High Voltage Buck Converter

Thread Starter

gdylp2004

Joined Dec 2, 2011
101
No. The "camel hump" occurs AFTER the inductor is discharged and the diode ceases conducting. It's a result of the inductor and the output cap being series resonant. See the attached simulation; I stopped the gate signal after 58 pulses. The time frame I zeroed in on was right after the startup was complete.



It's due to the resonance of L1 and the output capacitor being in series.
Ok, the LTSpice seems to be a good simulator and I've just downloaded it in hope to simulate my design before I starts asking anymore questions which could be explained using the software.

However when I run the simulation (transient analysis) in hope to see the charging voltage curve (which I should see the Vout = ~6.32V at 1s since R=1kΩ C=1mF), what I got is a single straight line which seems incorrect (see attached).

Do you know what went wrong?

Also, SgtWookie, did you download the Spice model of the IRF630N and IR2117 from IRF website directly? What I've found is only the PSpice model, are those compatible with LT Spice?

Thanks in advance.
 

Attachments

SgtWookie

Joined Jul 17, 2007
22,221
Ok, the LTSpice seems to be a good simulator and I've just downloaded it in hope to simulate my design before I starts asking anymore questions which could be explained using the software.
LTSpice is a good and free simulator. Like everything else, you need to understand the limitations of a simulation. It's only as good as the modelling of a real circuit; most everything is an approximation, and many parameters are not modeled - such as certain circuit parasitics (R, L, C). Those parasitics can cause a real-world circuit to perform very differently than a modeled circuit.

However when I run the simulation (transient analysis) in hope to see the charging voltage curve (which I should see the Vout = ~6.32V at 1s since R=1kΩ C=1mF), what I got is a single straight line which seems incorrect (see attached).

Do you know what went wrong?
Yes, you did not check the "Startup" box.
Right-click on your .tran statement, and on the dialog that pops up, check the box to the right of the line that reads:
"Start external DC supply voltages at 0V:"
and then click OK.

did you download the Spice model of the IRF630N and IR2117 from IRF website directly?
I downloaded the IR2117 PSpice model from the International Rectifier website, and created a symbol for it from the DIP8 symbol that comes with LTSpice.

I already had an IRF630 model kicking around here from something else I was doing. I don't always use a manufacturers' model for a component, as some of them require a great deal of overhead processing that simplified models do not. I have to balance my time between getting somewhat more accurate simulations, or getting help to more people.

What I've found is only the PSpice model, are those compatible with LT Spice?
Yes, PSpice models generally work, but there are various versions, and sometimes the models need certain statements to be re-worked to be compatible with LTSpice.

One of your biggest resources for LTSpice will be the LTSpice users' group on Yahoo! Groups. You need to sign up for a free Yahoo! account, and then find the LTSpice group, and request to join. There are a large number of useful models and symbols that have been tested using LTSpice, and a forum where you can ask LTSpice-specific questions.



Thanks in advance.[/QUOTE]
 

Thread Starter

gdylp2004

Joined Dec 2, 2011
101
Thanks SgtWookie.

Ok guys, now I've new problem. I've switched the duty cycle till 50% to allow the Buck operates in the CCM. And I've replace the HV DC rail with a High voltage DC PSU.

Upon ramping the HV DC rail slowly to 100V, I've noticed after Vdc > ~80V, to my horror, the Vgs starts to increase as well. It climbed till about > 20V (which is the Vgs(max) specified in the datasheet) and therefore I do not dare to increase my Vdc further to 100V.

Could anyone know why is this so?

And also, the increment of the Vgs was not the first observation made. The Vgs starts to transient and the transient magnitude increases with Vdc.
 

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Thread Starter

gdylp2004

Joined Dec 2, 2011
101
Hi guys,

I'm back. I am satisfied that the HCPL-3180 Avago optocoupler works as well as the IR2117 gate driver. In fact, I could have a pulse with peak amplitude of only 3.3V to the photodiode by tweaking the optocoupler series resistor. And I just love the optocoupler because it does not need any Vcc (IR2117 does), but only a bootstrap configuration.

Attached are my circuit connections (still using breadboard though for testing). Also, I've used a 10V z-diode to clamp V(gs).

Ok, here comes my next challenge as well as a little problem. In my past various testings, I've used a stand-alone low voltage DC PSU (10V) to provide the necessary source to charge up my bootstrap capacitor periodically. I would now like to remove that, and instead utilise power from the HV 100V DC rail.

As necessary, I've first done my research about auxiliary power supply and now that I share to hope to get more insights from members with good experience over here:

100kΩ resistor in series with 10V z-diode:

As seen in zener_setup.jpg, R=100kΩ in series with a zener of V(bk-dn) of 10V, therefore V(R)=100-10=90V. I(z)=V(R)/R=90/100k=0.9mA.

I've constructed the schematic on a breadboard as shown in zener_breadboard.jpg. I've chosen R = 120kΩ and z-diode 1watt 1N4740AC.

The 100V DC supply is then connected to the top part of the 120kΩ resistor and the zener reverse voltage is being recorded by an oscilloscope as shown in zener_oscope.jpg, with a reading of ~9.886V.

Here comes my question, if I connect this regulated 10V to my optocoupler as a replacement for the LV DC PSU, would the circuit readings change? What I believe is that this optocoupler would draw some average current, and hence in turn, changing the current flowing through the 120k resistor, that is, I(R)=I(z)+I(optocoupler). So to find out how much current will the optocoupler draw, I've measured with the original setup (the one with LV PSU to supply the bootstrap cap charge), the avg. current is about 7.10mA (see Optocoupler_Iin.jpg).

So will this work as a substitute for a separate LV PSU for charging the bootstrap cap?

Thanks in advance.
 

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SgtWookie

Joined Jul 17, 2007
22,221
I can hardly believe that you got ANYTHING to work on that breadboard, particularly how you wired it. There are big loops of wire running everywhere!!

Breadboards are fine for low-frequency analog stuff. When you start getting into the higher speeds, the parasitics kick in and ruin your day.

You need to use the "dead bug" technique, or use stripboard, or something similar - like making a custom board.

I don't know why you are trying to use an auxiliary supply rather than the boost diode and boost cap. The boost cap and diode are very efficient. Your 120k resistor and Zener will dissipate ~80mW power, so you'd need at least a 1/8 Watt resistor - 1/4 Watt would be better. Don't forget, you're going to need a bit extra current for the Zener, and you'll still need a decent-sized cap there. If the supply cap charge decreases too much, you'll start running the MOSFET in the resistive mode and burning them up.
 

Thread Starter

gdylp2004

Joined Dec 2, 2011
101
I can hardly believe that you got ANYTHING to work on that breadboard, particularly how you wired it. There are big loops of wire running everywhere!!

Breadboards are fine for low-frequency analog stuff. When you start getting into the higher speeds, the parasitics kick in and ruin your day.

You need to use the "dead bug" technique, or use stripboard, or something similar - like making a custom board.
Thanks SgtWookie for your reply, after this "last" implementation, I would wired the circuit onto a stripboard which I've made as shown in stripboard_structure.jpg.

