ENGINEERING FEATURE

Power Conversion for All

Whether it’s changing mains to DC or converting from one DC voltage to another, power conversion is an essential element of every electronic design. Arrow Electronics has many years of experience in supporting power conversion designs and combines a broad portfolio of AC/DC and DC/DC platforms and products with a host of power semiconductor and control components for designers looking to build their own discrete conversion circuits.


High Performance, Low Cost AC/DC Conversion

For many designers, the first requirement for power conversion is to change a mains AC voltage to a DC voltage that can be used or further stepped up or down to power individual rails and board level components. To address this requirement, a number of Arrow franchises offer dedicated AC/DC power supplies that can be quickly incorporated into a design. In recent years these platforms have seen ongoing increases in power density as manufacturers look to address commercial, legislative and environmental demands for higher levels of efficiency as well as design-related requirements for smaller overall form factors, minimal numbers of external components and a reduction in the need for cooling.

Arrow supplier Emerson Network Power, for example, offers AC/DC power supplies delivering from 25W to 6kW and has a range of low to medium power AC/DC power supplies that includes open frame and enclosed models, DIN rail power supplies, external power adapters and power factor correction modules. These low to medium power AC/DC power supplies offer an exceptionally wide variety of configuration options, suited to applications in communications, computing, storage, business systems, test, instrumentation and industrial equipment. Many of the supplies are also available with medical approvals.

Among these supplies is the latest low cost, high efficiency, high performance NPS-40 series, which offers both Information Technology Equipment (ITE) and non-patient contact/critical medical safety approvals. Delivering a maximum power output of 60W and output voltages from 5V to 48V, these supplies are ideal for use in ITE, light industrial systems and low power medical equipment such as dental and laboratory applications.


Figure 1: Emerson Network Power NPS40-M Series

The NPS-40-M AC/DC products feature a compact open frame design measuring just 50.8mm x 101.6mm and a height of only 25.4mm. Typical full load efficiency is 87% and full load, ambient operating temperature range is a wide -20°C to +70°C.

These single adjustable-output (±20%) power supplies operate from a 90VAC to 264VAC input and provide protection against overload and short-circuit conditions. The products also have a built-in Class B EMI filter and remote sense functionality.

Intelligent Supplies

Also proving increasingly popular with Arrow customers is the Emerson Network Power iMP series of intelligent power supplies.

Offering over 200 million standard combinations and incorporating onboard processing for programmability and smart communications, the iMP series of modular and digitally programmable power supplies allows designers to configure application-optimised AC/DC power solutions that can accommodate new or unforeseen power requirements as they occur. What’s more, the products offer comprehensive control and monitoring functionality via an I²C bus and are fully programmable through an easy-to-use PC-based GUI.

Figure 2: Emerson Network Power iMP Series

Optimised iMP supplies can be configured using power modules that offer six different power ratings (from 36W to 1500W) and single, dual and triple output options. Modules can be configured in a selection of four customisable cases accepting input voltages from 85VAC to 264VAC or 120VDC to 350VDC. Cases can accommodate up to seven individual modules with a choice of 25 standard output voltages ranging from 2VDC to 60VDC. The result is a flexible product range that offers over 200 million different configuration options and can be used to create single power supplies delivering up to 1500W and 21 different outputs.

All iMP series supplies comply with the EN 60601 medical standard for non-patient connected equipment and are fully programmable, with both the case and the individual power modules incorporating individual microcontrollers to maximise control flexibility. All communication between a host controller and the power supply is handled via the I²C bus using the standard PMbus protocol.

PoL DC/DC Conversion

Trends affecting the choice of DC/DC technologies include the need for ever more efficient conversion and the demand to satisfy a growing variety of voltage demands in a single application. Depending on the application requirements and voltages and powers involved, today’s engineers can choose from a wide variety of isolated and Point of Load (PoL) DC/DC converter modules and dedicated DC/DC conversion ICs on the Arrow linecard.

Murata Power Solutions has a long pedigree in the DC/DC converter sector, offering a wide range of isolated and PoL devices. Among its key launches this year has been the Okami™ family of DOSA compliant, non isolated, single, programmable output DC/DC converters. Okami modules are ideal for powering the latest generation FPGAs and DSPs, are drop-in replacements for other DOSA-compliant parts and are billed as a competitive alternative to discrete designs.


Figure 3: Murata Power Solutions Okami PoL Converter

Depending on the part chosen, Okami modules offer 5V or 12V inputs and output options of 3A, 5A, 10A and 16A. They provide high load capacitances to 1000µF and require virtually no de- rating across their rated temperature range.

Among the PoL converter options available from Emerson Network Power is the new high density LGA C Series of power conversion modules that offers users a cost effective, surface mount power solution capable of delivering from 15W to 100W of scalable power via a low profile land grid array package.


Figure 4: Emerson LGA C Series

LGA C Series power converters are packaged in a 16.26mm x 16.26mm outline with an identical footprint for all models (3A, 6A, 10A and 20A) to provide designers with a convenient power migration path if system requirements change. Input voltage ratings are from 3.0VDC to 13.8VDC (4.5VDC to 13.8VDC for the 20A model), making the power converters compatible with a variety of input bus voltages. The power converters also feature a wide, adjustable output range from 0.59VDC to 5.1VDC through external resistor trimming, reducing the number of module types needed to support multiple applications.

Isolated Converters

Arrow franchise Recom is also active in the DC/DC converter arena and among Recom’s most recent isolated converter products are the RNM and RPP series.


Figure 5: Recom RNM Series

Believed to be the smallest isolated converters of their type, RNM Econoline DC/DC converters are ultra compact, single output, unregulated devices for space-limited applications ranging from handheld devices to medical equipment.

