What are IGBT and When to Use Them

Since I’m currently trying to power my solid-state Tesla coil proper year dual inverter circuits I did some online research. Naturally you either want to use a half bridge or full bridge topology to light current flow through the primary coil in alternating directions.

For testing purposes I’ve been using and China MOSFETs in a bootstrap full bridge configuration and apparently this circuit concept is approved by very aesthetic automatics. I found on the internet by the decent chunk of online schematics also showcase another kind of switch known as an IGBT aka insulated gate bipolar transistor. Now the question is what’s the difference and when should I use the MOSFETs and when an IGBT let’s find out first off the basics just like with MOSFETs.

They exist an N channel type and a p-channel type IGBT but since p channel ones usually feature inferior characteristics they are rarely used as a practical example I will utilize the RR GP 58 B 60 P D 1 and channel i g bt whose spinouts can be found in the datasheet the G stands for gates C for collector and it for a middle and it is not a coincidence that labels were stolen from the MOSFETs for its gate pin entered BJT you would collector and a middle pin because if we take a look at the simplified equivalent circuit of an IGBT here we can see that it basically consists of an n-channel MOSFETs and a PNP BJT, but in our theory for now let’s rather create a simple light bulb switch circuits with the IGBT.

In such a standard circuit the emitter connects directly to ground well load connects between the supply voltage and the collector by then applying a voltage higher than the gate threshold voltage to guedes the IGBT turns on and by using higher gate voltages up to 15 volts the collector emitter voltage will always be lower additive in current flow which means less power losses just make sure not to exceed the maximum gate emitter voltage now after removing the voltage source from the gates the IGBT
apparently stays conducted the reason for that is its gates which basically behaves like MOSFET gates and thus can be modelled as a capacitor while we successfully charge it up to the gate voltage and the stern TIG bt on the charge will afterwards just sit there and let the lgbts stay conductors unless of course we connected to ground so that the capacitor can discharge and the IGBT can turn off to keep this process simple we can use a 10 kilo ohm pulldown resistor between the gate and the middle to discharge the gate automatically and thus save us a bit of trouble but if you’re working with for example a PWM signal above 20 kilo hertz using a dedicated driver IC you like the TC or 44:20 year is recommended and yes even though it states master driver it can also be used for IGBTs since they are so similar when it comes to the input side now all the IC basically does is connect indicate either to the supply voltage or ground to charge it up or discharge it this is important since we need a specific gate charge to turn the IGBT on and thus we must consider that the charge Q equals current I multiplied by the time T will fire frequencies T becomes smaller but Q is still constant which means we have to increase the gate current and the driver ICU will fit six m’kraan capability you can usually handle this job but not only that driver eye sees like the eye are 2 1 1 3 can also be used for bootstrap operation and thus can provide the mandatory higher gate voltage for high sites we a gbts which not only require the gate pressure of water to turn on but additionally the load voltage and speaking of turn on / turn off times if we compare the delay and rice / 4 times of the IGBT which is around one hundred and forty five nanoseconds and two hundred and forty nine o seconds with the times of a generic MOSFETs which is around 30 to 90 seconds and 169 seconds we can see that the MOSFET switch is faster this fact is also confirmed by these data times in the datasheet of the transistors and in conclusion that means that igbts are utilized for applications beneath 200 kilo Hertz and MOSFETs for everything above.

Now let’s get back to the light bulb example and see how much power loss each transistor creates the MOSFETs will be drain to source voltage drop of 0.02 4 volts at the current flow of 1.7 amps only creates a power loss of 0.04 watts while the IGBT year with its collector to emitter voltage drop of 0.7 9 volts at a current flow of 1 point 6 5 amps creates a power loss of 1 point 3 watts that is 32 times as much and the reason for that is that the MOSFET voltage drop Rises linear with the current flow which makes it behave like a constant resistance in its ohmic region the IGBT however X more like a BJT on the outputs and features a much higher voltage drop and thus resistance at a lower current flow but on the other hand become an IGBT it can handle more current than a MOSFETs and also reaches a current level in which it is more efficient combine that with the higher collector to emitter breakdown voltage in comparison to the MOSFETs drain to source breakdown voltage and you know that igbts are all in all practical to use is a medium fast high voltage high current switch so using them for solid state Tesla coil would definitely be possible