I don't know why you are trying to use an auxiliary supply rather than the boost diode and boost cap. The boost cap and diode are very efficient.
I apologize for not being clear in my previous post, I still really do want to continue to utilise the bootstrap config but instead of using a separate unit, a LV 30V(max) DC PSU to supply the bootstrap charge momentary, I would now like to obtain the charge or current from the 100V High DC rail. By doing this, I could simulate a more realistic situation because, ultimately at the end of the day, there would be only a 100V DC battery supplying power to all the sub-system, including the boostrap supply.

So in order to tap the votage from the 100V HV DC rail, I suggest the traditional zener (voltage regulator) method. Although many has said this method is usually inefficient, a 80mW power dissipation may be considerably low for a 100W supply unit, however, I would still consider any other methods which are better in efficiency.

I know it is a hard decision since it is not easy to trade off efficiency with complexity, afterall, I am willing to sacrifice a little more efficiency for simplicity.

Your 120k resistor and Zener will dissipate ~80mW power, so you'd need at least a 1/8 Watt resistor - 1/4 Watt would be better. Don't forget, you're going to need a bit extra current for the Zener, and you'll still need a decent-sized cap there. If the supply cap charge decreases too much, you'll start running the MOSFET in the resistive mode and burning them up.
I've in fact used LT Spice to simulate the z-diode voltage regulation method as an intended replacement for the LV DC PSU. What I could not understand is when I connect a pulsating current source to simulate the bootstrap drawing current periodically, the voltage at the zener's cathode could not maintain at 10V which I orginally believed it would be.

Is there some other components I would need to add or in fact this method won't work for my application at all?
 

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Last edited:

SgtWookie

Joined Jul 17, 2007
22,221
10v isn't going to work. You need to read the datasheet and figure out what is the minimum voltage you need on the boost cap in order to get it to work properly, and stay a couple of volts above that.

As far as the bootstrap drawing current periodically and the voltage at the Zener's cathode not maintaining 10v; I've basically told you how to fix that before.

You need to think how to interface the current supply at the Zener to the charge requirement of the boost cap. I'm giving you some very big hints here. I can't do the whole thing for you, or you won't learn anything.
 

Thread Starter

gdylp2004

Joined Dec 2, 2011
101
My apology as I did not know why my LT Spice did not work properly previously, hence asking such questions.

W/O changes, the following is my zener setup schematic and its waveform. It really looks cool as now the cathode does provide a constant 10V (or 15V after I change it), current through the resistor is also constant as well.

Unfortunately, it seems that I am unable to change the knee current of the diode that I am currently using. The one which I used in LT Spice has a 5mA test current but the z-diode I used on breadboard is of 50mA test current. 10X difference.
 

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SgtWookie

Joined Jul 17, 2007
22,221
My apology as I did not know why my LT Spice did not work properly previously, hence asking such questions.
LTSpice works just fine - it's the simulation that wasn't correct. ;)

W/O changes, the following is my zener setup schematic and its waveform. It really looks cool as now the cathode does provide a constant 10V (or 15V after I change it), current through the resistor is also constant as well.
Did you happen to check the power dissipation of the Zener and the resistor? You'll need a resistor rated for 13 Watts or more, and a Zener rated for 2 Watts.

Your simulation is still not right. You said previously that the driver is drawing an average of 7.1mA, but your simulation is drawing a fraction of that; 28% to be exact. You need to show it drawing a much shorter duration peak current, but still average to 7.1mA.

You need to research what the difference between an ideal voltage source and an ideal current source is.

Right now, you have close to an ideal current source (even though it is not regulated) - but what you really need is an ideal voltage source.

Unfortunately, it seems that I am unable to change the knee current of the diode that I am currently using. The one which I used in LT Spice has a 5mA test current but the z-diode I used on breadboard is of 50mA test current. 10X difference.
Why don't you use a more appropriate Zener model then?

Here, paste these into your LTC\SwitcherCad\lib\cmp\standard.dio file:
Rich (BB code):
.MODEL 1N746 D(IS=1E-11 RS=13.65 N=1.27 TT=5E-8 CJO=5.826E-10 VJ=0.75 M=0.33 BV=3.027 IBV=0.01 Vpk=3.3 mfg=Motorola_.5W type=zener)
.MODEL 1N747 D(IS=1E-11 RS=12.8 N=1.27 TT=5E-8 CJO=5.422E-10 VJ=0.75 M=0.33 BV=3.344 IBV=0.01 Vpk=3.6 mfg=Motorola_.5W type=zener)
.MODEL 1N748 D(IS=1E-11 RS=11.84 N=1.27 TT=5E-8 CJO=5.076E-10 VJ=0.75 M=0.33 BV=3.663 IBV=0.01 Vpk=3.9 mfg=Motorola_.5W type=zener)
.MODEL 1N749 D(IS=1E-11 RS=10.47 N=1.27 TT=5E-8 CJO=4.683E-10 VJ=0.75 M=0.33 BV=4.091 IBV=0.01 Vpk=4.3 mfg=Motorola_.5W type=zener)
.model 1N750 D(Is=.88f Rs=.25 Cjo=175p M=.55 nbv=1.7 bv=4.7 Vj=.75 Isr=1.86n Nr=2 Ibv=20.245m Ibvl=1.96m Nbvl=15 Tbv1=-21.3u Vpk=4.7 mfg=OnSemi type=Zener)
.MODEL 1N751 D(IS=1E-11 RS=7.708 N=1.27 TT=5E-8 CJO=4.068E-10 VJ=0.75 M=0.33 BV=4.946 IBV=0.01 Vpk=5.1 mfg=Motorola_.5W type=zener)
.MODEL 1N752 D(IS=1E-11 RS=6.168 N=1.27 TT=5E-8 CJO=3.766E-10 VJ=0.75 M=0.33 BV=5.477 IBV=0.01 Vpk=5.6 mfg=Motorola_.5W type=zener)
.MODEL 1N753 D(IS=1E-11 RS=4.685 N=1.27 TT=5E-8 CJO=3.463E-10 VJ=0.75 M=0.33 BV=6.106 IBV=0.01 Vpk=6.2 mfg=Motorola_.5W type=zener)
.MODEL 1N754 D(IS=1E-11 RS=3.721 N=1.27 TT=5E-8 CJO=3.209E-10 VJ=0.75 M=0.33 BV=6.726 IBV=0.01 Vpk=6.8 mfg=Motorola_.5W type=zener)
.MODEL 1N755 D(IS=1E-11 RS=3.359 N=1.27 TT=5E-8 CJO=2.959E-10 VJ=0.75 M=0.33 BV=7.433 IBV=0.01 Vpk=7.5 mfg=Motorola_.5W type=zener)
.MODEL 1N756 D(IS=1E-11 RS=3.858 N=1.27 TT=5E-8 CJO=2.749E-10 VJ=0.75 M=0.33 BV=8.123 IBV=0.01 Vpk=8.2 mfg=Motorola_.5W type=zener)
.MODEL 1N757 D(IS=1E-11 RS=5.672 N=1.27 TT=5E-8 CJO=2.523E-10 VJ=0.75 M=0.33 BV=8.987 IBV=0.01 Vpk=9.1 mfg=Motorola_.5W type=zener)
.MODEL 1N758 D(IS=1E-11 RS=8.483 N=1.27 TT=5E-8 CJO=2.334E-10 VJ=0.75 M=0.33 BV=9.830 IBV=0.01 Vpk=10 mfg=Motorola_.5W type=zener)
.MODEL 1N759 D(IS=1E-11 RS=14.95 N=1.27 TT=5E-8 CJO=2.008E-10 VJ=0.75 M=0.33 BV=11.70 IBV=0.01 Vpk=12 mfg=Motorola_.5W type=zener)
Those are 1/2 Watt Zener diodes. I will post some 1 Watt in the next reply.
 

