In a recent video, I Took a look at this little oil atomizer and as part of the package it came with a classic car USB charger type power supply and I thought let's reverse engineer this as well and it turned out to be really interesting. It's something that I've looked at before but never quite realized the significance of the chip which is very very interesting. So I've taken some pictures so we can jump straight into the action here and I shall Zoom down this and focus down onto it so we can get a nice good look at the circuitry. so in one save it we have put that there the USB output socket for the device that's being charged.

This is rated 700 milliamps. I Wouldn't recommend going much higher. Definitely don't plug your super duper big expensive iPhone or Android or tablet in because this chip is notable for an undesirable Theory mode which could blow up your phone. However, there's a LED in output to indicate when the unit is powered, but that's actually on the 12 volt side.

There's two capacitors and there's an inductor. This is the input capacitor 12 volt in Supply communion. This is the 5 volt output capacitor and this little inductor here is used to actually help it drop the voltage from 12 to 5 volts in a post manner. Let me bring in the other side of the circuit board we have the magic chip.

Now this has got a mortal number Mc34063, but the odd thing is it's manufactured by on. but Texas Instruments also make them. That's because this is a very, very, old chip in the same way. The 555 timer chip is a huge history, so is this.

It's such a useful power supply chip with just a selection of building blocks like Lego that this dates back to 1983 and it's still going stronger, still being manufactured and used in many products. So the incoming supplied to the circuit has this one Ohm resistor which is used as a fuse and also it will help in limit in Rush current. There is a provision on the circuit board for a mystery diode which basically goes between the positive and the negative connections and that's presumably to suppress reverse voltage glitches that might happen due to strange uh things like inductive loads being switched on the Um on the car, particularly when you turn the ignition on this, it can result in quite spiky, glitchy power wheels. For a while, we've got the incoming capacitor here, we've got uh, the inductor and I have diode that's used to increase the efficiency of this circuit greatly, and we've got the five volt capacitor here.

We've got the connector pins here, we've got a little timing capacitor for the chip, and we've got a feedback uh, voltage divider that gives a signal back to the chip to tell it when the output has reached 5 volts. And it's worth mentioning that by modifying these resistor values, you can adapt these little things to put out three volts or nine volts or various voltages not necessarily on a USB port right enough and other things. We've got a resistor here for the LED and then we've got the a 0.22 Ohm resistor, which is used for current sensing as part of the way the circuit operates. It's worth mentioning that these little programming resistors for the data pins that can set voltage levels aren't in place and they've also drilled these holes very big so the middle pins aren't used which is good in a way because um, this thing is a very low current device and it's notable this chip does not have thermal protection in one of its failure modes is that if you overload it to the point that it really gets baked I Think modern chips do have some current limiting facility, but it can go short circuit and if it does that, you'll end up with 12 volts finding its way out through to the five volt side, which is not a good thing for your electronic stuff.

Here is the schematic and then I'll show you the building blocks of this unit because uh, it does have a a very modular construction which makes it, which is why it's still about, which is why it's still a famous little trip I'm going to get closer. So here's the incoming Supply It's 12 volts. It can actually go up to 24 volts. And because this is a 35 volt 22 magnified capacitor, 24 volts is perfectly viable.

This chip is capable of coming up to I Think a maximum about 40 volts though I wouldn't really push it that far. We've got the one Ohm resistor here which has been used as the fuse and an English limiter. We've got the smoothing capacitor. We've got the 3k3 resistor in series the LED So it lights at fairly low current and just to indicate units on, they've done it in the 12 volt sign.

So the 5 volt side. Because it means that it's not taking away valuable regulated current available from that side, it's just better to use In the 12 volt side, there is the current sense resistor being switched through to the coil and in operation. What this unit does is here's the output capacitor. Here, It switches the 12 volt rail very briefly down through that resistor and through this inductor.

The inductor will push back against the current flow as it tries to build up a magnetic field and uh, when it's the field is risen up to a certain level either. I'm not sure if it's purely the timing capacitor times the on and off cycle or if it's purely cuts out on the over current, but when it detects the current is reached a certain level as dictated by the magnetic field reaching the pointer that just can't build up any more magnetic field to push back the current, the voltage across this will be sensed to. should the current has reached a high level and then the circuit will turn off. Now in the process of building the metric field in this inductor, it was trickle charging this capacitor, but now because this end was positive and this end was negative, the magnetic field collapses and this angle is positive and this angle is negative and finds a path to charge that capacitor via this diode.

So it doesn't just charge capacitor during the building automatic field when it's on, but also when it's collapsing and it makes it more efficient. And it does this in a series of pulses until the voltage at the output reaches a level that this potential divider will provide a feedback voltage of 1.2 volt, 1.25 volts as a threshold and at that point it goes into standby until it sees the voltage drop and then it boosts that capacitor up again and that is it. So bizarre Motorola Chip uh manufactured by on in Texas Instruments just because of that strange history. Now let me show you the block diagram of this new realized by.

It's a versatile because it's not just is this fitting in or do I have to zoom out a little bit like no, that's pretty good. That is pretty good. This isn't just a buck regulator, this can also be used as a boost regulator to boost the voltage off as well because inside it's not just a single purpose device. it's got these modules that could potentially find other uses.

So here is the 1.25 volt reference and it provides that to the Op Amp the comparator in this instance which Compares it to the voltage being measured by the potential divider across the output capacitor and when that reaches the 1.25 volts, the output of this changes state and it toggles this Um output driver on and off. The output driver is pulsed by the oscillator which has that timing capacitor but also has that current sensing circuit does it if you if it never reached that current sensing level, would it automatically keep oscillating at a fixed frequency? or does it basically use a capacitor as a timer to turn it on and then use the current sensing to turn it off? Not really sure I should really look into that more. but there's the output stage with two transistors. I think they're they're using the two transistors like this.

Because of its versatility, it opens up the possibility use it for other functions. And there there there's the Uh inductor limited current to the capacitor and uh, it's also got that little diode also going to the zero Volt or ground reel which Uh allows it to uh take the energy Booth When this has been charged and also discharged, the magnetic field has been built and then collapsed. Very neat little circuit, very functional. It's nice when you find these old integrated circuits in the past and they've got Uh.

Such useful functionality from the time. Like the 555 it's It's a timer chip with building blocks and it is used extensively in modern products because it's just a useful little Lego chip. Well, in the same way, the 555 is a useful voltage threshold and timer chip. The Mc34063, it turns out is a really useful power supply chip and creeps into many many applications.

Just keep in mind though, don't uh try and charge expensive devices from these little tiny plug-in chargers. They are usually only rated for low current, which makes them perfect for charging head torches, but they only need about 500 milliamp charge current or devices like this that Escort oil into the air of your car. Not sure why I'd want to do that, but um, as long as you keep the current low with these, it's absolutely fine. I Would guess that uh, if you plugged an Android phone into, do what many of them do and it would gradually creep the current top from a low level until it's still the voltage drop and then it would nudge back so it probably wouldn't overload it in that sense, but it's not worth the risk.

These are Best Kept only for powering small items. but there we go. What turned out is a simple teardown ended up being a bit of a history lesson in this. uh, 1980 was it 1983? This chip came out.

That's an amazing bit of History.