Buck-Boost Converter / DC-DC Regulator
- summary or tutorial about the circuit and operation of a buck-boost converter, a dc-dc converter able to provide voltages lower or higher than the input voltage.
SMPS Power Supply Circuits Primer & Tutorial Includes:
Switch mode power supply
How does SMPS work
Step down buck converter
Step up boost converter
Buck Boost converter
See also:
Power supply electronics overview
Linear power supply
Capacitor smoothing
Over-voltage protection
PSU specs
Digital Power
Power management bus: PMbus
Uninterruptible power supply
A simple buck converter can only produce voltages lower than the input voltage, and a boost converter, only voltages higher than the input. To provide voltages over the complete range a circuit known as a buck-boost converter is required.
There are many applications where voltages higher and lower than the input are required. In these situations a buck-boost converter is required.
Buck-Boost Converter basics
The buck-boost DC-DC converter offers a greater level of capability than the buck converter of boost converter individually, it as expected it extra components may be required to provide the level of functionality needed.
There are several formats that can be used for buck-boost converters:
- +Vin, -Vout: This configuration of a buck-boost converter circuit uses the same number of components as the simple buck or boost converters. However this buck-boost regulator or DC-DC converter produces a negative output for a positive input. While this may be required or can be accommodated for a limited number of applications, it is not normally the most convenient format.
Obviously the polarities (including the diode) within the buck-boost converter can be reversed to provide a positive output voltage from a negative input voltage. - +Vin, +Vout: The second buck-boost converter circuit allows both input and output to be the same polarity. However to achieve this, more components are required. The circuit for this buck boost converter is shown below.
Written by Ian Poole .
Experienced electronics engineer and author.
More Circuits & Circuit Design:
Op Amp basics
Op Amp circuits
Power supply circuits
Transistor design
Transistor Darlington
Transistor circuits
FET circuits
Circuit symbols
Return to Circuit Design menu . . .