Page 28 - PEN eBook NOVEMBER 2022

SEMICONDUCTORS POWER SUPPLIES

catastrophic damage. The power device and its gate the active region of the channel under the gate, thereby
driver need to work together to shut the device off, reduces I dsat and improves SCWT, though at an R DS(on)
with 1 µs previously considered as a normal response penalty that could range from 10% to 30%. When paired
time for this. Several studies on GaN HEMTs have with a desaturation detection (DESAT) gate driver, an
reported much shorter short-circuit withstand times 800-ns detection was obtained at V = 400 V and
ds
(SCWTs), thought to be from high current densities, the full V = 12 V. Several fast SC detection methods
gs
especially in low-R DS(on) devices. The SCWT drops have been proposed, and it’s clear that this field will
dramatically as the V is raised up, with many studies need significant development to validate the use of
ds
showing <500 ns at a V ≥ 400 V. A lower V also helps, GaN HEMTs in motor control applications, especially at
gs
ds
with the degradation in SCWT at high V thought to voltages ≥400 V.
gs
be from hole accumulation under the gate. A study to
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compare cascoded versus e-mode HEMTs showed that PACKAGING
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the I dsat fall in cascoded devices from the The cascode topology is more robust for gate voltage
short-circuit (SC) thermal event was lower than for and is hence more immune to parasitic inductance/
the e-mode devices, which makes them less robust to capacitance to a certain extent than the e-mode
the SC event. The larger percentage drop in I dsat on the counterparts. Some cascode devices have been
e-mode devices from self-heating helps to strengthen packaged in thermally robust packages like the
its SC behavior. TO-247. E-mode devices, to a large degree, are more
prone to gate noise issues, and careful consideration of
An SCWT safe operating region was presented in a package-related parasitics has to be done. As a result,
study in which the authors also studied the effects of a lot of the offerings for this have been in leadless
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repeated SC events. The study found that although a planar packages. Technology development at the Buck Converter IC with
single SC event at a V of 400 V and V of 6 V allowed package level is therefore essential to assure the high
ds
gs
for a large SCWT (>300 µs), repeated SC events thermal sinking needed in these high-power–density
resulted in an SCWT of only 20 ns under these bias devices. Having a Kelvin source connection also allows Adaptive Power Sharing
conditions. A significant derating of the V for more accurate gate control without the common
ds
and/or V was necessary to improve this time. The source inductance. GaN Systems has come up with
gs
authors concluded that the heat confinement in the an innovative GaNPX package that offers low thermal By Maurizio Di Paolo Emilio, editor-in-chief of Power Electronics News
thin GaN channel layer created mechanical stress, resistance.
which caused the failure. A method for improving SCWT
was patented by Transphorm. This approach, dubbed Power system design includes many tradeoffs In an interview with Hubie Noto, Silanna
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between design parameters, such as size, cost, Semiconductor’s director of product marketing, he said
efficiency, and load transient performance. To design that the SZPL3002A power IC meets an efficiency of
For More Information the power stage, various features like transient 98% by integrating a high-efficiency synchronous buck
tolerance, ripple voltage, and load characteristics must converter and an advanced port controller into a single
▶ Transphorm Inc. (2018). “Recommended External Circuitry for Transphorm GaN FETs.” Application note be established. System designers are concentrating 5 × 5-mm QFN package.
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0009. on enhancing the efficiency of power conversion
using new circuit topologies via better control of The PD controller acts from behind the scenes
▶ 2Sojka, P., Pipiska, M., & Frivaldsky, M. (2019). “GaN power transistor switching performance in hard- battery characteristics to develop a system with a intelligently by equalizing power. The device works with
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switching and soft-switching modes.” 2019 20th International Scientific Conference on Electric Power longer runtime and a smaller footprint. Low efficiency switching frequencies starting from 667 kHz and going
Engineering (EPE). corresponds to increased power dissipation, which down to 1 MHz.
▶ Böcker, J., Heucke, S., & Dieckerhoff, S. (2020). “Loss Separation in Hard- and Soft-Switching GaN HEMTs must be adequately handled. Lower switching
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operated in a 10 kW Isolated DC/DC Converter.” 2020 22nd European Conference on Power Electronics and frequencies lower switching losses, but higher “This device has another unique feature that we
Applications (EPE’20 ECCE Europe). switching frequencies provide greater performance and call power-saving mode,” said Noto. “When you don’t
quicker transient response. have any load connected, usually other people just do
▶ Huang et al. (2014). “Experimental study of 650V AlGaN/GaN HEMT short-circuit safe operating area standby, which can normally still consume power. In
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(SCSOA).” 2014 IEEE 26th International Symposium on Power Semiconductor Devices & IC’s (ISPSD).
Silanna Semiconductor has introduced an intelligent our case, if the user initially selects in the design to
▶ Fernandez et al. (Nov. 2017). “Short-Circuit Study in Medium-Voltage GaN Cascodes, p-GaN HEMTs, and power-sharing buck converter power IC. The new switch to power-saving mode, the DC/DC portions turn
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GaN MISHEMTs.” IEEE Transactions on Industrial Electronics, Vol. 64, Issue 11. SZPL3002A buck converter IC with an integrated off completely, but the PD controller is still running.
▶ Sun et al. (Sept. 2021). “Short Circuit Capability Characterization and Analysis of p-GaN Gate High- USB-PD/FC port controller reduces the amount of The PD controller then continues to monitor the DC
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Electron-Mobility Transistors Under Single and Repetitive Tests.” IEEE Transactions on Industrial components required to perform 65-W fast-charger line with less-than-microwatt consumption.”
Electronics. and adapter applications with up to four ports
substantially. This power IC features intelligent power The inbuilt port controller supports USB PD V3.0
▶ 7Bisi et al. (2022). “Short-Circuit Capability with GaN HEMTs.” 2022 International Reliability Physics sharing using a fully integrated USB-PD controller, MCU, Type-C interfaces as well as QC2.0-/3.0-/4.0-/5.0-
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Symposium (IRPS). and VCONN cable communications protocol within this type A/C connections. The controller facilitates
short-circuit current limiter (SCCL), effectively reduces highly efficient DC/DC buck converter. power sharing and port-power rebalancing capability

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