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| UPSRB01A Datasheet, PDF (5/7 Pages) Unisonic Technologies – HIGH PRECISION CC/CV PRIMARY SIDE SWITCHING REGULATOR | |||
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UPSRB01A
Preliminary
ï® OPERATION DESCRIPTION (Cont.)
LINEAR INTEGRATED CIRCUIT
Figure3. Adjustable output power by changing RCS
Figure4. Secondary current waveform
In CC operation, the CC loop control function of UTC UPSRB01A will keep a fixed proportion between secondary
inductance de-magnetization time (Tdemag) and switching cycle time (Tsw). The fixed proportion is
Tdemag
TSW
=
1
2
(2)
Thus the output current is given by:
Iout
=
1
2
Ã
NP
NS
à IPK
Ã
Tdemag
TSW
=
1
4
Ã
NP
NS
à IPK
(3)
Current Sensing and Leading Edge Blanking
Cycle-by-cycle current limiting is offered in UTC UPSRB01A. The switch current is detected by a sense resistor
into the CS pin. When the power switch is turned on, a turn-on spike will occur on this resistor. A 500ns leading-edge
blanking is built in to avoid false-termination of the switching pulse so that the external RC filtering is no longer
needed.
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
5 of 7
QW-R103-095.a
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