OB2362A
Adaptive Multi-Mode PWM Controller
GENERAL DESCRIPTION
FEATURES
OB2362A is a highly integrated current mode
PWM control IC optimized for high performance,
low standby power and cost effective offline
flyback converter applications.
At full loading, the IC operates in fixed frequency
(65KHz) mode. When the loading goes low, it
operates in Green mode with valley switching for
high power conversion efficiency. When the load is
very small, the IC operates in ‘Extended Burst
Mode’ to minimize the standby power loss. As a
result, high conversion efficiency can be achieved
in the whole loading range.
VCC low startup current and low operating current
contribute to a reliable power on startup and low
standby design with OB2362A.
OB2362A offers comprehensive protection
coverage with auto-recovery including Cycle-byCycle current limiting (OCP), over load protection
(OLP), VCC under voltage lockout (UVLO), over
temperature protection (OTP), and over voltage
protection (OVP). Excellent EMI performance is
achieved with On-Bright proprietary frequency
shuffling technique.
The tone energy at below 23KHz is minimized in
the design and audio noise is eliminated during
operation.
OB2362A is offered in SOT23-6 package.
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密
■
吉
■
Power on soft start reducing MOSFET Vds
stress
Multi-Mode Operation
65KHz fix frequency mode @ Full Load
Valley switching operation @ Green mode
Burst Mode @ Light Load & No Load
Frequency shuffling for EMI
Extended burst mode control for improved
efficiency and low standby power design
Audio noise free operation
Comprehensive protection coverage
o VCC Under Voltage Lockout with
hysteresis (UVLO)
o VCC Over Voltage Protection (VCC OVP)
o Cycle-by-cycle over current threshold
setting for constant output power limiting
over universal input voltage range
o Over Load Protection (OLP) with autorecovery
o External (if NTC resistor is connected at
PRT pin)or internal Over Temperature
Protection (OTP) with auto-recovery
o Output Over Voltage Protection(Output
OVP) with auto-recovery, and the OVP
triggered voltage can be adjusted by the
resistor connected between auxiliary
winding and PRT pin
o Output diode short protection with autorecovery
on
APPLICATIONS
ht
c
Offline AC/DC flyback converter for
■ General power supply
■ Power Adapter
ig
TYPICAL APPLICATION
Br
EMI
Filter
DC
Out
O
n-
AC IN
Vaux
OB2362A
GND GATE
FB
PRT
©On-Bright Electronics
VCC
CS
Confidential
-1-
Preliminary Datasheet
OB_DOC_DS_2362A02
OB2362A
Adaptive Multi-Mode PWM Controller
Absolute Maximum Ratings
Parameter
Value
GND
1
6
Gate
FB
2
5
VCC
PRT
3
4
CS
VCC DC Supply Voltage
VOVP-1V
FB Input Voltage
-0.3 to 7V
CS Input Voltage
-0.3 to 7V
PRT Input Voltage
-0.3 to 7V
Min/Max Operating
Junction Temperature TJ
-40 to 150 ℃
Operating Ambient
Temperature TA
-40 to 85 ℃
Min/Max Storage
Temperature Tstg
-55 to 150 ℃
to
Ordering Information
Part Number
Description
OB2362AMP
SOT23-6, Pb-free in T&R
密
Pin Configuration
吉
GENERAL INFORMATION
Lead
Temperature
260 ℃
(Soldering, 10secs)
Note: Stresses beyond those listed under
Package Dissipation Rating
Package
RJA(℃/W)
SOT23-6
200
ht
c
on
fid
e
Recommended operating condition
Symbol Parameter
Range
VCC
VCC Supply Voltage
12 to 26V
nt
ia
l
“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.
M:SOT23-6
P:Pb-free
O
n-
Br
ig
Marking Information
©On-Bright Electronics
Y:Year Code
WW:Week Code(01-52)
ZZZ: Lot code
A:Character Code
S: Internal code
Confidential
-2-
Preliminary Datasheet
OB_DOC_DS_2362A02
OB2362A
Adaptive Multi-Mode PWM Controller
TERMINAL ASSIGNMENTS
I/O
Description
VCC
P
Power Supply
CS
I
Current sense input
Gate
O
Totem-pole gate driver output for power MOSFET
GND
P
Ground
PRT
I
Multiple functions pin. Connecting a NTC resistor to ground for OTP detection.