SgtWookie

Joined Jul 17, 2007
22,221
Here are some 1W Zeners:
Rich (BB code):
.MODEL 1N4728 D(IS=5.97E-16 RS=0.659 TT=5.01E-8 CJO=3.63E-10 VJ=0.75 M=0.33 BV=3.251 IBV=0.0760 Vpk=3.3 mfg=Motorola_1W type=zener)
.MODEL 1N4729 D(IS=5.81E-16 RS=0.624 TT=5.01E-8 CJO=3.19E-10 VJ=0.75 M=0.33 BV=3.558 IBV=0.0690 Vpk=3.6 mfg=Motorola_1W type=zener)
.MODEL 1N4730 D(IS=6.63E-16 RS=0.795 TT=5.01E-8 CJO=2.83E-10 VJ=0.75 M=0.33 BV=3.851 IBV=0.0640 Vpk=3.9 mfg=Motorola_1W type=zener)
.MODEL 1N4731 D(IS=6.42E-16 RS=0.753 TT=5.01E-8 CJO=2.44E-10 VJ=0.75 M=0.33 BV=4.258 IBV=0.0580 Vpk=4.3 mfg=Motorola_1W type=zener)
.MODEL 1N4732 D(IS=6.71E-16 RS=0.811 TT=5.01E-8 CJO=2.14E-10 VJ=0.75 M=0.33 BV=4.659 IBV=0.0530 Vpk=4.7 mfg=Motorola_1W type=zener)
.MODEL 1N4733 D(IS=7.03E-16 RS=0.871 TT=5.01E-8 CJO=1.89E-10 VJ=0.75 M=0.33 BV=5.059 IBV=0.0490 Vpk=5.1 mfg=Motorola_1W type=zener)
.MODEL 1N4734 D(IS=7.32E-16 RS=0.924 TT=5.01E-8 CJO=1.64E-10 VJ=0.75 M=0.33 BV=5.561 IBV=0.0450 Vpk=5.6 mfg=Motorola_1W type=zener)
.MODEL 1N4735 D(IS=7.57E-16 RS=0.968 TT=5.01E-8 CJO=1.41E-10 VJ=0.75 M=0.33 BV=6.163 IBV=0.0410 Vpk=6.2 mfg=Motorola_1W type=zener)
.MODEL 1N4736 D(IS=7.76E-16 RS=1.000 TT=5.01E-8 CJO=1.23E-10 VJ=0.75 M=0.33 BV=6.766 IBV=0.0370 Vpk=6.8 mfg=Motorola_1W type=zener)
.MODEL 1N4737 D(IS=9.33E-16 RS=1.230 TT=5.01E-8 CJO=1.06E-10 VJ=0.75 M=0.33 BV=7.461 IBV=0.0340 Vpk=7.5 mfg=Motorola_1W type=zener)
.MODEL 1N4738 D(IS=1.06E-15 RS=1.410 TT=5.01E-8 CJO=9.28E-11 VJ=0.75 M=0.33 BV=8.160 IBV=0.0310 Vpk=8.2 mfg=Motorola_1W type=zener)
.MODEL 1N4739 D(IS=1.46E-15 RS=1.820 TT=5.01E-8 CJO=7.94E-11 VJ=0.75 M=0.33 BV=9.053 IBV=0.0280 Vpk=9.1 mfg=Motorola_1W type=zener)
.MODEL 1N4740 D(IS=2.91E-15 RS=2.710 TT=5.01E-8 CJO=6.89E-11 VJ=0.75 M=0.33 BV=9.937 IBV=0.0250 Vpk=10 mfg=Motorola_1W type=zener)
.MODEL 1N4741 D(IS=7.14E-15 RS=3.870 TT=5.01E-8 CJO=1.01E-10 VJ=0.75 M=0.33 BV=10.91 IBV=0.0230 Vpk=11 mfg=Motorola_1W type=zener)
.MODEL 1N4742 D(IS=9.67E-15 RS=4.260 TT=5.01E-8 CJO=9.42E-11 VJ=0.75 M=0.33 BV=11.91 IBV=0.0210 Vpk=12 mfg=Motorola_1W type=zener)
.MODEL 1N4743 D(IS=1.28E-14 RS=4.630 TT=5.01E-8 CJO=8.81E-11 VJ=0.75 M=0.33 BV=12.91 IBV=0.0190 Vpk=13 mfg=Motorola_1W type=zener)
.MODEL 1N4744 D(IS=5.32E-14 RS=6.470 TT=5.01E-8 CJO=7.83E-11 VJ=0.75 M=0.33 BV=14.89 IBV=0.0170 Vpk=15 mfg=Motorola_1W type=zener)
.MODEL 1N4745 D(IS=1.02E-13 RS=7.330 TT=5.01E-8 CJO=7.44E-11 VJ=0.75 M=0.33 BV=15.89 IBV=0.0155 Vpk=16 mfg=Motorola_1W type=zener)
.MODEL 1N4746 D(IS=4.19E-13 RS=9.150 TT=5.01E-8 CJO=6.78E-11 VJ=0.75 M=0.33 BV=17.88 IBV=0.0140 Vpk=18 mfg=Motorola_1W type=zener)
.MODEL 1N4747 D(IS=1.65E-12 RS=10.90 TT=5.01E-8 CJO=6.25E-11 VJ=0.75 M=0.33 BV=19.87 IBV=0.0125 Vpk=20 mfg=Motorola_1W type=zener)
.MODEL 1N4748 D(IS=3.11E-12 RS=11.70 TT=5.01E-8 CJO=5.82E-11 VJ=0.75 M=0.33 BV=21.87 IBV=0.0115 Vpk=22 mfg=Motorola_1W type=zener)
.MODEL 1N4749 D(IS=5.71E-12 RS=12.50 TT=5.01E-8 CJO=5.46E-11 VJ=0.75 M=0.33 BV=23.88 IBV=0.0105 Vpk=24 mfg=Motorola_1W type=zener)
.MODEL 1N4750 D(IS=2.22E-10 RS=17.20 TT=5.01E-8 CJO=5.02E-11 VJ=0.75 M=0.33 BV=26.84 IBV=0.0095 Vpk=27 mfg=Motorola_1W type=zener)
.MODEL 1N4751 D(IS=2.67E-09 RS=21.90 TT=5.01E-8 CJO=4.66E-11 VJ=0.75 M=0.33 BV=29.82 IBV=0.0085 Vpk=30 mfg=Motorola_1W type=zener)
.MODEL 1N4752 D(IS=2.67E-09 RS=26.50 TT=5.01E-8 CJO=4.38E-11 VJ=0.75 M=0.33 BV=32.81 IBV=0.0075 Vpk=33 mfg=Motorola_1W type=zener)
.MODEL 1N4753 D(IS=2.67E-09 RS=31.30 TT=5.01E-8 CJO=4.14E-11 VJ=0.75 M=0.33 BV=35.79 IBV=0.0070 Vpk=36 mfg=Motorola_1W type=zener)
.MODEL 1N4754 D(IS=2.67E-09 RS=36.00 TT=5.01E-8 CJO=3.93E-11 VJ=0.75 M=0.33 BV=38.78 IBV=0.0065 Vpk=39 mfg=Motorola_1W type=zener)
 

