Industry: SiC power electronics
Driving SiC switches Engineers can build motor drives and power supplies that
deliver very high levels of efficiency by combining frugal, fast SiC Super Junction Transistors with optimised gate drivers, argues Ranbir Singh from GeneSiC Semiconductor.
TODAY the silicon IGBT reigns supreme in motor drives and industrial automation systems, where it is used to process voltage and current waveforms and deliver optimum power for DC-DC conversion and AC-DC/DC-AC power conversion. But this device is under increasing threat from transistors built from SiC and GaN.
Both of these alternatives have several similar, attractive characteristics. For example, they have breakdown electric fields that are around an order of magnitude higher than that for silicon – these unlock the door to new device designs, which are much thinner than the incumbent and feature blocking layers with higher doping levels. Other strengths of these wide bandgap transistors, which stem from bandgaps that are around three times that of silicon, include the ability to operate at much higher temperatures and stand up to high-radiation environments. What’s more, in the case of SiC, the thermal conductivity of this material is much higher than that for silicon, so dissipated heat can be more readily extracted from the device. This, in turn, allows more power to be applied to the device before it exceeds a certain temperature.
GaN versus SiC Today, GaN power switches continue their relentless progress by increasing their blocking voltage capabilities, but are still limited to ratings less than 400 V in commercial offerings. The switches offered to date are normally-on (depletion mode) devices that require a negative gate bias to turn them off. Circuit designers find this a significant hindrance, so some switch makers deploy a low voltage silicon MOSFET in a Cascode configuration with the normally-on GaN FET to achieve a normally-off operation. Such a circuit element can be driven using standard silicon MOSFET drivers, but may suffer from parasitic inductances associated with such a connection.
When it comes to SiC, many companies are developing and producing different types of transistors, with their own advantages and disadvantages. At GeneSiC of Dulles, VA, we are pioneering SiC Super Junction Transistors (SJTs), which are gate-oxide free, normally-off, majority carrier devices. They are competing for sales with the likes of power MOSFETs (including planar DMOSFETs and trench-MOSFETs) and (normally- on and normally-off) JFETs.
Vast differences in the intrinsic material properties between SiC and silicon mean that although a particular device stole the show with the incumbent material, it is not necessarily destined to be the outright leader in the SiC arena. Instead, an alternative device may be more promising, because when it is made from SiC, it may exploit the best material properties of SiC, and minimise the use of properties where SiC lags behind silicon.
July 2013
www.compoundsemiconductor.net 41
Two of GeneSiC’s SiC devices: a 1200 V/ 6A SJT chip and a 10 kV/10 A SJT chip
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100 |
Page 101 |
Page 102 |
Page 103 |
Page 104 |
Page 105 |
Page 106 |
Page 107 |
Page 108 |
Page 109 |
Page 110 |
Page 111 |
Page 112 |
Page 113 |
Page 114 |
Page 115 |
Page 116 |
Page 117 |
Page 118 |
Page 119 |
Page 120 |
Page 121 |
Page 122 |
Page 123 |
Page 124 |
Page 125 |
Page 126 |
Page 127 |
Page 128 |
Page 129 |
Page 130 |
Page 131 |
Page 132 |
Page 133 |
Page 134 |
Page 135 |
Page 136 |
Page 137 |
Page 138 |
Page 139 |
Page 140 |
Page 141 |
Page 142 |
Page 143 |
Page 144 |
Page 145 |
Page 146 |
Page 147 |
Page 148 |
Page 149 |
Page 150 |
Page 151 |
Page 152 |
Page 153 |
Page 154 |
Page 155 |
Page 156 |
Page 157 |
Page 158 |
Page 159 |
Page 160 |
Page 161 |
Page 162 |
Page 163 |
Page 164 |
Page 165 |
Page 166 |
Page 167 |
Page 168 |
Page 169 |
Page 170 |
Page 171 |
Page 172 |
Page 173 |
Page 174 |
Page 175 |
Page 176 |
Page 177 |
Page 178 |
Page 179