ZHCS785H February   2012  – May 2019 SN6501


  1. 特性
  2. 应用
  3. 说明
    1.     Device Images
      1.      简化原理图
      2.      输出电压和效率与输出电流间的关系
  4. 修订历史记录
  5. Pin Configuration and Functions
  6. Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 Handling 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. Parameter Measurement Information
  8. Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Push-Pull Converter
      2. 8.3.2 Core Magnetization
    4. 8.4 Device Functional Modes
      1. 8.4.1 Start-Up Mode
      2. 8.4.2 Operating Mode
      3. 8.4.3 Off-Mode
  9. Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1. SN6501 Drive Capability
        2. LDO Selection
        3. Diode Selection
        4. Capacitor Selection
        5. Transformer Selection
          1. V-t Product Calculation
          2. Turns Ratio Estimate
          3. Recommended Transformers
      3. 9.2.3 Application Curve
      4. 9.2.4 Higher Output Voltage Designs
      5. 9.2.5 Application Circuits
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12器件和文档支持
    1. 12.1 器件支持
      1. 12.1.1 第三方产品免责声明
    2. 12.2 商标
    3. 12.3 静电放电警告
    4. 12.4 Glossary
  13. 13机械、封装和可订购信息


机械数据 (封装 | 引脚)
散热焊盘机械数据 (封装 | 引脚)

Push-Pull Converter

Push-pull converters require transformers with center-taps to transfer power from the primary to the secondary (see Figure 37).

SN6501 push_pull_conv_llsea0.gifFigure 37. Switching Cycles of a Push-Pull Converter

When Q1 conducts, VIN drives a current through the lower half of the primary to ground, thus creating a negative voltage potential at the lower primary end with regards to the VIN potential at the center-tap.

At the same time the voltage across the upper half of the primary is such that the upper primary end is positive with regards to the center-tap in order to maintain the previously established current flow through Q2, which now has turned high-impedance. The two voltage sources, each of which equaling VIN, appear in series and cause a voltage potential at the open end of the primary of 2×VIN with regards to ground.

Per dot convention the same voltage polarities that occur at the primary also occur at the secondary. The positive potential of the upper secondary end therefore forward biases diode CR1. The secondary current starting from the upper secondary end flows through CR1, charges capacitor C, and returns through the load impedance RL back to the center-tap.

When Q2 conducts, Q1 goes high-impedance and the voltage polarities at the primary and secondary reverse. Now the lower end of the primary presents the open end with a 2×VIN potential against ground. In this case CR2 is forward biased while CR1 is reverse biased and current flows from the lower secondary end through CR2, charging the capacitor and returning through the load to the center-tap.