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UC1100G View Datasheet(PDF) - Unisonic Technologies

Part Name
Description
Manufacturer
UC1100G Datasheet PDF : 6 Pages
1 2 3 4 5 6
UC1100
Preliminary
CMOS IC
OPERATION DESCRIPTION
The UTC UC1100 is a primary control unit for switch mode charger and adapter applications. It operates in
primary-side sensing and regulation. Opto-coupler and TL431 could be eliminated. Proprietary built-in CV and CC
control can achieve high precision CV/CC performance. It uses Pulse Frequency Modulation (PFM) method to build
discontinuous conduction mode (DCM) flyback power supplies.
Startup control
The VCC pin of UTC UC1100 is connected to the line input through a resistor. A large value startup resistor can be
used to minimize the power loss in application because the start current of UTC UC1100 is very low. When the VCC
voltage reaches VTH (ST), the internal startup circuit is disabled and the IC turns on.
Operating Current
The Operating current of UTC UC1100 is as low as 320uA. Good efficiency and very low standby power can be
achieved.
Constant Voltage Operation
The output voltage is defined by the transmission ratio between the secondary and auxiliary winding. The UTC
UC1100 captures the auxiliary winding feedback voltage at FB pin and operates in constant-voltage (CV) mode to
regulate the output voltage. The auxiliary voltage reflects the output voltage is given by:
VAUX
=
NA
NS
×VO
+
V
(1)
Where V indicates the drop voltage of the output diode.
Figure1. Auxiliary voltage waveform
Via a resistor divider connected between the auxiliary winding and FB, the VAUX is sampled at the Tsampling end
and it is hold until the next sampling. The sampled voltage is compared with 4V reference voltage and the error is
amplified. The error amplifier output reflects the load condition and controls the Toff time to regulate the output
voltage, thus constant output voltage can be achieved.
Constant Current Operation
When the sampled voltage is below 4V reference voltage and the error amplifier output reaches its maximum, thus
UTC UC1100 operates in constant-current (CC) mode. The CC point and maximum output power can be externally
adjusted by external current sense resistor Rcs. The larger Rcs, the smaller CC point is, and the smaller output
power becomes.
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
4 of 6
QW-R129-007.a
 

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