You can use this dinosaur also for high power boost and buck converters. The open driver collector and the open output collector and emitter allow the use of external low- or high-side drivers together with this device. You can connect the output emitter to ground and short the driver and output collectors and connect them across a resistor to a dc voltage of 12 V, which is also the operating voltage of the low- or high-side drivers. In this way it is possible to operate high-power MOSFETs for several 100 A of channel current. So, I have used the MC34063 as the controller for a boost converter which generates the power for a battery operated welding device of maximal 200 A at 30 V out of a Li-Ion battery with 22.6 V 100 Ah. The total input capacity of the power MOSFETs of 30 nF was operated with a MIC4420 low-side driver, which is capable to deliver a gate current of 6 A. The disadvantage of the MC34063 is its current limit detection differential voltage of 300 mV. So my shunt resistor is dissipating a maximum heat of 70 W, which is about half of the total loss of the power semiconductors (MOSFETs and Schottky diodes). But the efficiency is still well above 95%.
Great work in presenting this dc-dc buck converter. A couple of points for improvement that would have helped newbies. 1. Show conventional current flow rather than electron flow. I.e. conventional current flows from +ve battery to -ve battery terminals in the circuit. This also means the arrow heads in transistor's and diode will conduct with conventional current in that direction as well ( forward biased ). 2. After allowing current to build up in the series inductor and the switch opens the collapsing flux in the inductor causes the conventional current to keep flowing in the SAME direction as before the switch opened. The polarity of the inductor reverses to attempt to keep the current flowing in the SAME direction. The buck diode becomes forward biased as a result transfering the stored energy plus battery energy to the output filter capacitor. 3. With all the noise and switching transients it will be impossible to reliably trigger your DSO and get a stable trace. Best way to handle this is to simply stop the display acquisition and observe that single capture, start DSO capture again and then stop again to see if anything has radically changed. With acquisition stopped you can also scroll back and forward in time to see changes too. Hope this helps.
Hello Barry, Good points for 2 and 3. I use electron flow because this is typically what the technician is taught and they were the primary focus of the channel. Thanks for watching and the feedback.
Many times the 34063 is used in automotive 12V step-down converters. It is versatile in that it can control step-up, step-down and regulation at or near the supply voltage, iirc. sometimes referred to as buck-boost.
The wire diameter for the inductor should be selected according the maximum current you use in the inductor, which is not the average current at the output but the peak current where the detector switches off. At higher frequencies you also need to take the skin effekt into account. So sometimes it is preferred to use a bi- or multifilar winding.
Hi Kevin, that's because of mainly two things, the most important beeing the efficiency of DC-DC converters(80% or more) and the second which again depends on the first, beeing the total size of your circuit, transformer included. For example compare the size of old phone brick addapters to the ones that we have now. A lot smaller and a lot lighter too.
