An Introduction to Buck, Boost, and Buck-Boost Converters
2020/10/30
Switch-mode power conversion has been a cornerstone of modern electronics technology across sectors including utility, industrial, commercial, and consumer markets. In low-power DC/DC conversion applications, most modern power conversion is achieved using three main types of power converters: buck, boost, and buck-boost converters. This article examines the fundamentals of each converter type and explores their real-world applications.
Table of contents
What is a Buck Converter?
A buck or step-down converter is a DC/DC switch-mode power supply designed to reduce the input voltage of an unregulated DC supply to a stabilized lower output voltage. Buck converters are especially valued—compared to traditional voltage regulators—for their high efficiency, which can easily exceed 95%. The simplified circuit diagram illustrates how current flows through the circuit during a switching event.
Buck converters are commonly used in place of inefficient linear regulators to provide low-voltage on-board power in applications such as microprocessors, communication equipment, control systems, and more.
Buck converters are commonly used in place of inefficient linear regulators to provide low-voltage on-board power in applications such as microprocessors, communication equipment, control systems, and more.
What is a Boost Converter?
A boost or step-up converter is a DC/DC switch-mode power supply designed to increase the input voltage of an unregulated DC source to a stabilized higher output voltage. Similar to a buck converter, a boost converter uses an inductor, diode, capacitor, and power switch to regulate the output voltage, but the components are arranged differently. The simplified circuit diagram illustrates how current flows through the circuit during a switching event in a boost converter.
In a boost converter, the output voltage is controlled by adjusting the mark-space ratio of the PWM signal, allowing it to be equal to or greater than the input voltage Vin. Since power is conserved, a boost converter that delivers triple the input voltage can only supply one-third the current it draws from the source. Despite this trade-off, boost converters are widely used in battery-powered devices—for example, when two batteries provide 3V but are required to power a 5V circuit.
In a boost converter, the output voltage is controlled by adjusting the mark-space ratio of the PWM signal, allowing it to be equal to or greater than the input voltage Vin. Since power is conserved, a boost converter that delivers triple the input voltage can only supply one-third the current it draws from the source. Despite this trade-off, boost converters are widely used in battery-powered devices—for example, when two batteries provide 3V but are required to power a 5V circuit.
What is a Buck-Boost Converter?
A buck-boost converter can supply a regulated DC output from a power source whose voltage is either below or above the desired output voltage. The buck-boost converter circuit combines elements of both buck and boost converters; however, it typically has a larger footprint than either alternative. The simplified circuit diagram illustrates a typical current flow during a switching event in a buck-boost converter.
As you may have noticed in the circuit diagram, Vout is actually negative with respect to the supply potential, which can complicate certain designs. Buck-boost converters also require more expensive components since they need to withstand both the high maximum input voltage (Vin max) and the high input current at the minimum input voltage (Vin min), but they are useful in many applications. A very common use of buck-boost converters is in high power LED lighting, where, for example, lead-acid batteries supply a nominal 9–14V to a constant 12V LED load.
As you may have noticed in the circuit diagram, Vout is actually negative with respect to the supply potential, which can complicate certain designs. Buck-boost converters also require more expensive components since they need to withstand both the high maximum input voltage (Vin max) and the high input current at the minimum input voltage (Vin min), but they are useful in many applications. A very common use of buck-boost converters is in high power LED lighting, where, for example, lead-acid batteries supply a nominal 9–14V to a constant 12V LED load.
RECOM’s Efficient Switching Regulators for Low-Power Applications
For designers seeking compact and reliable switching regulators, RECOM offers a wide range of buck-boost converters that combine high efficiency with ease of integration. A notable example is the RBB10-2.0 series, a 10W switching regulator designed for industrial and commercial applications. This module supports a wide input voltage range and provides a stable, low-noise output with minimal external components required. Its compact footprint and robust design make it ideal for powering sensitive electronics such as microcontrollers, sensors, and communication devices, where efficiency and reliability are paramount.
Conclusion
The technologies of buck, boost, and buck-boost converters are utilized worldwide to provide regulated low-voltage DC/DC power in nearly every electronics market. RECOM’s buck, boost, and buck-boost converters offer an excellent solution for your low-power conversion needs.
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RBB10-2.0-EVM-1
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