As the input voltage to the totem pole is being switched, and the raising/falling voltage edge approaches the input voltage rail, then the input current significantly drops off. This means that input circuitry to the totem pole only needs to provide a small amount of current for the output to drive to a high current.
The gain in the NPN and PNP transistors is important, NOT necessarily the absolute maximum peak current that the transistors can handle but the actual high gain hold-up. Even if the Vcc rail voltage to the NPN on the top side is at a higher voltage, let's say 10V.Ģ. The output voltage tracks the input voltage therefore if you only have 0V to 5V input to the totem pole, it will only give you 0V to 5V on output (Not quite 5V as it is a little less). Some key points about using NPN-PNP totem pole are:ġ. Click this link for the Power Tip 42 (Part 1): Discrete devices-a good alternative to integrated MOSFET drivers. In terms of the NPN-PNP emitter follower configuration their is a good article on this by Robert Kollman on eetimes. A Youtube video on VFD breakdown I saw seemed to have independant totem poles for each but I'm not sure. Half Bridge/3Ph driver ICs or independent totem pole for each switch. Also it is extremely convenient to place them right next to the gate of the IGBT/MOSFET, so no stray inductance issues(Just 2 small transistors and a few smd resistors fit nicely next to the gate).Īlso most importantly, does anyone have any idea about what commercial VFD manufacturers use, i.e. Thus I can get an extremely powerful high current gate drive circuit at much less cost. What is drawing me towards the totem pole route is that a) It costs about 10 times less b) Current capacity is virtually no issue at all (Especially considering the fact that I will be using isolated supplies as it is and not be going for bootstrapping, and will have dead time in software itself) My question is that apart from the saving in space which allows for a compact design, what are the benefits of using off the shelf Gate Driver ICs ( like say IR2110,IR2186,IR2136) as opposed to making your own gate driver using a pair of npn,pnp transistors in totem pole configuration. I have been wondering about this for a while now, and couldn't find any proper comparison between the two.
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