UNISONIC TECHNOLOGIES CO., LTD
UCQ3738
Preliminary
CMOS IC
LOW COST POWER-SAVING
MODE PWM CONTROLLER FOR
FLYBACK CONVERTERS
DESCRIPTION
The UTC UCQ3738 provides a CCM/valley switching mixed
mode operation for better efficiency performance. The operation
mode stays at CCM at heavy load, and switch to valley switching at
light load.
The UTC UCQ3738 is a high performance current mode PWM
controller ideally suited for low standby power. Low VCC 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 UTC UCQ3738 contains protection with automatic recovery
including OLP (over load protection), OCP (cycle-by-cycle current
limiting), and UVLO (VCC over voltage clamp and under voltage
lockout). It also provides the protections including OTP (over
temperature protection), BNO(AC Brown Out protection) , LNO(AC
Over voltage protection), Programmable Propagation Delay Time ,
OVP (VCC or DC output over voltage protection) with automatic
recovery. To protect the power MOSFET, Gate-drive output is fixed
up to 16V max.
Leading-edge blanking on current sense input removes the signal
glitch, which offering minima external component count in the
design. Excellent EMI performance is achieved with UTC proprietary
smart frequency hopping technique together with soft driver control.
Audio noise is eliminated due to switch frequency more than 20kHz
during operation.
UTC UCQ3738 is packaged by using tiny SOT-26 package. It
has such applications as: battery charger, power adaptor, set-top
box power supplies, ink jet printers, open-frame SMPS.
FEATURES
* Proprietary smart frequency hopping for Improved EMI and output
Jittering ripple
* Cycle-by-cycle current limiting
* CCM/Valley Switching Operation
* Fixed switch frequency 60~70kHz
* Dynamic peak current limiting for constant output power
* Programmable Propagation Delay Time
* Gate output voltage clamped at 16V
* Adjustable DC output OVP/UVP
* Adjustable OTP (Over Temperature Protection) on CS Pin
* OLP/VCC OVP/OTP/BNO/LNO (automatic recovery)
* Internal Soft Start
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