Page 8 - PEN eBook October 2025

COVER STORY—DESIGN COVER STORY—DESIGN

Classic and totem-pole PFC (Source: Infineon Technologies)

Comparison of GaN transistor structures (Source: Infineon Technologies)
e-mode GaN is preferred over cascode, especially in For protection and control, CoolGaN™ Smart
higher-switching-frequency soft-switching applications. Sense enables accurate current sensing and fast
Limitations of cascode at high speed Soft switching vs. hard switching overcurrent protection. This improves the protection
Cascode GaN transistors add capacitance and charge CoolGaN™ e-mode devices are well-suited for both GaN enables higher frequency response while simplifying measurement circuitry
due to the silicon MOSFET in series, which increases soft- and hard-switching topologies, including totem-pole GaN does not shrink systems by default; higher and calibration.
the switching energy and requires slower turn-off. PFC and resonant LLC. The absence of reverse recovery in operating frequencies do. When engineers raise the
Designers often add ferrite beads, tuned gate resistors, native reverse conduction enables low-loss commutation frequency, magnetics and capacitors can become smaller GaN medium-voltage and bidirectional
and snubbers to stabilize operation, especially at high under soft switching. Under hard switching, the absence and lighter. Simply swapping silicon for GaN at the same switches block voltage in both directions
dV/dt. In soft-switching converters, the extra loss of minority-carrier reverse recovery, the low output frequency may yield only incremental gains. Infineon The CoolGaN™ bidirectional switch (BDS) provides
associated with the device charge and slower turn-off charge, and fast transitions support high efficiency and provides detailed models, layout guides, and application a smaller, lower-cost, higher-performance switch
is a common reason why designers avoid cascode GaN high power density. In contrast, the slower turn-off notes to help teams balance frequency, efficiency, solution than two back-to-back transistors. While the
transistors. These effects can offset GaN’s inherent and added snubber circuits required for cascode result thermal design, and EMI so that the full benefit of GaN is high-voltage BDS offers improved performance for
speed advantages in demanding high-voltage stages. in more losses and reduced performance. This is why realized. single-stage converter topologies and AC-connected
resonant converters, as well as other conventional
Making GaN easy: packages, integration, topologies that use an AC switch function, the
and protection medium-voltage BDS is often used as a
Ease of adoption is a priority: battery-disconnect switch, offering small size,
low cost, low loss for preventing overcharge, and
▶ Medium-voltage GaN in silicon-compatible RQFN overdischarge protection in one monolithic switch:
packages enables drop-in upgrades from silicon
MOSFETs. ▶ Symmetric forward and reverse blocking and
conduction without reverse recovery
▶ Options with an integrated Schottky diode
improve reverse conduction and efficiency in ▶ High-efficiency operation in both soft- and
synchronous and bidirectional stages. hard-switching modes

▶ AEC-Q101–qualified variants support automotive ▶ Robust SOA characteristics for demanding
use cases. transients

Beyond discrete devices, CoolGaN™ Drive combines ▶ Options that leverage integrated Schottky
two GaN transistors with a matched driver in one diodes in medium voltage for improved
package. Tight integration reduces parasitic inductance, reverse performance and low-loss
supports high-peak-current capability, and delivers commutation
clean, fast switching. Features such as undervoltage
lockout and interlock enhance robustness and help These attributes reduce losses, simplify thermal design,
Typical gate current and gate voltage waveforms for GIT (Source: Infineon Technologies) shorten design cycles. and enable compact, energy-efficient converter designs.

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