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WS3256 Product Description
High Precision Primary-Side Off-line PWM Power Switch
Features
precision in full input voltage range. CC/CV Control as
�
5uA ultra-low startup current
�
2mA Low operating current
�
±5% Constant Voltage Regulation at Universal AC
shown in fig.1.In CC Control, the current and output power
setting can be adjusted externally by the sense resistor Rs
input
�
at CS pin. In CV control, multi-mode operations are utilized
to achieve high performance and high efficiency. In
Primary-side Sensing and Regulation Without TL431
and Opto-coupler
cable drop compensation. Device operates in PFM in CC
�
Programmable CV and CC Regulation
�
Built-in Primary winding inductance compensation
�
Programmable cable drop compensation
�
Built-in soft start
�
Built-in Leading-edge blanking
�
Cycle by cycle over current protection (OCP)
�
VCC
over
voltage
addition, good load regulation is achieved by the built-in
mode as well at large load condition and it operates in
PWM with frequency reduction at light/medium load.
Vo
clamp
5%
&
under
voltage
lockout( UVLO)
�
Maximum Gate output voltage clamped at 12V
�
�
Frequency jittering
Io
Icc
Ultra low standby power (<100mW)
Fig.1 Typical CC/CV Curve
WS3256 offers power on soft start control and protection
Applications
coverage with auto-recovery features
Low power AC/DC offline SMPS for
including Cycle-by-Cycle current limiting, VCC
�
Cell Phone Charger
�
Digital Cameras Charger
�
Small Power Adapter
�
Auxiliary Power for PC, TV etc.
�
Linear Regulator/RCC Replacement
OVP, VCC clamp and UVLO. The gate-driven output is
clamped to maximum 12V to protect the internal MOSFET.
Excellent EMI performance is achieved by using the
soft-switching
and
frequency
jittering
at
the
totem-pole-gate-drive output. The WS3256 is the ideal
General Description
substitute of the linear power supply or the RCC-mod e
WS3256 is a high-integrated offline PWM controller,
power, for a better performance of the whole switch power
optimized for high performance low power AC/DC charger
system and a lower cost.
and adapter application.
WS3256 is available in DIP-8 package.
WS3256 operates in primary-side sensing and regulation.
Consequently, optocoupler and TL431 could be eliminated,
thus reduce the cost. It can achieve ±5% constant voltage
W/T-D021-Rev.A/1 May.2014
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WS3256 Product Description
Typical Application Circuit
VO
CO
NS
NP
AC
NA U X
VCC
GND
COMP
GND
IN V
CS
RS
G ra in
G ra in
W S3 2 5 6
Pin Definition and Device Marking
WS3256 is available in DIP8 package:
VCC
COMP
IN V
1
8
2
7
3
D IP 8
GND
D: DIP8
GND
6
D R A IN
4
5
CS
VCC
1
COMP
2
INV
3
CS
4
DRAIN
5/6
GND
7/8
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A:wafer information;
1:Ver.; a: Package Code
2C:Y+M(2=2012 C=12 Month
D R A IN
Pin Function Description
Pin
Pin
Name
Number
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WS 3256D8P
A1a
2C
(1,2…A=10,B=11,C=12)
Pin Type
Power
Loop
Compensation
Feedback Input
Current
Monitoring
Power transistor
drain
GND
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Function Description
Power supply
Loop Compensation for CV Stability
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 pin4.
Current sense input.
This pin connects directly to the primary lead of the transformer.
Ground
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WS3256 Product Description
Block Diagram
vcc
1
UVLO
5V
ROP
D R A IN
Insernal
S upply
5 /6
G a te
Driver
Po we r
M OSF ET
CC
Controller
Soft start
PWM
Generator
D ro p
Comp
OCP
2V
CLK
Genterator
EA
IN V
Sampler
3
CS
4
LEB
Sa mp lin g
Co n tro lle r
Frequency
Shuffling
2
GND
7 /8
COMP
Output Power Table
230VAC±15%
85-264VAC
Adapter1
Adapter1
24W
16W
Product
WS3256
Note
Note: Maximum practical continuous power in an Adapter design with sufficient drain pattern as a heat sink,at 50℃ ambient.
