What is DC-DC Converter

Basic Introduction:

DC-DC converters are power conversion products that convert a source of direct current (DC) from one voltage level to another. The power level range is wide from low (1 Watt) to high (K Watts). Furthermore, they are high-frequency power conversion circuits using high-frequency switching mode and transformers, inductors, and capacitors to keep the switching noise (EMI) to the acceptable level which could be the required level in certain applications such as industrial, medical, and railway.

 

The closed feedback loops keep the constant voltage output stable while changing input voltages and output currents. At high efficiency, in general, DC-DC converters are much more efficient and smaller than linear regulators. Their drawbacks of DC-DC Converters are the switching noise (EMI) and electronical complexity.

 

Purpose of using a DC-DC converter:

DC-DC converters are widely used in electronic devices from portable devices to large equipment. In general, electronic devices contain some sub-circuits and each sub-circuit has its own voltage level which could be different from the battery or the internal/external power supply.

 

Types of DC-DC converters:

DC-DC converters could be categorized into isolated and non-isolated. Isolation is the physical and electrical separation between one part of a circuit and another which is usually achieved by using a transformer for isolated DC-DC converters. The input and output DO NOT share a common ground.

 

In order to consider the safety requirement and avoid interference of noise from other sub-circuit, the isolation is needed.

 

DC-DC converters could also be categorized by topology. Here are common topologies which are buck, boost, and buck-boost.

 

Buck (step-down) DC-DC converter: steps the voltage down, making the output voltage lower than the input voltage. In short, it’s Vin>Vout

 

Boost (step-up) DC-DC converter: convert the voltage to higher, making the output voltage higher than the input voltage. In short, Vin

Buck-boost DC-DC Converter: steps the voltage up or down, making the output voltage equal to or higher or lower than the input voltage. In short, either Vin >= Vout or Vin<=Vout is ok.

 

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