1. Department of Electrical Engineering Southern Taiwan University of Science and Technology Robot and Servo Drive Lab. 2016/1/12 Reducing Switching Losses in BLDC Motor Drives by Reducing Body Diode Conduction of MOSFETs IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 51, NO. 2, MARCH/APRIL 2015 Cameron D. Brown, Member, IEEE, and Bulent Sarlioglu, Senior Member, IEEE P.1864~ P.1871 學生 : 林信佑 指導教授 : 王明賢

2. Department of Electrical Engineering Southern Taiwan University of Science and Technology 2016/1/12 Robot and Servo Drive Lab. 2 outline Abstract Introduction Pinch-off MOSFET Design Considerations SPICE SIMULATIONS Thermal Measurements Conclusion References

3. Department of Electrical Engineering Southern Taiwan University of Science and Technology 2016/1/12 Robot and Servo Drive Lab. 3 Abstract This paper presents a new power electronic topology that aims to reduce switching losses in hard-switched inverters for bruchless dc(BLDC) moter drives. The proposed topology for reducing body diode conduction includes the addition of a MOSFET in series with the rectifying switch and a SiC Schottky diode around the series switch combination. This paper focuses on theory, simulations, and experimental results

4. Department of Electrical Engineering Southern Taiwan University of Science and Technology 2016/1/12 Robot and Servo Drive Lab. 4 Introduction SILICON (Si) MOSFETs are good candidates for motor drive applications in the 100- to 600-V range. One advantage of using MOSFETs in bridge drive circuits is that the lower MOSFET in the totem pole can be turned on during the rectification portion of the switching cycle to allow current to flow backward through the channel. Another benefit of synchronous rectification is that it allows for simple multidirectional operation.

5. Department of Electrical Engineering Southern Taiwan University of Science and Technology traditional and pinch-off 2016/1/12 Robot and Servo Drive Lab. 5

6. Department of Electrical Engineering Southern Taiwan University of Science and Technology 2016/1/12 Robot and Servo Drive Lab. 6

7. Department of Electrical Engineering Southern Taiwan University of Science and Technology Pinch-off MOSFET voltage and current waveforms 2016/1/12 Robot and Servo Drive Lab. 7

8. Department of Electrical Engineering Southern Taiwan University of Science and Technology 2016/1/12 Robot and Servo Drive Lab. 8 Extension to Sine Motor Inverter Drives The six-step trapezoidal approach usually results in higher torque ripple at the output of the motor. However, for higher performance drives or high-accuracy servo drive applications it is better to use sinusoidal back electromotive force (EMF)

9. Department of Electrical Engineering Southern Taiwan University of Science and Technology Pinch-off MOSFET Design Considerations Because there is no reverse recovery current spike, top MOSFET turn-on stress is reduced. Higher frequency operation is possible in applications where the dead time would otherwise need to be increased to allow the current to leave the body diode and transfer into the parallel Schottky rectifier. The amount of delay needed depends on the application. Higher output current requires a longer delay. 2016/1/12 Robot and Servo Drive Lab. 9

10. Department of Electrical Engineering Southern Taiwan University of Science and Technology Power dissipation Power dissipation may be reduced due to dead-time reduction and the fact that during the remaining necessary dead time, the current flows in a low-voltage Schottky diode instead of a MOSFET body diode 2016/1/12 Robot and Servo Drive Lab. 10

11. Department of Electrical Engineering Southern Taiwan University of Science and Technology 2016/1/12 Robot and Servo Drive Lab. 11 Pinch-off MOSFET totem pole simulation circuit

12. Department of Electrical Engineering Southern Taiwan University of Science and Technology 2016/1/12 Robot and Servo Drive Lab. 12 Extension to Sine Motor Inverter Drives The simulations show that the switch node slew rate is significantly slower in the pinch-off MOSFET circuit, at approximately 17 MV/s, than the traditional totem pole at 1.14 GV/s about a factor of 10 reduction.

13. Department of Electrical Engineering Southern Taiwan University of Science and Technology 2016/1/12 Robot and Servo Drive Lab. 13

14. Department of Electrical Engineering Southern Taiwan University of Science and Technology 2016/1/12 Robot and Servo Drive Lab. 14 EXPERIMENTAL RESULTS Circuit card assembly developed for this effort.

