Power Topologies: An Interactive Handbook

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This handbook presents an overview of the most important DC-DC converter topologies. The main objective is to guide a designer in selecting the topology with its associated semiconductor devices. Be sure to interact with the embedded designs below, and feel free to take them into your own workspace to explore further!

Power Topologies
Buck Converter
Boost Converter
Inverting Buck-Boost Converter
SEPIC
Cuk Converter
Zeta Converter
Flyback Converter
Two Switch Flyback Converter
Active Clamp Forward Converter
Single Switch Forward Converter
Two Switch Forward Converter
Push-Pull Converter
Weinberg Converter
Half-Bridge Converter
Full-Bridge Converter

Buck Converter

A Buck converter steps down an input voltage to a lower output voltage level. Buck converters can be remarkably efficient (often higher than 90%), making them useful for tasks such as converting a computer's main (bulk) supply voltage (often 12V) down to lower voltages needed by USB, DRAM and the CPU (1.8V or less).

Boost Converter

A Boost converter steps up an input voltage to a higher output voltage level. A boost converter is sometimes called a step-up converter since it "steps up" the source voltage. Since power must be conserved, the output current is lower than the source current.

Inverting Buck-Boost Converter

An inverting Buck-Boost regulator converts a positive input voltage to a higher or lower negative output voltage level. It is equivalent to a Flyback Converter using a single inductor instead of a transformer.

SEPIC

A Single Ended Primary Inductor Converter (SEPIC) steps up/down an input voltage to a higher/lower output voltage level. SEPICs are useful in applications in which a battery voltage can be above and below that of the regulator's intended output. For example, a single lithium ion battery typically discharges from 4.2 volts to 3 volts; if other components require 3.3 volts, then the SEPIC would be effective.

Cuk Converter

A Cuk regulator converts a positive input voltage to a higher or lower negative output voltage level.  It uses a capacitor as its main energy-storage component, unlike most other types of converters which use an inductor. It is named after Slobodan Ćuk of the California Institute of Technology, who first presented the design.

Zeta Converter

A Zeta converter steps up/down an input voltage to a higher/lower output voltage level. The Zeta topology is a lesser known relative of the SEPIC topology. Both converters provide a positive output voltage that can be greater than, equal to or less than VIN while avoiding the complexity and cost of a buck-boost converter. The Zeta converter however, has the advantage of significantly reduced output ripple voltage.

Flyback Converter

A Flyback regulator converts an input voltage to a higher or lower, positive or negative output voltage level. The flyback converter is a buck-boost converter with the inductor split to form a transformer, so that the voltage ratios are multiplied with an additional advantage of isolation. When driving, for example, a plasma diode or a voltage multiplier, the rectifying diode of the boost converter is left out and the device is called a flyback transformer.

Two Switch Flyback Converter

A Two Switch Flyback regulator converts an input voltage to a higher or lower, positive or negative output voltage level. Adding a second MOSFET switch on the high side results in the voltage stress on each MOSFET being clamped to the input voltage. The leakage inductance enegry is also clamped and recycled back to the input to improve efficiency.

Active Clamp Forward Converter

An Active Clamp Forward regulator converts an input voltage to a higher or lower, positive or negative output voltage level. Power converters based on the forward topology are an excellent choice for applications where high efficiency and good power handling capability is required in the 50 to 500W power range.

Single Switch Forward Converter

A Single Switch Forward regulator converts an input voltage to a higher or lower, positive or negative output voltage level. Switch mode power supplies have become popular due to their capability to handle variable loads at a high efficiency and relatively small size and weight.

Two Switch Forward Converter

A Two Switch Forward regulator converts an input voltage to a higher or lower, positive or negative output voltage level. The second switch allows us to clamp the voltage on each MOSFET to the value of the input voltage.

Push-Pull Converter

A Push-Pull regulator converts an input voltage to a higher or lower, positive or negative output voltage level. The distinguishing feature of a push-pull converter is that the transformer primary is supplied with current from the input line by pairs of transistors in a symmetrical push-pull circuit. Push-pull converers have steadier input current, create less noise on the input line, and are more efficient in higher power applications.

Weinberg Converter

A Weinberg regulator is a Flyback current fed Push-Pull regulator and converts an input voltage to a higher or lower, positive or negative output voltage level. This circuit avoids the problem of overlap switching by the insertion of an inducter in the input circuit.

Half-Bridge Converter

A Half-Bridge regulator converts an input voltage to a higher or lower, positive or negative output voltage level. Although more complex than a flyback or forward converer, the half-bridge converter design can yield higher output power (potentially up to 500W) and use parts that are smaller and less expensive.

Full-Bridge Converter

A Full-Bridge regulator converts an input voltage to a higher or lower, positive or negative output voltage level. This configuration offers isolation in addition to stepping up or down the input voltage.

 

Notes

These reference topologies are modeled after TI's handbook. Descriptions of particular converters come from Wikipedia. If you have any comments or suggestions on this topic, feel free to share your thoughts below! Also, if you like this type of material and would like to see more interactive guides from SystemVision, let us know by suggesting a topic and tweet it to us at @SystemVisionMGC.

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