參數(shù)資料
型號： L6599ATDTR
廠商： STMICROELECTRONICS
元件分類： 穩(wěn)壓器
英文描述： SWITCHING CONTROLLER, 500 kHz SWITCHING FREQ-MAX, PDSO16
封裝： SOP-16
文件頁數(shù)： 10/31頁
文件大小： 861K
代理商： L6599ATDTR
Application information
L6599AT
18/31
Doc ID 15534 Rev 3
6.3
Soft-start
Generally speaking, the purpose of soft-start is to progressively increase the 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, so soft-start is attained by
sweeping the operating frequency from an initial high value until the control loop takes over.
With the L6599AT, the converter's soft startup is easily achieved with the addition of an R-C
series circuit from pin 4 (RFmin) to ground (see Figure 10, left).
Initially, capacitor CSS is totally discharged, so that the series resistor RSS is effectively
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
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 typically takes 5 times
constants RSSCSS. However, before this time interval completes, the output voltage comes
close to the regulated value and the feedback loop takes over, so that the optocoupler's
phototransistor determines the operating frequency from that moment onwards.
During this frequency sweep phase the operating frequency decays, following the
exponential charge of CSS. That is, initially it changes relatively quickly but the rate of
change gets slower and slower. This counteracts the non-linear frequency dependence of
the tank circuit that makes the converter's power capability change little as frequency is
away from resonance, and change very quickly as the frequency approaches the resonance
frequency (see Figure 10, right).
Figure 10.
Soft-start circuit (left) and power vs. frequency curve in a resonant
half-bridge (right)
As a result, the average input current increases smoothly, without the peaking that occurs
with linear frequency sweep, and the output voltage reaches the regulated value with almost
no overshoot.
Typically, RSS and CSS are selected based on the following relationships:
()
SS
min
start
R
//
RF
CF
3
1
f
=
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PDF描述
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
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(fēng)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(fēng)格:SMD/SMT 封裝 / 箱體:SOIC-8 封裝:Reel
L6599N 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(fēng)格:SMD/SMT 封裝 / 箱體:SOIC-8 封裝:Reel
L6599NR 功能描述:電壓模式 PWM 控制器 HV resonant CNTRL 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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