15. Department of Electrical Engineering Southern Taiwan University of Science and Technology 2016/1/12 Robot and Servo Drive Lab. 15 EXPERIMENTAL RESULTS

16. Department of Electrical Engineering Southern Taiwan University of Science and Technology 2016/1/12 Robot and Servo Drive Lab. 16 Thermal Measurements traditional bridge pinch-off MOSFET bridge one phase 2.8 A.

17. Department of Electrical Engineering Southern Taiwan University of Science and Technology Thermal image, pinch-off MOSFET bridge, one phase, 5.3 A. 2016/1/12 Robot and Servo Drive Lab. 17

18. Department of Electrical Engineering Southern Taiwan University of Science and Technology 2016/1/12 Robot and Servo Drive Lab. 18

19. Department of Electrical Engineering Southern Taiwan University of Science and Technology Efficiency Measurements 2016/1/12 Robot and Servo Drive Lab. 19

20. Department of Electrical Engineering Southern Taiwan University of Science and Technology 2016/1/12 Robot and Servo Drive Lab. 20 Conclusion A nearly 33% reduction in the power dissipation was measured with the pinch-off MOSFET configuration. Thermal measurement comparisons show a 42 ◦ C reduction in the temperature of the top MOSFET of the bridge containing the pinch-off circuit.

21. Department of Electrical Engineering Southern Taiwan University of Science and Technology 2016/1/12 Robot and Servo Drive Lab. 21 References [1] N. McNeill, R. Wrobel, and P. H. Mellor, “Synchronous rectification technique for high-voltage single-ended power converters,” in Proc. IEEE ECCE, 2010, pp. 264–271. [2] M. Mehrotra and B. J. Baliga, “Comparison of high voltage rectifier structures,” in Proc. 5th ISPSD ICs, May 18–20, 1993, pp. 199–204. [3] O. Al-Naseem, R. W. Erickson, and P. Carlin, “Prediction of switching loss variations by averaged switch modeling,” in Proc. 15th Annu. IEEE APEC Expo., 2000, vol. 1, pp. 242–248. [4] H. Kim, T. M. Jahns, and G. Venkataramanan, “Minimization of reverse recovery effects in hard-switched inverters using CoolMOS power switches,” in Conf. Rec. IEEE IAS Annu. Meeting, 2001, vol. 1, pp. 641–647.

22. Department of Electrical Engineering Southern Taiwan University of Science and Technology References [5] T. Reiter, D. Polenov, H. Probstle, and H. Herzog, “Optimization of PWM dead times in dc/dc-converters considering varying operating conditions and component dependencies,” in Proc. Eur. Conf. Power Electron. Appl., 2009, pp. 1–10. [6] R. Shillington, P. Gaynor, M. Harrison, and W. Heffernan, “Silicon carbide JFET reverse conduction characteristics and use in power converters,” IET Power Electron., vol. 5, no. 8, pp. 1282–1290, Sep. 2012. [7] J.-S. Lai et al., “A hybrid switch based soft-switching inverter for ultrahigh efficiency traction motor drives,” IEEE Trans. Ind. Appl., vol. 50, no. 3, pp. 1966–1973, May/Jun. 2014. [8] D. DeWitt, C. Brown, and S. Robertson, “The pinch-off circuit: Reducing noise and component stresses by eliminating body diode conduction in synchronous rectifiers,” in Proc. IEEE Appl. Power Electron. Conf., 2007, pp. 1531–1536. 2016/1/12 Robot and Servo Drive Lab. 22

23. Department of Electrical Engineering Southern Taiwan University of Science and Technology References [9] D. B. DeWitt, C. D. Brown, and S.M. Robertson, “System and method for reducing body diode conduction,” U.S. Patent 7 508 175, Mar. 24, 2009. [10] Z. Chen, Y. Yao, D. Boroyevich, K. Ngo, and P. Mattavelli, “A 1200 V, 60 A SiC MOSFET multi-chip phase-leg module for high-temperature, high frequency applications,” in Proc. IEEE Appl. Power Electron. Conf., 2013, pp. 608–615. [11] J. Zhu et al., “High-voltage superjunction VDMOS with low reverse recovery loss,” Electron. Lett., vol. 49, no. 3, pp. 219–220, Jan. 31, 2013. [12] T. Funaki, “A study on SiC devices in synchronous rectification of dc–dc converter,” in Proc. IEEE Appl. Power Electron. Conf., 2007, pp. 339–344. [13] S. Mappus, “DV/DT immunity improved in synchronous buck converters,” Power Electron. Technol., vol. 31, no. 7, pp. 30–36, Jul. 2005. 2016/1/12 Robot and Servo Drive Lab. 23