SgtWookie

Joined Jul 17, 2007
22,221
More 1W Zeners:
Rich (BB code):
.MODEL 1N4755 D(IS=2.67E-09 RS=40.70 TT=5.01E-8 CJO=3.71E-11 VJ=0.75 M=0.33 BV=42.77 IBV=0.0060 Vpk=43 mfg=Motorola_1W type=zener)
.MODEL 1N4756 D(IS=2.67E-09 RS=50.30 TT=5.01E-8 CJO=3.52E-11 VJ=0.75 M=0.33 BV=46.74 IBV=0.0055 Vpk=47 mfg=Motorola_1W type=zener)
.MODEL 1N4757 D(IS=2.67E-09 RS=59.80 TT=5.01E-8 CJO=3.33E-11 VJ=0.75 M=0.33 BV=50.72 IBV=0.0050 Vpk=51 mfg=Motorola_1W type=zener)
.MODEL 1N4758 D(IS=2.67E-09 RS=69.20 TT=5.01E-8 CJO=3.19E-11 VJ=0.75 M=0.33 BV=55.71 IBV=0.0045 Vpk=56 mfg=Motorola_1W type=zener)
.MODEL 1N4759 D(IS=2.67E-09 RS=78.50 TT=5.01E-8 CJO=3.03E-11 VJ=0.75 M=0.33 BV=61.71 IBV=0.0040 Vpk=62 mfg=Motorola_1W type=zener)
.MODEL 1N4760 D(IS=2.67E-09 RS=93.00 TT=5.01E-8 CJO=2.89E-11 VJ=0.75 M=0.33 BV=67.68 IBV=0.0037 Vpk=68 mfg=Motorola_1W type=zener)
.MODEL 1N4761 D(IS=2.67E-09 RS=117.0 TT=5.01E-8 CJO=2.76E-11 VJ=0.75 M=0.33 BV=74.65 IBV=0.0033 Vpk=75 mfg=Motorola_1W type=zener)
.MODEL 1N4762 D(IS=2.67E-09 RS=141.0 TT=5.01E-8 CJO=2.65E-11 VJ=0.75 M=0.33 BV=81.61 IBV=0.0030 Vpk=82 mfg=Motorola_1W type=zener)
.MODEL 1N4763 D(IS=2.67E-09 RS=190.0 TT=5.01E-8 CJO=2.54E-11 VJ=0.75 M=0.33 BV=90.51 IBV=0.0028 Vpk=91 mfg=Motorola_1W type=zener)
.MODEL 1N4764 D(IS=2.67E-09 RS=289.0 TT=5.01E-8 CJO=2.45E-11 VJ=0.75 M=0.33 BV=99.32 IBV=0.0025 Vpk=100 mfg=Motorola_1W type=zener)
Yet MORE Zeners:
Rich (BB code):
.MODEL BZX84C10/ZTX D IS=1.132E-15 N=1.030 RS=.11 IKF=1 XTI=3 EG=1.11 CJO=90.62E-12 M=.33 VJ=.6975 FC=.5 BV=10.11 IBV=.3255 TT=108.2E-9
.MODEL BZX84C11/ZTX D IS=544.3E-18 N=1.011 RS=.14 IKF=1 XTI=3 EG=1.11 CJO=80.82E-12 M=.327 VJ=.7056 FC=.5 BV=11.11 IBV=.3262 TT=122.6E-9
.MODEL BZX84C12/ZTX D IS=869.1E-18 N=1.02 RS=.12 IKF=1 XTI=3 EG=1.11 CJO=73.83E-12 M=.3306 VJ=.7651 FC=.5 BV=12.1 IBV=.2602 TT=144.3E-9
.MODEL BZX84C13/ZTX D IS=513.2E-18 N=1.001 RS=.1 IKF=1 XTI=3 EG=1.11 CJO=62.95E-12 M=.3341 VJ=.8633 FC=.5 BV=13.1 IBV=.2164 TT=173.1E-9
.MODEL BZX84C15/ZTX D IS=1.116E-15 N=1.027 RS=.11 IKF=1 XTI=3 EG=1.11 CJO=56.98E-12 M=.3326 VJ=.803 FC=.5 BV=15.1 IBV=.2165 TT=209.2E-9
.MODEL BZX84C16/ZTX D IS=556.3E-18 N=1.013 RS=.12 IKF=1 XTI=3 EG=1.11 CJO=52.99E-12 M=.3286 VJ=.7205 FC=.5 BV=16.09 IBV=.1623 TT=187.6E-9
.MODEL BZX84C18/ZTX D IS=723.9E-18 N=1.02 RS=.13 IKF=1 XTI=3 EG=1.11 CJO=44.99E-12 M=.3353 VJ=.828 FC=.5 BV=18.09 IBV=.1442 TT=281.3E-9
.MODEL BZX84C20/ZTX D IS=11.83E-15 N=1.08 RS=.09 IKF=1 XTI=3 EG=1.11 CJO=42.64E-12 M=.2707 VJ=.3905 FC=.5 BV=20.08 IBV=.1178 TT=295.8E-9
.MODEL BZX84C22/ZTX D IS=1.707E-15 N=1.042 RS=.14 IKF=1 XTI=3 EG=1.11 CJO=37.64E-12 M=.3301 VJ=.7799 FC=.5 BV=22.08 IBV=.1179 TT=310.2E-9
.MODEL BZX84C24/ZTX D IS=1.63E-15 N=1.039 RS=.13 IKF=1 XTI=3 EG=1.11 CJO=35.39E-12 M=.3309 VJ=.7731 FC=.5 BV=24.07 IBV=92.59E-3 TT=303.0E-9
.MODEL BZX84C27/ZTX D IS=53.96E-15 N=1.136 RS=.0987 IKF=1 XTI=3 EG=1.11 CJO=33.38E-12 M=.3006 VJ=.4245 FC=.5 BV=27.12 IBV=.2024 TT=346.2E-9
.MODEL BZX84C2V7/ZTX D IS=3.677E-15 N=1.059 RS=.12 IKF=1 XTI=3 EG=1.11 CJO=312.1E-12 M=.2052 VJ=.3971 FC=.5 BV=2.766 IBV=64.76E-3 TT=57.71E-9
.MODEL BZX84C30/ZTX D IS=2.669E-15 N=1.055 RS=.11 IKF=1 XTI=3 EG=1.11 CJO=30.05E-12 M=.3324 VJ=.7923 FC=.5 BV=30.12 IBV=.2024 TT=461.7E-9
.MODEL BZX84C33/ZTX D IS=9.428E-15 N=1.099 RS=.12 IKF=1 XTI=3 EG=1.11 CJO=27.62E-12 M=.3268 VJ=.7365 FC=.5 BV=33.12 IBV=.2024 TT=404.0E-9
.MODEL BZX84C36/ZTX D IS=6.202E-15 N=1.081 RS=.1 IKF=1 XTI=3 EG=1.11 CJO=25.70E-12 M=.3366 VJ=.7798 FC=.5 BV=36.12 IBV=.1799 TT=418.4E-9
.MODEL BZX84C39/ZTX D IS=7.921E-15 N=1.1 RS=.12 IKF=1 XTI=3 EG=1.11 CJO=23.83E-12 M=.3437 VJ=.7925 FC=.5 BV=39.11 IBV=.1245 TT=634.8E-9
.MODEL BZX84C3V0/ZTX D IS=4.311E-15 N=1.057 RS=.12 IKF=1 XTI=3 EG=1.11 CJO=291.5E-12 M=.2719 VJ=.5248 FC=.5 BV=3.066 IBV=64.76E-3 TT=64.92E-9
.MODEL BZX84C3V3/ZTX D IS=1.636E-15 N=1.028 RS=.13 IKF=1 XTI=3 EG=1.11 CJO=283.5E-12 M=.2019 VJ=.3905 FC=.5 BV=3.366 IBV=64.77E-3 TT=57.71E-9
.MODEL BZX84C3V6/ZTX D IS=522.2E-18 N=1.004 RS=.13 IKF=1 XTI=3 EG=1.11 CJO=256.6E-12 M=.2332 VJ=.4593 FC=.5 BV=3.666 IBV=64.77E-3 TT=389.5E-9
.MODEL BZX84C3V9/ZTX D IS=193.4E-15 N=1.219 RS=.1 IKF=1 XTI=3 EG=1.11 CJO=239.5E-12 M=.3295 VJ=.7686 FC=.5 BV=3.966 IBV=64.74E-3 TT=360.7E-9
.MODEL BZX84C43/ZTX D IS=228.7E-15 N=1.22 RS=.11 IKF=1 XTI=3 EG=1.11 CJO=21.92E-12 M=.3415 VJ=.7656 FC=.5 BV=43.1 IBV=.1079 TT=274.1E-9
.MODEL BZX84C47/ZTX D IS=19.1E-15 N=1.131 RS=.1 IKF=1 XTI=3 EG=1.11 CJO=21.05E-12 M=.35 VJ=.7818 FC=.5 BV=47.1 IBV=95.16E-3 TT=649.2E-9
.MODEL BZX84C4V3/ZTX D IS=187E-15 N=1.218 RS=.09 IKF=1 XTI=3 EG=1.11 CJO=221.2E-12 M=.3317 VJ=.7266 FC=.5 BV=4.367 IBV=69.05E-3 TT=331.8E-9
.MODEL BZX84C4V7/ZTX D IS=207.3E-15 N=1.224 RS=.14 IKF=1 XTI=3 EG=1.11 CJO=210.7E-12 M=.2286 VJ=.411 FC=.5 BV=4.771 + IBV=81.00E-3 
.MODEL BZX84C5V6/ZTX D IS=89.48E-15 N=1.203 RS=.09 IKF=1 XTI=3 EG=1.11 CJO=179.6E-12 M=.3067 VJ=.6563 FC=.5 BV=5.690 IBV=.1621 TT=562.7E-9
.MODEL BZX84C6V2/ZTX D IS=180.4E-15 N=1.228 RS=.09 IKF=1 XTI=3 EG=1.11 CJO=149.5E-12 M=.3207 VJ=.6676 FC=.5 BV=6.326 IBV=.654 TT=418.4E-9
.MODEL BZX84C6V8/ZTX D IS=137.8E-15 N=1.225 RS=.13 IKF=1 XTI=3 EG=1.11 CJO=129.3E-12 M=.3277 VJ=.735 FC=.5 BV=6.915 IBV=.4358 TT=620.4E-9
.MODEL BZX84C7V5/ZTX D IS=398.3E-15 N=1.270 RS=.12 IKF=1 XTI=3 EG=1.11 CJO=111.9E-12 M=.3294 VJ=.6802 FC=.5 BV=7.615 IBV=.4354 TT=476.1E-9
.MODEL BZX84C8V2/ZTX D IS=390.6E-15 N=1.271 RS=.12 IKF=1 XTI=3 EG=1.11 CJO=96.20E-12 M=.333 VJ=.7508 FC=.5 BV=8.315 IBV=.4354 TT=519.4E-9
.MODEL BZX84C9V1/ZTX D IS=522.2E-18 N=1.004 RS=.12 IKF=1 XTI=3 EG=1.11 CJO=96.83E-12 M=.3303 VJ=.7662 FC=.5 BV=9.215 IBV=.4354 TT=93.78E-9
Enough with the Zeners already!