Ordering Information
Package
IC Marking Information
Purchasing Device Name
8-Pin DIP-8, Pb-free
WS3256D8P
WS3256D8P
Recommended Operating Condition
Symbol
Parameter
Value
Unit
VCC
VCC supply voltage
10~30
V
TA
Operating temperature
-20~85
℃
Absolute Maximum Ratings
Parameter
Symbol
Drain voltage(off-state)
Drain Voltage (off state)
VCC
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Unit
-0.3~600
DC supply voltage
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Value
V
30
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WS3256 Product Description
VINV
INV input voltage
-0.3~7
V
VCS
CS input voltage
-0.3~7
V
VCOMP
COMP input voltage
-0.3~7
V
TJ
Max. Operating junction temperature
150
℃
TSTG
Min./Max. Storage temperature
-55~150
℃
ICC
VCC Clamp Continuous Current
10
mA
Note
Note: Stresses above 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 in the
Recommended Operating Conditions section are not implied. Exposure to absolute maximum-rated conditions for extended
periods may affect device reliability.
Electrical Characteristics (TA=25℃，VCC=16V, if not otherwise noted)
Supply Voltage (VCC)
symbol
parameter
Test condition
I_VCC_ST
Start up current
I_VCC_OP
Typ
Max
Unit
VCC=13V
5
20
uA
Operation Current
VCC=18V,INV=2V,CS=0V
2
3
mA
UVLO_ON
Turn on threshold Voltage
VCC falling
8.2
9.0
10.5
V
UVLO_OFF
Turn-off threshold Voltage
VCC rising
13.5
14.8
16.0
V
VCC_Clamp
VCC Zener Clamp Voltage
IVCC=10mA
28
29
31
V
Ramp VCC until gate shut down
27
28.3
30
V
1.935
1.975
2.015
V
Over
OVP
voltage
protection
Threshold
Min
Error Amplifier Section
Vref_EA
Reference voltage for EA
Gain
DC gain of EA
I_comp_max
Max.
Cable
compensation
current
INV=2V,COMP=0V
60
dB
37.5
uA
625
ns
Current Sense Section
TLEB
Leading edge Blanking Time
Zsense
Input impedance
TD_OC
OCP control delay
VTH_OC
OCP threshold
T_ss
Soft start time
50
kΩ
110
0.88
0.91
ns
0.94
17
V
ms
Oscillator Section
Freq_Max
IC Maximum frequency
60
Freq_Nom
System nominal switch frequency
Freq_startup
∆f/Freq
INV=0V,COMP=5V
Frequency shuffling range
67.5
75
khz
60
khz
14
khz
±6
%
MOSFET Section
MOSFET Drain-Source
BVdss
600
breakdown voltage
V
Static Drain to Source on
Ron
2.4
resistance
Ω
Note
Note: 1. Freq_Max indicates IC internal maximum clock frequency. In system application, the maximum operation frequency of
70 kHz nominal occurs at maximum output power or the transition point from CV to CC.
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WS3256 Product Description
Typical Operating Characteristics
UVLO (OFF ) (V )vs Temperature ( C )
UVLO (ON ) ( V ) vs Temperature ( C )
O
O
UVLO( OFF )( V )
UVLO ( ON )( V)
1 0 .5
1 0 .0
9 .5
9 .0
8 .5
8 .0
7 .5
-4 0
-1 0
20
50
80
1 6 .5 0
1 5 .5 0
1 5 .0 0
1 4 .5 0
1 4 .0 0
1 3 .5 0
1 3 .0 0
-4 0
11 0
-1 0
20
50
11 0
80
Temperature ( C )
O
Temperature ( C )
O
Istarup ( uA ) vs Temperature ( C )
O
Freq_Max ( kHz )vs Temperature ( C )
7 0 .0
Istarup ( uA )
Freq_Max ( kHz )
O
6 5 .0
6 0 .0
5 5 .0
3 .0
2 .5
2 .0
1 .5
1 .0
5 0 .0
-4 0
20
-1 0
50
80
-40
11 0
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50
80
11 0
Temperature ( C )
O
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20
O
Temperature ( C )
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WS3256 Product Description
Function Description
the output voltage can be sensed via the auxiliary winding.
