OB2211H (On-Bright Electronics)
Primary-Side PWM Power Switch

No Preview Available !

Click to Download PDF File for PC

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 (On-Bright Electronics)
Primary-Side PWM Power Switch

No Preview Available !

Click to Download PDF File for PC

GENERAL INFORMATION
Pin Configuration
The pin map is shown as below for SOP8
Ordering Information
Part Number Description
OB2211HCP
SOP8, Pb-free, Tube
OB2211HCPA SOP8, Pb-free, T&R
OB2211H
Primary-Side PWM Power Switch with CC/CV
Absolute Maximum Ratings
Parameter
Drain Voltage (off state)
Value
-0.3V to Bvdss
VDD Voltage
VDDG Voltage
VDD Zener Clamp
-0.3 to VDD_clamp
-0.3 to VDD_clamp
10 mA
Continuous Current
CS Input Voltage
-0.3 to 7V
INV Input Voltage
Min/Max Operating
-0.3 to 7V
-20 to 150 oC
Junction Temperature TJ
Min/Max Storage
-55 to 150 oC
Temperature Tstg
Lead Temperature
260 oC
(Soldering, 10secs)
Note: Stresses beyond those listed under “absolute maximum
ratings” may cause permanent damage to the device. These are
stress ratings only, functional operation of the device at these or
any other conditions beyond those indicated under “recommended
operating conditions” is not implied. Exposure to absolute
maximum-rated conditions for extended periods may affect device
reliability.
©On-Bright Electronics
-2-
Confidential
OB_DOC_DS_11HA0


OB2211H (On-Bright Electronics)
Primary-Side PWM Power Switch

No Preview Available !

Click to Download PDF File for PC

Marking Information
OB2211H
Primary-Side PWM Power Switch with CC/CV
TERMINAL ASSIGNMENTS
Pin Num Pin Name
1 VDDG
2 VDD
3 INV
4 CS
5/6 Drain
7/8 GND
I/O Description
P Internal Gate Driver Power Supply
P IC DC power supply Input
Inverting input of error amplifier (EA). Connected to resistor divider from
I primary sensing winding reflecting output voltage. PWM duty cycle is
determined by EA output and current sense signal at pin 4.
I Current sense input
O
HV MOSFET Drain Pin. The Drain pin is connected to the primary lead of
the transformer
P Ground
OUTPUT POWER TABLE
Product
OB2211H
230VAC±15%
Open Frame1
10W
85-264VAC
Open Frame1
7W
Notes:
1. Maximum practical continuous power in an open frame design with sufficient drain pattern as a heat sink, at 50ambient.
©On-Bright Electronics
-3-
Confidential
OB_DOC_DS_11HA0


OB2211H (On-Bright Electronics)
Primary-Side PWM Power Switch

No Preview Available !

Click to Download PDF File for PC

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


OB2211H (On-Bright Electronics)
Primary-Side PWM Power Switch

No Preview Available !

Click to Download PDF File for PC

OB2211H
Primary-Side PWM Power Switch with CC/CV
ELECTRICAL CHARACTERISTICS
(TA = 25OC, VDD=VDDG=16V, if not otherwise noted)
Symbol
Parameter
Test Conditions
Min Typ Max Unit
Supply Voltage (VDD) Section
I DD ST
Standby Current
I DD op
Operation Current
UVLO(ON)
VDD Under Voltage
Lockout Enter
UVLO(OFF)
VDD Under Voltage
Lockout Exit
VDD_clamp
IDD=10mA
Current Sense Input Section
TLEB
LEB time
Vth_oc
V th_OC test
Td_oc
Propagation delay
ZSENSE_IN
Input Impedance
T_ss Soft start time
VDD=13.5V
Operation supply current
INV=1.25V, CS=0V, -
VDD=VDDG=20V
7.5
5
1.0
8.5
14.0 15
38
10 uA
mA
2.0
9.5 V
16.0 V
V
540
780 820 860
300
50
4
ns
mV
ns
Kohm
ms
CV Section
Freq
Freq_Burst
f/Freq
Normal mode frequency
Burst Mode Base
Frequency
Frequency shuffling range
45 50 55
22
+/-4
KHz
KHz
%
CC Section
Freq
Oscillation Frequency
Minimum frequency
Maximum frequency
12
50
KHz
KHz
Error Amplifier section
Vref_EA
Reference voltage for EA
1.21 1.25 1.29 V
Power MOSFET Section
BVdss
Mos Drain-Source
Breakdown Voltage
Rdson
Static, Id=0.4A
600
12
15
V
Ώ
©On-Bright Electronics
-5-
Confidential
OB_DOC_DS_11HA0


OB2211H (On-Bright Electronics)
Primary-Side PWM Power Switch

No Preview Available !

