EMI noise problem, documents on the resolution of EMI problems, causes of gate oscillation, maintaining high efficiency, development of a new product
The oscillation of the gate-drive circuit adversely affected EMI noise.
The causes of the EMI noise were identified by systematically analyzing the countermeasures we had learned through experience.
Application notes describing the causes and theory of EMI noise based on simulation results without relying on engineers’ personal experience
Previously, engineers used to rely on their personal experience to solve EMI noise problems. Instead, Toshiba analyzed simulation results and waveforms to find solutions. Application notes that summarize the analysis results are now available.
Company E, a manufacturer of server power supply units, was testing a new product. Its efficiency target was 94%. While the new power supply unit met the efficiency target, its design team was having difficulty reducing EMI noise.
While groping for a solution, the design team of Company E heard second hand about Toshiba’s application notes on EMI noise. As demonstrated in the application notes, measurements of turn-off waveforms indicate a correlation between the oscillation of a gate drive circuit and the intensity of EMI noise (Figure 1).
Engineers used to rely on their individual experience when changing a gate resistor, placing a drain-source capacitor and modifying the circuit layout. In the past, engineers typically relied on their experience to identify the causes of EMI noise. Now, our application notes provide theoretical explanations for the benefits of each EMI solution.
In addition, the application notes contain the results of simulation showing that gate oscillation is caused by changes in drain current (Ids) as well as changes in voltage due to the source inductance (Ls) (Figure 2).
Figure 2 Mechanism of Gate Oscillation upon Turn-Off
Toshiba advised the design team of Company E to add a capacitor between gate and source in order to prevent gate oscillation. Consequently, the design team developed a new product with reduced EMI noise while maintaining high efficiency.
Reducing the size of a control relay unit / semiconductor / long service life / board size reduction / countermeasure for the effects of magnetic fields
Photocoupler for IGBT/MOSFET drive / optical isolation / alleviating an overcurrent problem / design support by specialized engineers
High-voltage MOSFET / super-junction MOSFET / standard switching speed / high switching speed / high-speed diode
45-V MOSFET / latest MOSFET / low RDS(ON) / low Qoss / power supply development
Low-voltage MOSFET / Qoss reduction / low on-resistance / double-sided-cooling package / reducing the size of a DC-DC converter