ZHCSJY8E june   2019  – february 2021 UCC256402 , UCC256403 , UCC256404

PRODUCTION DATA  

  1. 1 特性
  2. 2 应用
  3. 3 说明
  4. 4 Revision History
    1.     Device Comparison Table
  5. 5 Pin Configuration and Functions
    1.     Pin Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 Switching Characteristics
    7. 6.7 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Hybrid Hysteretic Control
      2. 7.3.2 Regulated 13-V Supply
      3. 7.3.3 Feedback Chain
        1. 7.3.3.1 Optocoupler Feedback Signal Input and Bias
        2. 7.3.3.2 FB Pin Voltage Clamp
        3. 7.3.3.3 "Pick Lower Value" Block and Soft Start Multiplexer
        4. 7.3.3.4 Pick Higher Block and Burst Mode Multiplexer
        5. 7.3.3.5 VCR Comparators
      4. 7.3.4 Resonant Capacitor Voltage Sensing
      5. 7.3.5 Resonant Current Sensing
      6. 7.3.6 Bulk Voltage Sensing
      7. 7.3.7 Output Voltage Sensing
      8. 7.3.8 High Voltage Gate Driver
        1. 7.3.8.1 Adaptive Dead Time Control
      9. 7.3.9 Protections
        1. 7.3.9.1 ZCS Region Prevention
        2. 7.3.9.2 Over Current Protection (OCP)
        3. 7.3.9.3 Bias Winding Over Voltage Protection (BWOVP)
        4. 7.3.9.4 Input Under Voltage Protection (VINUVP)
        5. 7.3.9.5 Input Over Voltage Protection (VINOVP)
        6. 7.3.9.6 Boot UVLO
        7. 7.3.9.7 RVCC UVLO
        8. 7.3.9.8 Over Temperature Protection (OTP)
    4. 7.4 Device Functional Modes
      1. 7.4.1 High Voltage Start-Up
      2. 7.4.2 X-Capacitor Discharge
      3. 7.4.3 Burst Mode Control
        1. 7.4.3.1 Soft-Start and Burst-Mode Threshold
        2. 7.4.3.2 BMTL/BMTH Ratio Programming
      4. 7.4.4 System State Machine
        1.       Application and Implementation
          1. 8.1 Application Information
          2. 8.2 Typical Application
            1. 8.2.1 Design Requirements
            2. 8.2.2 Detailed Design Procedure
              1. 8.2.2.1  LLC Power Stage Requirements
              2. 8.2.2.2  LLC Gain Range
              3. 8.2.2.3  Select Ln and Qe
              4. 8.2.2.4  Determine Equivalent Load Resistance
              5. 8.2.2.5  Determine Component Parameters for LLC Resonant Circuit
              6. 8.2.2.6  LLC Primary-Side Currents
              7. 8.2.2.7  LLC Secondary-Side Currents
              8. 8.2.2.8  LLC Transformer
              9. 8.2.2.9  LLC Resonant Inductor
              10. 8.2.2.10 LLC Resonant Capacitor
              11. 8.2.2.11 LLC Primary-Side MOSFETs
              12. 8.2.2.12 LLC Rectifier Diodes
              13. 8.2.2.13 LLC Output Capacitors
              14. 8.2.2.14 HV Pin Series Resistors
              15. 8.2.2.15 BLK Pin Voltage Divider
              16. 8.2.2.16 ISNS Pin Differentiator
              17. 8.2.2.17 VCR Pin Capacitor Divider
              18. 8.2.2.18 BW Pin Voltage Divider
              19. 8.2.2.19 Soft Start and Burst Mode Programming
            3. 8.2.3 Application Curves
  8. 8 Power Supply Recommendations
    1. 8.1 VCC Pin Capacitor
    2. 8.2 Boot Capacitor
    3. 8.3 RVCC Pin Capacitor
  9. 9 Layout
    1. 9.1 Layout Guidelines
    2. 9.2 Layout Example
  10. 10Device and Documentation Support
    1. 10.1 Documentation Support
      1. 10.1.1 Related Documentation
    2. 10.2 Related Links
    3. 10.3 Receiving Notification of Documentation Updates
    4. 10.4 Community Resources
    5. 10.5 Trademarks
      1.      Mechanical, Packaging, and Orderable Information

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7.4.1 High Voltage Start-Up

UCC256402 and UCC256404 uses a self bias start up scheme, thus eliminating the need for a separate auxiliary supply. When AC power is first plugged in, the PFC and LLC are both off. The internal JFET on the HV pin will be enabled and will start to deliver current from a source connected from the HV pin to the VCC capacitor. The charge current is small when VCC pin voltage is below VCCShort , and then becomes larger when VCC pin voltage is above VCCShort.Once the VCC pin voltage exceeds its VCCStartSwitching threshold, the current source will be turned off and RVCC will be enabled to turn on the PFC. When the PFC output voltage reaches a certain level, the LLC is turned on. When the LLC is operating and the output voltage is established, the bias winding will supply current for both the PFC and the LLC controller devices.

UCC256403 does not include a high voltage start-up feature. It requires an external auxiliary supply to power on the IC. The HV pin needs to be grounded when using the UCC256403.