WS3256 is a high-integrated offline PWM controller,
During MOSFET turn-on time, the load current is supplied
optimized for high performance low power AC/DC charger
from the output filter capacitor Co. The current in the primary
and adapter application. WS3256 operates in primary-side
winding ramps up. When MOSFET turns off, the primary
sensing and regulation. Consequently, opto-coupler and
current transfers to the secondary at the amplitude of
TL431 could be eliminated, thus reduce the cost. High
precision CC/CV control can meet most adapter and charger
Is =
NP
*Ip
Ns
application requirements.
The auxiliary voltage reflects the output voltage, given by
Startup Current and Startup Control
V AUX =
Startup current of WS3256 is designed to be extremely low
N AUX
* (Vo + ∆V )
NS
at 5uA, so that VCC could be charged up above UVLO
Where △V indicates the drop voltage of the output Diode.
threshold level and device starts up quickly. A large value
Via a resistor divider connected between the auxiliary
startup resistor can therefore be used to minimize the power
winding and INV, the auxiliary voltage is sampled at the end
loss, predigest the design of startup circuit and provides
of the demagnetization and it is hold until the next sampling.
reliable startup in application.
The sampled voltage is compared with Vref (2V) and the
error is amplified. The error amplifier output COMP reflects
Operating Current
the load condition and controls the PWM switching
The operating current of WS3256 is low at 2mA. Excellent
frequency to regulate the output voltage, thus the constant
efficiency is achieved with low operating current together
output current can be achieved.
and multi-mode control circuit.
When sampled voltage is below Vref and error amplifier
output COMP reaches its maximum, the switching frequency
CC/CV Operation
is controlled by the sampled voltage thus the output voltage
WS3256 is designed to produce good CC/CV control
to regulate the output current, thus the constant output
characteristic as shown in the fig.1. In charger applications,
current can be achieved.
a discharged battery charging starts in the CC portion of the
curve until it is nearly full charged and smoothly switches to
Adjustable CC point and Output Power
operate in CV portion of the curve. In an AC/DC adapter, the
In WS3256, the CC point and maximum output power can
normal operation occurs only on the CV portion of the curve.
be externally adjusted by eaternal current sense resistor Rs
The CC portion provides output current limiting. In CV
at CS pin. The output power is adjusted through CC point
operation, the output voltage is regulated through the
change. The larger Rs, the smaller CC point is, and the
primary side control. In CC operation mode, WS3256 will
smaller output power becomes, and vice versa.
Vo
regulate the output current constant regardless of the output
voltage drop.
Large R s
Small R s
Principle of Operation
To achieve high precision CC/CV control, system needs to
be designed in DCM mode for flyback system. In DCM mode,
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WS3256 Product Description
limit comparator is disabled and thus cannot turn off the
Fig.2 Adjustable output power by changing Rs
internal MOSFET during the blanking period. PWM duty
Operation switching frequency
cycle is determined by the current sense input voltage and
The switching frequency of WS3256 is adaptively controlled
the EA output voltage.
according to the load conditions and the operation modes.
The operation switching frequency at maximum output
power is set to 60KHz internally. In DCM mode, the
maximum output power is given by
PoMAX
Programmable Cable Drop Compensation
Cable drop compensation is implemented to achieve good
load regulation in WS3256. An offset voltage is generated at
1
2
= LP FSW I P
2
INV by an internal current flowing into the resister divider.
