Abstract

The body diode of SiC MOSFETs in a SiC power adapter has high forward drop and small reverse recovery charge. The SiC power adapter must account for this loss in dead-time freewheeling and bridge commutation, and topology choice of the SiC power adapter is also affected.

1. Forward Drop of the Body Diode

The body diode of SiC MOSFETs in the SiC power adapter shows a forward drop in the several-volt range, well above the few tenths of a volt of silicon. During dead time, freewheeling through the body diode multiplies that drop by current into extra loss, more visible in topologies with long freewheeling intervals in the SiC power adapter. If synchronous rectification relies on the body diode, heating of the SiC power adapter must be checked against package capability.

2. Reverse Recovery Charge and Commutation Risk

Reverse recovery charge of the SiC power adapter body diode is roughly an order of magnitude below silicon, yet still non-zero. In bridge circuits, recovery during commutation creates current spikes and ringing in the SiC power adapter, and severe cases cause shoot-through. Loop inductance in the SiC power adapter amplifies the spike, so layout shortens loops and applies suitable gate resistance.

3. Schottky Diodes in Power Factor Correction

Higher power versions of the SiC power adapter often include a power factor correction front end, where reverse recovery of silicon diodes causes clear loss in continuous conduction mode. SiC Schottky diodes in the SiC power adapter give nearly zero recovery, cutting switching loss and EMI. Forward drop of the Schottky rises with current, so selection checks drop and thermal resistance at rated current.

4. Dead Time and Freewheeling Loss Balance

Dead time in the SiC power adapter balances shoot-through risk against freewheeling loss, since long dead time extends body diode conduction. Delay of the SiC power adapter shifts with temperature, so dead time is rechecked at the worst case. Adaptive dead time or paralleled Schottky diodes reduce freewheeling loss in the SiC power adapter at the cost of control complexity.

5. Body Diode Degradation and Long-term Reliability

With sustained body diode conduction, basal plane dislocations in the SiC crystal of the SiC power adapter may expand and raise forward drop, a phenomenon known as bipolar degradation. If the SiC power adapter is designed for frequent body diode conduction, vendor degradation data and screening conditions should be reviewed. Paralleling Schottky diodes reduces the conduction share of the body diode and eases degradation risk in the SiC power adapter.

Conclusion

The body diode in a SiC power adapter is both convenience and burden; freewheeling loss and degradation risk belong in topology decisions. Simsukian assesses freewheeling schemes by operating mode. Overseas buyers are welcome to contact Simsukian to confirm topology configurations of the SiC power adapter.

FAQ

Q1: Does Simsukian support OEM and ODM orders?

A1: Yes, Simsukian supports OEM & ODM customization, including logo, casing, parameter and packaging adjustment.

Q2: What certifications can Simsukian provide?

A2: Simsukian can provide CE, RCM, FCC, UL, CCC, KC/KCC, PSE, SAA certification certificates. The company holds ISO9001 and ISO14001 system certifications.

Q3: What is the sample lead time?

A3: Sample preparation takes 5 working days.

Q4: What trade terms can be accepted for cooperation?

A4: Simsukian supports FOB, and EXW can be discussed upon customer request.

Q5: What is the warranty period for the products?

A5: The product warranty period is 1 year.

References

1. Simsukian Official Website

2. JEDEC JESD22-A108 Temperature, bias and operating life

3. IEC 61000-3-2 Electromagnetic compatibility – Harmonic current emissions