參數(shù)資料
型號： L6599AN
廠商： STMICROELECTRONICS
元件分類： 穩(wěn)壓器
英文描述： SWITCHING CONTROLLER, DIP16
封裝： ROHS COMPLIANT, DIP-16
文件頁數(shù)： 16/36頁
文件大小： 1595K
代理商： L6599AN
L6599A
Application information
Doc ID 15308 Rev 5
23/36
7.3
Soft-start
Generally speaking, purpose of soft-start is to progressively increase converter's power
capability when it is started up, so as to avoid excessive inrush current. In resonant
converters the deliverable power depends inversely on frequency, then soft- start is done by
sweeping the operating frequency from an initial high value until the control loop takes over.
With the L6599A converter's soft start-up is simply realized with the addition of an R-C
series circuit from pin 4 (RFmin) to ground (see Figure 27, left).
Initially, the capacitor CSS is totally discharged, so that the series resistor RSS is effectively
in parallel to RFmin and the resulting initial frequency is determined by RSS and RFmin
only, since the optocoupler's phototransistor is cut off (as long as the output voltage is not
too far away from the regulated value):
Equation 4
The CSS capacitor is progressively charged until its voltage reaches the reference voltage
(2 V) and, consequently, the current through RSS goes to zero. This conventionally takes 5
times constants RSSCSS but, before that time, the output voltage will have got close to the
regulated value and the feedback loop taken over, so that it will be the optocoupler's
phototransistor to determine the operating frequency from that moment onwards.
During this frequency sweep phase the operating frequency will decay following the
exponential charge of CSS, that is, initially it will change relatively quickly but the rate of
change will get slower and slower. This counteract the non-linear frequency dependence of
the tank circuit that makes converter's power capability change little as frequency is away
from resonance and change very quickly as frequency approaches resonance frequency
(see Figure 27, right).
Figure 27.
Soft-start circuit (left) and power vs. frequency curve in an resonant
half-bridge (right)
As a result, the average input current will smoothly increase, without the peaking that occurs
with linear frequency sweep, and the output voltage will reach the regulated value with
almost no overshoot.
Typically, RSS and CSS will be selected based on the following relationships:
()
SS
min
start
R
//
RF
CF
3
1
f
=
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
L6599ATD 功能描述:電壓模式 PWM 控制器 Sgl Output 13.3 V 200 KHz SOIC-16 Nrw RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓撲結(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
L6599ATDTR 功能描述:開關(guān)變換器、穩(wěn)壓器與控制器 IMPROVED High-Volt RESONANT CONTROLLER RoHS:否 制造商:Texas Instruments 輸出電壓:1.2 V to 10 V 輸出電流:300 mA 輸出功率: 輸入電壓:3 V to 17 V 開關(guān)頻率:1 MHz 工作溫度范圍: 安裝風格:SMD/SMT 封裝 / 箱體:WSON-8 封裝:Reel
L6599ATN 制造商:STMicroelectronics 功能描述:
L6599D 功能描述:軟開關(guān) PWM 控制器 Hi Vltg resonant Controller RoHS:否 制造商:Fairchild Semiconductor 輸出端數(shù)量: 輸出電流: 開關(guān)頻率: 工作電源電壓:30 V 電源電流: 最大工作溫度:+ 105 C 最小工作溫度:- 40 C 安裝風格:SMD/SMT 封裝 / 箱體:SOIC-8 封裝:Reel
L6599DTR 功能描述:軟開關(guān) PWM 控制器 Hi Vltg resonant Controller RoHS:否 制造商:Fairchild Semiconductor 輸出端數(shù)量: 輸出電流: 開關(guān)頻率: 工作電源電壓:30 V 電源電流: 最大工作溫度:+ 105 C 最小工作溫度:- 40 C 安裝風格:SMD/SMT 封裝 / 箱體:SOIC-8 封裝:Reel
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