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參數(shù)資料
| 型號： | CS51220ED16 |
| 英文描述： | Analog IC |
| 中文描述： | 模擬IC |
| 文件頁數(shù)： | 15/16頁 |
| 文件大?。?/td> | 184K |
| 代理商： | CS51220ED16 |
CS51220
http://onsemi.com
8
APPLICATIONS INFORMATION
THEORY OF OPERATION
Feed Forward Voltage Mode Control
Conventional voltage mode control uses a fixed ramp
signal for pulse width modulation, typically utilizing the
oscillator output as the ramp signal. Since the only feedback
signal comes from the output, this results in inferior line
regulation
and
audio
susceptibility.
A
significant
improvement in line regulation and line transient response
can be achieved using Feed Forward Voltage Mode Control,
implemented using the CS51220 controller.
The enhancement comes from generating the ramp signal
using a pull–up resistor from the FF pin to the line voltage
and a capacitor to ground. The slope of the ramp then
depends on the line voltage. At the start of each switch cycle,
the capacitor connected to the FF pin is charged through the
resistor connected to the input voltage. Meanwhile, the VO
pin goes high to turn on a power mosfet through an external
gate driver. When the rising FF pin exceeds the COMP input
pin, as driven through the regulation feedback loop, VO goes
low and turns off the external switch. Simultaneously, the FF
capacitor is quickly discharged and set for the next switching
cycle.
Overall, both input and output voltages control the
dynamics of the duty cycle. As illustrated in Figure 3, with
a fixed input voltage the output voltage is regulated solely
by the error amplifier. For example, an elevated output
voltage pulls down the COMP pin through an external error
amplifier. This in turn causes duty cycle to decrease. On the
another hand, if the input voltage varies, the slope of the FF
pin ramp reacts correspondingly and immediately. As an
example shown in Figure 4, when the input voltage goes up,
the slope of the ramp signal increases, which reduces duty
cycle and counteracts the change. For line variations, feed
forward control requires less response from the error
amplifier, which improves the transient speed and DC
regulation.
Figure 3. Pulse Width Modulated by the Output
Voltage with a Constant Input Voltage
VIN
COMP
FF
VOUT
CT
VO
Figure 4. Pulse Width Modulated by the Input Voltage
with a Constant Output Voltage
VIN
COMP
FF
VOUT
CT
VO
The feed forward feature can also be employed for
volt–second clamp, which limits the maximum product of
input voltage and switch on time. This clamp is used in
circuits, such as forward and flyback converters, to prevent
the transformer from saturating. Calculations used in the
design of the volt–second clamp are presented in the Design
Guidelines section on page 12.
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| CS51220EDR16 | 功能描述:IC REG CTRLR DIV ISO PWM 16-SOIC RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:4,000 系列:- PWM 型:電壓模式 輸出數(shù):1 頻率 - 最大:1.5MHz 占空比:66.7% 電源電壓:4.75 V ~ 5.25 V 降壓:是 升壓:無 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 85°C 封裝/外殼:40-VFQFN 裸露焊盤 包裝:帶卷 (TR) |
| CS51221 | 制造商:CHERRY 制造商全稱:CHERRY 功能描述:Enhanced Voltage Mode PWM Controller |
| CS51221/D | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Enhanced Voltage Mode PWM Controller |
| CS51221_09 | 制造商:ONSEMI 制造商全稱:ON Semiconductor 功能描述:Enhanced Voltage Mode PWM Controller |
| CS51221ED16 | 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 |
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