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Low power AC/DC offline SMPS for
Cell Phones/Cordless phones Charger
Digital Cameras Charger
Small Power Adapter
Auxiliary Power for PC, TV etc.
Linear Regulator/RCC Replacement

5uA ultra-low startup current
2mA Low operating current
±5% Constant Voltage Regulation at Universal AC input
Primary-side Sensing and Regulation Without TL431 and Opto-coupler
Programmable CV and CC Regulation
Built-in Primary winding inductance compensation
Programmable cable drop compensation
Built-in soft start
Built-in Leading-edge blanking
Cycle by cycle over current protection (OCP)
VCC over voltage clamp & under voltage lockout( UVLO)
Maximum Gate output voltage clamped at 12V
Frequency jittering
Ultra low standby power (<100mW)


Structure Type

Part NO.



App. Watt












External Set


General Description
WS3254 is a high-integrated offline PWM power switch, optimized for high performance low power AC/DC charger and adapter application.
WS3254 operates in primary-side sensing and regulation.Consequently, optocoupler and TL431 could be eliminated,thus reduce the cost.It can achieve ±5% constant voltage precision in full input voltage range. CC/CV Control as shown in fig.1. In CC Control, the current and output power setting can be adjusted externally by the sense resistor Rs at CS pin. In CV control,multi-mode operations are utilized to achieve high performance and high efficiency. In addition, good load regulation is achieved by the built-in cable drop compensation.Device operates in PFM in CC mode as well at large load condition and it operates in PWM with frequency reduction at light/medium load.
WS3254 offers power on soft start control and protection coverage with auto-recovery features including Cycle-by-Cycle current limiting, VCC OVP, VCC clamp and UVLO. The gate-driven output is clamped to maximum 12V to protect the internal MOSFET.
Excellent EMI performance is achieved by using the soft-switching and frequency jittering at the totem-pole-gate-drive output. The WS3254 is the ideal substitute of the linear power supply or the RCC-mode power,for a better performance of the whole switch power system and a lower cost.
WS3254 is available in DIP8 package.
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