Half wave rectification light LED

 

§01 And a half Wave rectification

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   This is a capacitor ,  This is a transformer .  If you put them in the circuit ,  What effect will it have on signal transmission ？  For transmission signals , They all have DC isolation , Communication function .  Here's a question , If the load is a LED The lamp . Flow through LED The lamp is a one-way direct current ,  Which circuit can light up LED？

  

Transformer experiment

   Now use the one at hand 9V Experiment with the transformer in the power supply .  It includes a 220V Transformer and rectifier voltage stabilizing circuit .  Separate the transformer .  This is the transformer used in the experiment .  Make it into a transformer that can be used in experiments .  The effective value of its output voltage is 13.2V.  Through the oscilloscope ,  It can be seen that its peak voltage is 18V.

  

test LED

Without capacitance

   This is to build a test circuit on the bread board ,  It connects the low voltage output of the transformer to the load , The load is made up of resistors R1 and LED form .  You can add capacitance in the connection circuit , To test LED Lighting condition .

  
  Next, measure the condition without connected capacitance ,  You can see LED Illuminated . I saw in the video LED Flashing , In fact, this is due to LED Only the positive half cycle current of the output voltage , So its flashing frequency is 50Hz, It is very close to the shooting frequency of the camera , Beat frequency occurred , So it looks flashing .  All in all , Without capacitance , Only the transformer can be lit LED Of .
  

With capacitance

   Next, measure the case with capacitance ,  Add one in the load circuit 100uF The capacitance of ,  This is the process of increasing capacitance . You can see LED Just lit up at the beginning , Then it went out quickly .

  

Equivalent circuit

   According to the previous experiment, we can see ,  The capacitive coupling circuit cannot be lit continuously LED, The inductive coupling circuit can be continuously lit LED.  For capacitive coupling , With the flow LED One way current flows , The voltage at both ends of the capacitor increases , Until the peak value of the input voltage signal is exceeded ,LED It went out .  For inductive coupled circuits ,  Because it is the conversion of electric energy twice , That is, input electric energy is converted into magnetic energy , Magnetic energy is then converted into electrical energy .  Therefore, there is always AC voltage on the output coil ,LED Can be lit continuously .  This circuit shows the capacitance , The difference between transformer coupling .

  

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