For the PDF version of this article, click here.
DSCs Lower Cost of Full Digital Control for Power Supplies
Microchip Technology has introduced a family of 16-bit digital signal controllers (DSCs) for common, multi-loop switch-mode power supplies (SMPSs) and other power-conversion applications. The dsPIC30F1010 and dsPIC30F2020/2023 (dsPIC30F202X) DSCs feature a high-speed 1-ns resolution pulse-width modulator (PWM) and a 2-Msample/s, 10-bit A-D converter.
The dsPIC devices are suited for designing ac-dc converters, isolated dc-dc converters, embedded power-supply controllers, power inverters and UPSs. Power supplies with multiple outputs, coordinated load sharing, hot-swap capability, output coordination, integrated power factor correction (PFC) or extensive fault handling are among the applications expected to immediately see cost and performance benefits from a DSC-based design.
“Power supplies with higher power or complexity are now poised at a price threshold that is amenable to digital control,” said Sumit Mitra, vice president of Microchip's Digital Signal Controller division. “Our dsPIC SMPS families were developed with input from leading power-supply manufacturers to tip the scale in favor of a digital approach. These devices accelerate innovation by giving early adopters newfound flexibility to create new topologies that were formerly impractical for analog approaches. Early adopters expect to achieve superior levels of customization, resulting in power supplies that are more competitive in their markets.”
The DSCs enable full control of the power-conversion process via software running on the DSC and through its high-performance peripherals (see the figure). Together, the DSC's PWM, A-D converter and analog comparator form what the company describes as an “Intelligent Power Peripheral,” which uses Microchip's Configurable Control Fabric to coordinate the operation of the comparators, PWM and A-D converter.
The Configurable Control Fabric is set up via software, so that, at startup, the modules are configured as desired. This feature allows the controller to operate independently, minimizing the work load on the internal CPU; it precisely times A-D conversions and controls the PWM's response to fault conditions. The control fabric makes the controller adaptable to a wide range of control methods, while also providing fail-safe control.
The A-D converter on the DSC differs from those typically found on microprocessors or DSPs. Unlike those A-D converters, which assume a synchronous system, the DSC's multichannel A-D converter handles asynchronous inputs, allowing the designer to specify down to the nanosecond when to sample the signal being measured. The A-D converter contains a series of independent sample-and-hold (S/H) circuits that are separate from the converter with separate triggers for each S/H circuit. The 10-bit A-D converter has up to 12 input channels and samples at up to 2 Msamples/s.
The PWM on the dsPIC30F1010 and dsPIC30F202X offers seven modes of operation, including standard, complementary, push-pull and variable-phase. The dsPIC30F1010 devices have 6 kbytes of Flash, two PWM generators and six channels of A-D conversion. The dsPIC30F202X have 12 kbytes of Flash, four PWM generators and either 8 channels (dsPIC30F2020) or 12 channels (dsPIC30F2023) of A-D conversion. All devices operate from a 3-V to 5.5-V supply. According to measurements taken on prototype silicon, full-speed operating current is on the order of 100 mA.
Additional features include two or four high-speed analog comparators, 30-MIPS performance at 5 V, and -40°C to 125°C operation. An optional PWM dither mode can be used for EMI reduction.
The dsPIC30F1010 is available in 28-pin SOICs, SPDIPs and QFNs; the dsPIC30F2020 in 28-pin SOICs, SPDIPs and QFNs; and the dsPIC30F2023 in 44-pin TQFPs and QFNs. Unit pricing starts at $2.99 in 10,000-unit quantities. General sampling is expected this month with volume production expected in August.
IC Brings Digital Control to Low-Power AC-DC Adapters
The iW1688 primary feedback controller from iWatt applies digital control techniques to improve the design of low-cost, low-power ac-dc adapters. Using a combination of sampling techniques and an area-efficient digital engine, the controller provides a powerful control loop that enables tight regulation, high efficiency and small size for 2-W to 5-W ac adapters.
“[The iW1688] significantly simplifies meeting tighter no-load power requirements while eliminating external components that add both cost and reliability issues, such as optocouplers,” says Doyle Slack, vice president of marketing. “Using the iW1688, customers can easily meet existing and pending requirements such as Energy Star and the California Energy Commission.”
The iW1688 implements all of the control functions required to design a low-power supply using primary feedback control. Until now, tight supply regulation required secondary feedback loops that added both component and reliability concerns. The iWatt controller eliminates those extra components while integrating features such as robust overvoltage and undervoltage shutdown and internal constant-current control.
The iW1688 senses voltage and current on a cycle-by-cycle basis at the full 40-kHz operating frequency and makes adjustments on each cycle to respond quickly and accurately to load changes or fault conditions. This same control loop also provides internal compensation, eliminating the external components that are normally required.
