You can’t keep the MOSFET output switch on forever, no inductor is ideal – they have saturation currents. So now that we have that understanding, we can move on to the finer details.ġ. There was a lot left out, but it was worth it to make the working of the boost converter absolutely clear. These steps happen many thousands of times (depending on the frequency of the oscillator) to maintain the output voltage under load.īoost Converter Operation - The Fine Pointsīy now many of you already have questions about this oversimplified explanation. I recommend that you go through the steps once again very slowly and understand them intuitively. The output capacitor is now charged to a higher voltage than before, which means that we have successfully stepped up a low DC voltage to a higher one! This means that the anode of the diode is now at a higher voltage than the cathode (remember, the cap was already charged to supply voltage in the beginning) and is forward biased.
#REAL CUK CONVERTER WAVEFORMS SERIES#
If we forget the rest of the circuit elements and notice only the polarity symbols, we notice that the inductor now acts like a voltage source in series with the supply voltage. It responds to this by generating a large voltage with the opposite polarity of the voltage originally supplied to it using the energy stored in the magnetic field to maintain that current flow. So it does not like the sudden turning off of the current. The very nature of an inductor is to maintain smooth current flow it doesn’t like sudden changes in current. The MOSFET is turned off and the current to the inductor is stopped abruptly. Note the polarity of the voltage applied across the inductor. Also, a magnetic field builds up around the inductor. The power source isn’t immediately short circuited, of course, since the inductor makes the current ramp up relatively slowly. Note that the output capacitor stays charged since it can’t discharge through the now back-biased diode. All the current is diverted through to the MOSFET through the inductor. Our signal source goes high, turning on the MOSFET. The output capacitor is charged to the input voltage minus one diode drop. With that knowledge, we can go through the working of the boost converter step by step. To understand the working of a boost converter, it is mandatory that you know how inductors, MOSFETs, diodes and capacitors work. I’ll say at the outset that it is a very rewarding field. It’s time to take a really deep breath, we’re about to plunge into the depths of power electronics. The biggest advantage boost converters offer is their high efficiency – some of them can even go up to 99%! In other words, 99% of the input energy is converted to useful output energy, only 1% is wasted. It was a requirement that these converters be as compact and as efficient as possible. They’re so simple because they were originally developed in the 1960s to power the electronics systems on aircraft. It is less cumbersome than an AC transformer or inductor. This can be something as simple as a 555 timer or even a dedicated SMPS IC like the famous MC34063A IC.Īs you can see, there are only a few parts required to make a boost converter. Also needed is a source of a periodic square wave. All it consists of is an inductor, a semiconductor switch (these days it’s a MOSFET, since you can get really nice ones these days), a diode, and a capacitor. As the name suggests, it takes an input voltage and boosts or increases it. They’re called switch mode because there’s usually a semiconductor switch that turns on and off very rapidly.Ī boost converter is one of the simplest types of switch mode converter. Anything that has too many steps is inefficient this is a good life lesson too.Įnter the world of switch mode DC-DC converters! It is possible to convert one DC voltage to another, however, the methods are slightly on the clever side.Īnd no, it does not involve the conversion of DC to AC and back again. That too, in most cases, the current draw is quite decent.Įventually, we ask ourselves the question, is it possible to convert one DC voltage to another? Or maybe we have a 3.3V supply when our chip needs 5V. We need 12 volts but have only a 9-volt battery.
We’ve all come across pesky situations where we need a slightly higher voltage than our power supplies can provide.
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