But even NPN regulator, since there are several configurations with PNPs or with MOSFETs.Īnd this is a good time to define what dropout voltage actually is. In general, real NPN regulators are not actually very low in dropout, and we’ll see why on the next slide. These days, most any linear regulator is often called an LDO, which stands for low dropout regulator. That integrated comes from integrated circuit, or IC. The next evolution after discrete linear regulators was the integrated NPN regulator. If your AC to DC or HVDC supply doesn’t start up during initial testing, it’s almost always because of the setup circuit and or the aux winding. Also, the reason that bipolar transistors are preferred over MOSFETs, even though MOSFETs have a lot more selection, is that it’s harder to know how much reverse voltage is needed from source to gate to make sure a MOSFET is really and truly off. As soon as that auxiliary voltage exceeds the combination of VZ plus VBE, that is to say, the Zener voltage breakdown plus a VBE transistor, then Q1 turns off and barely any power is dissipated. What isn’t shown is the connection to the line coming into the emitter of Q1, which is an output from an auxiliary winding. This type of circuit is used all the time to get supplies that run from high voltage but use low voltage silicon to start up. I’ve drawn the pass element as an NPN transistor, but n-MOSFETs with work, too. There’s a reference, usually a Zener diode, a current limiting resistor to keep the reference from overheating, and a pass element. It would be more accurate to say that in the beginning there were vacuum tube based power supplies, so let’s call this the quote on quote beginning of modern power supplies. This slide is for all my viewers who love both science fiction and power management. If you want to get in touch with me, there’s my email, You can see here that the hair changes a little bit, but that cheesy smile always stays the same. Here, you can see me, I’m your host, Chris Richardson, and a couple of badge photos from my history, first in 2005 at National Semiconductor, later on at Texas Instruments in 2011 after they bought National Semiconductor, and finally in 2013, when I founded Power Induced Design. In this session, we’re going to look at linear power supplies, thermal management, and then the basis of DC to DC switching power supplies. If you’ve already designed 100 buck regulators, you can probably skip this session, but I bet there’s at least something in these next 25 slides or so that even seasons professionals would find useful or insightful. Welcome to Part 1-1 of the Power Induced Design Power Supply Design Series, Topologies and Fundamentals, brought to you by Power Electronics News.
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