Author Topic: Boost converter DCM- Measuring current with current sense resistor  (Read 421 times)

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Offline FerdinSTopic starter

  • Contributor
  • Posts: 11
  • Country: si
Hello everyone;

My project is to make boost converter. From 18V  approx 0.5 A to approx 100V and max 0.085A.
I am using those components:
- 220 uH inductor
- 3uF capacitor
- SQJ454EP-T1_GE3 - mosfet.

Because I have to measure income current and output current I am using 2 current resistors, as it is shown on the picure :


because I have to make this "voltage drop" current sense resistors I am using rail to rail operational amplifiers so that voltage goes to max. 3.3 V, bcs my ADC on IC is measuring max that.
It is shown on the picture:
1049420-1

When I am measuring current now it is shown that the voltage drop on current sense resistors is too high. Also tried to put on output voltage around 100 V and it seems my resistors got burned, so it really has to be too high voltage drop on current sense resistor.
I am asking now, is 0.5 and 0.05 ohm too high ?
Also what resistor should I use on the out put ? I tried with 1k - and also 20k ohm and it seems that it gives me same result.

Thank you a lot for your kind answers. ;)
 


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