Connecting a resistor from Vaux can adjust OVP trigger voltage and detect
transformer core demagnetization. If both OTP and OVP are needed, a diode
should be connected between PRT pin and the NTC resistor.
FB
I
Feedback input pin. The PWM duty cycle is determined by voltage level into this pin
and the current-sense signal at Pin CS.
O
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Br
ig
ht
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to
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密
Pin Name
©On-Bright Electronics
Confidential
-3-
Preliminary Datasheet
OB_DOC_DS_2362A02
OB2362A
Adaptive Multi-Mode PWM Controller
FUNCTIONAL BLOCK DIAGRAM
S
S
Valley
Diode short
Internal
blocks
OSC
Diode
short
GND
OLP
Multi
Mode
Control
Temp
sense
OTP
OVP
EX OVP
Valley
Slope
compensation
密
LEB
CS
AVDD
OLP
FB
O
n-
Br
ig
ht
c
on
Valley
Detector
PWM
Comparator
Timer
PRT
Vocp
fid
e
EX OTP
OCP
Comparator
Diode
short
吉
VCC
AVDD
to
Vref&
Iref
GATE
l
UVLO
Soft Driver
R
OVP
nt
ia
OVP
Logic
Control
Q
©On-Bright Electronics
Confidential
-4-
Preliminary Datasheet
OB_DOC_DS_2362A02
OB2362A
Adaptive Multi-Mode PWM Controller
ELECTRICAL CHARACTERISTICS
I_VCC_Operation
Operation Current
I_VCC_Burst
Burst Current
VCC=UVLO(OFF)-1V,
measure
leakage
current into VCC
VDD=18V,CS=4V,
FB=3.5V,measure
I(VCC)
CS=0V,FB=0.5V,
measure I(VCC)
VCC Under Voltage Lockout
Enter
VCC Under Voltage Lockout
Exit (Recovery)
Pull-up PMOS active
UVLO(ON)
UVLO(OFF)
6.8
16
Unit
2
5
uA
2.5
3
mA
0.6
0.7
mA
7.3
7.8
V
18
V
17
10
FB=3V,CS=0V. Slowly
VCC Over Voltage Protection
OVP
ramp VCC, until no 26.5 28
threshold voltage
gate switching.
Feedback Input Section(FB Pin)
VFB_Open
VFB Open Loop Voltage
5.1
Avcs
PWM input gain ∆VFB/∆VCS
3.5
Maximum
duty Max
duty
cycle
@
77
80
cycle
VCC=18V,VFB=3V,VCS=0V
Vref_green
The threshold enter green mode
2.1
Vref_burst_H
The threshold exits burst mode
1.33
The threshold enters burst
Vref_burst_L
1.23
mode
Short FB pin to GND
IFB_Short
FB pin short circuit current
0.21
and measure current
Open loop protection, FB
VTH_OLP
4.4
Threshold Voltage
Open loop protection,
Td_OLP
60
Debounce Time
ZFB_IN
Input Impedance
30
Current Sense Input(CS Pin)
SST_CS
Soft start time for CS peak
2
T_blanking
Leading edge blanking time
300
From Over Current
Over Current Detection and Occurs till the Gate
Td_OC
90
Control Delay
driver output start to
turn off
Internal
Current
Limiting
VTH_OC
Threshold Voltage with zero
0.43 0.45
duty cycle
VTH_OC_Clamp
OCP CS voltage clamper
0.72
PRT pin
Output current for external OTP
IRT
94
100
detection
VOTP
Threshold voltage for external
0.95 1
V
29.5
83
V
ht
c
mA
V
ig
ms
Br
KΩ
ms
ns
n-
Confidential
-5-
%
V
V
ns
O
©On-Bright Electronics
V
V
V/V
on
fid
e
nt
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l
Vpull-up
Typ. Max
密
VCC Start up Current
Min
to
Istartup
Test Conditions
吉
(TA = 25℃, VCC=18V, unless otherwise noted)
Symbol
Parameter
Supply Voltage (VDD)
0.47
V
V
106
uA
1.05
V
Preliminary Datasheet
