当前位置：首页 > 技术先锋

Use thermal analysis to predict an IC's transient behavior and avoid overheating

• 
  

  (Eq. 12)

  
  

  Equations 11 and 12 are useful for predicting chip temperature (either package or die) when the heat-generating source is outside the package. One example could be a nearby high-current MOSFET that dissipates lots of heat.
  
  When we know kA and θJA we can calculate the temperature at different times. Alternatively, if P is a complex function of time, we can use the above equations to evaluate temperature as a time-based simulation and use MATLAB® software to write a program that plots temperature as a function of time.
  
  The θJA value is provided in data sheets. However, when a setup imposes conditions other than those of the JEDEC standard, that published θJA value for these calculations can cause errors. The JEDEC standard 51-3 states, "It should be emphasized that values measured with these test boards cannot be used to directly predict any particular system application performance, but are for the purposes of comparison between packages."2 Thus, to properly estimate temperature, you should either measure θJA for the prototype board or es贴片电感timate it directly as explained below.
  
  

  Heat flow from a die to the environment

  Consider the system of Figure 3, in which a three-body system (similar to a chip) generates heat on the die and dissipates it through the epoxy and package to the environment. Body 1 is the die, Body 2 is the epoxy, and Body 3 is the chip package.
  
  
  Figure 3. Compare this thermal three-body model with the Figure 2 model. Here the flow of heat generated on the die is more complicated.
  
  To solve for θJA in this system, we must define the equations for all three bodies.
  
  Body 1:

  (Eq. 13)

  
  

  Body 2:

  (Eq. 14)

  
  

  Body 3:

  (Eq. 15)

  
  

  Where:
  TB1, TB2, TB3 are the instantaneous temperatures of Bodies 1, 2, and 3.
  P12 is po绕行电感器wer in the form of heat transferred from Body 1 to Body 2.
  P23 is power in the form of heat transferred from Body 2 to Body 3.
  PG is the power generated on Body 1 or directly transferred to Body1.
  
  Power generated by the die (PG) minus power absorbed by the die is:

  (Eq. 16)

  
  

  Power received by the epoxy minus power absorbed by the epoxy is:

  (Eq. 17)

  
  

  Substituting Equations 16 and 17 in Equations 13, 14, and 15:

  (Eq. 18)

  
  

  (Eq. 19)

  
  

  (Eq. 20)

  
  

  The solution of this three-body system in Equations 18, 19, and 20 can be complicated, but the use of Laplace transforms makes it easier. The form of the solution is:

  用于小型荧光灯的25W迷你型镇流器荧光灯是一种以最少电能消耗(流明/瓦)产生白光的最廉价方法。现在，小型荧光灯的每年销售规模达数亿只，而对荧光灯可靠性的要求也不断提高。如今的照明系统需要镇流器控制功能以驱动小型荧光灯，但这样增加了成本

  太阳能发电系统对半导体器件的需求分析 太阳能逆变器是整个太阳能发电系统的关键组件。它把光伏单元可变的直流电压输出转换为清洁的50Hz或60Hz的正弦电压源，从而为商用电网或本地电网供电。因为太阳电池板的光电转换效率可能受到阳光照射的角度

  计算机电源“白金”化 80+TM 和计算机产业拯救气候行动计划 (Climate Savers Computing) 给计算机电源设立了一个强有力的效率标准。这些标准的 白金 级别规定计算机电源在 20% 额定负载状态下

   3/8   首页 上一页 1 2 3 4 5 6 下一页 尾页

上一篇：开关电源中功率MOSFET的驱动技术荟萃

下一篇：随动转向大灯&侧向辅助灯解析