In last month's blog, I called into question the need for current mode control, given the availability of fast digital voltage mode control. Outrageous? I don't think so - digital power supply control will impact many of the accepted standards in our industry. This in turn gives rise to yet another dynamic: more sophisticated control strategies will enable innovation in power supply topologies, so the ultimate beneficiary of digital control is the switch mode drive train itself! This is a major paradigm shift - the combination of advanced control methods and novel power stage designs will spawn an entire new breed of power supplies that redefine state-of-the-art performance benchmarks.
Doubtful? Consider this: switch mode topology evolution has been largely stagnate for some time " we have our "standard" topologies like full-bridge, two-switch forward, flyback and so on. Do these basic architectures represent the technological limit of what is possible in power supply architecture?? I think not " certainly more sophisticated topologies are possible but mandate a level of control sophistication too complex to implement with op amps. With digital control, simple inner/outer loop control strategies evolve into more elaborate multiple loop architectures with each loop optimizing specific system parameters (look ma, no error amp!). New magnetics technologies use complex, digitally generated switching algorithms. Advanced compensation strategies supplant static pole/zero techniques in favor of nonlinear Z-domain strategies that optimize supply response at every value of line and load! Sounds like good fodder for drive train innovation to me.
So let's connect the dots: as drive train technology leverages the full capabilities of digital control, system control implementation moves further out of the reach of analog control. In the end, digital control does to analog switching supplies what DVD did to VHSwhat CDs did to audio cassettes..what digital photography did to film cameraswhat digital fuel injection did to carburetors.
You say you don't think so? Well, I'd love to hear your point of view " please get on your analog computer and shoot me an email.
Don is Director of Applications Engineering for Silicon Labs and you can reach him at Don Alfano.