Application notes

  • Switching Characteristics of UnitedSiC Gen 3 SiC FETs at Elevated Temperatures

    One unique characteristic of UnitedSiC Gen 3 SiC FETs is that its switching losses and Qrr decrease at elevated temperature, making the device more efficient once it heats up. This paper explains in detail the reason behind this characteristic.

  • Through-Hole Lead Bending

    It is often necessary for board assemblers to bend the leads of a through-hole technology (THT) device when constrained by heat sink orientation, board and system space, etc. While the package may be formed into different configurations for board mounting, care must be taken in order avoid damage such as plating strip-off, cracked package, or delamination. This application note contains options and guidelines for reliable lead bending.

  • Gate Drive and Protection of Three-Level Inverters

    There are multiple variants of three-level neutral point clamped inverters. Most are derivatives of two circuit topologies: one with four series-connected FETs and two clamp diodes, the other with two series-connected FETs and two clamp FETs. The first one is diode neutral point clamped but simply called neutral point clamped (NPC). The second one is transistor neutral point clamped (TNPC), and the phase leg schematic resembles a sideways letter T. There are different tradeoffs between these two topologies, but in the end the gate drive requirements and implementation are very similar.

  • Switching Fast SiC FETs with a Snubber

    The emergence of fast switching WBG devices has dramatically enhanced power density in a range of power conversion circuits such as active rectifiers, LLC bridges, Phase shifted full bridges, Dual active bridges to name a few. These circuits form the backbone of efficient AC-DC and DC-DC stages in battery chargers for EVs, forklifts, solar inverters and power supplies, especially where
    power density is key.

  • From Continuous-Time Domain to Microcontroller Code

    Control theory is one of the many aspects of electronic theory required for power electronic design. With the ever increasing popularity of digital control, it is important to have a good understanding of the basics of digital control. Many textbooks have been written about system modeling and control theory, but what can be difficult to find is a clear explanation of how to take an existing continuous-time model and convert it to something that can actually be programmed
    into a microcontroller.

  • 650V Cascode in LLC Second Stage Power Conversion for Servers

    The 80 Plus certification program is used to classify power supplies in terms of efficiency and power factor. Supplies with the highest overall efficiency and power factor can be certified to the 80 Plus Titanium level. Titanium power supplies have the lowest energy cost, and are one of the pieces in improving operational computer efficiency.

  • SiC in Solar Inverter Topologies

    The design of a renewable energy inverter involves many tradeoffs, including cost, electrical specifications, efficiency, features, reliability, installation cost, etc. Adding to these assorted considerations is the radically improved performance of SiC versus silicon-based semiconductors and their cost differences, which makes evaluating various topology options like comparing apples to oranges and pears.

  • UnitedSiC JFET in Active Mode Applications

    Power MOS devices, which include power MOSFETs of various construction materials and gate structures, as well as JFETs and IGBTs are three-terminal devices with current flow controlled by the gate. In most power electronic applications, the gate is driven to either block current flow with the device fully off; or fully on with minimal conduction loss.

  • Soldering and Rework of UnitedSiC THT Devices

    This document provides recommendations for soldering and rework of UnitedSiC through-hold technology (THT) devices, including (but not limited to) TO-247 with three or four leads, and TO-220. Included are recommendations for production assembly soldering as well as rework.

  • 1.5 kW Totem-pole PFC Using 650V UnitedSiC SiC Cascodes

    Bridgeless totem-pole PFC can be used to improve efficiency over conventional boost PFC by reducing the number of semiconductor devices in the conduction path from three to two. Silicon based totem-pole PFC have been limited to critical conduction mode (CrM) due to the high Qrr of silicon switches.

  • High Voltage Phase Shift Full Bridge Design with SiC Cascode

    The unique combination of features of the silicon carbide (SiC) cascode opens possibilities for new circuits, or for expanding the operating boundaries of existing circuits. The phase shift full bridge (PSFB) is a perfect example, now capable of operating efficiently and economically with 800 V input.

  • 1.7 kV JFET Eases High Voltage Utility Power Supply Design

    Systems that incorporate High Voltage Rails (~ 800 V) are typically controlled by circuitry that utilizes much lower voltages. Microprocessors, communication protocols, and sensors require a variety of voltages. A common approach to generate these voltages is with the flyback topology. In this design, a 1.7kV JFET in the cascode configuration is used as the main power switch in a flyback utility power supply.

  • Turn-Off Characteristics of SiC JBS Diodes

    SiC junction barrier schottky (JBS) diodes, as majority carrier devices, have very different turn-off characteristics from conventional Si PiN diodes. The specification data presented in the datasheets are not enough to fully cover the turn-off characteristics of SiC JBS diodes. This application note presents comprehensive experimental results to reveal the turn-off behavior of SiC JBS diodes and serves as a supplement to the datasheets.

  • Importing UnitedSiC Models into LTSPICE

    United Silicon Carbide provides standard text based SPICE models to all their commercially released products. To fully utilize these models they need to be imported into a circuit simulator. This application note details the process to add UnitedSiC models to LTSPICE, and apply them to a simple example.

    LTSPICE Model File Download: ZIP TAR

  • Overview of UnitedSiC Normally-On JFETs

    The performance improvements of Silicon Carbide switching devices compared against standard Silicon devices are well documented. What can be confusing are the drive requirements for the various SiC devices and the variation between suppliers. This document is designed to be used in conjunction with the data sheet to enable designers to confidently design with United Silicon Carbide (UnitedSiC) normally on xJ Series 1.2kV JFETs.

  • Cascode Configuration Eases Challenges of Applying SiC JFETs

    The high switching speeds and low RDS(ON) of high-voltage SiC JFETs can significantly improve the efficiency and power density of many power conversion applications. However, the conventional view of these devices is that, despite the parametric advantages, JFETs are difficult to implement due to non-standard drive voltages and a lack of an intrinsic diode when switching inductive loads.

  • SiC Cascode in 440 VAC – 800 VDC Power Factor Correction

    With the introduction of wide bandgap switching devices, good efficiencies at higher switching frequencies become attainable, while producing more cost effective solutions by lowering the required inductance. This article will explore the design tradeoffs for efficiency and power factor in implementing designs at higher frequencies (>75kHz).

  • Utilizing Silicon Carbide in 80 Plus Current Average Power Factor Correction

    In an attempt to improve the efficiency and power factor of computing power supplies, the computer industry has created a voluntary certification program called “80 Plus”. In this application note, a silicon carbide cascode switch and boost diode will be evaluated in a 1 kW hard switch Power Factor Correction (PFC) board with respect to its suitability in 80 Plus applications.

  • Cascode Facilitates Simple Startup

    Offline converters present a challenge in starting up, due to the mismatch between the high voltage input, and the low voltage power supply requirements of the controller IC. A typical application uses a string of resistors, Zener diodes and a high voltage BJT combination to generate ~ 12 V to power the controller until the feedback winding can generate enough energy to power the IC at an operational voltage. This application note will describe a self-generated startup voltage that can be used by taking advantage of a cascode configuration.