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OB2211H PDF 데이터시트 : 부품 기능 및 핀배열

부품번호 OB2211H
기능 Primary-Side PWM Power Switch
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OB2211H 데이터시트, 핀배열, 회로
OB2211H
Primary-Side PWM Power Switch with CC/CV
GENERAL DESCRIPTION
OB2211H is an offline PWM Power switch for low
power AC/DC charger and adaptor applications. It
operates in primary-side sensing and regulation.
Consequently, opto-coupler and TL431 could be
eliminated. Proprietary Constant Voltage (CV) and
Constant Current (CC) control is integrated as shown
in the figure below.
In CC control, the current and output power setting
can be adjusted externally by the sense resistor Rs at
CS pin. In CV control, multi-mode operations are
utilized to achieve high performance and high
efficiency. Device operates in fixed frequency mode
at large load conditions, frequency reduction mode at
light/medium load and ‘Extended burst mode’ at
No/light load conditions.
OB2211H offers power on soft start control and
protection coverage with auto-recovery features
including Cycle-by-Cycle current limiting, VDD
clamp and UVLO. Excellent EMI performance is
achieved with On-Bright proprietary frequency
shuffling technique together with soft switching
control at the totem pole gate drive output.
OB2211H achieves better CC control accuracy and
higher system efficiency through PWM control than
its sibling part OB2211.
FEATURES
„ Primary-side Sensing and Regulation Without
TL431 and Opto-coupler
„ Multi-mode Operation for High Efficiency
„ Programmable CV and CC Regulation
„ Adjustable Constant Current and Output Power
setting
„ Frequency Shuffling and Adjustable Gate Drive
Greatly Improving EMI
„ Power on Soft-start Time (4ms)
„ “Extended Burst Mode Control” for Improved
Efficiency and Minimum Standby Design
„ Built-in Leading Edge Blanking (LEB)
„ Cycle-by-Cycle Current Limiting
„ VDD Under Voltage Lockout with Hysteresis
(UVLO)
„ VDD Clamp
APPLICATIONS
Low Power AC/DC offline SMPS for
„ Cell Phone Charger
„ Digital Cameras Charger
„ Small Power Adaptor
„ Auxiliary Power for PC, TV etc.
„ Linear Regulator/RCC Replacement
OB2211H is offered in SOP8 package.
Fig 1. Typical CC/CV Curve
TYPICAL APPLICATION
©On-Bright Electronics
-1-
Confidential
OB_DOC_DS_11HA0




OB2211H pdf, 반도체, 판매, 대치품
BLOCK DIAGRAM
PWM,
&
Control
Logic
Frequency
Shuffling
OB2211H
Primary-Side PWM Power Switch with CC/CV
VDDG 1
Soft
Driver
Drain
5/6
Power
MOSFET
CC/CV
Operation
Burst mode
controller
VDD
2
POR
UVLO
Soft start
LEB
Regulator
Internal
supply
8
GND
PWM
Genterator
EA
Error Amplifier
1.25V
CS
4
INV
3
©On-Bright Electronics
-4-
Confidential
OB_DOC_DS_11HA0

4페이지










OB2211H 전자부품, 판매, 대치품
OB2211H
Primary-Side PWM Power Switch with CC/CV
OPERATION DESCRIPTION
OB2211H is cost effective PWM power switch
optimized for off-line low power AC/DC
applications including battery chargers and
adaptors. It operates in primary side sensing and
regulation, thus opto-coupler and TL431 are not
required. Proprietary CC control and built-in error
amplifier can achieve a good CC/CV performance.
z Startup Current and Start up Control
Startup current of OB2211H is designed to be very
low so that VDD could be charged up above UVLO
threshold and starts up quickly. A large value
startup resistor can therefore be used to minimize
the power loss in application.
z Operating Current
The Operating current of OB2211H is as low as
1mA. Good efficiency is achieved with the low
operating current together with ‘Extended burst
mode’ control features.
z Soft Start
OB2211H features an internal 4ms soft start to
minimize the component electrical over-stress
during power on startup. As soon as VDD reaches
UVLO(OFF), the control algorithm will ramp peak
current voltage threshold gradually from nearly
zero to normal setting of 0.82V. Every restart is a
soft start.
z CC/CV Operation
OB2211H is designed to produce good CC/CV
control characteristic as shown in the Fig. 1.
In charger applications, a discharged battery
charging starts in the CC portion of the curve until
it is nearly full charged and smoothly switches to
operate in CV portion of the curve.
In an AC/DC adapter, the normal operation occurs
only on the CV portion of the curve. The CC
portion provides output current limiting. In CV
operation, the output voltage is regulated through
the primary side control.
To support OB2211H proprietary CC/CV control,
system needs to be designed in DCM mode for
flyback system. Under normal operation, when INV
is less than Vref, the system works in CC control,
Otherwise, the system works in CV control.
z Error Amplifier (EA)
Connected to a resistor divider from the primary
side sensing winding, the inverting input of the
Error Amplifier (EA) is compared to an internal
reference voltage of 1.25V to regulate the output
voltage. The EA output is internally connected to
the PWM generator and controls the duty cycle.
z Adjustable CC point and Output Power
In OB2211H, the CC point and output power
can be externally adjusted by external current
sense resistor Rs at CS pin. The output power
is adjusted through CC point change. The
larger Rs, the smaller CC point is, and the
smaller output power becomes, and vice versa
as shown in Fig.2.
Vo
Large Rs
Small Rs
Io
Fig. 2 Adjustable output power by changing Rs
z Extended Burst Mode Operation
At light load or zero load condition, most of the
power dissipation in a switching mode power
supply is from switching loss, the core loss of the
transformer and the loss on the snubber circuit. The
magnitude of power loss is in proportion to the
switching frequency. Lower switching frequency
leads to the reduction on the power loss and thus
conserves the energy.
OB2211H self adjusts the switching frequency
according to the loading condition. The switch
frequency is reduced at light/no load condition to
improve the conversion efficiency. At light load/no
load condition, the output of the Error amplifier
(EA) drops below the burst mode threshold level
and device enters Burst Mode control. The
frequency control also eliminates the audio noise at
any loading conditions.
z Operation switching frequency
The switching frequency of OB2211H is adaptively
controlled according to CC/CV operation. No
external frequency setting components are required.
©On-Bright Electronics
-7-
Confidential
OB_DOC_DS_11HA0

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