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I’m trying to understand the theory behind buck converters.

From what I understand, the circuit represented by the schematic above should reduce voltage (which it does correctly), but should also increase current in the process.

This does not seem to be the case.

The current (measured by the ampere meter after the 30 ohm resistor) is only going from 0 to 1mA, the same as the input current.

What am I missing?

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2 Answers 2

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What am I missing?

You have used a constant current supply and, that will always force its current through the MOSFET from source to drain irrespective of how you might be controlling the gate. So, that is what you inevitably see. Try using a constant voltage supply at the input power feed.

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Simulate this with LTspice and connect the ground to the circuit.

Use a capacitor directly after the current source, because the way you did it, it would not work. The current through the coil has to change and this is not possible with your circuit.

The current after the MOSFET is switched on will be exactly 0A, then increase and after the switching off of the MOSFET it will decrease.

Take a look at the circuit of the step down converter datasheets of ST or Analog Devices.

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