Rich (BB code):
.MODEL BZX79C5V1 D(IS=2.4710E-9 N=2.0880 RS=1.0000E-3 IKF=4.900 CJO=95.650E-12 M=.3487 VJ=.7022 ISR=10.010E-21 BV=5.30 IBV=.8623 TT=140E-9 Vpk=5.1 mfg=NXP type=zener)
.MODEL BZX79C5V6 D(IS=2.4710E-9 N=2.0880 RS=1.0000E-3 IKF=5.400 CJO=95.650E-12 M=.3487 VJ=.7022 ISR=10.010E-21 BV=5.80 IBV=.8623 TT=140E-9 Vpk=5.6 mfg=NXP type=zener)
.MODEL BZX79C6V2 D(IS=2.4710E-9 N=2.0880 RS=1.0000E-3 IKF=5.900 CJO=95.650E-12 M=.3487 VJ=.7022 ISR=10.010E-21 BV=6.50 IBV=.8623 TT=140E-9 Vpk=6.2 mfg=NXP type=zener)
.MODEL BZX79C6V8 D(IS=2.4710E-9 N=2.0880 RS=1.0000E-3 IKF=6.500 CJO=95.650E-12 M=.3487 VJ=.7022 ISR=10.010E-21 BV=7.10 IBV=.8623 TT=140E-9 Vpk=6.8 mfg=NXP type=zener)
.MODEL BZX79C7V5 D(IS=2.4710E-9 N=2.0880 RS=1.0000E-3 IKF=7.000 CJO=95.650E-12 M=.3487 VJ=.7022 ISR=10.010E-21 BV=8.00 IBV=.8623 TT=140E-9 Vpk=7.5 mfg=NXP type=zener)
.MODEL BZX79C8V2 D(IS=2.4710E-9 N=2.0880 RS=1.0000E-3 IKF=7.600 CJO=95.650E-12 M=.3487 VJ=.7022 ISR=10.010E-21 BV=8.70 IBV=.8623 TT=140E-9 Vpk=8.2 mfg=NXP type=zener)
.model BZX84C10L D(Is=.6n Rs=.5 Cjo=150p nbv=5 bv=10 Ibv=1m Vpk=10 mfg=OnSemi type=Zener)
.model BZX84C12L D(Is=.6n Rs=.5 Cjo=150p nbv=5 bv=12 Ibv=1m Vpk=12 mfg=OnSemi type=Zener)
.model BZX84C15L D(Is=.6n Rs=.5 Cjo=110p nbv=6 bv=15 Ibv=1m Vpk=15 mfg=OnSemi type=Zener)
.model BZX84C6V2L D(Is=1.5n Rs=.5 Cjo=185p nbv=3 bv=6.2 Ibv=1m Vpk=6.2 mfg=OnSemi type=Zener)
.model BZX84C8V2L D(Is=.8n Rs=.5 Cjo=135p nbv=3 bv=8.2 Ibv=1m Vpk=8.2 mfg=OnSemi type=Zener)
 

