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High Precision CC/CV Primary-Side PWM Power Switch

DESCRIPTION

RS2138 is a high performance offline PWM Power switch for low power AC/DC charger and adaptor applications. It operates in primary -side sensing and regulation. Consequently, opto-coupler and 431 could be eliminated. Proprietary Constant Voltag e (CV) and Constant Current (CC) control is integrated as shown in the figure 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. RS2138 offers power on soft start control and protection coverage with auto -recovery features including Cycle -by-Cycle current limiting, VDD OVP, VDD clamp and UVLO. Excellent EMI performance is achieved with Frequency Jiggling.

FEATURES

 5% Constant Voltage Regulation, 5% Constant Current Regulation at Universal AC Input  Primary‐ side Sensing and Regulation without 431 and Opto-coupler  Power on Soft-start  Built-in Leading Edge Blanking (LEB)  Cycle-by-Cycle Current Limiting  VDD Under Voltage Lockout with Hysteresis (UVLO)  Programmable CV and CC Regulation  Adjustable Constant Current and Output Power Setting  Built-in Secondary Constant Current Control with Primary Side Feedback  Built-in Adaptive Current Peak Regulation  Built-in Primary Winding Inductance Compensation  Program Cable Drop Compensation  VDD OVP and VDD Clamp  Available in an DIP-8 Package  RoHS Compliant and 100% Lead (Pb)-Free and Green (Halogen Free with Commercial Standard)

APPLICATIONS

 Cell Phone Charger  Digital Cameras Charger  Small Power Adaptor  Auxiliary Power for PC, TV etc.  Linear Regulator/RCC Replacement Figure 1. Typical CC/CV Curve

V1.0 2 January 2013 BLOCK DIAGRAM APPLICAION CIRCUIT

V1.0 3 January 2013 ORDER INFORMATION Device Device Code RS2138 Y Z Y is package & Pin Assignments designator: P: DIP-8 Z is Lead Free designator: P: Commercial Standard, Lead (Pb) Free and Phosphorous (P) Free Package G: Green (Halogen Free with Commercial Standard) PIN ASSIGNMENTS PIN DESCRIPTION Pin Name Description Pin No. VCC Power supply 1 COMP Loop compensation for CV stability 2 INV The voltage feedback from auxiliary winding. Connected to resistor divider from auxiliary winding reflecting output voltage. PWM duty cycle is determined by EA output and current sense signal at pin 4. CS Current sense input 4 DRAIN HV MOSFET drain pin. The Drain pin is connected to the primary lead of the transformer 5, 6 GND Ground 7, 8

V1.0 9 January 2013 IMPORTANT NOTICE Princeton Technology Corporation (PTC) reserves the right to make corrections, modifica tions, enhancements, improvements, and other changes to its products and to discontinue any product without notice at any time. PTC cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a PTC product. No circuit patent licenses are implied. Princeton Technology Corp. 2F, 233-1, Baociao Road, Sindian Dist., New Taipei City 23145, Taiwan Tel: 886-2-66296288 Fax: 886-2-29174598 http://www.princeton.com.tw