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| UPSRB02 Datasheet, PDF (5/7 Pages) Unisonic Technologies – HIGH PRECISION CC/CV PRIMARY SIDE SWITCHING REGULATOR | |||
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UPSRB02
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 UPSRB02 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)
Programmable Cable drop Compensation
UTC UPSRB02 has a built-in cable voltage drop compensation to achieve good load regulation. An offset voltage
is generated at FB pin by an internal current flowing into the resistor divider. The current is inversely proportional to
the voltage of VC pin. As a result, it is inversely proportional to the output load current. The voltage drop across the
cable is compensated by this offset voltage at FB pin. It can also be programmed by adjusting the resistance of the
divider to compensate the drop for various cable lines used.
Improve dynamic response
At light or no load, an internal current ICS is flowing into CS pin. The current ICS is inversely proportional to the
voltage of VC pin, the maximum current ICS is limited to ICS_max.
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
5 of 7
QW-R103-079.a
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