Kelvin source connection benefits MOSFET efficiency in hard switching topologies
The efficiency benefit will be highest in various hard switching topologies such as Continuous Conduction Mode Power Factor Correction (CCM PFC), Boost and Two Transistor Forward (TTF).
The new package offers improved efficiency by reducing switching losses by up to 8%. This equates to 5W lower power dissipation on the MOSFET in a CCM PFC running at 1.2KW, which means 0.4% extra full load efficiency compared to the same MOSFET in the standard 3-pin TO 247 package. The new TO 247-4 is available from two companies: both Infineon and STMicroelectronics are introducing this package providing customers with a high-quality alternative source.
“The latest generation of Superjunction MOSFETs is able to switch several hundreds of volts and several tens of amperes within a few nanoseconds. To reach the full benefit of the chip technology the package is an important factor to set up an appropriate system environment which is crucial to reach the next level of energy efficiency,” said Jan-Willem Reynaerts, Product Segment Head of High Voltage Power Conversion at Infineon Technologies. “This new TO 247-4 pin package for High Voltage MOSFETs, today being introduced by Infineon as well as STMicroelectronics, is setting new energy efficiency standards.”
An additional benefit of the Kelvin source configuration in the TO 247-4 is the ease of use for the PCB layout due to its new pin arrangement with the exposed drain and the source between gate and drain. This reduces the critical drain to gate coupling, which often causes gate oscillations at turn off with high dv/dt rates of the Drain-Source Voltage (V DS). Furthermore, the increase of creepage distance between drain and source improves system reliability. The new package is optimised for high power applications such as server, telecom and solar energy.
CoolMOS C7 – the latest generation of Infineon’s Superjunction power transistors, which has been announced recently –will be the first Infineon MOSFET family using the TO 247-4 pin package.
ST will first use the package to house an MDmesh V Super-Junction MOSFET: the new TO247-4 4-lead package provides, ST comments, “a direct source connection used only for switching control, whereas conventional packages provide one connection for both switching and power. The extra lead increases switching efficiency, which reduces energy losses and allows higher-frequency operation for more compact power supplies”.
“The TO247-4 is highly cost-effective and requires only minimal modification of the PCB layout when replacing a standard TO-247 device, which simplifies adoption in power systems,” commented Maurizio Giudice, Marketing Director, Power Transistor Division, STMicroelectronics. “Our new MDmesh devices using this package will enable better environmental performance of end equipment by improving energy efficiency in active modes.”
The TO247-4 package features an innovative internal construction implementing a Kelvin connection to the source. This connection bypasses the common source inductance of the main power connection, enabling up to 60% of switching losses to be eliminated and allowing designers to use higher switching frequencies that require smaller filtering components. The specific device from ST is theW57N65M5-, priced from $10.00 (1,000).
Infineon, www.infineon.com/c7
ST Micro, www.st.com/to247-4-pr
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