OB_DOC_DS_2362A02
OB2362A
Adaptive Multi-Mode PWM Controller
Td_output_ovp
In-chip OTP
OTP enter
170
OTP exit
Oscillator
Normal Oscillation Frequency
ᇞf_OSC
Frequency jittering
F_shuffling
Shuffling frequency
ᇞf_Temp
Frequency
Stability
ᇞf_VCC
Frequency Voltage Stability
F_Burst
Gate driver
Burst Mode Switch Frequency
VDD=18V,FB=3V,
CS=0V
V_clamping
Output low level @ VDD=18V,
Io=5mA
Output high level @ VCC=18V,
Io=20mA
Output clamp voltage
Output rising time 1.2V ~ 10.8V
@ CL=1000pF
Output falling time 10.8V ~ 1.2V
@ CL=1000pF
ig
T_r
Cycles
150
℃
120
℃
65
70
to
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fid
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ia
Temperature
ht
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VOH
5
+/-6
on
VOL
KHz
%
32
Hz
1
%
1
%
23
KHz
1
6
V
V
11
V
100
ns
30
ns
O
n-
Br
T_f
60
uA
吉
FOSC
180 190
密
Ioutput_ovp
OTP
Current threshold for adjustable
output OVP
Output OVP debounce time
©On-Bright Electronics
Confidential
6
Preliminary Datasheet
OB_DOC_DS_2362A02
OB2362A
Adaptive Multi-Mode PWM Controller
CHARACTERIZATION PLOTS
VDD = 18V, TA = 25℃ condition applies if not otherwise noted.
UVLO(ON)(V) vs Tem perature
UVLO(OFF)(V) vs Tem perature
7.20
7.00
-40
-10
20
50
80
15.80
15.00
-40
110 140
-10
110 140
-40
-10
20
50
80
fid
e
nt
ia
Ton_cmp(uS)
8.00
7.60
7.20
6.80
6.40
6.00
l
Fosc_nom(Khz)
68.00
66.00
64.00
62.00
60.00
110 140
on
Temperature(℃)
-40
20
50
80
Vth_ocp(V)
ht
c
ig
-10
110 140
-40
n-
101.5
101.0
IRT(uA)
102.0
28.94
28.58
28.22
27.86
27.50
50
80
-10
20
50
80
110 140
100.6
100.1
99.6
-40
110 140
-10
20
50
80
110 140
Temperature(℃)
Temperature(℃)
©On-Bright Electronics
110 140
IRT(uA) vs Tem perature
29.30
20
80
Temperature(℃)
OVP(V) vs Tem perature
-10
50
0.500
0.480
0.460
0.440
0.420
0.400
Temperature(℃)
-40
20
Vth_ocp(V) vs Tem perature
Br
-40
-10
Temperature(℃)
Vref_OTP(V) vs Tem perature
Vref_OTP(V)
80
Ton_cm p(uS) vs Tem perature
70.00
O
50
to
Fosc_nom (Khz) vs Tem perature
OVP(V)
20
Temperature(℃)
Temperature(℃)
1.100
1.060
1.020
0.980
0.940
0.900
吉
7.60
7.40
密
19.00
18.20
17.40
16.60
UVLO(OFF)(V)
UVLO(ON)(V)
8.00
7.80
Confidential
7
Preliminary Datasheet
OB_DOC_DS_2362A02
OB2362A
Adaptive Multi-Mode PWM Controller
0.9
0.8
0.7
0.6
0.5
0.4
0
10
20
30
40
50
60
密
Vth_oc(V)
Duty vs Vth_oc
70
O
n-
Br
ig
ht
c
on
fid
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to
吉
Duty(%)
©On-Bright Electronics
Confidential
8
Preliminary Datasheet
OB_DOC_DS_2362A02
OB2362A
Adaptive Multi-Mode PWM Controller
OPERATION DESCRIPTION
OB2362A is a highly integrated current mode
PWM control IC optimized for high performance,
low standby power and cost effective offline
flyback converter applications. The ‘extended
burst mode’ control greatly reduces the standby
power consumption and helps the design easier to
meet the international power conservation
requirements.
密
core loss of the transformer and the loss of 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.
