直流电源交换电路

电路能力测试-1：直流电源交换电路
  Circuit Knowledge Test-1: DC-DC Switching Regulator
  
  If MP1580 switching frequency set at 400 KHz, and DC regulator output 5V, then please plot the switching wave-shape at  pin-3 with line input V and V.假设MP1580工作在400 KHz,且稳压输出为5V,画出输入电压分别为12V 及 16V时，IC pin-3的正确波形。
  
  
  Now the DC regulated output is 5V. If we want to change the DC regulated output to 9V, what value of RP86 and RP89 are suitable for this change.目前的直流稳压输出为5V，如果希望提升为9V输出，如何修改RP86 及 RP89的数值。
  
  
  Explain the charge and discharge functions of MA701, LP15, CP61 components in details. 说明MA701, LP15, CP61元件的冲放电功能。
  
  

  
  
  Same condition as the Question-4: If MP1580 IC with SOP-8 package dissipation 160°C/W, then what surface temperature will be for MP1580 at 25°C room temperature?同上第四题，MP1580采用SOP-8包装的传热系数为160°C/W，计算其室温25°C时的IC表面温度。
  
  
  What is the maximum allowable ripple voltage at 5V DC regulated output to assure 40 db S/N if this 5V will supply for a video function IC? 当直流稳压输出5V，用来供应影像电路时，为了确保达到40 db S/N，求其最大容许连波电压数值。
  
  
  Explain the function of CP59, LP17, LP16 components? 说明CP59, LP17, LP16元件的功能。
   
  试题解答
  Circuit Knowledge Test-1: DC-DC Switching Regulator
  ANS-1:
  
  ANS-2:
  RP86=62K, RP89=1K8.
  (R86+R89+R87)/R87 = 5.0/Vref then Vref=5.0/4.12=1.22
  RN86+RN89 = (9.0/Vref * R87) –R87 = 63.8K (62K + 1K8)
  RP86=62K, RP89=1K8.
   
  ANS-3:
  Switching pulse comes from ICP9 pin-3 and charge through LP15 to CP61 during switching-on duty-cycle. The inductive voltage across LP15 will then charge through DP8 to CP61 during switching-off duty-cycle. (Note that inductive current will produce reverse voltage across coil LP15)
   
  ANS-4:
  120 mA
  DC input power = 5 * 0.24 / 0.85 = 1.41 Wthen DC input current = 1.41/12 = 120 mA.
   
  ANS-5:
  58.6 °C
  Power loss = 1.41-1.2 = 0.21 W then Thermal heat rise Tht = 160 * 0.21 = 33.6 °C
  Final junction temperature Tj = 25 + 33.6 = 58.6 °C
   
  ANS-6:
  50 mVpp.
  Because 40 db means 1% level, then 5 Volt d-c>
  ANS-7:
  CP59: Boot-straping capacitor for driving output power FET.
  LP17: Filter choke for filtering switching pulse generated from ICP9.
  LP16: Filter choke for filtering switching noise to reach 40 db noise limit.