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Full SiC module boosts efficiency

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By Nick Flaherty


The BSM300D12P2E001 1200V/300A full SiC power modules include a 2-in-1 type, suitable for configuring a half-bridge circuit with a single module, and a chopper type that can be used to configure a step-up circuit using a single module. There are modules that use both SiC-MOSFETs and SiC-SBDs (Schottky barrier diodes) and modules that use only SiC-MOSFETs.

IGBT power modules that combine Si-IGBTs and FRDs (fast recovery diodes) are widely used as power modules that handle large currents. IGBT modules are plagued by large switching losses due to Is, but The full SiC modules reduce the switching losses from IGBT tail currents and fast recovery diodes (FRD) recovery currents.

An SiC-MOSFET does not have a tail current during switching off like that of an IGBT, and so the off-switching losses Eoff are much lower. As there is almost no reverse recovery current, reverse recover loss (Err) is far lower as well. The on-swtching loss Eon is also reduced by about 30%, so that the overall switching loss can be decreased by 77%. As SiC modules are capable of fast switching, the results indicate that when operating at 30 kHz, switching losses can be cut by 60%. Or, the frequency can be increased sixfold without increasing losses.

By reducing switching losses, efficiency is improved and heat generation is cut. As a result, cooling equipment can be simplified. For example, heat sinks can be made smaller, and water cooling or forced air cooling can be replaced with natural air cooling. These lead in turn to smaller overall system sizes and reduced costs.

Higher operating frequencies through fast switching contribute to miniaturization of such peripheral components as reactors and capacitors. This is the same as for typical switching power supply circuits. Moreover, in SiC-SBDs there is no short-pulse reverse recovery phenomenon, and so PWM control is possible without being concerned about abnormal surge voltages when short pulses occur. This provides smaller inverter size and power supply sizes while improving efficiency.

www.rohm.com


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