reaches its
V
CC
start threshold. During power-down, the UVL com-
parator allows the controller to operate until the V
CC
stop
threshold is reached. The CS51221 requires only 50μA dur-
ing startup. The output stage is held at a low impedance
state in lock out mode.
During power up and fault conditions, the soft-start
clamps the Comp pin voltage and limits the duty cycle.
The power up transition tends to generate temporary duty
cycles much greater than the steady state value due to the
low output voltage. Consequently, excessive current
stresses often take place in the system. Soft Start technique
alleviates this problem by gradually releasing the clamp on
the duty cycle to eliminate the in-rush current. The dura-
tion of the Soft Start can be programmed through a capaci-
tance connected to the SS pin. The constant charging cur-
rent to the SS pin is 50μA (typ).
V
IN
V
COMP
FF
R
T
C
T
GATE
I
OUT
V
OUT
V
COMP
FF
V
IN
R
T
C
T
GATE
+
-
V
IN
COMP
FF
FB
V
OUT
Error Amplifier
C
R
Latch & Driver
PWM
Feedback Network
-+
Power Stage
GATE
Theory of Operation
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| CS51221EN16 | Enhanced Voltage Mode PWM Controller |
| CS51221 | Enhanced Voltage Mode PWM Controller |
| CS51221EDR16 | Enhanced Voltage Mode PWM Controller |
| CS5124 | High Performance, Integrated Current Mode PWM Controllers |
| CS5126XD8 | High Performance, Integrated Current Mode PWM Controllers |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| CS51221ED16G | 功能描述:電壓模式 PWM 控制器 Enhanced Current Mode PWM Controller RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓?fù)浣Y(jié)構(gòu):Buck 輸出電壓:34 V 輸出電流: 開關(guān)頻率: 工作電源電壓:4.5 V to 5.5 V 電源電流:600 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 封裝 / 箱體:WSON-8 封裝:Reel |
| CS51221EDR16 | 功能描述:電壓模式 PWM 控制器 Enhanced Current RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓?fù)浣Y(jié)構(gòu):Buck 輸出電壓:34 V 輸出電流: 開關(guān)頻率: 工作電源電壓:4.5 V to 5.5 V 電源電流:600 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 封裝 / 箱體:WSON-8 封裝:Reel |
| CS51221EDR16G | 功能描述:電壓模式 PWM 控制器 Enhanced Current Mode PWM Controller RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓?fù)浣Y(jié)構(gòu):Buck 輸出電壓:34 V 輸出電流: 開關(guān)頻率: 工作電源電壓:4.5 V to 5.5 V 電源電流:600 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 封裝 / 箱體:WSON-8 封裝:Reel |
| CS51221EDTB16G | 功能描述:電壓模式 PWM 控制器 ANA PWM CTR TSSOP RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓?fù)浣Y(jié)構(gòu):Buck 輸出電壓:34 V 輸出電流: 開關(guān)頻率: 工作電源電壓:4.5 V to 5.5 V 電源電流:600 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 封裝 / 箱體:WSON-8 封裝:Reel |
| CS51221EDTB16R2G | 功能描述:電壓模式 PWM 控制器 ANA PWM CTR TSSOP RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓?fù)浣Y(jié)構(gòu):Buck 輸出電壓:34 V 輸出電流: 開關(guān)頻率: 工作電源電壓:4.5 V to 5.5 V 電源電流:600 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 封裝 / 箱體:WSON-8 封裝:Reel |
發(fā)布緊急采購(gòu)，3分鐘左右您將得到回復(fù)。