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Digital Power: Is Its Time Finally Here?

I've had the opportunity to lay my hands on power management devices classified as “digital controllers.” The opportunity came when I worked at Intersil. I regularly get press releases touting new digital controllers. My reaction is generally, “Great, another one; so what?” I react that way because, in my experience, these devices never got much traction.

I knew they were good products — well engineered and would work as advertised. But they were a hard sell. I talked to a lot of engineers about the previous generation parts. Some of the guys with whom I spoke, I'd known for 10 years, so I knew what they knew and vice-versa. But even with that audience, the reaction was usually “Meh — nice part, but what we have now is fine. I don't want to take the time to learn to use something new.”

With this new part that I'm looking at as I write this (the ZL8800), I think someone has finally got not just the technology right, but the user interface, too. The part is a dual channel, dual phase controller. The first thing to remember is that it's a controller , intended to have external power FETs attached. So you'd use this for power supplies that were sufficiently high power that external (big) FETs were needed.

Dual channel/dual phase means that you can use this part in one of two ways. You can build either two separate switchers, as shown in Figure 1:

Figure 1

Two independent switchers with one controller (Source: Intersil)

Two independent switchers with one controller
(Source: Intersil)

Or you can build a single power supply whose switching elements are operating 180° out of phase; that reduces ripple in the output voltage. That circuit is shown in Figure 2:

Figure 2

A two-phase switcher (Source: Intersil)

A two-phase switcher
(Source: Intersil)

These are both simplified schematics of course, but the actual circuitry is not much more complex. There are no external components needed for compensation. That's taken care of via the digital control loop. The control loop produces very fast transient response and reduces the size of the output filter caps that you'd expect to need.

To design a power supply system, you use the software provided by Intersil. It has an easy to learn and use GUI that lets you drag and drop blocks representing as many supplies as you need. Then you can interconnect them and specify sequencing. You can use the same software to monitor the supplies in operation. Typical parameters that you would likely monitor are input voltage and current, output voltage and current, switching frequency, the duty cycle of the power FETs, and operating temperature.

The simplified schematics from Figures 1 and 2, above, can be compared to the actual circuitry that you can see on one of the Eval boards. It's not much more complex. There is some extra circuitry on the Eval board, but it's there to make testing easier. A production version of the circuitry would take up far less real estate than what you see represented in Figure 3.

Figure 3

ZL8800 Eval board (Source: Intersil)

ZL8800 Eval board
(Source: Intersil)

One more important detail: For power supplies that are part of critical equipment that need to be monitored and whose performance must be logged, these parts are ideal. They contain non-volatile memory and can log their operating points. So, if something does go wrong, you can tell what caused the problem. You can also use the logged data to help predict when maintenance will be required. This is useful in hot-swappable supply modules that are part of UPS systems.

Have you used any digital power supply devices from any of the several manufacturers that offer them? How well did they perform?

— Brad Albing, Editor-in-Chief, Planet Analog and Integration Nation Circle me on Google+

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16 comments on “Digital Power: Is Its Time Finally Here?

  1. Davidled
    November 11, 2013

    Power efficiency versus temperature would be described in the most switching power supply.  This chip would be used for disabling other chip active mode as providing DC power about 0 Volt if programming ability is provided in the chip.

  2. etnapowers
    November 12, 2013

    I find very interesting the Inter Device Communication pin of Figure 1: I guess it gives the chance to coordinate many digital controllers by sharing the data logged into the memory of each controller.

  3. etnapowers
    November 12, 2013

    The digital controller has a vout range of 0.54 V to 5.5 V, how is it set? Is there a way to set the output voltage required by the load by utilizing an external control signal ?

  4. fmarti03
    November 12, 2013

    Correct, the communication allows for simplification of complex functions. The below was taken from the ZL8800 Datasheet, which is available via the website.

    http://www.intersil.com/content/intersil/en/products/power-management/zilker-labs-digital-power/digital-pwm-controllers/ZL8800.html?_charset_=UTF-8

    Intersil's proprietary single wire DDC (Digital-DC) serial bus enables the ZL8800 to communicate between other Intersil ZL ICs. By using the DDC, the ZL8800 achieves complex functions such as inter-IC phase current balancing, sequencing, and fault spreading, eliminating complicated power supply managers with numerous external discrete components.

  5. fmarti03
    November 12, 2013

    Changes to the Vout Parameter are discussed in the Knowledge Center for the Intersil website.

    http://www.intersil.com/en/products/power-management/zilker-labs-digital-power/digital-power-knowledge-center.html#1

    Vout can be changed via the GUI. The GUI allows for this at several places.

    1) Power Tree Block – Essentially a High Level Diagram of the System Power Architecture.

    2) Dialog Box – Via the Voltage Output Readout in the Monitoring section

    3) Command Line Tool – as a command line

    In the Knowledge Center their is a video labeled:

    Monitoring and configuring a Digiatl Power Eval Board with Intersil's Power Navigator
    At ~2:30 into the video this is discussed and an example of each can also be seen.

    Depending upon the system requirements the External Control Signal would be an input to the system's MCU. Based upon the control signal the MCU would then configure the ZL8800's registers (VOUT) to meet the desired system requirements.

  6. etnapowers
    November 13, 2013

    This pin increases the overall reliability and the costs of the system, because the power managers are not required.

  7. samicksha
    November 13, 2013

    adding to comment Daej, additional features can include overcurrent, overvoltage, and short circuit protection, and temperature compensation.

  8. etnapowers
    November 13, 2013

    That's a good feature: usually to program the Vout the user has to realize an analogic control signal,but, in this case, it's not necessary because the MCU can control directly the memory of the IC , it's a really nice feature.

  9. Davidled
    November 13, 2013

    I wonder if Intersil develops the communication line and Dialog Box in the Smartphone or Mini PC. As Smartphone is ubiquitous, in the future, any device need to be connected to this kind of gadget.

  10. Netcrawl
    November 13, 2013

    That's not impossible everything could happen right now, smartphones are getting much more sophiticated and much more powerful,its getting too much attention these days, we're seeing too much ionnovation and devlopment in some of today's processors and smartphones technologies.

  11. Brad_Albing
    November 23, 2013

    @etnapowers – You're right about the Inter Device Communication pin on the IC — that lets multiple ICs talk to each other and coordinate aspects such as sequencing of supplies' turn-on and turn-off.

  12. Brad_Albing
    November 23, 2013

    @DaeJ – Are you thinking about an app that could run on a smartphone that would let you program these ICs? Is that what you meant?

  13. Davidled
    November 23, 2013

    Yes, App of smartphone would be very portable for Field engineer. They could reprogram it in the App.

  14. Brad_Albing
    November 24, 2013

    @DaeJ — seems like a good idea. Not sure if the folks at Intersil are looking into that. But I'll aask them. Stand by.

  15. SunitaT
    November 30, 2013

    Digital power adaptation is a power scheme that is measured by digital ckts, in much the similar way as will be by means of analog ckts, to supervise, communicate, monitor and control looping.

  16. SunitaT
    November 30, 2013

    App of smartphone would be very portable for Field engineer. 

    @DaeJ, true. that is a very interesting idea. I dont think such Apps are already available. I am sure such apps will be of great help to field engineer.

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