SgtWookie

Joined Jul 17, 2007
22,221
I just realized that I'd forgotten to put some LTSpice-specific data in these models so that the breakdown voltages would show up in the selection list, so I updated these; replace them in your standard.dio:
Rich (BB code):
.MODEL BZX84C2V7/ZTX D IS=3.677E-15 N=1.059 RS=.12   IKF=1 XTI=3 EG=1.11 CJO=312.1E-12 M=.2052 VJ=.3971 FC=.5 BV=2.766 IBV=64.76E-3 TT=57.71E-9 Vpk=2.7 mfg=Zetex type=Zener
.MODEL BZX84C3V0/ZTX D IS=4.311E-15 N=1.057 RS=.12   IKF=1 XTI=3 EG=1.11 CJO=291.5E-12 M=.2719 VJ=.5248 FC=.5 BV=3.066 IBV=64.76E-3 TT=64.92E-9 Vpk=3.0 mfg=Zetex type=Zener
.MODEL BZX84C3V3/ZTX D IS=1.636E-15 N=1.028 RS=.13   IKF=1 XTI=3 EG=1.11 CJO=283.5E-12 M=.2019 VJ=.3905 FC=.5 BV=3.366 IBV=64.77E-3 TT=57.71E-9 Vpk=3.3 mfg=Zetex type=Zener
.MODEL BZX84C3V6/ZTX D IS=522.2E-18 N=1.004 RS=.13   IKF=1 XTI=3 EG=1.11 CJO=256.6E-12 M=.2332 VJ=.4593 FC=.5 BV=3.666 IBV=64.77E-3 TT=389.5E-9 Vpk=3.6 mfg=Zetex type=Zener
.MODEL BZX84C3V9/ZTX D IS=193.4E-15 N=1.219 RS=.1    IKF=1 XTI=3 EG=1.11 CJO=239.5E-12 M=.3295 VJ=.7686 FC=.5 BV=3.966 IBV=64.74E-3 TT=360.7E-9 Vpk=3.9 mfg=Zetex type=Zener
.MODEL BZX84C4V3/ZTX D IS=187E-15   N=1.218 RS=.09   IKF=1 XTI=3 EG=1.11 CJO=221.2E-12 M=.3317 VJ=.7266 FC=.5 BV=4.367 IBV=69.05E-3 TT=331.8E-9 Vpk=4.3 mfg=Zetex type=Zener
.MODEL BZX84C4V7/ZTX D IS=207.3E-15 N=1.224 RS=.14   IKF=1 XTI=3 EG=1.11 CJO=210.7E-12 M=.2286 VJ=.411  FC=.5 BV=4.771 IBV=81.00E-3             Vpk=4.7 mfg=Zetex type=Zener
.MODEL BZX84C5V6/ZTX D IS=89.48E-15 N=1.203 RS=.09   IKF=1 XTI=3 EG=1.11 CJO=179.6E-12 M=.3067 VJ=.6563 FC=.5 BV=5.690 IBV=.1621    TT=562.7E-9 Vpk=5.6 mfg=Zetex type=Zener
.MODEL BZX84C6V2/ZTX D IS=180.4E-15 N=1.228 RS=.09   IKF=1 XTI=3 EG=1.11 CJO=149.5E-12 M=.3207 VJ=.6676 FC=.5 BV=6.326 IBV=.654     TT=418.4E-9 Vpk=6.2 mfg=Zetex type=Zener
.MODEL BZX84C6V8/ZTX D IS=137.8E-15 N=1.225 RS=.13   IKF=1 XTI=3 EG=1.11 CJO=129.3E-12 M=.3277 VJ=.735  FC=.5 BV=6.915 IBV=.4358    TT=620.4E-9 Vpk=6.8 mfg=Zetex type=Zener
.MODEL BZX84C7V5/ZTX D IS=398.3E-15 N=1.270 RS=.12   IKF=1 XTI=3 EG=1.11 CJO=111.9E-12 M=.3294 VJ=.6802 FC=.5 BV=7.615 IBV=.4354    TT=476.1E-9 Vpk=7.5 mfg=Zetex type=Zener
.MODEL BZX84C8V2/ZTX D IS=390.6E-15 N=1.271 RS=.12   IKF=1 XTI=3 EG=1.11 CJO=96.20E-12 M=.333  VJ=.7508 FC=.5 BV=8.315 IBV=.4354    TT=519.4E-9 Vpk=8.2 mfg=Zetex type=Zener
.MODEL BZX84C9V1/ZTX D IS=522.2E-18 N=1.004 RS=.12   IKF=1 XTI=3 EG=1.11 CJO=96.83E-12 M=.3303 VJ=.7662 FC=.5 BV=9.215 IBV=.4354    TT=93.78E-9 Vpk=9.1 mfg=Zetex type=Zener
.MODEL BZX84C10/ZTX  D IS=1.132E-15 N=1.030 RS=.11   IKF=1 XTI=3 EG=1.11 CJO=90.62E-12 M=.33   VJ=.6975 FC=.5 BV=10.11 IBV=.3255    TT=108.2E-9 Vpk=10 mfg=Zetex type=Zener
.MODEL BZX84C11/ZTX  D IS=544.3E-18 N=1.011 RS=.14   IKF=1 XTI=3 EG=1.11 CJO=80.82E-12 M=.327  VJ=.7056 FC=.5 BV=11.11 IBV=.3262    TT=122.6E-9 Vpk=11 mfg=Zetex type=Zener
.MODEL BZX84C12/ZTX  D IS=869.1E-18 N=1.02  RS=.12   IKF=1 XTI=3 EG=1.11 CJO=73.83E-12 M=.3306 VJ=.7651 FC=.5 BV=12.1  IBV=.2602    TT=144.3E-9 Vpk=12 mfg=Zetex type=Zener
.MODEL BZX84C13/ZTX  D IS=513.2E-18 N=1.001 RS=.1    IKF=1 XTI=3 EG=1.11 CJO=62.95E-12 M=.3341 VJ=.8633 FC=.5 BV=13.1  IBV=.2164    TT=173.1E-9 Vpk=13 mfg=Zetex type=Zener
.MODEL BZX84C15/ZTX  D IS=1.116E-15 N=1.027 RS=.11   IKF=1 XTI=3 EG=1.11 CJO=56.98E-12 M=.3326 VJ=.803  FC=.5 BV=15.1  IBV=.2165    TT=209.2E-9 Vpk=15 mfg=Zetex type=Zener
.MODEL BZX84C16/ZTX  D IS=556.3E-18 N=1.013 RS=.12   IKF=1 XTI=3 EG=1.11 CJO=52.99E-12 M=.3286 VJ=.7205 FC=.5 BV=16.09 IBV=.1623    TT=187.6E-9 Vpk=16 mfg=Zetex type=Zener
.MODEL BZX84C18/ZTX  D IS=723.9E-18 N=1.02  RS=.13   IKF=1 XTI=3 EG=1.11 CJO=44.99E-12 M=.3353 VJ=.828  FC=.5 BV=18.09 IBV=.1442    TT=281.3E-9 Vpk=18 mfg=Zetex type=Zener
.MODEL BZX84C20/ZTX  D IS=11.83E-15 N=1.08  RS=.09   IKF=1 XTI=3 EG=1.11 CJO=42.64E-12 M=.2707 VJ=.3905 FC=.5 BV=20.08 IBV=.1178    TT=295.8E-9 Vpk=20 mfg=Zetex type=Zener
.MODEL BZX84C22/ZTX  D IS=1.707E-15 N=1.042 RS=.14   IKF=1 XTI=3 EG=1.11 CJO=37.64E-12 M=.3301 VJ=.7799 FC=.5 BV=22.08 IBV=.1179    TT=310.2E-9 Vpk=22 mfg=Zetex type=Zener
.MODEL BZX84C24/ZTX  D IS=1.63E-15  N=1.039 RS=.13   IKF=1 XTI=3 EG=1.11 CJO=35.39E-12 M=.3309 VJ=.7731 FC=.5 BV=24.07 IBV=92.59E-3 TT=303.0E-9 Vpk=24 mfg=Zetex type=Zener
.MODEL BZX84C27/ZTX  D IS=53.96E-15 N=1.136 RS=.0987 IKF=1 XTI=3 EG=1.11 CJO=33.38E-12 M=.3006 VJ=.4245 FC=.5 BV=27.12 IBV=.2024    TT=346.2E-9 Vpk=27 mfg=Zetex type=Zener
.MODEL BZX84C30/ZTX  D IS=2.669E-15 N=1.055 RS=.11   IKF=1 XTI=3 EG=1.11 CJO=30.05E-12 M=.3324 VJ=.7923 FC=.5 BV=30.12 IBV=.2024    TT=461.7E-9 Vpk=30 mfg=Zetex type=Zener
.MODEL BZX84C33/ZTX  D IS=9.428E-15 N=1.099 RS=.12   IKF=1 XTI=3 EG=1.11 CJO=27.62E-12 M=.3268 VJ=.7365 FC=.5 BV=33.12 IBV=.2024    TT=404.0E-9 Vpk=33 mfg=Zetex type=Zener
.MODEL BZX84C36/ZTX  D IS=6.202E-15 N=1.081 RS=.1    IKF=1 XTI=3 EG=1.11 CJO=25.70E-12 M=.3366 VJ=.7798 FC=.5 BV=36.12 IBV=.1799    TT=418.4E-9 Vpk=36 mfg=Zetex type=Zener
.MODEL BZX84C39/ZTX  D IS=7.921E-15 N=1.1   RS=.12   IKF=1 XTI=3 EG=1.11 CJO=23.83E-12 M=.3437 VJ=.7925 FC=.5 BV=39.11 IBV=.1245    TT=634.8E-9 Vpk=39 mfg=Zetex type=Zener
.MODEL BZX84C43/ZTX  D IS=228.7E-15 N=1.22  RS=.11   IKF=1 XTI=3 EG=1.11 CJO=21.92E-12 M=.3415 VJ=.7656 FC=.5 BV=43.1  IBV=.1079    TT=274.1E-9 Vpk=43 mfg=Zetex type=Zener
.MODEL BZX84C47/ZTX  D IS=19.1E-15  N=1.131 RS=.1    IKF=1 XTI=3 EG=1.11 CJO=21.05E-12 M=.35   VJ=.7818 FC=.5 BV=47.1  IBV=95.16E-3 TT=649.2E-9 Vpk=47 mfg=Zetex type=Zener
 

