Most ICs operate on DC, so DC/DC converters are important.
DC/DC converter, works with inductors, capacitors and resistors
After selecting the parts, you also need to pay attention to creating the PCB layout.


Consumers want more features in new electronic products. In addition, governments around the world are strengthening power regulations to minimize fossil fuel use and reduce power consumption in order to prevent global warming.

Accordingly, electronic products have pursued higher performance, lower power consumption, and higher efficiency than in the past. In order for electronic products to achieve higher performance, lower power consumption, and higher efficiency, they must be supported by efficient power design.

One of the most important components in the design of electronic power supplies is the converter. For example, electronic devices that operate on wall power require an AC/DC converter that converts AC 220V to DC. This is because most ICs operate only on DC. The DC/DC converter is also important.

“The numerous ICs used in electronic products each have different operating voltage and voltage accuracy requirements,” said Kang Dae-ho, a senior researcher at ROHM Technical Center. “A power supply with unstable voltage can cause problems such as IC malfunction and characteristic deterioration.”

At this time, a DC/DC converter is used to convert or stabilize the voltage required by numerous ICs inside electronic products. Developers must choose between two voltage regulators to implement a DC/DC converter.

The first is a linear regulator. A linear regulator, where the relationship between input and output operates linearly, is also called a series regulator because the control element is located between the input and output.

The second is a switching regulator. The switching regulator turns on the switching element (MOSFET) until the output voltage reaches the required voltage, and supplies power from the input to the output. When the output voltage reaches the desired value, the switching element turns off, so that the input voltage is not consumed. The switching regulator repeats this operation at high speed to regulate the output voltage.

Senior Kang said, “Unlike switching regulators, linear regulators can only perform step-down operations and do not perform step-up or step-down operations,” and explained, “When the difference between the input voltage and the output voltage is large, the efficiency decreases.” He added, “The circuit configuration is simple and, because it does not switch, it has the advantage of having less noise.”

◇ Selection of peripheral components as important as the DC/DC converter

Implementing a DC/DC converter does not end with just selecting a regulator. “A DC/DC converter cannot operate with just an IC,” explained Kang. “It operates with peripheral components such as an output inductor, input/output capacitors, and voltage adjustment resistors.”

He gave examples of how capacitors are used to reduce noise and ripple, and how inductors are used to store and release energy during switching and to smooth switching pulses. As such, the components surrounding the DC/DC converter are important because they affect the output voltage characteristics.

Once the component selection is complete, it is also important to create a layout pattern for the PCB to be used. Senior Kang said, “Because the performance of the DC/DC converter is affected by noise countermeasures and wiring impedance, care must be taken with the wiring and component placement in the layout.”

The material of the device can also be considered. Recently, various materials have been developed and commercialized to overcome the fundamental limitations of silicon (Si). A representative example is silicon carbide (SiC).

Senior Kang said, “SiC has a dielectric breakdown field strength about 10 times higher than that of Si, and can withstand high voltages of up to several thousand V,” and “It has a small ON resistance per unit area, so it is superior in terms of power loss.”

In addition, he explained, “In order to improve the increase in ON resistance due to high withstand voltage in Si, IGBTs are mainly used instead of MOSFETs at voltages over 600 V, but there is a problem of high switching loss.” He added, “On the other hand, SiC-based MOSFETs have excellent high-speed switching performance.”

◇ Power design, basic knowledge and tool utilization are important

The algorithms of new technologies such as 5G, AI, IoT, big data, and cloud are complex and power-consuming. Recent electronic products are faced with the challenge of implementing them in places where the power supply is unstable.

To meet these market demands, developers need a solid foundation in power design and the ability to use a variety of tools to quickly achieve what they want. However, it is not easy to design the circuit surrounding the DC/DC converter by yourself while keeping in mind the parts mentioned above.

Senior Kang said, “For the design of circuits surrounding DC/DC converters, ROHM indicates recommended component constant values on the data sheets of its ICs,” and “We provide a simulation tool on our website that can verify power components and driver ICs together.”

Lastly, Senior Kang emphasized, “Rohm is disclosing various materials on basic operating principles and circuit design through ‘TechWeb,’ a power design technology information site,” and “We are also deploying various tools.”