Glossary Definition for Buck-Boost Converter

Glossary Term: Buck-Boost Converter 


What is a Buck-Boost Converter?

A buck-boost DC-DC converter (Figure 1), also called a buck-boost regulator, is an electrical or electronic circuit that is one of the three most commonly used DC-DC switching regulator topologies. A buck-boost converter produces a DC output voltage that can be either bigger or smaller in magnitude than its DC input voltage. As its name suggests, it combines the functions of a buck converter (used for DC voltage step-down) and a boost converter (used for DC voltage step-up).

simplified buck boost converter circuit

Figure 1. Simplified buck-boost converter circuit

What is a buck-boost converter used for?

A buck-boost converter is commonly used to create a constant DC output voltage from a variable DC input voltage source.

Where are buck-boost converters used?

Buck-boost converters are commonly used in mobile phones. The source of power in a mobile phone is a rechargeable battery which gradually discharges as the phone is used. This causes the battery voltage to slowly fall. If the battery were connected directly to the electronic circuits in the phone, the performance of the phone would vary as the battery voltage fell (the screen would get darker and the microphone volume would become lower). To prevent this happening, a buck-boost converter is used to provide a constant voltage to the phone’s electronic circuits, regardless of the battery voltage. For example, the voltage of a fully charged typical lithium-ion battery might be 3.8V. This might gradually fall to 2.8V as the battery discharges. By placing a buck-boost converter between the battery and the electronics, a stable voltage of 3.3V could be used to power the electronic circuits, meaning the performance of the phone would not degrade as the battery voltage fell, until it fully discharged, at which point the phone would power off.

Learn more:

  • Buck/Boost
  • Buck-Boost Regulator

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