LE3_3a Leistungsdiode (PIN Diode) - Aufbau, Kennlinie und Verluste

Now we want to see how the power

diode

works from the user's point of view, that is, the power

diode

is the practical implementation. We want to take a quick look at this pin structure and then resolve the differences with the signal diode. First of all, in terms of structure, the power diode has this pin structure, it was the paint. I have RP plus the doped area up here, then this lightly doped one was decided and then again the additional heavily doped layer, the amputated area of ​​the connection is the anode of the connection. at the end plus the annotated sentence is the cathode, we use the same symbol for the normal signal diode, that means I will also use the symbol for all diodes here, we define the flow voltage in the same direction as with a normal signal diode , that means here. the final voltage and current in this direction and also the characteristic curve quite similar to the canonical stuff we have with the normal signal diode.

I would like to record it here now, that is, now we have recorded the current flow over the flow. voltage here and then we have this typical diode behavior here and we can see here In fact, we have a diode behavior on one hand here the forward range, that is, for positive voltage here the diode will start to conduct and a threshold voltage is 0 the Current increases exponentially, so with power diodes you will notice very quickly that there is no real exponential characteristic here but rather a pronounced part, i.e. here the differential resistance 1 to rd plays a role there in the reverse direction which we will see which we have here On the one hand, this blocking zone in this zone only a small saving current HSBC - CS comes out of the diode and then somewhere at the point where the diode breaks down, we have an avalanche breakdown like in the normal diode and now here this breakdown voltage will now appear at significantly higher values ​​for the pin diodes than with the small signal diodes, meaning we have a breakdown voltage perhaps in the range of 100 volts to a few kilovolts, which we can achieve with power diodes, there is also a difference in the step range, in fact, with the suction on the power diodes, larger voltages will arise in the step range at this point, which means that here this world voltage, this parameter, so to speak, will not be known to us by both signals.

The electronics at 0.67 wanted that we normally have diodes that insert the power electronics into the walls. A larger voltage source maybe can say 0.8 volts to 1.2 volts or even more, which means the voltage drops will generally be larger, of course, they are too large currents for us. then we have in power density, which actually means here about the same behavior as with signal diode differences, we have higher voltage, which means we only go through higher voltages due to these intrinsic or weakly noted corrects there and in let- Through In this area we will normally have larger voltage drops but we can still carry larger currents at the same time, that is, here was a brief summary of these differences in the signal diode.

Then, as I said, on the one hand we have. we have the highest voltage, on the other hand we have a larger proportion or stronger effect in the front area of ​​the residential part. Now I call it area that gives us with this 1 but this resistance rd we have a higher flow voltage because of These values ​​and structure, of course, we have this intrinsic layer or the weakly doped layer and this will now cause that if we then observe a behavior switching behavior that needs to be taken into account in particular, i.e. we have a more pronounced switching behavior compared to the signal diode, so the switching behavior is more pronounced and good.

Now we want to take a look at the models we are working with with this diode. In fact, we use the same models for the power diodes. For signal diodes, that's what we'll look at here as well. First, we will start with the characteristic curve in the direct range. That means knowing this by first looking at the samples plotted against the voltage on the diode. , then here we will also say that okay, actually this behavior is initially complicated for us and the circuits. With this we will calculate the approximation through a tangent nutrition, that is, we will make a tangent approximation at the work point here that we will create. the tangent here at this point.

The slope of the tangents will be the value of the differential resistance and the point of intersection of the tangent will be the value 0 and now at this point we can, so to speak, replace the diode with a model. , that is, we can replace the diode that we now say was a nonlinear model with a model of the series decision of an ideal diode plus a voltage source ut 0 plus a differential resistor. In this direction, that means that this will be the model that we work with and depending on what the requirements are, we will now simplify this model even further.

That means we have already read and learned about electronics. There are three different models. The simplest would be now. Here we say that we only take the. ideal diode, which here means only the ideal, what do we have then we have the characteristic behavior that we had already seen in the introduction to power semiconductor components, that is, on the one hand we have this blocking area here the diode is off and on the On the other hand we have this unfortunate flow voltage area of ​​0 volts, the diode turns on so that we turn on the model, the characteristic curve for the ideal diode at 0 volts at this point, that means that here only in the model, this is the ideal Then the following model nex best honor is enough for many cases if it has the ideal diode plus the burnout voltage, that is, in many cases it is enough to look at a chronic circuit in terms of performance, then I have the feature.

