I have seen that a boost converter uses the spikes of an inductor to step up the capacitor voltage as this spike is stored on the capacitor.

Why don't we get a similar effect in the buck converter? A spike will also be produced there as the current from the inductor has to be maintained in that case as well. One reason I am getting is that the spike of the inductor in the case of the buck is not enough to boost the capacitor since in the case of the buck converter the voltage is completely off while in the boost we have Vin+spike voltage. Please correct me if I am wrong and give me a reason for such behavior.

  • \$\begingroup\$ ah, "spike" is not the same as "spike". Look at where the switch sits relative to inductor and load in both architectures. Also consider the polarity of the voltage spike and the direction of currents. \$\endgroup\$ Commented Aug 19, 2023 at 11:11
  • \$\begingroup\$ In the boost converter, the diode isolates the high-voltage output capacitor from the low input voltage, the diode stops the output from discharging even if the input is much smaller, the capacitor voltage can be gradually "pumped up" in many cycles. In a buck converter, the inductor and the output capacitor are directly connected to the input voltage. \$\endgroup\$ Commented Aug 19, 2023 at 11:28
  • \$\begingroup\$ "The spike of the inductor" is an imprecise way of thinking about this. It isn't difficult to work out in detail what's going on in either kind of circuit during both the charging (inductor current increasing) and discharging (inductor current decreasing) parts of the switching cycle. \$\endgroup\$
    – Dave Tweed
    Commented Aug 19, 2023 at 11:38

1 Answer 1


Kindly correct me if I am wrong and give me a reason for such behavior.

A buck converter can only force current (and energy) into the inductor when the input supply voltage is greater than the output voltage. As the output voltage approaches the input voltage, less and less energy can be stored and ultimately, when Vout = Vin, you can't put energy into the inductor and, you can't generate a higher voltage on the output. You can see this in the basic diagram of a buck converter:

enter image description here

With a boost converter, the energy stored in the inductor is only dependent on the input supply voltage, the MOSFET conduction time and the inductance. Because of this, you can keep putting energy into the inductor irrespective of the output voltage level and, as a consequence, you can raise the output voltage to a level that is many times the input voltage.


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