And let's take a look at the Motor Roller slash ON Semiconductor sorry still keeps calling the Motorola every time I see the old Motor Roller prefix of MC but the MC 34264 uh 262 sorry power factor uh controller it's just an 8 Pin dip package comes Ino as well. It's got a Uh 2% internal band Gap reference, zeroc current detectors, uh, quadrant multipliers, and uh, various other stuff. So let's take a look at the Uh internal simplified block diagram here. as you can see not a huge amount of Uh circuitry in there.

There's an internal Uh band Gap voltage reference that's an over voltage comparison comparator which comes from the Uh voltage feedback which goes into an error amplifier. There's a compensation pin pin uh, the input from the multiplier is here. there's the output uh driver and there's a current sense uh input as well with the zero current detect input because it has to uh s it has to uh know when there's zero current and we'll take a look at that and there's a Power Pin and that's pretty much it. There's not much else, but we'll see if we scroll down here and we go to typical configurations we can actually have a look at.

um, it's well worth uh reading this. it's got introdu and how a power factor correction system actually works and we'll have a look at what happens if you don't have a power factor correction circuit. uh, you've got the basic Uh AC uh Mains coming in here full wave Bridge rectifier as we saw in the schematic. and if the power factor correction Uh, circuitry wasn't there, you got the bulk storage capacitor.

So Fullwave Bridge rectifier straight into the Um storage capacitor generating a high voltage DC which then goes into your Uh DC Todc converter which then Powers your load. Now the problem with that is that looking at the waveforms here, you can see the AC Uh line waveform here, which is the dashed, the outer dashed one there. that's the ideal, the 50 HZ or 60 HZ Mains input. and because uh, you, the energy is stored in the bulk capacitors here.

the voltage Peak you're only going to draw um, a current Spike So this waveform here this spiky one here is the current uh drawn during the peak period of the waveform and that's quite. It's going to be a large current draw, so you're actually going to drag down the line voltage the Main's voltage just a little bit and it's going to Sag as they say as they call there they call that line sag and so you're going to get these current pulses at the positive and negative Peaks at the main input and that's not very good at all for Uh for getting a power factor correction of one. And in fact, they tell you here that this configuration can give you uh, commonly a power factor ratio of 0.5 to7 and that's not great at all now. I Don't think this is the place to actually get into a detailed discussion on uh, how a Power Factor Correction Preon converter Works a current mode one like we've got here.

If you want to, uh, get the details of this, by all means, download the data sheet. it'll be linked in um in the Uh notes there. So, but this is basically um, what we've got. We've added a PFC Power Factor Correction Preon converter between the bridge rectifier and the bulk storage capacitor we had before, and the rest of you can DC to DC converters all the same.

And of course, you got the high frequency bypass capacitor in here. and you would have noted that on the Uh on the schematic for this um, Uh model as well. But we're looking at the MC 34362 Power Factor Correction Preon converter and there's basically series inductor here with a mosfet uh, pulling that down to ground and an output diode and you'll note that that is, basically um, a boost converter. That's basically that's exactly the same configuration um, as you get for a boost DC Todc converter.

but the whole basic concept of it is it's going to uh, switch the mosfet down here so that you get a half sinus soidal, um, average, uh current. basically. uh, drawn from your inductor current. So that's a series induct series current through your inductor.

You're going to have these Peak values, but they're going to average out and smooth out, um, over your AC Mains or half of your AC Mains waveform like that. So instead of having just one big spike here like you would get without uh, this power factor correction circuit in here, you get multiple spikes spread out over half of the sinusoidal waveform and that's and that averages out and then include and that improves your power factor. Uh, correction. And if you take a look at the rest of it here, it tells you all about the different functional block diagrams inside the device.

and I Highly recommend. Uh you. It makes for some great bedtime reading. Got the error amplifier, the multiplier which is pretty much the key to how it all works over voltage, comparative, zero current detectors, current sets, compara latch how it all works, and uh, it's great stuff.

I Highly recommend it And bingo down here. We've got our design equations and uh, there's a whole bunch of them down here and well, you might have, um, seen, uh, me, go through similar equations like this before for right? DC to DC converter uh devices And the problem. One of the problems with uh, this is that, uh, let's say you're trying to calculate the required uh, well, you know you want it. Wants to know the required converter output power? Well, what is that? Because this is a generic bench power supply, the the user could be taken anywhere from zero output power right up to the maximum 600 watts or so.

So um, really, uh, these values are going to be all over the shop and you have to um design and do various tradeoffs for various Um output, uh, powers and things like that. So um, maybe you would take it, you know, at the maximum output power, but you'd have to go through the formulas to see how much uh, your power factor and other things traded off at lower Uh output. Powers So um, you would have to go through the formulas. Be my guest.

Great stuff to do at bed time. I Love it! And uh, how? the internal block diagram and the basic Um application circuit is down here. there's the mosfet. there's the Uh Transformer exactly how we see it there.

and uh, here's a typical table of some power factor controller test data and we've got power factors of 0.999 down to 0.996 so it's going to be pretty close to one. So these things work pretty well. and if you take a brief look at the application circuit here, you can see the main inductor T here. but it's actually a Transformer because it's got a secondary winding here that goes down to ground.

and that uh Taps effectively allows you to tap off the Uh output, read the output current, and that's exactly what happens on Pin five here, which detects uh, zero output current. Pin Eight is the VCC Uh pin, so it just filters that there and Powers the actual device and Pin three down here is our multiplier. uh input and you'll notice the uh, it's just a voltage divider here from the directly from the uh, uh, I ified Main's input. So that's reading.

That's going to be reading the the harmonics off there that come from the full wave Bridge rectifier and that goes in to the multiplier and the rest of the device. And there's our output driver which drives the mosfet which pulls that down to ground once again through a current sense resistor there. So um, that's basically all there is to it and we see that uh got some typical waveforms here, which is quite nice and uh, if you want to, uh, take a look. Typical test things: error amplifiers, error output comp Ah, current waveform Spike suppression all sorts of things.

Highly recommend you. Uh, download this. Oh, look at the old school layout. look at the old school taped layout there I Love that brilliant gez that' be home anywhere in the 1970s, but it can't really be that old.

Nobody care cared about power factor correction back in the 70s did they? except for huge, uh, maybe big, uh, industrial stuff or things like that? Certainly not at the Uh bench. uh, Power Supply Lab power Supply level I Don't think anyway? Um I Highly recommend you. Uh, download this data sheet and uh, uh, you know, print it out and uh, have some good bedtime reading. It's most interesting.