What is the role of an inductor in a buck or boost converter?

The inductor is the heart of a buck or boost converter. Its role is to store energy and smooth current flow. Let’s break it down:

 Core Role of the Inductor

1. Energy Storage:

   • When the switch (MOSFET) is ON, current flows through the inductor and it stores energy in its magnetic field.

   • When the switch is OFF, the inductor releases this stored energy to the load (and capacitor), maintaining current flow.

2. Current Smoothing:

   • Inductors resist sudden changes in current.

   • This property ensures that the load current is more stable, reducing ripple and protecting sensitive circuits.

3. Voltage Conversion Mechanism:

   • In a buck converter (step-down):

     • The inductor smooths the chopped DC from the switching transistor.

     • It ensures average output voltage is lower than input.

   • In a boost converter (step-up):

     • The inductor stores energy when the switch is ON.

     • When the switch turns OFF, the inductor releases energy, adding to the input voltage, producing a higher output voltage.

 Operation in Each Converter

Buck Converter (Step-Down)

• Switch ON: Inductor charges, current increases, energy stored in magnetic field.

• Switch OFF: Inductor discharges, current continues to flow to load via diode/MOSFET.
   Role: Keeps current flowing smoothly while stepping voltage down.

Boost Converter (Step-Up)

• Switch ON: Inductor charges from input, current ramps up.

• Switch OFF: Inductor discharges through diode into capacitor + load, raising voltage above input.
   Role: Provides extra energy to step voltage up.

 Important Inductor Parameters in Converters

• Inductance (L): Determines current ripple and transient response.

• Saturation Current (Isat): Current at which the inductor core saturates (loses ability to store more energy).

• DCR (DC Resistance): Lower DCR means less heat and higher efficiency.

• Core Material: Ferrite or powdered iron, optimized for switching frequencies (100 kHz – few MHz).

 Easy Analogy

Think of the inductor like a spring for current:

• When compressed (switch ON), it stores energy.

• When released (switch OFF), it pushes current forward smoothly.

 In short:

• In a buck, the inductor smooths and delivers current at a lower voltage.

• In a boost, it stores and releases energy to raise the voltage.

• Without the inductor, the converter would just be a switch chopping voltage — not useful DC power.