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UCC28070-Q1 参数 Datasheet PDF下载

UCC28070-Q1图片预览
型号: UCC28070-Q1
PDF下载: 下载PDF文件 查看货源
内容描述: 交错连续导通模式PFC控制器 [INTERLEAVING CONTINUOUS CONDUCTION MODE PFC CONTROLLER]
分类和应用: 功率因数校正控制器
文件页数/大小: 43 页 / 883 K
品牌: TI [ TEXAS INSTRUMENTS ]
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UCC28070-Q1  
SLUSA71A JULY 2010REVISED JUNE 2011  
www.ti.com  
Current Synthesizer  
One of the most prominent innovations in the UCC28070 design is the current synthesizer circuitry that  
synchronously monitors the instantaneous inductor current through a combination of on-time sampling and  
off-time down-slope emulation.  
During the on-time of the GDA and GDB outputs, the inductor current is recorded at the CSA and CSB pins  
respectively via the current transformer network in each output phase. Meanwhile, the continuous monitoring of  
the input and output voltage via the VINAC and VSENSE pins permits the UCC28070 to internally recreate the  
inductor current's down-slope during each output's respective off-time. Through the selection of the RSYNTH  
resistor (RSYN), based on the equation below, the internal response may be adjusted to accommodate the wide  
range of inductances expected across the wide array of applications.  
During inrush surge events at power-up and ac drop-out recovery, VSENSE < VINAC, so the synthesized down  
slope becomes zero. In this case, the synthesized inductor current will remain above the IMO reference and the  
current loop drives the duty cycle to zero. This avoids excessive stress on the MOSFETS during the surge event.  
Once VINAC falls below VSENSE the duty cycle increases until steady-state operation resumes.  
Waveform at  
CSx input  
Synthesized  
down-slope  
Current Synthesizer  
output to CA  
Figure 19. Inductor Current's Down Slope  
10´ N ´ L mH ´k  
B ( )  
(
)
CT  
R
RSYN kW =  
( )  
R W  
S ( )  
(12)  
Variables  
LB = Nominal Zero-Bias Boost Inductance (μH),  
RS = Sense Resistor (),  
NCT = Current-sense Transformer turns ratio,  
kR = RB/(RA+RB) = the resistor-divider attenuation at the VSENSE and VINAC pins.  
20  
Copyright © 20102011, Texas Instruments Incorporated  
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