High Precision CC/CV Primary-Side PWM Controller
OB2531
Product Specification
GENERAL DESCRIPTION
OB2531 is a high performance offline PWM
controller 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. In addition, good load regulation is
achieved by the built-in cable drop compensation.
Device operates in PFM in CC mode as well at
large load condition and it operates in PWM with
frequency reduction at light/medium load.
OB2531 offers power on soft start control and
protection coverage with auto-recovery features
including Cycle-by-Cycle current limiting, VDD
OVP, VDD clamp and UVLO. Excellent EMI
performance is achieved with On-Bright
proprietary frequency shuffling technique.
High precision constant voltage (CV) and constant
current (CC) can be achieved by OB2531.
.
FEATURES
5% Constant Voltage Regulation at Universal
AC input
High Precision Constant Current Regulation at
Universal AC input
Primary-side Sensing and Regulation Without
TL431 and Opto-coupler
Programmable CV and CC Regulation
Adjustable Constant Current and Output
Power Setting
Built-in Secondary Constant Current Control
with Primary Side Feedback
Built-in Adaptive Current Peak Regulation
Built-in Primary winding inductance
compensation
Programmable Cable drop Compensation
Power on Soft-start
Built-in Leading Edge Blanking (LEB)
Cycle-by-Cycle Current Limiting
VDD Under Voltage Lockout with Hysteresis
(UVLO)
VDD OVP
VDD Clamp
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Fig.1. Typical CC/CV Curve
TYPICAL APPLICATION
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APPLICATIONS
Low Power AC/DC offline SMPS for
Cell Phone Charger
Digital Cameras Charger
Small Power Adapter
Auxiliary Power for PC, TV etc.
Linear Regulator/RCC Replacement
OB2531 is offered in SOT23-6 package.
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Preliminary Datasheet
OB_DOC_DS_253101
士
High Precision CC/CV Primary-Side PWM Controller
OB2531
GENERAL INFORMATION
Pin Configuration
The pin map is shown as below for SOT23-6.
Package Dissipation Rating
Package
RθJA (℃/W)
SOT23-6
200
Absolute Maximum Ratings
Parameter
VDD Voltage
VDD Zener Clamp
Continuous Current
COMP Voltage
CS Input Voltage
INV Input Voltage
Max Operating Junction
Temperature T
J
Min/Max Storage
Temperature T
stg
Lead Temperature
(Soldering, 10secs)
Value
-0.3 to V
DD
_clamp
10 mA
-0.3 to 7V
-0.3 to 7V
-0.3 to 7V
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Ordering Information
Part Number
Description
OB2531MP
SOT23-6, Pb-free, T&R
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.
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Note:
Stresses beyond those listed under “absolute maximum
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-40 to 150
℃
-55 to 150
℃
260
℃
Preliminary Datasheet
OB_DOC_DS_253101
士
High Precision CC/CV Primary-Side PWM Controller
OB2531
Marking Information
TERMINAL ASSIGNMENTS
Pin Num
1
2
3
4
5
6
Pin Name
GND
GATE
CS
INV
COMP
VDD
I/O
P
O
I
I
I
P
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Description
Ground
Totem-pole gate drive output for power MOSFET.
Current sense input. Connected to MOSFET current sensing resistor
node.
The voltage feedback from auxiliary winding. Connected to resistor
divider from auxiliary winding reflecting output voltage. PWM duty cycle
is determined by EA output and current sense signal at pin 3.
Loop Compensation for CV Stability
Power Supply
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Preliminary Datasheet
OB_DOC_DS_253101
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士
High Precision CC/CV Primary-Side PWM Controller
OB2531
ELECTRICAL CHARACTERISTICS
(TA = 25℃, VDD=16V, if not otherwise noted)
Symbol
Parameter
Supply Voltage (VDD) Section
Operation supply current
-
INV=2V, CS=0V,
VDD=18V
VDD falling
VDD rising
Ramp VDD until gate
shut down
I
DD ST
I
DD op
UVLO(ON)
UVLO(OFF)
V
DD
_clamp
OVP
Standby Current
Operation Current
VDD Under Voltage Lockout
Enter
VDD Under Voltage Lockout Exit
Over voltage protection
Threshold
LEB time
Over current threshold
OCP Propagation delay
Input Impedance
Soft start time
Test Conditions
VDD=13V
Min Typ
5
2
Max Unit
20
3
uA
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50
85
1.97 2
8
Maximum VDD operation voltage I
DD
=10mA
TLEB
Vth_oc
Td_oc
Z
SENSE
_IN
T_ss
Freq_Max
Note 1
Freq_Nom
Freq_startup
△
f/Freq
Vref_EA
Gain
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INV=0V, Comp=5V
INV=2V, Comp=0V
Io=20mA
Io=20mA
CL=0.5nF
CL=0.5nF
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Current Sense Input Section
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Frequency Section
IC Maximum frequency
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System Nominal switch
frequency
on
Frequency shuffling range
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Error Amplifier section
Reference voltage for EA
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I_COMP_MAX
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DC gain of EA
Max. Cable compensation
current
Output Low Level
Output High Level
Gate Drive Output Section
VOL
1
16
650
40
V
V
V
nS
nS
VOH
T_r
T_f
O
V_clamp
Output Clamp Voltage Level
Output Rising Time
Output Falling Time
Note:
1. Freq_Max indicates IC internal maximum clock frequency. In system application, the maximum operation frequency of 94Khz
nominal occurs at maximum output power or the transition point from CV to CC.
©On-Bright Electronics
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8.6
9.4
10.6 V
13.9 15.2
28.5
27.5
16.4 V
V
V
27
30
29
280
880 910
110
17
94
75
24
+/-6
102
940
ns
ns
%
2.03 V
60
55
Preliminary Datasheet
OB_DOC_DS_253101
士
mA
mV
Kohm
ms
KHz
KHz
KHz
dB
uA
微控制器 MCU
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