The controller is fully qualified and in volume production. Packaged in an RoHS-compliant 5-lead SOT-23, the iW1688 is priced at $0.31 in 10,000-piece quantities. For more details, visit www.iwatt.com.
Growing Number of Vendors Offer Digital Power ICs
The second edition of the Darnell Group's report on market opportunities in digital power reveals an increase in the number of power-converter companies that have introduced products incorporating digital power management and control IC solutions since the first edition of the report was issued in March 2005. These solutions include both hybrid (analog and digital) and “pure digital” designs. The new report, “Emerging Markets in Digital Power Electronics: Component, Converter and System Level Opportunities 2nd Edition,” also finds that system makers are seriously considering the benefits of digital control and coming up with their own, often proprietary, needs.
These trends are occurring at various levels of implementation. The report proposes five levels of digital control for partitioning purposes: (1) Power Conversion, which “closes the loop” in the power converter; (2) Converter Management, which is digital control inside the power converter but outside the loop; (3) Board Management, which is digital power control and management of the power converter at the pc board level; (4) Rack Management, which is digital power management of the system; and (5) Facility Management, which is digital power management at the facility level.
The report looks at levels 1 through 3, although demands at the facility level, such as data centers, are expected to drive the adoption of digital control at the converter level. In particular, energy efficiency and the problem of cooling large server farms will play an important role in digital power management and implementation.
According to Darnell, the worldwide digital IC market — which includes VR loop controllers, non-VR loop controllers, PFC loop controllers, converter management ICs and system ICs — is expected to be $169 million in 2006, increasing to $796 million in 2011, a compound annual growth rate of 36.4%. Conservative, moderate and aggressive market penetration rates are used to present various scenarios of the potential served available markets, although the report assumes the digital ICs will experience a moderate adoption rate.
It is still too early for definitive regional forecast projections of digital power management and control products. Therefore, the report makes projections for worldwide, North America, Europe and Asia based on current unit sales of power-supply products in the applications identified as having the most potential for adoption of digital control, along with the expectations companies have about their own sales and where they see potential for future revenue.
The power supplies that Darnell selected as good opportunities for digital control are: external ac-dc power supplies (adapters and battery chargers); embedded ac-dc power supplies; isolated dc-dc converters; nonisolated dc-dc converters (point-of-load converters and voltage regulators); telecom rectifiers; external dc-dc converters used in communications power systems; and electronic lighting ballasts.
According to the report, VR controllers currently dominate digital power-supply sales, and point-of-load converters are the largest emerging digital power-supply market. However, Darnell predicts that will change over the forecast period, with other power products taking significant market share from these two segments.
Acknowledging that digital power management and control is still emerging, this report provides perceptions of the current market, based on a benchmarking survey of semiconductor, power-converter and system makers. In emerging markets such as digital power, leadership is fluid and, hence, it is not appropriate to base it on who is shipping the largest dollar value of products.
The important question the survey attempts to answer is not necessarily who is currently in the lead, but what companies will emerge as the leaders in the digital power market.
Although digital power is only a small portion of today's power electronics industry, its growth and development are expected to play a major role in the future of power conversion and power management. According to the report, the market at both the semiconductor and power-conversion levels is expected to remain extremely competitive, with large multinational corporations competing with smaller regional companies for market share.
In addition, a growing number of partnerships, acquisitions and alliances among companies is expected to have a significant impact in the growth and development of this industry. This report concludes with profiles of companies that are providing commercial digital products or technologies at IC, power converter and power-system levels.
The report also features a chapter on the competitive environment, including a description of features among various products. To obtain a copy of “Emerging Markets in Digital Power Electronics: Component, Converter and System Level Opportunities 2nd Edition,” contact the Darnell Group at [email protected] or (951) 279-6684.
Vendors Discuss Obstacles to Digital Power
Though targeting very different power-supply applications, the digital power chips described in this section illustrate that chip vendors are still striving to overcome barriers to digital power design. This subject provides the basis for some thought-provoking discussion in the latest installment of the Digital Power Q&A. In this feature, experts from Intersil, Microchip, Primarion, Silicon Laboratories, Texas Instruments and Zilker Labs discuss how factors such as cost, complexity, product availability and ease-of-use present obstacles to the adoption of digital power technology. See if you agree with their prognosis.
In the latest Power Electronics Technology online Guest Commentary, Keith Curtis of Microchip Technology, sheds some light on an approach that may help surmount these digital design hurdles. In “Sometimes It's Hearts and Minds, Not Price and Delivery,” Curtis recounts how his company overcame the objections of seasoned analog designers to the use microcontrollers in power-supply designs. For both of these features, see the “Spotlight on Digital Power” online at http://powerelectronics.com/digital_power/.