The switching frequency is internally adjusted at
no load or light load condition. The switch
frequency reduces at light/no load condition to
improve the conversion efficiency. At light load or
no load condition, the FB input drops below
Vref_burst_L (the threshold enter burst mode) and
device enters Burst Mode control. The Gate drive
output switches when FB input rises back to
Vref_burst_H (the threshold exit burst mode).
Otherwise the gate drive remains at off state to
minimize the switching loss and reduces the
standby power consumption to the greatest
extend.
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Soft Start
OB2362A features an internal 2ms (typical) soft
start to soften the electrical stress occurring in the
power supply during startup. It is activated during
the power on sequence. As soon as VCC reaches
UVLO(OFF), the CS peak voltage is gradually
increased from 0.05V to the maximum level.
Every restart up is followed by a soft start.
Demagnetization Detection
The transformer core demagnetization is detected
by monitoring the voltage activity on the auxiliary
windings through PRT pin. This voltage features a
flyback polarity. After the on time (determined by
the CS voltage and FB voltage), the switch is off
and the flyback stroke starts. After the flyback
stroke, the drain voltage shows an oscillation with
nt
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Operating Current
The Operating current of OB2362A is low at
2.5mA (typical). Good efficiency is achieved with
OB2362A low operation current together with the
‘extended burst mode’ control features.
吉
Startup Current and Start up Control
Startup current of OB2362A is designed to be
very low so that VCC could be charged up above
UVLO threshold level and device starts up quickly.
A large value startup resistor can therefore be
used to minimize the power loss yet achieve a
reliable startup in application.
a frequency of approximately 1 / 2
on
where
Frequency shuffling for EMI improvement
The frequency shuffling (switching frequency
modulation) is implemented in OB2362A. 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.
L pCd ,
L p is the primary self inductance of
primary winding of the transformer and Cd is the
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ht
c
capacitance on the drain node.
The typical detection level is fixed at -50mV at the
PRT pin. Demagnetization is recognized by
detection of a possible “valley” when the voltage
at PRT is below -50mV in falling edge.
O
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Br
Multi Mode Operation for High Efficiency
OB2362A is a multi mode controller. The
controller changes the mode of operation
according to the FB pin voltage. At the normal
operating condition, the IC operates in traditional
fix frequency （65KHz）PWM mode.
As the output load current is decreased , the IC
enter into green mode smoothly from the PWM
mode. In this mode , the switching frequency will
start to linearly decrease from 65KHz to 23KHz,
meanwhile the valley turn on can be realized by
monitoring the voltage activity on auxiliary
windings through the PRT pin. So the switching
loss is minimized and the high conversion
efficiency can be achieved.
At light load or no load condition, most of the
power dissipation in a switching mode power
supply is from switching loss of the MOSFET, the
©On-Bright Electronics
Current Sensing and Leading Edge Blanking
Cycle-by-Cycle current limiting is offered in
OB2362A current mode PWM control. The switch
current is detected by a sense resistor into the CS
pin. An internal leading edge blanking circuit
Confidential
9
Preliminary Datasheet
OB_DOC_DS_2362A02
OB2362A
Adaptive Multi-Mode PWM Controller
密
吉
to
fid
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Driver
The power MOSFET is driven by a dedicated gate
driver for power switch control. Too weak the gate
driver strength results in higher conduction and
switch loss of MOSFET while too strong gate
driver strength results the compromise of EMI.
A good tradeoff is achieved through the built-in
totem pole gate design with right output strength
and dead time control. The low idle loss and good
EMI system design is easier to achieve with this
dedicated control scheme.
l
Internal Synchronized Slope Compensation
Built-in slope compensation circuit adds voltage
ramp into the current sense input voltage for PWM
generation. This greatly improves the close loop
stability at CCM and prevents the sub-harmonic
oscillation and thus reduces the output ripple
voltage.
On-Bright proprietary dual function of external
OTP and output OVP provides feasible and
accurate detection of external OTP through NTC
resistor and output OVP. The dual function is
realized through time-division technology as
shown in the figure.
For external OTP detection, when switch control
signal S1= “1”, about 20uA (typical) current flows
out from PRT pin. When switch control signal S0=
“1”,about 120uA (typical) current flows out from
PRT pin. The PRT pin voltage difference △Votp
at phase S0
and S1 phase is equal to
RT ROVP
VOTP
100uA .
ROVP RT
When △Votp
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