SNVS900B DECEMBER   2012  – December 2015 TPS92560

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and 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 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 VCC Regulator
      2. 7.3.2 MOSFET Driver
      3. 7.3.3 ADJ Pin
        1. 7.3.3.1 Output OVP
      4. 7.3.4 AC1 and AC2 Pins
      5. 7.3.5 Detection of Power Source
      6. 7.3.6 Current Regulation
      7. 7.3.7 Switching Frequency (Boost Configuration)
      8. 7.3.8 Inductor Selection (Boost Configuration)
      9. 7.3.9 Input Surge Voltage Protection
    4. 7.4 Device Functional Modes
      1. 7.4.1 Thermal Shutdown
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Applications
      1. 8.2.1 Boost Application Design Example
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1 Calculate Values for the ADJ Resistors
          2. 8.2.1.2.2 Calculate the Sense Voltage and Sense Resistor Value
          3. 8.2.1.2.3 Calculate the Inductor Value
        3. 8.2.1.3 Application Curve
      2. 8.2.2 Boost Application Circuit With LED Current Regulation
        1. 8.2.2.1 Design Requirements
        2. 8.2.2.2 Application Curves
      3. 8.2.3 SEPIC Application Circuit With LED Current Regulation
        1. 8.2.3.1 Design Requirements
        2. 8.2.3.2 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Community Resources
    2. 11.2 Trademarks
    3. 11.3 Electrostatic Discharge Caution
    4. 11.4 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

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発注情報

8 Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality.

8.1 Application Information

In the applications that need true regulation of the LED current, the intrinsic input current control loop can be changed to monitor the LED current by adding an external LED current sensing circuit. Figure 18 and Figure 23 show the example circuits for true LED current regulation in boost and SEPIC configurations respectively. In the circuits, the U3 (TL431) maintains a constant 2.5-V voltage drop on the resistors, R3 and R7. Because the U2 (TL431) maintains a constant voltage drop on the R3, the power dissipation on the output current sensing resistor, R7 can be minimized by setting a low voltage drop on the R7. Because the change of the current flowing through the R7 reflects in the change of the cathode current of U3 and eventually adjusts the ADJ pin voltage of the TPS92560, the LED current is regulated independent of the change of the input voltage.

TPS92560 SEPIC_APP.gif Figure 16. Typical Application Circuit of the TPS92560 Using SEPIC Configuration
TPS92560 BOOST_APP.gif Figure 17. Typical Application Circuit of the TPS92560 Using Boost Configuration

8.2 Typical Applications

8.2.1 Boost Application Design Example

TPS92560 BOOST_APP.gif Figure 18. TPS92560 in Boost Configuration With Input Current Regulation

8.2.1.1 Design Requirements

The specifications of the boost application circuit in Figure 18 are as listed as follows:

  • Input Voltage: VIN = 12 V
  • LED Stack Voltage: VLED = 21 V
  • Input Current: IIN(nom) = 500 mA
  • Input Power = 6 W
  • overvoltage Level: VVP(OVP) = 40 V
  • Switching Frequency: fSW = 1.4 MHz

8.2.1.2 Detailed Design Procedure

8.2.1.2.1 Calculate Values for the ADJ Resistors

First choose a value for RADJ2 in the range of 1 kΩ and 10 kΩ. For this example RADJ2 = 1 kΩ is chosen. Then calculate RADJ1 for the desired OVP level using Equation 25.

Equation 25. TPS92560 desex_Radj1_eq_snvs900.gif

Choose the nearest standard resistor value of RADJ1 = 102 kΩ.

8.2.1.2.2 Calculate the Sense Voltage and Sense Resistor Value

Given the calculated ADJ resistor values the sense voltage (VSEN) can be calculated using Equation 26.

Equation 26. TPS92560 desex_Vsen_eq_snvs900.gif

Given a current sense voltage of 206 mV the current sense resistor value (RSEN) can be calculated using Equation 27.

Equation 27. TPS92560 desex_Rsen_eq_snvs900.gif

The nearest standard value if 0.412Ω so choose RSEN = 0.412Ω.

8.2.1.2.3 Calculate the Inductor Value

Given a desired switching frequency of 1.4 MHz the inductor value can be calculated using Equation 28.

Equation 28. TPS92560 desex_L1_eq_snvs900.gif
Equation 29. TPS92560 desex_L_eq_snvs900.gif

Choose the closest standard inductor value of L = 22 µH.

8.2.1.3 Application Curve

TPS92560 C012_SNVS900.png
Figure 19. Efficiency

8.2.2 Boost Application Circuit With LED Current Regulation

TPS92560 Boost_Iout_reg.gif Figure 20. Using the TPS92560 in Boost Configuration With LED Current Regulation

8.2.2.1 Design Requirements

The specifications of the boost application circuit in Figure 18 are as as follows:

  • Objective input voltage: 3 VDC to 18 VDC / 12 VAC( 50 Hz or 60 Hz) / Generic MR16 electronic transformer
  • LED forward voltage: 20 VDC typical
  • Output current: 300 mA typical (at 12-VDC input)
  • Output power: 6 W typical (at 12-VDC input)

8.2.2.2 Application Curves

All curves taken at VIN = 3 V to 18 VDC in boost configuration, with 300mA nominal output current, 6 serial LEDs. TA = 25°C.

TPS92560 C017_SNVS900.png
Figure 21. LED Current vs Input Voltage
TPS92560 C018_SNVS900.png
Figure 22. Efficiency vs Input Voltage

8.2.3 SEPIC Application Circuit With LED Current Regulation

TPS92560 SEPIC_Iout_reg.gif Figure 23. Using the TPS92560 in SEPIC Configuration With LED Current Regulation

8.2.3.1 Design Requirements

The specifications of the SEPIC application circuit in Figure 18 are as listed as follows:

  • Objective input voltage: 3 VDC to 18 VDC / 12 VAC (50 Hz or 60 Hz) / Generic MR16 electronic transformer
  • LED forward voltage: 13 VDC typical
  • Output current: 300 mA typical (at 12-VDC input)
  • Output power: 4 W typical (at 12-VDC input)

8.2.3.2 Application Curves

All curves taken at VIN = 3 V to 18 VDC in SEPIC configuration, with 300-mA nominal output current, 4 serial LEDs. TA = 25°C.

TPS92560 C019_SNVS900.png
Figure 24. LED Current vs Input Voltage
TPS92560 C020_SNVS900.png
Figure 25. Efficiency vs Input Voltage