Despite their small size of just 8.3mm x 8.3mm x 6.8mm, the RNM series offers isolation of 1kVDC as standard, with 2kVDC available as an option. The devices operate across the industrial operating temperature range of -40°C to +85°C without de-rating and up to +100°C with de-rating. Isolation capacitance is 20pF minimum and isolation resistance 10GΩ.

These 1W converters require no external components and devices are available in a number of voltage variants, producing 3.3V, 5V, 9V, 12V and 15V outputs from regulated inputs of 3.3V, 5V, 12V or 15V. This wide combination of input/output choices allows designers to use the RNM series for step-up or step-down purposes or to generate negative supply rails from a positive supply. Output voltage accuracy is ±5% while line-voltage regulation is typically 1% of the input voltage. Load regulation is 10% to 20%, depending on RNM type. Output ripple and noise is typically 75mV peak to peak, while typical operating frequency is 100kHz and no-load power consumption is as low as 0.1W.

Recom also offers the PowerlinePlus series of 20W to 50W power range DC/DC converter modules, which incorporate the company’s proprietary ICE (Innovation in Converter Excellence) technology. This combines a number of innovative techniques to minimise internal heat dissipation and maximise heat transfer into the ambient environment.

The devices are fully protected with undervoltage lock-out protection, as well as overload, overcurrent and overvoltage protection, plus short-circuit current limiting. Each PowerlinePlus converter has an integrated heat sink to deliver more power over a wider temperature range while requiring less space and cost than equivalent solutions available on the market. Coping with temperatures of between -45°C and +120°C, these modules satisfy the requirements of many military, avionics and high-end industrial applications.

Conversion ICs

As well as the platforms and modules described above, Arrow also offers a wide variety of integrated and discrete ICs that allow designers to implement their own power conversion designs. Arrow franchises such as Analog Devices, Freescale Semiconductor, International Rectifier, Linear Technology, National Semiconductor and Texas Instruments, for example, offer switchers, regulators, MOSFETs and many of the other parts needed to optimise a discrete conversion design.

Among the parts available from Texas Instruments are synchronous and non synchronous DC/DC converter ICs including the company’s SWIFT™ family of synchronous, step-down DC/DC converters for PoL designs. Also known as switchers with integrated FETs, SWIFT regulators integrate several key active components: low R_DS(on) resistance power MOSFETs, MOSFET drivers, pulse width modulation comparator and an error amplifier. SWIFT devices, available in a monolithic package, serve a broad range of applications, such as telecom, computing, industrial and consumer PoL applications with input voltage ranges as wide as 65V and output currents as high as 14A.

Linear Technology has a comprehensive portfolio of DC/DC converter ICs. The company’s family of inductorless (charge pump) DC/DC converters, for instance, can be used to step up, step down or invert an input voltage. By eliminating the inductor, these switched capacitor converters provide a small solution footprint and simplify overall design. Furthermore, by incorporating spread spectrum technology on-chip, both input and output noise are significantly reduced.

Recently Linear also announced the LT3970, a 350mA, 40V step-down switching regulator with integrated boost and catch diodes. The device is ideal for industrial and automotive applications and features a Burst Mode^® operation that keeps quiescent current under 2.5µA in no-load standby conditions.


Figure 6: Linear Technology LT3970

The LT3970 has a 4.2V to 40.0V input voltage range and its 550mA switch can deliver up to 350mA of continuous output current to voltages as low as 1.21V. Switching frequency is user programmable from 200kHz to 2.2MHz, enabling the designer to optimise efficiency while avoiding critical noise-sensitive frequency bands. The combination of its 10 lead, 3mm x 2mm DFN-10 (or MSOP) package and high switching frequency keeps external inductors and capacitors small, providing a very compact, thermally efficient footprint. Other features include a power-good flag, soft-start capability and output short protection.

For engineers looking to design their own AC/DC power supply Arrow franchise STMicroelectronics has the VIPerPlus family. Following the successful introduction of the first device, VIPer17, in 2008, STMicroelectronics has added the VIPer15/16/25/27/28 devices to form a broad family of AC/DC converters that minimise both standby power consumption and the number of external components required, while enabling easy compliance with Blue Angel, Energy Star and other low-power norms and directives.


Figure 7: STMicroelectronics ViperPlus

The family is ideal for energy-saving power supplies operating from all worldwide mains voltages in home appliances including coffee makers to washing machines and dishwashers, consumer equipment such as LCD TVs, DVD players and STBs, domestic and architectural lighting, chargers for mobile phones, digital cameras, portable audio players, toys and cordless appliances such as shavers.

All VIPerPlus devices include the controller, the start-up circuitry and an 800V avalanche-rugged power MOSFET in the package. New integrated functions and high breakdown voltage help to improve the robustness and the reliability of the power supplies, reduce the external component count and provide both higher efficiency in operating mode and an ultra-low standby power consumption that is less than 50mW at 265V and can be reduced to 30mW with optimised transformer design.

The 800V avalanche-rugged power MOSFET is specifically optimised for the VIPerPlus. The fixed-frequency PWM controller with jittering and the quasi-resonant innovative topology maximise the efficiency in operating mode while reducing the EMI filter costs. Best-in-class standby power allows customers to meet the most demanding energy-saving regulations while protection features include accurate, adjustable overvoltage and overload protection, hysteretic overtemperature protection, two levels of overcurrent protection and open-loop failure disconnection.

By integrating a high-voltage start-up current generator as well as essential drain-current control during the converter start-up phase, VIPerPlus eliminates the need for a start-up resistor, reduces stress on the secondary diode and helps to prevent transformer saturation. The embedded SenseFET eliminates external sensing components, allowing a precise drain-current limit. Detection of a fault initiates the devices’ auto-restart function, which prevents damage to the power supply or the load.

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