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PDF UC1108 Data sheet ( Hoja de datos )
| Número de pieza | UC1108 | |
| Descripción | LOW-POWER OFF-LINE PRIMARY SIDE REGULATION CONTROLLER | |
| Fabricantes | Unisonic Technologies | |
| Logotipo |  |
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UNISONIC TECHNOLOGIES CO., LTD
UC1108
Preliminary
LOW-POWER OFF-LINE
PRIMARY SIDE REGULATION
CONTROLLER
DESCRIPTION
The UTC UC1108 is a primary control unit for switch mode charger
and adapter applications. The controlled variable is transferred by an
auxiliary winding from the secondary to the primary side. The device
uses Pulse Frequency Modulation (PFM) method to build
discontinuous conduction mode (DCM) flyback power supplies.
The UTC UC1108 operates in primary-side sensing and regulation.
Opto-coupler and TL431 could be eliminated. It also eliminates the
need of loop compensation circuitry while maintaining stability. The
UC1108 achieves excellent regulation and high average efficiency, yet
meets the requirement for no-load consumption less than 30mW.
The UTC UC1108 has the built-in programmable cable voltage
drop compensation function, which make it flexible to accommodate
various cables with different gauges and lengths
The UTC UC1108 achieves high precision CV/CC regulation and
high power efficiency. It offers comprehensive protection coverage
with auto-recovery features including Cycle-by-cycle current limiting,
output over voltage protection, feedback loop open protection, short
circuit protection, leading edge blanking, VCC under voltage lockout,
etc.
FEATURES
* 30mW No-load Input Power
* Primary side control for eliminating opto-coupler and secondary
CV/CC control circuitry
* Proprietary CC tightening technique to achieve vertical CC profile
* Programmable output cable voltage drop compensation
* Compensation for external component temperature variations
* Random frequency adjustment to reduce system EMI
* Flyback topology in DCM operation
* Built-in soft start
* Over voltage protection
* Short circuit protection
ORDERING INFORMATION
Ordering Number
UC1108G-S08-R
Package
SOP-8
CMOS IC
SOP-8
Packing
Tape Reel
UC1108G-S08-R
(1)Packing Type
(2)Package Type
(3)Green Package
(1) R: Tape Reel
(2) S08: SOP-8
(3) G: Halogen Free and Lead Free
www.unisonic.com.tw
Copyright © 2015 Unisonic Technologies Co., Ltd
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UC1108
Preliminary
OPERATION DESCRIPTION (Cont.)
CMOS IC
Constant Current Operation
When the sampled voltage is below 4V reference voltage and the error amplifier output reaches its maximum,
thus UTC UC1108 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.
Figure3. Adjustable output power by changing Rcs
Figure4. Secondary current waveform
In CC operation, the CC loop control function of UTC UC1108 will keep a fixed proportion between secondary
inductance de-magnetization time (Tdemag) and switching cycle time (Tsw). The fixed proportion is
Thus the output current is given by:
Tdemag
Tsw
=
4
7
(2)
Iout
=
1
2
×
NP
NS
×Ipk ×
Tdemag
Tsw
=
2
7
×
NP
NS
×Ipk
(3)
Current Sensing and Leading Edge Blanking
Cycle-by-cycle current limiting is offered in UTC UC1108. 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.
Drive BJT
The driver is a push pull stage with the supply voltage VCC. It provides the driving current for the external power
bipolar transistor. The output signal is current-limited to IOUT(SOURCE).
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
5 of 8
QW-R103-098.a
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| Páginas | Total 8 Páginas | |
| PDF Descargar | [ Datasheet UC1108.PDF ] | |
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