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ComponentsActive / Semiconductor

Switching Regulator (Buck/Boost)

IC (Power)

An integrated circuit that efficiently converts voltage levels using switching elements and inductors, either stepping down (buck) or stepping up (boost) input voltage.

Schematic symbol

Integrated circuit (DIP)

How switching regulator (buck/boost) appears in a circuit diagram.

Types & variants

Buck (step-down)Boost (step-up)Buck-BoostSEPICCukCharge pumpInverting

Key specs

Input voltage range

V

Min/max voltage the regulator can accept as input.

Output voltage

V

Regulated voltage level the IC maintains at its output.

Output current

A

Maximum current the regulator can supply while maintaining regulation.

Efficiency

%

Ratio of output power to input power. Higher = less heat waste.

Switching frequency

kHz/MHz

Rate at which the internal switches operate. Affects size of inductors/capacitors.

Laws that govern it

  • Self-inductance formula — v = L di/dtv = L × di/dt, E = ½LI²

    v = L·di/dt is the converter: the inductor is charged from the input then dumped to the output, so the duty cycle sets the voltage ratio.

  • Lenz's lawthe minus sign in EMF = −N × dΦ/dt

    The coil's refusal to have its current interrupted is what generates the boost voltage — the flyback spike put to work instead of suppressed.

  • Watt's lawP = V × I = I²R = V²/R

    Power in ≈ power out: step 12 V down to 5 V at 2 A and the input only draws about 0.9 A, unlike a linear regulator that draws the full 2 A.

Each law is stated in full — with its diagram, variables and worked meaning — on the electrical laws page.

How it compares

Markings

SMD packages typically have a part number (e.g., LM2596, MP2307DN). Through-hole versions may have the number printed on the top. Datasheet required for exact identification.

Standard values

Common input: 4.5-40V (wide range), 12V (automotive). Common output: 3.3V, 5V, 12V. Current ratings: 0.5A, 1A, 2A, 3A, 5A.

How to choose

1) Determine input voltage range and required output voltage/current. 2) Calculate required efficiency to manage heat. 3) Select switching frequency based on size/EMI constraints. 4) Consider shutdown and enable features. 5) Check thermal requirements and heatsink needs.

Pinout & package

Typically 5-8 pins: VIN, GND, SW (switch), VOUT, FB (feedback), EN (enable). Common packages: TO-220 (through-hole), TO-263, QFN-4/5/8, DIP-8 (through-hole).

Example circuits

  • Buck converter for powering 3.3V logic from 5V or 12V
  • Boost converter for LED driving from 1.5V battery
  • Buck-boost for maintaining stable output with varying input (e.g., battery discharge)
  • Power supply for microcontrollers with brownout protection

Common failures

Overheating (thermal shutdown or permanent damage), output voltage drift, failure to start (bad input caps), oscillations/noise on output. Physical signs: burn marks, bulging capacitors, discoloration.

How to test

1) Check input voltage at VIN pin with power applied. 2) Measure output voltage at VOUT pin (should be within spec). 3) Check switching node (SW pin) with oscilloscope for expected waveform. 4) Measure output voltage under load to ensure regulation.

Substitutes

Use same input/output voltage range and current rating or higher. Different topologies (buck vs buck-boost) can't be directly substituted. Ensure pinout and feedback configuration match.

Where to buy

DigiKeyMouserLCSCRobuAmazon