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零件编号 | OB2212 | ||
描述 | Primary-Side Regulation PWM Power Switch | ||
制造商 | On-Bright | ||
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1 Page
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
OB2211/OB2212
Primary-Side Regulation PWM Power Switch
z Frequency shuffling for EMI improvement
The frequency Shuffling/jittering (switching
frequency modulation) is implemented in
OB2211/2. The oscillation frequency is modulated
with a pseudo random source so that the tone
energy is spread out. The spread spectrum
minimizes the conduction band EMI and therefore
eases the system design.
protection triggering. The output of OB2211 is shut
down when VDD drops below UVLO(ON) limit
and Switcher enters power on start-up sequence
thereafter.
z Current Sensing and Leading Edge
Blanking
Cycle-by-Cycle current limiting is offered in
OB2211/2 current mode PWM control. The switch
current is detected by a sense resistor into the CS
pin. An internal leading edge blanking circuit chops
off the sensed voltage spike at initial internal power
MOSFET on state due to snubber diode reverse
recovery and surge current of power MOSFET due
to Drain/Source Cap so that the external RC
filtering on sense input is no longer needed. The
PWM duty cycle is determined by the current sense
input voltage and the EA output voltage.
z Adjustable Drive Capability
The internal power MOSFET in OB2211/2 is
driven by a dedicated gate driver for power switch
control. Too weak the gate drive strength results in
higher conduction and switch loss of MOSFET
while too strong gate drive compromises EMI.
A good tradeoff is achieved through the built-in
totem pole gate design with right output strength
control. The gate drive strength can be adjusted
externally by a resistor connected between VDD
and VDDG The low idle loss and good EMI system
design is possible with this dedicated control
scheme.
z Protection Control
Good power supply system reliability is achieved
with its rich protection features including Cycle-by-
Cycle current limiting (OCP), VDD over voltage
protection and clamp, Power on Soft Start, and
Under Voltage Lockout on VDD (UVLO).
VDD is supplied by transformer auxiliary winding
output. PWM output of OB2211 is shut down when
VDD is higher than 30V due to over voltage
©On-Bright Electronics
On-Bright Confidential to MicroBridge
-8-
OB_DOC_DS_1100
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页数 | 10 页 | ||
下载 | [ OB2212.PDF 数据手册 ] |
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