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Analog vs. Digital: The Power Struggle Continues!

Editor: This is a guest blog By Jeff Rodriguez, VP of engineering services, XP Power. I love the part about analog still being king. Yes!

If you are a power supply design engineer or an EE or ASE who selects power solutions for your end-system, then there is no doubt you have stood at the crossroads and pondered the dilemma of whether to go analog or digital with your power train. The good news is we find that the actual answer lies somewhere in the middle… borrowing the best aspects of both approaches.

Power supplies are making their way up the food chain as a primary consideration when designing a new system. Historically, a power applications engineer used to spend most of his or her time trying to figure out how to fit the system power into the “afterthought” mechanical space left by the design team.

Today we find system engineers depending on the power supply to do more than just provide analog-world attributes of conversion, conditioning, and protection. Supplies are now expected to handle power management as well. System engineers want to be able to communicate with the power supply, to get real time information, and to control the power supply entering the digital realm.

Monitoring of real time information such as voltage levels, current levels, faults, alarms, and time-based logging of that information gives a systems engineer the ability to maximize system run-time through predictive failure analysis and to minimize downtime by having more data to offer a repair engineer. Controlling supply translates into being able to turn outputs on and off in a fixed sequence and in timing, changing output parameters such as voltage and current, and optimizing cooling fan speeds for noise minimization and fan life.

Although the monitoring and control can be achieved through analog means, we find that going to our digital tool bag is often a more practical in terms of design, support, implementation, and long-term management of the power system. When you start to consider signals and control in multiple domains, such as level and time, and optimizing those domains to meet your specific needs, you can see that changing firmware is much more manageable than dialing in resistor values during initial system evolution.

Digital management literally allows for a vendor to email you a new file for upload to the monitoring and control chip to see if your new configuration works. If not, go right back to the old configuration and create another one. No change to hardware means faster integration and lower cost of integration.

The dawn of digital in power supplies initially focuses on the PWM and the main switching control of the supply. Although being able to digitally change and monitor critical core parameters of the supply seemed appealing at first, we have found that the benefits that come with a digital “heart,” in most cases, are not justified when weighed against the complications associated with a DSP design.

Analog is still king when it comes to the core power conversion. It’s tried and true, trusted in the industry, and more readily available. It has shorter design cycles and fewer bugs when it comes to new product releases. We also want some of the benefits we discovered on our digital design journey, so we have held on to those, but on a secondary level of monitoring and control. The root alarm and control circuits are analog, but the interface to those circuits is filtered through a digital layer that gives us the best of both worlds.

There may be a time where DSP becomes the norm. For now, analog is going to be around for a while, while living in harmony with the digital benefits that power management systems are begging for in today’s marketplace.

Editor: What do you think about analog vs. digital as the problem relates to power?

8 comments on “Analog vs. Digital: The Power Struggle Continues!

  1. Victor Lorenzo
    May 9, 2014

    Hi Steve, thanks for bringing this guest block. It is very interesting.

    I totaly agree on “borrowing the best aspects of both approaches”. We need to be open minded and creative. With present days SoCs, especially with 32 bit Cortex M3 and M4 devices, we can integrate many functional and power management blocks that not so long ago required tenths of components and chips. We still need to excersice our analog designer skills for the power management and communications parts thought using C/C++ for programming the CPU.

  2. samicksha
    May 13, 2014

    We still count on Analog as signal processing can be done in real time and consumes less bandwidth, parallely Digital do not gurantee any such processing.

  3. Netcrawl
    May 13, 2014

    @samicksha Digital provides real-time, precisely optimized power conversion utilizing advanced algorithms, and I believe that when we the overall design costs are taken into consideration, digital has the potential to cut these costs significantly.  

    Analog implementations comes with hidden costs and some limitations- the fixed circuit based on the previous works cannot be implemented “as is” for a new designs, it will simply require new layout or board. In digital its quite easy, design can be easily cut and pasted from one board to another, chnages can be quickly implemented through software or GUI.   

  4. Netcrawl
    May 13, 2014

    @Victor For some analog still the best option but if we consider today's complex and difficult to support sockets(FPGA), I think digital has the potential and incredible value, and should be the first one that you take to implement this technology, and that the perception that digital is expensive is just a myth.  

  5. samicksha
    May 14, 2014

    I agree you about using Digital can reduce or cut cost but not sure about real time. Have you ever experianced any device or application.

  6. Victor Lorenzo
    May 14, 2014

    @Netcrawl (…)and that the perception that digital is expensive is just a myth .

    It is very dependent on the application, but those TinyAVR and CortexM0+ devices around there, some of them with sub-1$ price, are just great for many low cost applications.

    Now we have very powerful sub-2$ Cortex M3/M4 devices too.

  7. samicksha
    May 15, 2014

    @Netcrawl: I guess there is no guarantee that digital signal processing can be done in real time .

  8. RedDerek
    May 16, 2014

    Thinking back, I believe Intel started referencing digital into power supplies with the microprocessor core requiring a tweak of the core supply voltage to optimize performance. Newer supply configurations for microprocessor cores not only involve multi-phases, but also the ability of the processor to change the output voltage on the fly (typically in the range from 1.2V down to 0.8V). This way the processor can operate efficiently at different speeds under different modes in order to operate more efficiently for both processing power and power efficiency.

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