Thread Starter

gdylp2004

Joined Dec 2, 2011
101
Thanks SgWookie!

That is so many Zener diodes! I do appreciate it really.

As you suggested, I've consulted members from the LTspice group @ Yahoo and has learned how to implement the actual ultrafast recovery diode, Schottky diode as well as the IRF640 nMOS subckt model.

However to my unexpectation, my simulated results (see driver.jpg) did not concur with my actual results when I did test in my lab before, that is weird because, I am pretty sure, whatever components in the LTspice was selected exactly to what I've used on the breadboard. Could it be the parasitic effects which cause these differences?

Also, ironically, when I made little changes to the Cout and Rload, to 10μF and 10Ω respectively, I am getting simulations closer to my result, that is, for some whatsoever reason, the circuit now works (see driver2.jpg).

Btw, Merry X'mas!
 

Attachments

SgtWookie

Joined Jul 17, 2007
22,221
Merry Christmas, yourself! :)

That is so many Zener diodes!
It's a pretty good "starter set". :)

I just saw your thread about the diode and MOSFET in the LTSpice group.
New diode:
.MODEL Dmur120rl d
+IS=9.82553e-09 RS=0.0304418 N=1.57716 EG=0.849638
+XTI=0.5 BV=200 IBV=0.000002 CJO=5.37397e-11
+VJ=1.24876 M=0.515449 FC=0.5 TT=1.63843e-08
+KF=0 AF=1
My modifications:
.MODEL MUR120 D(IS=9.82553e-09 RS=0.0304418 N=1.57716 EG=0.849638 XTI=0.5 BV=200 IBV=0.000002 CJO=5.37397e-11 VJ=1.24876 M=0.515449 FC=0.5 TT=1.63843e-08 KF=0 AF=1 Vpk=200 Iave=1.0 mfg=OnSemi type=silicon)

I changed the model name from "Dmur120rl"; removing the leading D and the remainder uppercase; lower case letters can be difficult to read properly; the suffix "rl" was removed because that is specifically for ordering them on a reel instead of bulk or ammopack - the electrical characteristics are the same for all shipping types. Notice that I added "Vpk=200" and "Iave=1.0". Vpk, Iave, mfg, and type are strictly for identification in the selection list. They don't have to be present for the model to work, but it makes finding them by peak voltage/breakdown voltage and type much easier. The mfg is handy in order to indicate where the source of the model was.

Note that Vpk= is not necessarily the exact same as BV=, particularly in the case of Zeners, but it will be close.

You have the STPS3150 in your schematic. I found the following model here:
http://www.ee.siue.edu/~alozows/courses/PowerElectronics/spice/SoftOnMosfet/DIODE_ST_10.lib
.MODEL STPS3150 D
+ IS=1.5063E-6 N=1.6111 RS=6.9175E-3 IKF=98.769E-3 XTI=2 EG=.69 CJO=295.34E-12
+ M=.46994 VJ=.44352 ISR=10.010E-21 NR=4.9950 FC=0.5 TT=0

and changed it to:
.MODEL STPS3150 D (IS=1.5063E-6 N=1.6111 RS=6.9175E-3 IKF=98.769E-3 XTI=2 EG=.69 CJO=295.34E-12 M=.46994 VJ=.44352 ISR=10.010E-21 NR=4.9950 FC=0.5 TT=0 BV=150 Vpk=150 Iave=3.0 mfg=STMicro type=Schottky)
using information from STMicro's datasheet here:
http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/CD00003323.pdf

Note that the average current rating is 3A. I added BV=150 because the model I found didn't have it.

However to my unexpectation, my simulated results (see driver.jpg) did not concur with my actual results when I did test in my lab before, that is weird because, I am pretty sure, whatever components in the LTspice was selected exactly to what I've used on the breadboard. Could it be the parasitic effects which cause these differences?

