UPSR104G-AG6-R Datasheet, PDF (4/8 Pages) Unisonic Technologies – CMOS IC

UPSR104
Preliminary
CMOS IC
 OPERATION DESCRIPTION
The UTC UPSR104 is a primary controller 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. The device integrates PWM controller to enhance the performance of
discontinuous conduction mode (DCM) flyback converters.
Startup Control
The V_DD pin of UTC UPSR104 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 UPSR104 is very low. When the
VDD voltage reaches V_{TH (ON)}, the internal startup circuit is disabled and the IC turns on.
Operating Current
The Operating current of UTC UPSR104 is as low as 1.6mA. 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
UPSR104 captures the auxiliary winding feedback voltage at INV pin and operates in constant-voltage (CV) mode to
regulate the output voltage. The auxiliary voltage reflects the output voltage is given by:
V_AUX
=
N_A
N_S
×（V_O
+
∆V）
(1)
Where ∆V indicates the drop voltage of the output diode.
Via a resistor divider connected between the auxiliary winding and INV, the V_AUX is sampled at the Tsampling end
and it is hold until the next sampling. The sampled voltage is compared with 2.0V reference voltage and the error is
amplified. The error amplifier output reflects the load condition and controls the Toff time and the Ipk to regulate the
output voltage, thus constant output voltage can be achieved.
Constant Current Operation
When the sampled voltage is below 2.0V reference voltage and the error amplifier output reaches its maximum,
thus UTC UPSR104 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
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QW-R103-113.a