RS5RJ RICOH Co.,Ltd., RS5RJ Datasheet - Page 7

• Manufacturer Part Number: RS5RJ
• Description: Vfm Step-up Dc/dc Converter With Voltage Regulator And Detector
• Manufacturer: RICOH Co.,Ltd.

OPERATION OF STEP-UP DC/DC CONVERTER
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.
Step.1 : LxTr is turned on and current IL (= i1 ) flows, so that energy is charged in L. At this moment, IL(=i1 ) is
Step.2 : When LxTr is turned off, Schottky diode (SD) is turned on in order that L maintains IL at ILmax, so that
Step.3 : IL (=i2) is gradually decreased, and in the case of discontinuous mode, IL reaches ILmin (=0) after a time
is maintained constant by controlling the oscillator frequency (fosc).
Step-up DC/DC Converter charges energy in the inductor when Lx Transistor (LxTr) is ON, and discharges the
The operation will be explained with reference to the following diagrams:
In the case of the VFM control system, with the on-time period (ton) maintained constant, the output voltage
increased from ILmin (= 0) to reach ILmax in proportion to the on-time period (ton) of LxTr.
current IL (= i2) is released.
period of topen, so that SD is turned off.
V
IN
< Basic Circuits >
i1
L
L
X
Tr
SD
i2
CL
V
OUT
I
OUT
IL
< Current through L >
IL min
ton
T=1/ fosc
IL max
toff
topen
RS5RJ
t
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