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Brainstorm: Digital Power

Thu, 09/30/2010 - 9:27am
Edited by Jason Lomberg, Technical Editor

How do you feel about the current state of digital power?

David Norton TDK-LambdaDavid Norton, TDK-Lambda Americas, www.us.tdk-lambda.com

Certainly digital power control has not gained the popularity in the industry at the rate predicted two years ago, but I am very pleased with its adoption within TDK-Lambda’s Engineering community.

During the development of TDK-Lambda’s EFE series of digitally controlled AC-DC power supplies three years ago, the advantages of designing with microcontrollers became very apparent. Often a new technology does not live up to the initial promises, but we realized increased efficiency, improved noise immunity, increased power density, reduced parts count and the ability to use our proprietary algorithms to prevent component overstress.

Our “Analog” Engineers, who were skeptical at first, quickly embraced the digital technology and are now some of the biggest advocates. They like being able to change control loops using software, rather than with component or pcb changes.

After the launch of the EFE series, our customers started to reap the benefits; effectively purchasing a standard power supply with small modifications to the operating software. Such changes allow different load share characteristics, peak power capabilities or the ability to start up into non-linear loads.

Digital power control is firmly entrenched as a core technology within our mid-power Engineering groups. 

Mark's portrait--tiMark Hagen, Texas Instruments, www.ti.com

Today, the value of regulating a voltage with a digital controller can be summed up in two statements. First, it allows a delay decision about power (for example, sequence and soft start timing, OC thresholds, voltage trim setting and loop compensation) until after the board returns from the factory. Second, a digital loop enables cost-effective monitoring of voltage, current, temperature and duty cycle.

For experienced power supply designers, the first value statement does not seem like that big a deal. However, for large systems with many voltage rails and fast development cycles, the ability to adjust the power bring-up sequence or increase the OC threshold on a 200 board build through the tester interface, instead of sending the boards back to the board assembly house can shave weeks off the schedule.  

The second value statement is important to designers of complex infrastructure systems with multiple voltage rails and stringent quality of service (QOS) requirements.  Texas Instruments' digital controllers, such as the UCD9240 controller or F2802x/3x Piccolo microcontrollers, have the ability to monitor the dynamic behavior of a voltage regulation loop. By combining the concepts of statistical process control with monitoring, it is possible to predict some impending failures. For instance, by monitoring duty cycle and output current, one can create an estimate efficiency.  Or by using the build in network analyzer, phase margin can be monitored.  If this is sampled on a regular basis, the digital power controller can predict the health of a power system. 

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