Also, ironically, when I made little changes to the Cout and Rload, to 10μF and 10Ω respectively, I am getting simulations closer to my result, that is, for some whatsoever reason, the circuit now works (see driver2.jpg).
This is where it helps a great deal to understand the limitations of the model.

Earlier in the thread, you mentioned that you were using a 470uH inductor. I pointed out that in the datasheet at the specified current, the measured uH would be around 200 instead of 470. This is because the inductor was nearing core saturation; it's ability to store additional magnetic energy is quickly getting lower. When the core fully saturates, the inductance drops like a rock; and all there is left is the resistance of the winding, whatever the winding itself's inductance value would be, and other parasitics.

One sneaky way around the limitation of the inductor model could be to use an external resistance to represent the inductors' stated resistance as a current sense circuit, with a voltage controlled switch enabling a much smaller inductance to be placed in parallel with the existing inductor. This makes the plumbing more complex, but it's not horiffic at this stage.
 

SgtWookie

Joined Jul 17, 2007
22,221
Have a look at the attached.

I've added a couple of switches in parallel with the inductor, and have assigned them turn-on voltage levels, and inductances.

I don't show the current thru SW2, as it really ramps up fast. You can try running the model yourself and measuring it.

The current through SW1 really doesn't show what's happening with your real-world inductor, as when the switch trips around 3.3A through R-L1, S1's current is zero, and it takes awhile to build up.

I replaced your fixed resistor load with a constant 2A load; which would be equivalent to 25 Ohms if the output is 50V. The 2A load is constant unless the output is at zero volts; this current source won't keep sinking current once there is 0v across itself.

If you decide to run my model, you will need to replace my IRF640 with yours, and my IR2117 symbol with yours.

For your "real world" circuit, unless you're capturing the first 5mS or so immediately after the buck converter is supplied with power, you aren't seeing what's actually occurring during start-up. The peak currents through the inductor would be quite high; as will the peak output voltage.
 

Attachments

Last edited:

SgtWookie

Joined Jul 17, 2007
22,221
Here, I'm just showing the part about inductor saturation in the attached simulation.

S1 doesn't have much effect in comparison to when S2 kicks in. When saturation occurs, current skyrockets.

Compare that to the plot of a real inductor going into saturation on this page:
http://dos4ever.com/flyback/flyback.html#ind2
Ronald Dekker has created a great resource for hobbyists, students and even professionals that might've forgotten or never known the basics on making your own inductors and testing them.

This is the image I'm referring to:

A real inductor at saturation.

The inductors in LTSpice are ideal; as if they were air core inductors; air core inductors don't saturate, but it takes a heck of a lot more wire to get the same inductance.

Hope this helps you understand what's going on more.
 

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gdylp2004

Joined Dec 2, 2011
101
Thank you.

If I am not wrong, your intention to include those 2 switches is to simulate a more realistic inductor as when the inductor current ramps up to a "bending" point, the point which indicates the inductance starts to veer off, you close one switch to lower the effective L, and closes the 2nd switch, hence further lowering the effective L till a point where it no longer further saturates. Inductance in parallel is being calculated the same way as getting the effective resistance in parallel.

And to model an as accurate as possible inductor used in my circuit, I would need to perform Ronald Dekker's inductor test to obtain the current vs. inductance profile and adjust SW1 & 2 accordingly. Or perhaps I should just use a RLC meter so that I could measure the Effective Series Resistance (ESR) and check if it is current dependent as well?

Also, I do not understand why do you short the o/p terminal together in your last simulation in attempt to show me saturation effect of an inductor.

Thanks.
 
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SgtWookie

Joined Jul 17, 2007
22,221
Thank you.

If I am not wrong, your intention to include those 2 switches is to simulate a more realistic inductor as when the inductor current ramps up to a "bending" point, the point which indicates the inductance starts to veer off, you close one switch to lower the effective L, and closes the 2nd switch, hence further lowering the effective L till a point where it no longer further saturates.
You got it right, up to the point where you said "...lowering the effective L till a point where it no longer further saturates. "

The whole point of having the switches in there is an attempt to simulate the saturation of a single inductor. Now, this is not an ideal solution, as the current through L1 continues to increase at the same rate and storing the additional energy; you can get an idea of that by the difference in the plots of I(L1) and I(R_L1). However, it's still a considerable improvement in the model over a single inductor.

I'm attaching two simulations that are very similar modeled on Ronald Dekkers' inductor test bench with a couple of modifications.

The 1st attachment only has S2 in parallel with L1, the 15uH inductor gets switched in when the current is about 3.59 Amperes. The two inductors in parallel means that the total inductance will be less than 15uH. You can see how sharply the current increases.

The 2nd attachment has both S1 and S2 in parallel with L1. You can see how the current increase is much more gradual in this simulation. S1 and L1 being in parallel works out to be about 203uH. I'm not certain which model would be more accurate for your inductor; as data is only given at two points. You'll notice that there is a marked difference in the greatest current flows.

Inductance in parallel is being calculated the same way as getting the effective resistance in parallel.
Yes.

And to model an as accurate as possible inductor used in my circuit, I would need to perform Ronald Dekker's inductor test to obtain the current vs. inductance profile and adjust SW1 & 2 accordingly.
If you want to get the actual profile, then yes. As I mentioned above, I don't know exactly what your curve will look like, but it will probably look something close to one of the two simulations.

Or perhaps I should just use a RLC meter so that I could measure if the Effective Series Resistance (ESR) is current dependent as well?
You won't be able to determine the inductance at a given current though. That's what you need to find out; inductance vs current.

Also, I do not understand why do you short the o/p terminal together in your last simulation in attempt to show me saturation effect of an inductor.
I was lazy and just left those other items in there. Had I known it would cause you confusion, I would have deleted them and left just a ground symbol. That area was no longer the output; it was ground.
 

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gdylp2004

Joined Dec 2, 2011
101
Thanks SgtWookie.

I've research some basic linear regulators to power up my IR2117 gate driver and has come across 2 basic topologies. The series and shunt linear regulator as found in http://en.wikipedia.org/wiki/Linear_regulator & http://www.tpub.com/neets/book7/27k.htm.

It is said that the series linear regulator is favored over the shunt version as it is usually more efficient than the other.

I've used both methods i) a current probe and ii) measure the p.d. across the newly added 1Ω resistor (Rsense) in series with Vcc and the driver and realise that both methods could not measure the current for an unknown reason, most probably the current is too small to display on the o-scope.

But this is not critical because in the end, I've used a DMM and found that the Icc(avg) is about 41mA. This 41mA would be the current rating of my load when designed a suitable linear regulator.

As seen in attached, I've used LTspice and successfully simulated 2 topologies (Starting to love LTspice :D).

I've slowly adjusted and fine tuned the R1 & R2 respectively and realised that the main culprits for wasting power in the shunt and series regulator are R2 & Q1 respectively, in about the range of (3.6-4W), about 4% in a 100W system!

Although I've searched there are off-the-shelve IC for linear regulator with very high efficiency, are there any other topology which may happens to be a little more efficient than the 2 mentioned, or we could only further improve on the series regulator.

Hope to have some hints over here, so I could proceed with my own research and readings in the right direction.

Thanks in advance.
 

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