TIDUFA5 December   2024

 

  1.   1
  2.   Description
  3.   Resources
  4.   Features
  5.   Applications
  6.   6
  7. 1System Description
    1. 1.1 Key System Specifications
  8. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Design Considerations
      1. 2.2.1 Small Compact Size
      2. 2.2.2 Transformerless Design
    3. 2.3 Highlighted Products
      1. 2.3.1  BQ25790 IIC Controlled, 1–4 Cell, 5A Buck-Boost Battery Charger
      2. 2.3.2  TPS3422 Low-Power, Push-Button Controllers With Configurable Delay
      3. 2.3.3  SN74LVC1G74 Single Positive-Edge-Triggered D-Type Flip-Flop With Clear and Preset
      4. 2.3.4  TPS259470 2.7V–23V, 5.5A, 28mΩ True Reverse Current Blocking eFuse
      5. 2.3.5  TPS54218 2.95V to 6V Input, 2A Synchronous Step-Down SWIFT Converter
      6. 2.3.6  TPS54318 2.95V to 6V Input, 3A Synchronous Step-Down SWIFT Converter
      7. 2.3.7  LM5158 2.2MHz, Wide VIN, 85V Output Boost, SEPIC, or Flyback Converter
      8. 2.3.8  TPS61178 20V Fully Integrated Sync Boost With Load Disconnect
      9. 2.3.9  LMZM23601 36V, 1A Step-Down DC-DC Power Module in 3.8mm × 3mm Package
      10. 2.3.10 TPS7A39 Dual, 150mA, Wide-VIN, Positive and Negative Low-Dropout (LDO) Voltage Regulator
      11. 2.3.11 TPS74401 3.0A, Ultra-LDO With Programmable Soft Start
      12. 2.3.12 TPS7A96 2A, Ultra-Low Noise, Ultra-high PSRR RF Voltage Regulator
      13. 2.3.13 LM3880 3-Rail Simple Power Sequencer With Fixed Time Delay
      14. 2.3.14 DAC53401 10-Bit, Voltage-Output DAC With Nonvolatile Memory
      15. 2.3.15 INA231 28V, 16-bit, I2C Output Current, Voltage, and Power Monitor With Alert in WCSP
  9. 3System Design Theory
    1. 3.1 Input Section
      1. 3.1.1 Buck-Boost Charger
      2. 3.1.2 Power On or Off
    2. 3.2 Designing SEPIC and Cuk Based High-Voltage Power Supply
      1. 3.2.1 Basic Operation Principle of SEPIC and Cuk Converters
      2. 3.2.2 Dual High-Voltage Power Supply Design Using Uncoupled Inductors With SEPIC and Cuk
        1. 3.2.2.1 Duty Cycle
        2. 3.2.2.2 Inductor Selection
        3. 3.2.2.3 Power MOSFET Verification
        4. 3.2.2.4 Output Diode Selection
        5. 3.2.2.5 Coupling Capacitor Selection
        6. 3.2.2.6 Output Capacitor Selection
        7. 3.2.2.7 Input Capacitor Selection
        8. 3.2.2.8 Programming the Output Voltage With Adjustable function
    3. 3.3 Designing the Low-Voltage Power Supply
      1. 3.3.1 Designing the TPS54218 Through WEBENCH Power Designer
      2. 3.3.2 ±5V Transmit Supply Generation
    4. 3.4 System Clock Synchronization
    5. 3.5 Power and Data Output Connector
    6. 3.6 System Current and Power Monitoring
  10. 4Hardware, Testing Requirements, and Test Results
    1. 4.1 Hardware Requirements
    2. 4.2 Test Setup
    3. 4.3 Test Results
      1. 4.3.1 Efficiency Test Result
      2. 4.3.2 Line Regulation Testing Result
      3. 4.3.3 Spectrum Test Result
  11. 5Design and Documentation Support
    1. 5.1 Design Files
      1. 5.1.1 Schematics
      2. 5.1.2 BOM
      3. 5.1.3 PCB Layout Recommendations
        1. 5.1.3.1 High-Voltage Supply Layout
    2. 5.2 Tools and Software
    3. 5.3 Documentation Support
    4. 5.4 Support Resources
    5. 5.5 Trademarks

3.2.2.1 Duty Cycle

For a SEPIC converter operating in a continuous conduction mode (CCM) use Equation 10 to calculate the duty cycle.

Equation 10. D = V o u t p u t + V D V i n + V o u t p u t + V D

For the high-voltage designs used in this reference design, the LM5158 can reach a duty cycle of 93% from 100kHz to 250kHz. Using Equation 10, the calculated duty cycle was 93.8%. So, the parts are running in current discontinue mode slightly. But with internal minimum 3.26A MOSFET and compact size, the parts were selected for HVPS and can be output maximum ±25mA current. Assume the efficiency of circuit is 0.7, then the input current is (75 × 0.025 × 2) / (5 × 0.7) = 1.072A. The maximum current is approximately 2.57A if the designer selects exactly the same two inductors. It is clear that LM5158 supports a discontinue current mode. VD is the forward voltage drop of the diode D1.