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PDF UC3837 Data sheet ( Hoja de datos )
| Número de pieza | UC3837 | |
| Descripción | LOW COST POWER-SAVING MODE PWM CONTROLLER | |
| Fabricantes | Unisonic Technologies | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de UC3837 (archivo pdf) en la parte inferior de esta página. Total 10 Páginas | ||
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UNISONIC TECHNOLOGIES CO., LTD
UC3837
Preliminary
LINEAR INTEGRATED CIRCUIT
LOW COST POWER-SAVING
MODE PWM CONTROLLER
FOR FLYBACK CONVERTERS
DESCRIPTION
The UC3837 is a high performance current mode PWM
controller ideally suited for low standby power. Low VDD startup
current make the power reliable on startup design and a large
value resistor could be used in the startup circuit to minimize the
standby power. At no load condition, the IC operates in
power-saving mode for lower standby power, decreasing frequency
for Higher conversion efficiency at light load condition.
The internal slope compensation improves system stability at
high PWM duty cycle output. Leading-edge blanking on current
sense input removes the signal glitch, which offering minimal
external component count in the design. Excellent EMI
performance is achieved with UTC proprietary frequency hopping
technique (ZL201020615247.1) together with soft driver control.
Audio noise is eliminated due to switch frequency more than 20kHz
during operation.
The UC3837 has such applications as: battery charger, power
adaptor, set-top box power supplies, ink jet printers, open-frame
SMPS.
54
6
1 23
SOT-26
FEATURES
* UTC proprietary frequency hopping technology for Improved EMI * Programming BNO for higher security
performance.
* Fixed switch frequency 65kHz
* Power-saving mode for high light-load and standby efficiency
* Gate output voltage clamped at 15V
* Soft Start
* Low start-up current
* Dynamic peak current limiting for constant output power
* Cycle-by-cycle Current Limiting
* Built-in synchronized slope compensation
* Under voltage lockout (UVLO)
* OTP,OLP,OVP and VDD clamp for higher security
* Few external components required
ORDERING INFORMATION
Ordering Number
UC3837G-AG6-R
Package
SOT-26
Packing
Tape Reel
UC3837G-AG6-R
(1)Packing Type
(2)Package Type
(3)Green Package
(1) R: Tape Reel
(2) AG6: SOT-26
(3) G: Halogen Free and Lead Freee
www.unisonic.com.tw
Copyright © 2015 Unisonic Technologies Co., Ltd
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QW-R103-069.B
1 page  
UC3837
Preliminary
LINEAR INTEGRATED CIRCUIT
OPERATION DESCRIPTION
The UC3837 devices integrate many useful designs into one controller for low-power switch-mode power
supplies. The following descriptions highlight some of the features of the UC3837 series.
Start-up Current
The start-up current is only 5μA. Low start-up current allows a start-up resistor with a high resistance and a
low-wattage to supply the start-up power for the controller. For AC/DC adaptor with universal input range design, a
2.5~3MΩ, 1/8W startup resistor could be used together with a VDD capacitor to provide a fast startup and low power
dissipation solution.
Power-Saving Mode Operation
The proprietary Power-Saving Mode function provides linearly decreasing the switching frequency under
light-load conditions for higher efficiency. The feedback voltage, which is sampled from the voltage feedback loop, is
taken as the reference. Once the feedback voltage dropped below the threshold voltage, the switching frequency
starts to decrease. This Power-Saving Mode function dramatically reduces power consumption under light-load
conditions. The 22KHz minimum frequency control also eliminates the audio noise at any loading conditions.
At zero load condition, 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. The UC3837 enter burst mode at standby condition to minimize the switching loss and reduces the standby
power consumption. Power supplies using the UC3837 can easily meet even the strictest regulations regarding
standby power consumption.
Switch Frequency Set
The maximum switch frequency is fixed to 65KHz. Switch frequency is modulated by output power POUT during IC
operating. At no load or light load condition, most of the power dissipation in a switching mode power supply 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. So lower
switch frequency at lower load, which more and more improve IC’s efficiency at light load. At from no load to light
load condition, The IC will operate at from Burst mode to Reducing Frequency Mode. The relation curve between fSW
and POUT/POUT (MAX) as followed Fig.1.
Fig.1 The relation curve between fSW and relative output power POUT/ POUT (MAX)
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
5 of 10
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5 Page | ||
| Páginas | Total 10 Páginas | |
| PDF Descargar | [ Datasheet UC3837.PDF ] | |
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