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OB2212 PDF 데이터시트 : 부품 기능 및 핀배열

부품번호 OB2212
기능 Primary-Side Regulation PWM Power Switch
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OB2212 데이터시트, 핀배열, 회로
OB2211/OB2212
Primary-Side Regulation PWM Power Switch
GENERAL DESCRIPTION
OB2211/OB2212 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 from design. 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.
OB2211/OB2212 offers power on soft start control
and complete protection coverage with auto-recovery
features including Cycle-by-Cycle current limiting,
VDD over-voltage clamp and UVLO, fail-safe
protection for open loop fault condition. Excellent
EMI performance is achieved with On-Bright
proprietary frequency shuffling technique together
with soft switching control at the totem pole gate
drive output with No-Y cap design.
FEATURES
„ Primary-side Sensing and Regulation With No
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 Over Voltage Shutdown and Clamp
„ Auto-restart in Over Voltage condition
„ Fail-safe protection for open loop fault condition
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
OB2211 is offered in SOP8 package.
OB2212 is offered in DIP8 package
Fig 1. Typical CC/CV Curve
TYPICAL APPLICATION
©On-Bright Electronics
On-Bright Confidential to MicroBridge
-1-
OB_DOC_DS_1100




OB2212 pdf, 반도체, 판매, 대치품
BLOCK DIAGRAM
PWM,
&
Control
Logic
Frequency
Shuffling
OB2211/OB2212
Primary-Side Regulation PWM Power Switch
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
On-Bright Confidential to MicroBridge
-4-
OB_DOC_DS_1100

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OB2212 전자부품, 판매, 대치품
OB2211/OB2212
Primary-Side Regulation PWM Power Switch
OPERATION DESCRIPTION
OB2211 and OB2212 are 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 OB2211/2 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 OB2211/2 is as low as
1mA. Good efficiency is achieved with the low
operating current together with ‘Extended burst
mode’ control features.
z Soft Start
OB2211/2 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
OB2211/2 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 added cycle-by-cycle current
limiting protection. In CV operation, the output
voltage is sensed on the primary side and the
sensed signal controls the duty cycle through a
built-in error amplifier (EA).
To support OB2211/2 proprietary CC/CV control,
system needs to be designed in DCM mode for
flyback system. When INV is equivalent or larger
than 1.25V, the system works in CV control,
Otherwise, the system works in CC 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 OB2211/2, 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.
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.
OB2211/2 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 OB2211/2 is internally
set and adjusted according to CC/CV operation. No
external frequency setting components are required.
©On-Bright Electronics
On-Bright Confidential to MicroBridge
-7-
OB_DOC_DS_1100

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