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

封装选项

机械数据 (封装 | 引脚)
散热焊盘机械数据 (封装 | 引脚)
订购信息

7.3.3.3 "Pick Lower Value" Block and Soft Start Multiplexer

This part of the circuit consists of 3 elements:

  • A pick lower block
  • A MUX which selects AVDD or SS signal as the second input to the pick lower block
  • An SS control block which handles the charge and discharge of the SS capacitor in the case of a ZCS fault

The pick lower block has two inputs. The first input is FBreplica. The second input is selected between AVDD and LL/SS pin voltage. The output of the block is the lower of the two inputs.

The MUX selects between SS and AVDD. The selection is based on SSEnd (soft start end) signal, which is an output of the SS Ctrl block. SSEnd is high when SS is higher than FBreplica, and the soft start process has been initiated by the state machine, and there is no ZCS condition. Switching to AVDD after soft start has ended helps make sure that during non-soft start or non-ZCS fault condition, FBreplica signal is always sent through the pick lower block. It also releases the LL/SS pin to perform the light load threshold programming.

The SS control block handles the charge and discharge of the SS capacitor in the case of a ZCS fault. It resets the SSEnd signal when ZCS happens, so the effect of pulling down on LL/SS pin to increase the switching frequency can pass through the pick lower block.