**1. Introduction**

Nowadays, with the advent of smart energy environments, the demand for cyber-physical systems [1] and the growth in switch-mode converter applications [2–6], electromagnetic compatibility (EMC) issues are becoming more and more significant [7]. Among many methods of improving EMC of converters, we may use improved control techniques. In addition to the primary function of controlling energy conversion, such a control technique can reduce the level of conducted electromagnetic interference (EMI) by spreading the harmonics on a broader frequency range [6,8]. A Field-Programmable Gate Array (FPGA) may be used for the cyber-physical implementation of such controls. It should be added that FPGA may be much more flexible and may cover more applications than other commonly used control devices such as microcontrollers (*μC*) or digital signal processors (DSP). In particular, FPGAs allow for the building of hardware circuits of the modified Pulse Width Modulators (PWM), unlike *μC* or DSP's, where the built-in PWM circuit cannot be changed.

In a typical PWM circuit, the user may set the fundamental switching frequency (*f sw*) and the duty cycle (*D*). The parameter *D* controls the output voltage of the converters and thus affects the energy conversion process. The *fsw* of the PWM signal is practically irrelevant to the voltage transfer function of the converter, and of the primary energy conversion. However, it affects the losses in the switch-mode converter and the parameters of the reactance elements. Conducted EMI generated by the converter are grouped around the *fsw* and its harmonics [8,9]. Any modification of *fsw* leads to changes in EMI emission.

Traditionally, pseudo-random modulators (RanM) can be used as a switch control strategy, which can reduce the level of EMI [8,10]. In such type of modulation, the frequency of the PWM signal is randomly changed in the selected range. As a consequence, disturbance energy is distributed more evenly across a wider spectrum. The development of a random modulation requires a combination of changes in the frequency *f sw* (or the period) of the PWM signal with a pseudo-random number generator. Therefore, the range of pseudo-random numbers must be adapted to the specific hardware platform. In addition, the probability density function (PDF) of such a pseudo-random stream should be analysed in terms of the emission of conducted disturbances.

The design of RanM in FPGA may be challenging. The modern graphical programming tools such as LabVIEW may facilitate the design process. Nevertheless, in LabVIEW, there is still some inconvenience associated with fixed-point operations, and with the lack of some arithmetic operations, e.g., divide. Therefore, this manuscript demonstrates how to provide an FPGA-based control system for a DC/DC converter that limits the level of conducted EMI. The presented algorithms, based on LabVIEW engineering software, do not change the essential functions or parameters of the converter. During the design of algorithms, we take into account the PDF of frequency changes, and we propose a method of shaping the PDF in FPGA without arithmetic division and using only fixed-point operations. For the presented algorithms, we perform the EMI evaluation in an experimental system. The CISPR-A frequency band was considered as the primary frequency range for tests.