Click to Download PDF File for PC

CHARACTERIZATION PLOTS
OB2211H
Primary-Side PWM Power Switch with CC/CV
©On-Bright Electronics
-6-
Confidential
OB_DOC_DS_11HA0


OB2211H (On-Bright Electronics)
Primary-Side PWM Power Switch

No Preview Available !

Click to Download PDF File for PC

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


OB2211H (On-Bright Electronics)
Primary-Side PWM Power Switch

No Preview Available !

Click to Download PDF File for PC

OB2211H
Primary-Side PWM Power Switch with CC/CV
z Frequency shuffling for EMI improvement
The frequency Shuffling (switching frequency
modulation) is implemented in OB2211H. The
oscillation frequency is modulated so that the tone
energy is spread out. The spread spectrum
minimizes the conduction band EMI and therefore
eases the system design.
z Current Sensing and Leading Edge
Blanking
Cycle-by-Cycle current limiting is offered in
OB2211H 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 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 OB2211H 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 clamp, Power
on Soft Start, and Under Voltage Lockout on VDD
(UVLO).
VDD is supplied by transformer auxiliary winding
output. The output of OB2211H is shut down when
VDD drops below UVLO(ON) limit and Switcher
enters power on start-up sequence thereafter.
©On-Bright Electronics
-8-
Confidential
OB_DOC_DS_11HA0


OB2211H (On-Bright Electronics)
Primary-Side PWM Power Switch

No Preview Available !

Click to Download PDF File for PC

OB2211H
Primary-Side PWM Power Switch with CC/CV
PACKAGE MECHANICAL DATA
Symbol
A
A1
A2
b
c
D
E
E1
e
L
θ
Dimensions In Millimeters
Min
1.350
Max
1.750
0.100
0.250
1.300
1.550
0.330
0.510
0.170
0.250
4.700
5.150
3.800
4.000
5.800
6.200
1.270 (BSC)
0.400
1.270
0º 8º
Dimensions In Inches
Min
0.053
Max
0.069
0.004
0.010
0.051
0.061
0.013
0.020
0.006
0.010
0.185
0.203
0.150
0.157
0.228
0.244
0.050 (BSC)
0.016
0.050
0º 8º
©On-Bright Electronics
-9-
Confidential
OB_DOC_DS_11HA0


OB2211H (On-Bright Electronics)
Primary-Side PWM Power Switch

No Preview Available !

Click to Download PDF File for PC

OB2211H
Primary-Side PWM Power Switch with CC/CV
IMPORTANT NOTICE
RIGHT TO MAKE CHANGES
On-Bright Electronics Corp. reserves the right to make corrections, modifications, enhancements,
improvements and other changes to its products and services at any time and to discontinue any product or
service without notice. Customers should obtain the latest relevant information before placing orders and should
verify that such information is current and complete.
WARRANTY INFORMATION
On-Bright Electronics Corp. warrants performance of its hardware products to the specifications applicable at
the time of sale in accordance with its standard warranty. Testing and other quality control techniques are used
to the extent it deems necessary to support this warranty. Except where mandated by government requirements,
testing of all parameters of each product is not necessarily performed.
On-Bright Electronics Corp. assumes no liability for application assistance or customer product design.
Customers are responsible for their products and applications using On-Bright’s components, data sheet and
application notes. To minimize the risks associated with customer products and applications, customers should
provide adequate design and operating safeguards.
LIFE SUPPORT
On-Bright Electronics Corp.’s products are not designed to be used as components in devices intended to
support or sustain human life. On-bright Electronics Corp. will not be held liable for any damages or claims
resulting from the use of its products in medical applications.
MILITARY
On-Bright Electronics Corp.’s products are not designed for use in military applications. On-Bright Electronics
Corp. will not be held liable for any damages or claims resulting from the use of its products in military
applications.
©On-Bright Electronics
- 10 -
Confidential
OB_DOC_DS_11HA0




OB2211H.pdf
Click to Download PDF File