I am working on a new power converter, which will likely see significant sales into China. Similar designs by my company have a history of being cloned by entities in that region. To mitigate this, I'm considering ways of obfuscating my design. Code protection on my microprocessor, outer-layer power planes, and blind vias all come to mind as possibilities. Are these reasonable means to my end? Are there others I should consider?
The easiest way is (if possible in your situation) is to get a custom IC made that contains some logic integral to your product. This alone will not assure that it will not be reverse-engineered (IC's are decapped and analyzed all the time, of course), but it's something that would work.
I would recommend the method suggested in another answer to seal the thing in epoxy (like how the commodore 64 and VIC-20 PSU's worked) but those were known for overheating and exploding and catching fire and a lot of other fun stuff. If you are using a switching voltage regulator or similar, this might still be okay. JUST NO LINEAR REGULATORS.
wash the markings off of IC's. I would like to say that this behavior ticks me off as a hobbyist, but I understand it from the other perspective as well. So do what you think is best.
If your product contains program code stored on a Mask ROM, EPROM, or similar, or if it contains basically any IC logic at all, see if you can get an ASIC chip made (I'm assuming you know this, but i will elaborate anyway for other readers: Application Specific Integrated Circuit). These are essentially custom manufactured IC's that for various reasons, cost or otherwise, are cheaper or better than standard equivalent chips. These could have different pinouts or voltage ratings or whatever. This makes the reverse engineers spend more time just trying to read the code out of the chip!
If you are designing a chip, go ahead and make all kinds of vias to nowhere and so on, since it doesn't cost a penny more to add more crap to the dye. You could even draw doodles on the inside if you wanted to go overboard with it (and if it isn't military grade equipment or something).
Nothing can totally stop dedicated reverse-engineers. But it may be possible to deter them until the product is no longer profitable.
A power converter does not sound like there is much to protect. Frankly, code protection (while I would not suggest leaving it out) is not much of a disincentive to copy. It can be reverse engineered or (more likely) broken quite cheaply by technical means (don't ask). You could consider embedding an "Easter Egg" that would give you an easy indication of copyright infringement as opposed to reverse engineering.
The other things you suggest may slow down someone a bit, but once the decision to clone has been made, I don't think you'll get very much relief from that. As Olin says, most things you can do increase your cost without increasing value to your end user, and give the cloner another advantage. If the product is at all successful, there will be imitators. Even if it isn't there might be.
Frankly, I think your best bet is to use non-engineering methods such as IP protection. Some of the folks I have worked with (PRD area) have recently had decent results in stopping cloning of their products using legal technology. It may help that they employ reasonable numbers of locals in their factories (low thousands). While the remedies are not large amounts of money by Western standards, I know of cases where equipment and product has been seized. You do have to file the appropriate patents and engage a local legal firm (and possibly private investigators) to get this to happen. On the plus side, a legal "dream team" is not impossibly expensive. You may also be able to stop entry of infringing products at your borders, depending on the country, type of protection, etc.
I remember a poor Belgian fellow freaking out at a trade show because his Chinese contract manufacturer was displaying "his" proprietary SMPS design for sale to any takers (okay, they said it was "a bit different"). I was similarly upset when my really special design (sort of a Kelvin-Varley thing they thought was impossible to make, but I showed them how) showed up in a printed catalog from the component manufacturer. Fortunately, they had no clue whatsoever as to the application, so I doubt it caused much harm. Things are ummm different there.
It's all about how much trouble you want to go through for what level of protection. Someone with enough determination and funding will be able to reverse-engineer your product no matter what you do. Therefore, talk of preventing cloning doesn't make sense, only how much trouble you want to make someone go thru to clone it, and how much extra product cost you can afford to still have a product anyone wants to buy.
Processor code protection is pretty much a no-brainer since it's cheap and easy and reasonably effective. Outer layer planes with blind vias starts to drive your price up. Only you can say how much that's worth. Remember, it's not worth anything to your customers, who will be forced to pay for these measures.
If the volumes are high, you can get IC manufacturers to do custom labels for you without much additional cost per part.
Just a few thoughts
Wash the markings from the ICs. Some IC vendors can produce ICs with your custom markings, which only you can interpret.
Magnetics are hard to reverse-engineer. Obfuscate those. Unfortunately, I don't have concrete recipes for obfuscating magnetics.
Potting the board with epoxy. It may or may not be possible to pot the whole power converter, because of heat dissipation. If there is a separate controller board, you could pot that. Potting adds to cost.
Blind vias would increase the cost of your PCBs, which may or may not be practical, depending on the nature of the device.
I have seen boards with outer power planes that were easy to decipher by looking at an X-ray of the board. An X-ray provides a gray scale image where more layers are darker. Perhaps you can do something clever by accounting for this.
Removing potting compounds is done with nasty chemicals such as methylene chloride. According to the safety sheet, this reacts with some common materials.
You could remark the parts with incorrect but plausible part numbers, provide misleading service manuals, and cite coverage by patents on non-working circuits.
You could design and brand your own unique parts, most easily with an OTP part. Also offer them for sale through a gray-market distributor, and don't provide a data sheet. These parts should have no usage other than cloning your design. Design for intermittent operation or fast wear-out in the for-sale version.