ZHCSJY0B June 2012 – June 2019 LMR12015 , LMR12020
PRODUCTION DATA.
- 1 特性
- 2 应用
- 3 说明
- 4 修订历史记录
- 5 Pin Configuration and Functions
- 6 Specifications
- 7 Detailed Description
-
8 Application and Implementation
- 8.1 Application Information
- 8.2
Typical Application
- 8.2.1
Detailed Design Procedure
- 8.2.1.1 Custom Design With WEBENCH® Tools
- 8.2.1.2 Inductor Selection
- 8.2.1.3 Input Capacitor
- 8.2.1.4 Output Capacitor
- 8.2.1.5 Catch Diode
- 8.2.1.6 Boost Diode (Optional)
- 8.2.1.7 Boost Capacitor
- 8.2.1.8 Output Voltage
- 8.2.1.9 Feedforward Capacitor (Optional)
- 8.2.1.10
Calculating Efficiency and Junction Temperature
- 8.2.1.10.1 Schottky Diode Conduction Losses
- 8.2.1.10.2 Inductor Conduction Losses
- 8.2.1.10.3 MOSFET Conduction Losses
- 8.2.1.10.4 MOSFET Switching Losses
- 8.2.1.10.5 IC Quiescent Losses
- 8.2.1.10.6 MOSFET Driver Losses
- 8.2.1.10.7 Total Power Losses
- 8.2.1.10.8 Efficiency Calculation Example
- 8.2.1.10.9 Calculating the LMR2015/20 Junction Temperature
- 8.2.2 Application Curves
- 8.2.3 LMR12015/20 Circuit Examples
- 8.2.1
Detailed Design Procedure
- 9 Layout
- 10器件和文档支持
- 11机械、封装和可订购信息
8.2.1.10 Calculating Efficiency and Junction Temperature
The complete LMR12015/20 DC/DC converter efficiency can be calculated in the following manner.
Or
Calculations for determining the most significant power losses are following. Other losses totaling less than 2% are not discussed.
Power loss (PLOSS) is the sum of two basic types of losses in the converter, switching and conduction. Conduction losses usually dominate at higher output loads, where as switching losses remain relatively fixed and dominate at lower output loads. The first step in determining the losses is to calculate the duty cycle (D).
VDS is the voltage drop across the internal NFET when it is on, and is equal to:
VD is the forward voltage drop across the Schottky diode. It can be obtained from the Electrical Characteristics section of the schottky diode datasheet. If the voltage drop across the inductor (VDCR) is accounted for, the equation becomes:
VDCR usually gives only a minor duty cycle change, and has been omitted in the examples for simplicity.