RS5RJ5817A-T1 查看數據表（PDF） - RICOH Co.,Ltd.
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RS5RJ5817A-T1 Datasheet PDF : 30 Pages
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RS5RJ
OPERATION OF STEP-UP DC/DC CONVERTER
Step-up DC/DC Converter charges energy in the inductor when Lx Transistor (LxTr) is ON, and discharges the
energy with the addition of the energy from Input Power Source thereto when LxTr is off, so that a higher output
voltage than the input voltage is obtained.
The operation will be explained with reference to the following diagrams:
< Basic Circuits >
i2
L
SD
IOUT
VIN
i1
VOUT
LX Tr
CL
< Current through L >
IL
IL min
IL max
topen
t
ton
toff
T=1/ fosc
Step.1 : LxTr is turned on and current IL (= i1 ) flows, so that energy is charged in L. At this moment, IL(=i1 ) is
increased from ILmin (= 0) to reach ILmax in proportion to the on-time period (ton) of LxTr.
Step.2 : When LxTr is turned off, Schottky diode (SD) is turned on in order that L maintains IL at ILmax, so that
current IL (= i2) is released.
Step.3 : IL (=i2) is gradually decreased, and in the case of discontinuous mode, IL reaches ILmin (=0) after a time
period of topen, so that SD is turned off.
In the case of the VFM control system, with the on-time period (ton) maintained constant, the output voltage
is maintained constant by controlling the oscillator frequency (fosc).
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