SCT2H12NZ：1700 V High Voltage SiC-MOSFETCombining with SiC AC-DC Converter Control IC Greatly Boosts Efficiency

ROHM is putting resources into development of power devices. The SCT2H12NZ, which was recently announced and is already in mass production, is an SiC-MOSFET that achieves a high 1700 V voltage rating. With this, a high-voltage version is added to a lineup that already includes 650 V and 1200 V versions. While offering a high 1700 V voltage, this MOSFET exploits SiC characteristics to greatly lower the on-resistance. Further, by combining the device with a flyback converter control IC for SiC-MOSFETs, efficiency can be boosted considerably. In addition to the most advanced power devices, ROHM is also pressing forward with development of control devices that make full use of the performance of such power devices.

Gate Drive Optimization Essential to Fully Elicit the Performance of SiC-MOSFETs

In order to fully utilize the performance of a SiC-MOSFET, driving of the SiC-MOSFET, that is, the gate drive, must be optimized. ROHM is devoting efforts not only to development of SiC-MOSFETs, but to development of control devices as well, so that anyone can easily design a power supply using a SiC-MOSFET. The BD7682FJ-LB is a flyback converter control IC developed on the assumption that a SiC-MOSFET is used as a power switch.

In addition to low EMI operation by soft switching of quasi-resonant control and low current consumption operation under light loading using burst mode, this IC is also provided with a gate clamp circuit to optimize SiC MOSFET driving, in an advanced design provided with various protection functions. Moreover, this product is intended for industrial equipment, and so long-term supply guarantee (-LB) is provided.

<BD7682FJ-LB>

• Quasi-resonant type (low EMI)
• Gate-clamp circuit for driving SiC-MOSFET
• Operating power supply voltage range
  (VCC)：15.0 V to 27.5 V
• Burst operation at light load,
  frequency reduction function
• Operating current: 0.80 mA (typ.),
  at burst operation: 0.50 mA (typ.)
• Low current consumption during
  standby: 19 μA
• Maximum oscillation frequency: 120 kHz (typ.)
• Operating temperature range: -40°C to 105°C
• SOP-J8 package
  (6.0 mm × 4.9 mm, 1.27 mm pitch)
• VCC UVLO and VCC OVP protection,
  Cycle by cycle over-current protection,
  ZT trigger mask function, ZT OVP,
  and brownout
• Long-term supply guarantee
  for industrial equipment

BD7682FJ-LB Block Diagram and Application
Circuit Example
(Click to enlarge)

Efficiency Improved 6% for Si-MOSFET Solutions

On comparing an AC-DC converter configured from the SCT2H12NZ and the BD7682FJ-LB with a circuit using a Si-MOSFET, it was confirmed that efficiency is improved 6% (comparison on a ROHM’s reference board). At the same time, heat generation can be reduced, so that the circuit can also be miniaturized. Below, the evaluation board and data comparing efficiency are presented.

This evaluation board for the SCT2H12NZ and the BD7682FJ-LB is sold on the Internet as the BD7682FJ-LB-EVK-402, and so an optimized SiC-MOSFET-based flyback converter can be evaluated immediately. In addition to this flyback converter evaluation board, ROHM also provides gate drive evaluation boards for full SiC modules and other products. SiC-MOSFETs, which boast characteristics superior to those of conventional Si MOSFETs, must be optimized in the circuit in which they are to operate, and evaluation in a state in which there are no reference boards is particularly difficult. In any case, we would recommend use of these evaluation boards to engineers who want to try running a SiC device, or who want to conduct development tasks efficiently. Please have a look at the SiC support page of the ROHM corporate website.

• SiC-MOSFET
• AC-DC converter
• Full SiC power module