Page 71 - PEN eBook July 2023

Design

As research continues, the required waveform evolves, which can increase the challenge for power
design. The unipolar pulses of early IRE have evolved into bipolar pulses, which may be symmetric
or asymmetric.

The voltage required is typically in the 1-kV to 3-kV range, with some applications requiring up to
5 kV with currents up to 65 A. Pulse widths are typically in the range of 100 ns to 100 µs, with
burst-mode frequencies up to 5 MHz. The associated slew rates for the pulse are both significant
and challenging.

The power supply requires features like overcurrent protection and voltage/current monitoring, as
well as compliance with relevant medical safety standards and EMI/EMC regulations.

ARCHITECTURE OF A PFA SOLUTION

Typically, a power solution for a PFA application consists of multiple stages, converting from the
AC mains input to the HV pulsed DC output required for treatment. A block diagram of a typical
design is shown, although this is a simplified view, as the AC/DC front end will usually have multiple
outputs to power peripheral devices like displays and the HMI.

Figure 4: Block diagram of a typical PFA solution using a modular approach

The first stage is the AC input and power-factor correction (PFC), shown in orange. This addresses
critical compliance parameters, including primary-secondary isolation, leakage current, EMI filtering
and PFC. The input can be any AC mains voltage (or even a DC voltage), and the output will typically
be an isolated DC voltage of about 380 V.

One technology suitable for front-end PFC is Advanced Energy’s Artesyn AIF04ZPFC series of full-

brick PFC modules, which accept a universal 85- to 264-VAC input and present a unity power
factor. The modules, which can also be configured to accept a DC input within the range of 120 to
370 VDC, are rated at 1,600 W, have a high conversion efficiency of 95% and provide a nominal non-
isolated output voltage of 380 VDC. Featuring an industry-standard 2.4 × 4.6-inch full-brick form
factor and a height of only 0.5 inches, the modules have a power density of 290 W/in. . An enable
3

JULY 2023 | www.powerelectronicsnews.com 71