参数资料
型号: L6599D
厂商: STMICROELECTRONICS
元件分类: 稳压器
英文描述: 0.8 A SWITCHING CONTROLLER, 500 kHz SWITCHING FREQ-MAX, PDSO16
封装: LEAD FREE, SOP-16
文件页数: 14/36页
文件大小: 636K
代理商: L6599D
L6599
Application information
21/36
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 L6599 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 28).
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):
The CSS capacitor is progressively charged until its voltage reaches the reference voltage
(2V) and, consequently, the current through RSS goes to zero. This conventionally takes 5
time 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 counteracts 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
Figure 28. Soft-start circuit
f
start
1
3CF
R F
min
R
SS
||
()
---------------------------------------------------------------
=
L6599
Css
4
1
RFmin
RFmin
RSS
CSS
| Z ( f ) |
相关PDF资料
PDF描述
L6599N 0.8 A SWITCHING CONTROLLER, 500 kHz SWITCHING FREQ-MAX, PDIP16
L6599TR 0.8 A SWITCHING CONTROLLER, 500 kHz SWITCHING FREQ-MAX, PDSO16
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L6610N 6-CHANNEL POWER SUPPLY SUPPORT CKT, PDIP24
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相关代理商/技术参数
参数描述
L6599DTR 功能描述:软开关 PWM 控制器 Hi Vltg resonant Controller RoHS:否 制造商:Fairchild Semiconductor 输出端数量: 输出电流: 开关频率: 工作电源电压:30 V 电源电流: 最大工作温度:+ 105 C 最小工作温度:- 40 C 安装风格:SMD/SMT 封装 / 箱体:SOIC-8 封装:Reel
L6599N 功能描述:软开关 PWM 控制器 Hi Vltg resonant Controller RoHS:否 制造商:Fairchild Semiconductor 输出端数量: 输出电流: 开关频率: 工作电源电压:30 V 电源电流: 最大工作温度:+ 105 C 最小工作温度:- 40 C 安装风格:SMD/SMT 封装 / 箱体:SOIC-8 封装:Reel
L6599NR 功能描述:电压模式 PWM 控制器 HV resonant CNTRL RoHS:否 制造商:Texas Instruments 输出端数量:1 拓扑结构:Buck 输出电压:34 V 输出电流: 开关频率: 工作电源电压:4.5 V to 5.5 V 电源电流:600 uA 最大工作温度:+ 125 C 最小工作温度:- 40 C 封装 / 箱体:WSON-8 封装:Reel
L6599TR 制造商:STMICROELECTRONICS 制造商全称:STMicroelectronics 功能描述:High-voltage resonant controller
L65B 制造商:Electro-Mech 功能描述: