Depending on the operating voltage of each device
DC/DC converter that provides stable power supply
You need to be able to evaluate electrical characteristics to complete the design.


A DC/DC converter is a device that converts DC (direct current) to DC, and is also called a linear regulator or switching regulator depending on the conversion method.

Most devices on a PCB operate only on DC. Each device has its own operating voltage range and different voltage accuracy requirements.

A DC/DC converter is required because if an unstable voltage is supplied, problems such as malfunction or deterioration of device characteristics may occur.

DC/DC converters affect not only power design but also the overall product design. Therefore, power design engineers must be able to evaluate electrical characteristics such as load regulation, inductor current, output voltage, and power efficiency.

We asked Na Hee-won, Senior Researcher at ROHM Korea Technical Center, about the capabilities engineers need to have to evaluate the electrical characteristics of DC/DC converters.


Q. What are some things to keep in mind when evaluating the electrical characteristics of a DC/DC converter?
A. The measurement results should not vary depending on the evaluation environment and method at the time of evaluation. It is most important to be familiar with the exact evaluation method for each characteristic evaluation item and to evaluate them so that the same results are achieved.


Q. What are the reasons for the decrease in power efficiency of DC/DC converters?
A. △Conduction loss occurring from the on-resistance of the switch element, △Switching loss occurring during the switching operation, △Charging loss of the switch gate, △Parasitic diode loss occurring during dead time, △IC power consumption loss, △Loss due to inductor winding resistance, etc.


Q. Why should I measure load regulation?
A. Load regulation is an item that checks how much the output voltage fluctuates depending on the load current. The most important role of a DC/DC converter is to output a stable voltage. If the output voltage fluctuates, there is a possibility that the device that uses the output of the DC/DC converter as input may malfunction, so it must be checked.


Q. How important is the inductor in a DC/DC converter?
A. To understand the importance of inductors, you need to know the operating characteristics of DC/DC converters. DC/DC converters supply power by turning on the input voltage side switch when the output voltage drops to maintain a stable output voltage. At this time, magnetic energy is stored in the inductor.

Conversely, when the output voltage increases, the switch on the ground side is turned on. At this time, the magnetic energy stored in the inductor becomes current and is supplied to the load. The DC/DC converter repeats these two operations to create a stable output voltage. This is why inductors are needed in DC/DC converters.


Q. Why is it necessary to measure the output voltage of a DC/DC converter?
A. When a DC/DC converter repeats switching operations, ripple voltage and spike noise occur in the output voltage. Since devices such as SoC and FPGA require high output voltage accuracy, such as ±2% or less, the inspector must check the output voltage accuracy of the device using an oscilloscope.


Q. What measuring equipment is needed for evaluation?
A. Basically, a DC/DC converter requires a power supply to supply input power and an electronic load to regulate the output load. An oscilloscope to measure switching waveforms, inductor current, and output voltage stability, as well as voltage and current probes, are also required, as well as a multimeter to measure the exact efficiency.


Q. Does ROHM provide DC/DC converter design support to engineers?
A. ROHM currently has a diverse lineup of DC/DC converters depending on the input voltage range and output current range. We also share circuit design information and cases through Tech Web.

In addition, we provide simulation tools that verify power devices and driver ICs simultaneously free of charge, and we are continuously adding to the lineup of ICs that can be simulated.