SMPS

Introduction The world of digitally controlled switchmode power supplies has always held a certain allure for me: the idea that you could sample things like output voltage and current, apply some DSP techniques, and then based on that output a gate drive signal in real time, giving you whatever response you want out of your buck/boost converter just seems so… insanely cool. That being said, a lot of times these require a good understanding of the control loop architecture and parameters of switchmode power supplies to be able to properly stabilize, which has proven to be quite the barrier to entry....

Yes, I was a lot more naive than I thought when I first dove into this project. Unsurprisingly, there is a lot that could go wrong with a boost converter if you try to implement one from scratch. In this article, I’m going to discuss a few of the main gotchas that really shattered my initial expectations. Inductor Saturation After the success of the kinda terrible boost converter back in chapter 3, I thought it’d be cool to aim higher and actually try to design something in a more proper fashion, i....

The good, and perhaps bad, thing about passions and hobbies is that the energy to zealously pursue them ebbs and flows as the days, weeks, months or even years go past. Just recently, I experienced a strangely strong desire to just go out there and design something again out of frusration over what we’re “learning” at university, so here we are. Preface: Why LCSC Because DigiKey/Farnell/RS wouldn’t give me free shipping until I spent tonnes of cash, and even then, the VAT here in the UK is just crazy… It’s times like this when I really, really miss being in Malaysia....

Background As I have only recently come to realize, inductor selection for boost converters is not a trivial matter at all. Every inductor I tried saturated way too early, causing progress for the SMPS Chronicles Boost Converter project to grind to a halt. After many frustrating afternoons, and several blown parts and melted breadboard holes, I had enough. Inspired by this video on the RF Man YouTube channel (really nice channel by the way), I decided to build a dedicated jig that would allow me to easily measure the saturation current of the any inductor that I was about to use....

The inspiration for this series of articles came from Microchip’s TB3103 and TB3104 , which outlined the implementation of current mode controlled buck and boost converters using the PIC16F753’s internal analog peripherals, which include an operational amplifier, a comparator, PWM, etc. As a hobbyist, I’ve always found stuff like transfer functions, bode plots (the more complex ones), and SPICE to be really intimidating. I am aware of what these are, and why they are used in circuit design, but I’ve never really sat down and worked with them before, much less explore their nitty gritty details....

The entire point of SMPS’s is that they are efficient. That, compounded with the fact that I started this experiment with the aim to better understand the design principles behind switchmode power supplies, meant that I couldn’t resist taking a few basic measurements to assign some numbers to the (very crappy) boost converter from chapter 2 . I was going to build it out on a piece of perfboard first to reduce breadboard parasitics and to make sure that the intermittent connection issues I was having with my breadboard weren’t going to cause any issues down the line....

With the addition of these 3 components, I had a fully functional boost converter! However, it is not without its (huge) caveats, and let’s just say that along the way, Murphy has paid me many, many visits. In Chapter 1 , we talked about the sawtooth generator, which connects directly to the an opamp responsible for generating a PWM gate drive signal. So, I thought it made sense to take a closer look at that next....