The curve here in this first case shifted to the right by the voltage value t0, which means that we have the on state when we exceed the 0 voltage path on the diode and we have the off state until we are below this voltage and that is actually enough. In many cases, if you want to roughly estimate losses like we described for this diode, you can actually design most circuits, and if you then want to be a little more precise, for example to determine power loss, then you create the complete model. , i.e. the ideal diode plus the threshold voltage plus the differential resistance rd, which means that we then take into account that we get an additional voltage drop at this point the higher the current, which means that that's it, so the continuation of the model would be, on the one hand, we will continue with the diode off here as long as we are smaller than that.

But in one state, the voltage drop continues to increase with increasing current and then we have these approximate torque lines here, which then describe the model in reality. shown above and that is what we often use in power electronics, that is, in this additional voltage drop across the resistor rdr, af yes, the voltage is below zero and here, in front, again , the ideal diode and that is enough if you estimate the power losses. At this point, let's imagine, for example, the calculation of static losses which actually means three different models depending on what models we want to do without considering the system and if we want to understand the circuit model b, if we want to understand the circuit and quickly estimate the losses and then c the model if we want to determine the losses a little more precisely at this point we now want to talk about determining diode loss power or static behavior, which means we have never looked at calculating losses in the physical state or that a behavior looks at the static behavior of the diode and we base it on the model that we just saw, that's actually what we mean when we say Well, to calculate the losses, we will replace our diode with a model, i.e. this model, ideal diode plus the Swiss voltage plus the differential resistances.

Now let us derive an example of how we determine the power loss in such an arrangement, that is, what it really is. The interesting thing is that we have to relate the voltage. and current with each other as variables that vary in time to determine the instantaneous power loss and from this we can determine the average power loss if we have periodic time predecessors as is usual in power electronics, which would then be the power losses. light here. means here, well, now we will look at this from this model on the right to determine the losses in a state in which the ideal diode will now conduct, that is, if we look at this, we will now start in a state of the next model, the diode is closed here.

This is the ideal diode that conducts ideally and then we just have the voltage drop ut 0 + the voltage drop across this differential resistor rd. This voltage drop is, of course, rd times f and if we look at that now, then. This total voltage drop must be equal to the voltage drop across the diode. That means we can say that the voltage for the diode is the constant value of this world voltage plus rd maly f and we get the current power loss if we save at this point. and we multiply the sp of tsf by here or here in the current, we multiply this expression again by the rate, then we have 0 x f + r d once squared, where of course it is not a function on time and wind energy, i.e. , the actual energy loss. that is implemented, is the integral over a period if.

Because of power electronics, we have people's usual periodic time, which means that here psp would be 1 through the integral from 0 to 10 through PVC or ddt or that from point 1 through the integral from 0 to 20 times f + r the marlies in the square dt and now we can divide that, which means that we can now divide this integral into two parts and then add constant factors in front of each one, 10 means here, for example, facto at zero is constant and rd is also constant at an operating point, which means I can say that I played this integral at 0 x 1 by subjecting the integral 0 to c over pdf plus a second integral rd multiplied by 1 1 through the subject the integral 0 to ttf in the square dt and in fact, now I was looking at this first expression, this first integral is right now.

The average value of the current through the diode bfr rich and the second integral which is multiplied here by rd is equal to the definition of the effective value of this current ef except for one root, that is, it is effective squared and therefore we can say that the power loss here The diode delight losses are calculated using, on the one hand, the average value of the current, the Germans To estimate the power loss in the diodes, that is why these characteristic curve models of torque are so important. We know the current curve and we only have to determine the average value and the effective value from the characteristic curve of the diode. for example, in the data sheet we determine here, for example, in tangents he and the parameter ard or ut 0 is specified in some data sheets and can then be used in the application to determine the light losses, that is, the losses, using the formula shown here when on