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Número de pieza OB2298
Descripción PWM Controller
Fabricantes On-Bright Electronics 
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OB2298 datasheet

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OB2298 pdf
OB2298
PWM Controller with PFC Standby Control
ELECTRICAL CHARACTERISTICS
(TA = 25OC, VDD=18V, if not otherwise noted)
Symbol
Parameter
Supply Voltage (VDD) Section
Istartup
VDD start up current
I_VDD
UVLO(ON)
UVLO(OFF)
OVP(Latch)
VDD(De-Latch)
Ivdd_latch
TD_OVP
VDD_Clamp
T_Softstart
Operation current
VDD under voltage
lockout enter
VDD under voltage
lockout exit (Startup)
VDD over voltage
latch trigger
VDD latch release
threshold voltage
VDD bleeding
current at latch
shutdown
VDD OVP Debounce
time
VDD zener clamp
voltage
Soft start time
Feedback Input Section(FB Pin)
AVCS
PWM input gain
VFB_Open
FB open voltage
Test Conditions
VDD =14V, Measure
current into VDD
VFB=3V
VDD=8V
I(VDD ) = 10 mA
VFB /Vcs
IFB_Short
VTH_0D
VTH_GM
VTH_BM_on
VTH_BM_off
VTH_PL
TD_PL
ZFB_IN
VTH_PFC_off
VTH_PFC_on
FB pin short circuit
current
Zero duty cycle FB
threshold voltage
Green mode FB
threshold voltage
Burst mode on FB
threshold voltage
Burst mode off FB
threshold voltage
Power limiting FB
threshold voltage
Power limiting
debounce time
Input impedance
PFC off FB threshold
voltage
PFC on FB threshold
voltage
Current Sense Input(CS Pin) Section
T_blanking
CS input leading
edge blanking time
VTH_OC
Internal current
limiting threshold
Short FB pin to GND,
measure current
Zero duty cycle
©On-Bright Electronics
-5-
Min Typ Max Unit
5 20 uA
2.3 mA
8 9 10 V
14.5 15.5 16.5 V
26 28 30 V
6.5 V
45 uA
100
30
4
2.4
5.5
1.1
1
1.7
1.3
1.4
4.4
225
5
1.6
1.7
uSec
V
mSec
V/V
V
mA
V
V
V
V
V
mSec
Kohm
V
V
300
0.57 0.6
nSec
0.63 V
Confidential
OB_DOC_DS_9800
Free Datasheet http://www.datasheet4u.com/

5 Page

OB2298 arduino
OB2298
PWM Controller with PFC Standby Control
OPERATION DESCRIPTION
OB2298 integrates PFC IC power control functions
to supply PFC IC power and shuts it down at
No/Light load or any fault conditions. It is
compatible with main stream PFC ICs in the market.
The versatile protections and high performance
make it very suitable for medium-to-large power
applications.
z PFCVCC Power On/off Control
In applications with output power of greater than
75W, PFC pre-regulator is mandatory to meet the
requirement of power factor, that is, a PFC pre-
regulation is in the first stage and followed by a
PWM controlled power conversion. However, this
two-stage conversion makes it difficult to meet
standby power requirement. To meet both
requirements for power factor and standby, the PFC
stage is off at No/Light conditions.
OB2298 provides the direct control for the
operation of PFC stage. PFCVCC pin can be
directly connected to PFC controller’s power
supply by a built-in low impedance power switch.
In this way, PFC stage is controlled by PWM stage.
OB2298 is compatible with main stream PFC ICs
in the market. OB2298 shuts down the front end
PFC stage at three situations: any fault occurs,
No/Light load conditions and during start up
sequence. Fig.1 illustrates a startup sequence and
PFC On/off control at light loadings.
Figure 1
z Startup Current and Start up Control
Startup current of OB2298 is designed to be very
low so that VDD could be charged up above
UVLO(OFF) threshold level and device starts up
quickly. A large value startup resistor can therefore
be used to minimize the power loss yet reliable
startup in application. For a typical AC/DC SMPS
with universal input range design, a 2 M, 1/8 W
startup resistor could be used together with a VDD
capacitor to provide a fast startup and yet low
power dissipation design solution.
z Operating Current
The Operating current of OB2298 is low at 2.3mA
typically. Ultra low standby power is achieved with
OB2298 low operating current together with
extended burst mode control schemes.
z Extended Burst Mode Operation
At No load/Light load condition, most of the power
dissipation in a SMPS is from switching loss on the
MOSFET transistor, the core loss of the
transformer and the loss on the snubber circuit. The
magnitude of power loss is in proportion to the
number of switching events within a fixed period of
time. Reducing switching events leads to the
reduction on the power loss and thus conserves the
energy. OB2298 self adjusts the switching mode
according to the loading condition. At from no load
to light/medium load condition, the FB input drops
below burst mode threshold level. Device enters
Burst Mode control. The Gate drive output switches
only when VDD voltage drops below a preset level
and FB input is active to output an on state.
Otherwise the gate drive remains at off state to
minimize the switching loss thus reduce the
standby power consumption to the greatest extend.
The nature of high frequency switching also
reduces the audio noise at any loading conditions.
z Oscillator/Frequency Shuffling Operation
A fixed 65KHZ frequency oscillator is built in
OB2298, and the proprietary frequency shuffling
method can soften the EMI signature by spreading
the energy in the vicinity of the main switching
component. The magnitude of shuffling lies in the
ranged of ±4% of the main switching frequency.
z Current Sensing and Leading Edge
Blanking
Cycle-by-Cycle current limiting is offered in
OB2298 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 sense voltage spike at initial MOSFET on
state due to snubber diode reverse recovery so that
the external RC filtering on sense input is no longer
needed. The current limit comparator is disabled
and cannot turn off the external MOSFET during
the blanking period. The PWM duty cycle is
determined by the current sense input voltage and
the FB input voltage.
©On-Bright Electronics
- 10 -
Confidential
OB_DOC_DS_9800
Free Datasheet http://www.datasheet4u.com/

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