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Case 3: Selection of a MOSFET to improve the efficiency of a server power supply
Keywords: High-voltage MOSFET, super-junction MOSFET, standard switching speed, high switching speed, high-speed diode

Storage servers in data room Domestic Room

The design team launched a project for a new power supply unit with improved efficiency, but ran into a wall...
How did the team solve the problem?
DTMOSIV mid- to high-voltage super-junction MOSFET series fabricated using a single-epitaxial process

Product Overview


Drawing on many years of experience, Toshiba Electronic Devices & Storage Corporation offers an extensive lineup of 500- to 800-V super-junction MOSFETs with standard and high-speed switching, and high-speed diode options.


  • Low rate of increase in on-resistance with temperature due to the use of a single-epitaxial process
  • Low switching loss due to a reduction in Coss

Problem-Solving Examples

Solution for Company A, a power supply unit manufacturer (Employee population: 3,500)


Company A received an inquiry from an information equipment manufacturer for a high-efficiency power supply unit that can be used with multiple server models. In order to open up new business opportunities, Company A chose to create a new design for the power supply unit.
Although its design team tried to create a power supply unit with higher efficiency, it was having difficulty in raising the switching performance to a level close to the initial specification targets. The design team sought advice from the manufacturers of major semiconductor components to be used in the power supply unit, but it could not break the deadlock. The scheduled completion date was drawing close, but the design team had yet to find a solution. So, what was the solution? What did they do to create a power supply unit with higher efficiency?

Using the mid- to high-voltage DTMOSIV MOSFET series

At his wit’s end, an engineer of Company A went to a New Products Show held by Toshiba Electronic Devices & Storage Corporation to obtain advice from its engineers. Toshiba immediately sent a field application engineer (FAE) to Company A to learn about the current situation and analyze the circuit in question. As a result, it was found out that Company A had chosen MOSFETs with low on-resistance in order to reduce power losses while trying to obtain an 80 PLUS efficiency level certification for large power supply units. However, the increased gate charge of low-on-resistance MOSFETs caused the switching speed to decrease and therefore switching losses to increase. Since reducing on-resistance loss causes the switching losses to increase, it is necessary to select the optimal devices. However, the design team of Company A had trouble finding MOSFETs that would best meet its needs.
Toshiba’s DTMOS IV is a super-junction MOSFET series fabricated using a single-epitaxial process to achieve significant reductions in on-resistance and gate charge (Qg). Featuring an extensive product lineup, the DTMOS IV series allowed the design team to select MOSFETs that would best suit its specific needs. The lineup of both standard and high-speed MOSFETs was also appealing to the design team.


The new power supply unit incorporating MOSFETs of Toshiba’s mid- to high-voltage DTMOSIV series was highly regarded and adopted by the information equipment manufacturer.

List of Problem-Solving Examples

Case 1: Selection of a MOSFET to meet power supply specifications: DC-DC converter

Low-voltage MOSFET, Qoss reduction, low on-resistance, double-sided-cooling package, reducing the size of a DC-DC converter

Case 2: Selection of a MOSFET to increase the withstand voltage margin: Power supply product

45-V MOSFET, latest MOSFET, development of a low-RDS(ON) and low-Qoss power supply product 

Case 4: EMI noise solutions based on the results of simulation

EMI noise problem, documents on the resolution of EMI problems, causes of gate oscillation, maintaining high efficiency, development of a new product 

Case 5: Using a photocoupler to solve a problem of an industrial robot caused by overcurrent

Photocoupler for IGBT/MOSFET drive, optical isolation, alleviating an overcurrent problem, design support by specialized engineers

Case 6: Using a solid-state relay to reduce the size and prolong the service life of power supply units for Programmable Logic Controller

Reducing the size of a control relay unit, semiconductor, long service life, board size reduction, countermeasure for the effects of magnetic fields 


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·Before creating and producing designs and using, customers must also refer to and comply with the latest versions of all relevant TOSHIBA information and the instructions for the application that Product will be used with or for.