Three MOSFETs Aim to Unleash Efficiency and Power Density
With a focus on conduction loss, size, and speed, the power MOSFETs may pave the way for unprecedented efficiency and power density in a range of applications.
The latest generations of power MOSFETs focus on reduced conduction losses, compactness, and faster speeds. These features enhance the performance of power electronics systems and address the demands of various industries such as automotive, renewable energy, and telecommunications.
Toshiba's new super-junction MOSFET series is explained in more detail below. Image courtesy of Toshiba
This article highlights new power MOSFETs aiming to improve power supply efficiency in various applications, including e-mobility.
Toshiba's Super-junction N-Channel Power MOSFET
Toshiba has expanded its N-channel power MOSFETs portfolio with its new 600 V super-junction structure DTMOSVI series, targeted for data centers, switching power supplies, and power conditioners for photovoltaic generators. The new series, including its first product TK055U60Z1, features optimized gate design and process to reduce on-resistance per unit area by around 13% and drain-source on-resistance x gate-drain charge by 52% compared to Toshiba's DTMOSIV-H series products with similar voltage ratings.
Comparison of drain-source on-resistance and gate-drain charge between DTMOSVI and DTMOSIV-H. Image courtesy of Toshiba
The new product also features a TOLL (TO-leadless) package, allowing Kelvin connection of the source terminal for the gate driver to suppress oscillations during switching.
Infineon's 1200 V CoolSiC Series
Infineon's new generation of automotive 1200 V CoolSiC MOSFETs comes in the TO263-7 package and features high power density and efficiency, bi-directional charging, and reduced system cost. The series offers 25% lower switching losses than its earlier generation, leading to a smaller form factor and increased power density.
1200 V CoolSiC MOSFET. Image courtesy of Infineon
Its gate-source threshold voltage is higher than 4 V and has a reliable turn-off at 0 V, allowing for bipolar driving and reducing the system cost for DC-DC applications. Due to these features and very low on-resistance, KOSTAL Automobil Elektrik uses these MOSFETs in its next-generation onboard charging platform for Chinese original equipment manufacturers (OEMs).
ROHM's Low On-Resistance N-Channel MOSFETs
ROHM also recently developed new N-channel MOSFETs with models covering 40, 60, 80, 100, and 150 V. The RS6xxxxBx/RH6xxxxBx series is designed for applications working on 24, 36, and 48 V power supplies, such as base stations, servers, and motors for industrial and consumer equipment. These applications require minimal power loss.
ROHM claims to have optimized the trade-off between the two critical parameters leading to power losses: on-resistance, which is inversely proportional to chip size, and gate-drain charge, which is proportional to chip size. The company reconciled this trade-off by using copper clip connections and improving the gate structure.
ROHM’s new N-channel MOSFETs. Image courtesy of ROHM
The ROHM MOSFETs feature an on-resistance of 2.1 milli-ohms, approximately 50% lower than conventional devices. Moreover, the company claims a 40% improvement in gate-drain charge compared to conventional products. ROHM says it will continue to develop MOSFETs with even lower on-resistance that reduce power consumption and increase the power density of various applications.
Why the Focus on Conduction Loss, Size, and Speed?
This roundup of new MOSFETs from Toshiba, Infineon, and ROHM highlights the key features setting next-generation MOSFETs apart from previous devices: conduction loss, size, and speed.
MOSFETs achieve improved conduction losses when the transistor is in on-state. To reach this state, manufacturers use innovative designs and materials. For instance, super-junction MOSFETs feature a vertical structure with multiple P-N junctions for better electron mobility and electric field distribution to minimize resistance. Low conduction losses enhance the power conversion efficiency significantly.
Advancements in packaging technologies have also played a critical role in reducing the size of power MOSFETs and reducing losses. New packaging options, such as power-flat packages (PFP) and power quad flat no-lead (PQFN) packages, offer a small footprint and improved thermal management, allowing higher power density. In addition, techniques like flip-chip and direct bond copper (DBC) enable better thermal conductivity, enhancing reliability and miniaturization.
Another critical aspect of power MOSFETs is speed. Faster switching speeds contribute to overall system efficiency. Manufacturers enhance the switching speed by developing new gate driver technologies and improving the internal structures of power MOSFETs. Newer device technologies like silicon carbide (SiC) and gallium nitride (GaN) have significantly improved the operating frequencies and reduced switching losses.