Page 55 - Power Electronics News - December 2020

Semiconductors Semiconductors

Anup Bhalla (08:01): No, this is a great requirements and the complexity of topology loss, and then the drivers will get hotter. So you silicone on diodes. So silicone diodes have been

question. Because silicon carbide, initially the require? have to pay attention to that. used in power electronics for a while. With
products that were put in the market, they were the silicon carbide, the voltage range for short
put into the market using TO-247 older packages, Anup Bhalla (10:13): Yeah. So this is a very Anup Bhalla (12:01): And in this area, the SIC way diodes can now be extended to more than
which have a lot of inductance. And therefore broad question, actually. So let’s start with the FETs that we make is a good option because you 3000 volts, I guess. So, which are the benefits
you really cannot use the switching speed of question of gate drive first. So for silicon carbide can drive zero to 10 volts again. So the drivers of silicon carbide Schottky diodes and why it is
silicon carbide properly because the ringing is too MOSFETs, you are usually driving the gates at are not getting too hot. Now, the FETs will all the best tool, the best switches for continuous
much, the gate rings too much. And so the next voltage levels that are much closer to the Vgs offer great switching losses so there they can be conduction mode, CCM switching application?
stage was to introduce the Kelvin type package max in the positive and the negative direction. used in MOSFETs, our FETs, they can all be used
where there’s a Kelvin connection for the gate. And you’d have to be more careful about voltage at these high frequencies. That’s not a problem. Anup Bhalla (14:04): Yeah. So the silicon

But still, if it’s a TO package, it still has a lot of spikes so they don’t exceed the positive voltage You have 650 volt devices, 1200 volt devices now carbide Schottky diode actually was the first
inductance, right? And so the discretes that are maximum and especially the negative side available from all vendors. And so if you wanted device that became popular for Silicon Carbide.
made, are today being sold with those kinds of because that can cause instability. So that’s to use it to create a multilevel like a TNPC, also And it’s still probably a big chunk of the overall
packages. Still being used a lot in those packages where silicon carbide MOSFETS, we make SIC it’s no problem. Usually people say that the wide- business. And the reason it’s popular is that it
and they do suffer from this inductance problem. FETs, which are Cascode, so all this doesn’t bandgap devices can switch so fast. If you’re has no store charge at all. It has a reasonable
matter. You can drive the gate as you need to for replacing an IGBT, don’t do a three level solution, forward drop. It’s not that low, but it’s a
Anup Bhalla (08:42): So now you see, you’ll your application and similar to an IGBT. just do a two level solution because it’s simpler, reasonably low forward drop, but it has no store

see our company and many companies have cheaper, and you can get some efficiency out of it. charge. And because it has no store charge
more surface mount products. These surface Anup Bhalla (10:53): So when you’re mixing when you use it in hard switching mode against
mount products not only make for the speeds, them up, you may have to pay attention to the Anup Bhalla (12:44): I think this is true, but a silicon super junction device or an IGBT, it can
not only make assembly easier, but they the gate driving, how you’re doing it because silicon if you are looking for peak performance and easy really reduce the Eon loss. So you can run at
possibility for lower inductance. They have Kelvin carbide MOSFETs need better gate drives. If you filtering, I think that TNPC type structure on the a much higher frequency and then your power
connection [MDPE2] for the gate, they have lower need short circuit protection, it has to be much NPC type structure made with silicon carbide switch doesn’t get too hot. So the main benefit it
package inductance. So step by step, this is faster with silicon carbide MOSFETs. But with our multilevel can be quite amazing in how much brings is that you can actually run hard switching
improving. But I really think even in modules you SIC FETs and IGBTs, you can use the older type of improvement it can give you. So it’s a trade off, at a higher frequency without the power switch
see, there is a lot of effort being made to reduce desat with the longer short circuit for stand time. depending on your application, your budget, overheating by cutting Eon losses. So that’s good.

the inductance in the power modules. And it’s a how cost sensitive your application is, but now
step by step evolution. I think what’s the future Anup Bhalla (11:14): Now it comes to, when the devices are there for everything. Two level Anup Bhalla (14:53): And as you go to high
could be the drivers integrated with the FETs you think about high-frequency, let’s think topologies, three level topologies, the pricings are voltages though, I think the situation changes
to help really using all of the switching speed about in hard switching applications, usually there. because the Schottky itself has a pretty high
capability of silicon carbide. people don’t go too much higher than a hundred forward drop and other structures may become
kilohertz. So those gate drivers, like for totem- Maurizio Di Paolo Emilio (13:15): It’s the popular. You may have some level of bipolar
Maurizio Di Paolo Emilio (09:22): Yeah. pole PFC for example, so those kinds of gate same. injection allowed in a high voltage device. I

So during the transition phase from silicon drive, there’s a lot of gate drivers you can get also think it’s a possibility in high voltage that
IGBT to silicon carbide MOSFET, we can find in the market now for that. And then of course, Anup Bhalla (13:15): It’s similar. And the MOSFETs or FETs with integrated Schottky diodes
mixed topologies that have to be considered. specialized gate drivers for silicon carbide advantage that we bring is that because our will be popular because you can integrate a
And in this case, silicon carbide MOSFET can MOSFETs. But when you try to do a soft switching devices work with silicon levels of voltages, you Schottky into the FET without much penalty in
be used for high frequency switches and the application like LLC, and you’re running at can go much higher than frequency without the the area. So it’s cost effective, right? You don’t
silicon IGBT for low-frequency switches. So what 300 or 500 kilohertz, now you’re talking about gate driver getting hot. need to get another Schottky. You just integrate
that’s the driving of the silicon carbide powers competing with super junction FETs that are it in the same chip. And then once you’ve got
which is involved from a design point of view? switching zero to 10 volts. If you start switching Maurizio Di Paolo Emilio (13:24): Mm- that, you can also use synchronous conduction
And what do the working frequencies efficiency minus five to 15, there’s a lot more gate charge hmm (affirmative). Yeah. So just switch on to control the power loss even more. So in high

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