Where Lp indicate the inductance of primary winding and Ip
The current is inversely proportional to the voltage across
pin COMP, as a result, it is inversely proportional to the
is peak current of primary winding.
The change of the primary winding inductance results in
the change of the maximum output power and constant
output current in CC mode. To compensate the change
from variations of primary winding inductance, the
switching frequency is locked by an internal loop such that
output load current, thus the drop due to the cable loss can
be compensated. As the load current decreases from
full-load to no-load, the offset voltage at INV will increase. It
can also be programmed by adjusting the resistance of the
divider to compensate the drop for various cable lines used.
the switching frequency is
Gate Drive
FSW =
1
The gate drive strength which is too weak leads to over
2TDemag
switch loss of MOSFET while too strong gate drive output
Since TDemag is inversely proportional to the inductance, as a
compromises in the over EMI. A good tradeoff between
result, the product Lp and Fsw is constant, thus the
output strength and dead time control is achieved through
maximum output power and constant current in CC mode
the design of the built-in totem pole gate. The low standby
will not change as primary winding inductance changes. Up
dissipation and good EMI system design is easier to achieve
to ±10% variation of the primary winding inductance can be
through this dedicated devise. For MOSFET gate protection,
compensation.
an internal 12V clamp is added at higher than expected VCC
input.
Frequency Shuffling
Excellent EMI performance is achieved by using frequency
Protection Controls
jittering in WS3256.
Excellent system stability is achieved by the comprehensive
protection of WS3256. Including Cycle-by-Cycle current
Current Sensing and Leading Edge Blanking
limiting (OCP), VCC Clamp, Under Voltage Lockout on VCC
Cycle-by-Cycle current limiting is offered in WS3256. The
(UVLO).
switch current is detected by a sense resistor into the sense
Device restarts when VCC voltage drops below UVLO limit.
pin. An internal leading edge blanking circuit chops off the
It is clamped when VCC is higher than threshold value. The
sense voltage spike at initial MOSFET on state due to
power MOSFET is shut down when VCC drops below UVLO
snubber diode reverse recovery so that the external RC
limit and device enters power on start-up sequence
filtering on sense input is no longer required. The current
thereafter.
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WS3256 Product Description
Package Information
DIP-8 Package Outline Dimensions
D2
θ1
C1
C
C4
θ2
C2
C3
θ3
A2
A5
A1
D1
A3
D
A4
B
A
Winsemi
Dimensions in Millimeters
Symbol
Dimensions in Inches
Min
Max
Min
Max
A
9.00
9.50
0.354
0.374
B
6.10
6.60
0.240
0.260
C
3.0
3.4
0.118
0.134
A1
1.474
1.574
0.058
0.062
A2
0.41
0.53
0.016
0.021
A3
2.44
2.64
0.096
0.104
A4
0.51TYP
0.02TYP
A5
0.99TYP
0.04TYP
C1
6.6
C2
7.30
0.260
0.50TYP
0.287
0.02TYP
C3
3.00
3.40
0.118
0.134
C4
1.47
1.65
0.058
0.065
D
7.62
9.3
0.300
0.366
D1
0.24
0.32
0.009
0.013
D2
7.62TYP
0.3TYP
W/T-D021-Rev.A/1 May.2014
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WS3256 Product Description
NOTE:
1.We strongly recommend customers check carefully on the trademark when buying our product, if there is any
question, please don't be hesitate to contact us.
2.Please do not exceed the absolute maximum ratings of the device when circuit designing.
3.Winsemi Microelectronics Co., Ltd reserved the right to make changes in this specification sheet and is
subject to change without prior notice.
CONTACT:
Winsemi Microelectronics Co., Ltd.
ADD:Futian District, ShenZhen Tian An Cyber Tech Plaza two East Wing 1002
Post Code : 518040
Tel : +86-755-8250 6288
FAX : +86-755-8250 6299
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