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What is Buck-boost converter?

A DC-DC converter that can produce voltages both lower and higher than its input. In the basic inverting form, energy is stored in the inductor while the switch is on and released to the output through a diode while it is off, so the output polarity is opposite to the input and its magnitude is the input voltage × D ÷ (1 − D). At D = 0.5 the magnitude equals the input, and at D = 0.25 it is one third of it. As a non-inverting alternative, a four-switch configuration that combines a buck and a boost stage is used in devices whose battery voltage crosses the output voltage.

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Japanese name: 昇降圧チョッパ(バックブーストコンバータ)

Buck-boost converter appears in 2 practice questions across 1 topic, including Power Electronics Circuits.

Field: Power Electronics Circuits

Try it: questions about Buck-boost converter

For an ideal buck-boost chopper (inverting buck-boost converter) with an input voltage of 12 V and a duty cycle of 0.6, which of the following is the magnitude of the output voltage in continuous conduction mode?

  1. A7.2 V
  2. B18 V
  3. C30 V
Show answer and explanation

Answer: B. 18 V

In an inverting buck-boost converter, energy from the input is stored in the inductor while the switch is on and released to the output through the diode while it is off. From the volt-second balance of the inductor, Vin × D = Vout × (1 − D), the magnitude of the output voltage is Vout = Vin × D/(1 − D) = 12 × 0.6/0.4 = 18 V. The output polarity is opposite to that of the input (negative with respect to ground). It works as a step-down converter for D < 0.5 and a step-up converter for D > 0.5, and at D = 0.5 the output magnitude equals the input.

Buck-boost converter in the explanations

Questions that mention Buck-boost converter (2)

  1. For an ideal buck-boost chopper (inverting buck-boost converter) with an input voltage of 12 V and a duty cycle of 0.6, which of the following is the magnitude of the output voltage in continuous conduction mode?
  2. Which of the following is the correct basis for deriving the ideal output voltage Vout = D × Vin of a buck converter?

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DC-DC converter calculatorDuty cycle, inductor ripple current and output voltage ripple for buck, boost and buck-boost

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Buck converter Duty cycle Continuous conduction mode Boost converter Back EMF Electrical transformer Induction motor Inverter Power factor Power factor correction

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