Over the years, integrated circuit (IC) power management designers have implemented clever solutions in regulator architectures to squeeze out as much efficiency as possible and enhance power supply designs.
In the 1960's, linear voltage regulators were the only game in town. Before that it was vacuum tubes. In the 1970's, designers used switching regulators, which were followed by current mode control regulators in the 1980's. In the new millennium, resonant mode converters were the solution of choice. Designers progressively craft newer and more efficient solutions to achieve "greener" power management.
After nearly 10 years into the 21st century, power supply designers use embedded processors for adaptive control to enhance regulators for point-of- load (POL) conditions and overall power architectures, such as AC to DC configurations, because they achieve power factor correction with a neat software algorithm. Designers also use embedded processors today to provide almost a quantum leap in efficiency, especially under light load conditions, and added versatility.
Digital signal processors (DSPs), microcontrollers (MCUs), user-friendly software, graphic user interfaces (GUIs), and great evaluation boards enable a power supply designer to ease into the transition to digital power. Any power supply designer can achieve an efficient digital power supply design with additional help from E2E and online support communities on suppliers' websites. There is no need to be a software programmer or controller expert to achieve an efficient design.
Historically, designers would ask, "What are other companies designing with digital power?" Now, companies are forging ahead by establishing digital power development in labs. Those companies wishing to enhance the features and efficiency of power supply designs as part of an existing offering are also turning to digital power. Supplier evaluation and development kits help speed the design process with "canned" software and Gerber files to complete the design. "Special sauce" is also available for the digital or software guru who wants to add capability to a design.
What is a digital voltage regulator?
Analog power designers are well aware of the feedback mechanism containing an analog compensator and an analog pulse width modulator (PWM) (see Figure 1) in an analog voltage regulator.
Figure 1: Analog and Digital voltage regulators using controllers as the feedback mechanism (Courtesy of Texas Instruments).
But in a digital voltage regulator we have "digital control," which means sampling the feedback information using an Analog to Digital Converter (ADC) and closing the feedback loop numerically. The compensator uses digital signal processing techniques to execute the control effort in the form of PWM duty ratio(s). This enables inherent monitoring and management of the converter(s). (See Figure 1).
Texas Instruments (TI) offers many control card application kits and development kits in the familiar C2000 Microcontroller Series. TI's flexible and configurable digital power solutions include various digital controllers, digital power stage IC's, which include TI's own NEXFET series of power MOSFET's, and digital power stage modules, which include magnetics to round out a design.
TI solutions cover a wide range of digital power applications; including power optimized digital controllers for PFC control and for the isolated DC to DC stage:
- Gate drive and bias solutions.
- F28xxx fully programmable digital microcontrollers.
TI's portfolio contains UCD9xxx Digital PWM System Controllers for non-isolated DC to DC converter designs using a multi-rail synchronous digital pulse width modulation (PWM) output. For examples, see the controllers listed here.
TI also offers isolated DC to DC or AC to DC power supply designs, such as the F28x Piccolo- and Delfino-based series of microcontrollers that provide high resolution PWM outputs and highly integrated control peripherals (see Figure 2).
Figure 2: High-resolution PWM capability of the F280x/F280xx series microcontrollers (Courtesy of Texas Instruments).
The aforementioned controllers interface with TI's series of UCD7xxx synchronous buck power driver chips with integrated Power FETs, TI's NEXFET series of discrete MOSFETs, or fully tested power train modules in the PTD family with integrated magnetics. Designers should use the Fusion Digital Power Designer software (S/W) with PC-based GUI to configure the devices.
Microchip Technology offers an extensive portfolio of digital power development boards; reference design and software tools, including application software, development tools, training resources and application notes (see Figure 3).
Microchip Intelligent Power Supply designs include four levels of integration. For each successive level, the MCU has greater functionality in the power supply design. Level one features ON/OFF Control; level two features proportional control, level three features topology control, and level four features full digital control.
The Microchip microcontrollers range from PIC10F and PIC12F in Level one to dsPIC30F and dsPIC33F in Level four.
Figure 3: Getting started with digital power using Microchip solutions (Image Courtesy of Microchip).
Intersil's Zilker Labs Digital Power Products are digital DC/DC controllers, digital DC/DC converters, and synchronous MOSFET drivers. The company recently introduced its first fully encapsulated digital power module, the ZL9101M. Intersil's PowerNavigator development tool allows easy control and monitoring of Zilker Labs digital DC devices via the SMBus interface.
ADI offers the ADP1043A Secondary Side Digital Controller for isolated power supply designs, and comprehensive GUI's are included. PMBus provides microcontroller connections.
The following suppliers provide production-ready offerings for digital power using a modular approach:
- CUI Inc. offers Digital Power Modules in V-Infinity's Novum Product line.
- Emerson/Astec offer Digital Control of Switching Power Converters in its board-mounted DC/DC converters.
A designer can greatly enhance digital power training by using the many free online training seminars from the aforementioned suppliers. Single- and multi-day workshops are also available for in-depth training from industry experts. So take the plunge into digital power. After all, digital circuits are simply transistors operating outside of the linear range in the saturated region. In the following articles in this series, we define building blocks of power supply design and how to begin and analyze a design and deliver a final product.