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PDF L2273 Data sheet ( Hoja de datos )
| Número de pieza | L2273 | |
| Descripción | Current Mode PWM Controller | |
| Fabricantes | LIZE | |
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Shenzhen LIZE Electronic Technology Co., Ltd
Current Mode PWM Controller
L2273
SPECIFICATION
L2273
Current Mode PWM Controller
VERSION 1.0
reserves the right to change this documentation without prior notice
1 page  
Shenzhen LIZE Electronic Technology Co., Ltd
Current Mode PWM Controller
L2273
Pin Assignment & Marking Information
reserves the right to change this documentation without prior notice
5 Page 
Shenzhen LIZE Electronic Technology Co., Ltd
Current Mode PWM Controller
L2273
Application Information
The L2273 is a highly integrated PWM
controller IC optimized for offline flyback
converter applications in sub 60W power range.
The extended burst mode control greatly
reduces the standby power consumption and
helps the design easily meet the international
power conservation requirements.
Start up Control
L2273 has especially Start-up circuit .As
application circuit,Vdd active Start-up circuits
using external N-mos and BJT respectively
Prior to start-up, the N-mos or the BJT is
turned on, allowing the start-up current to
charge the VDD bypass capacitor.r. When
the VDD bypass capacitor is charged to a
voltage higher than the start-up threshold
VDD(ST),the N-mos and BJT will be turned
off .The N-mos and BJT will be turned off all
the time until the voltage of VDD bypass
capacitor lower than UVLO.The voltage of VS
will control the N-mos and BJT can low
Standby power .
Operating Current
The Operating current of L2273 is low at
1.5mA.Good efficiency is achieved with L2273
low operating current together with extended
burst mode control features.
Frequency shuffling for EMI
improvement
The frequency Shuffling (switching frequency
modulation) is implemented in L2273. The
oscillation frequency is modulated with a
random source so that the tone energy is spread
out. The spread spectrum minimizes the
conduction band EMI and therefore reduces
system design challenge.
ended Burst Mode Operation
At zero load or light load condition, majority of
the power dissipation in a switching mode
power supply is from switching loss on the
MOSFET transistor, the core loss of
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.L2273 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 and
reduces the standby power consumption to the
greatest extend.The frequency control also
eliminates the audio noise at any loading
conditions.
Oscillator Operation
The switching frequency of briard is internally
fixed at 65kHz.No external frequence setting
components are required for PCB desigh
simplifecation .
Current Sensing and Leading Edge
Blanking
Cycle-by-Cycle current limiting is offered in
L2273 current mode PWM control. The switch
current is detected by a sense resistor into the
sense 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 required.
The current limit comparator is disabled and
thus cannot turn off the external MOSFET
during the blanking period. PWM duty cycle is
determined by the current sense input voltage
and the FB input voltage.
reserves the right to change this documentation without prior notice
11 Page | ||
| Páginas | Total 15 Páginas | |
| PDF Descargar | [ Datasheet L2273.PDF ] | |
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