Application Appetites Pressurize The Power Designers

July 1, 2005
Paul Whytock reports from the PCIM 2005 conference in Nuremberg and concludes that product-hungry customers are keeping the pressure on power players to innovate.

The all-pervading atmosphere at PCIM 2005 was one of an industry at peace, but not complacent, with itself. The dark recessional days of 2001 to 2003 are well behind the power electronics industry and, generally speaking, companies are trading well and have plenty to occupy themselves with in coming up the new products and systems that developing applications demand.

Most exhibiting companies were only too aware that failure to meet future application needs would quickly deplete their financial performance. Power electronics is a pressure business and complacency in R&D departments could dearly cost companies.

As Professor Leo Lorenz Dr.-Ing, the president of the European Centre for Power Electronics, pointed out at the opening conference session, power technology development must always be looking forward. He sees a tremendous increase in power density and efficiency for power-conversion systems with a doubling of power density every two years for AC/DC converters.

The technology that will drive this development includes low-loss semiconductors; dedicated circuit topologies such as Resonant, ZVS, Snubber, Phase Shift, ITTF, Bridgeless Input, and Synchrony Rectifier; and, of course, the creation of new materials for thermal management. Also expected to play a role will be packaging developments, new generations of advanced passives, and simulation tools with increased capability.

But the PCIM conference was not all about future developments. There were plenty of new product announcements.

IR DIRECTFET MOSFET CHIPSET International Rectifier used the event to launch its DirectFET MOSFET chip set that maximises DC bus-converter efficiency when used with the company's IR2086S full-bridge bus-converter IC.

The chipset enables a bus-converter solution capable of delivering 336W with 97% efficiency in a footprint 29% smaller than a quarter-brick converter, claims the company.

The IRF6646 and IRF6635 are optimised for 48V regulated and 36 to 60V input bridge topologies in isolated DC-DC bus converters, synchronous buck non-isolated DC-DC topologies, 18V to 36V input forward and push-pull converters for mobile communication, and secondary-side synchronous rectification in regulated, output isolated DC-DC applications.

A typical industry standard, 300W quarter-brick contains as many as ten MOSFETs (four in the primary side and six in the secondary side), a pulse-width-modulated (PWM) IC, and two half-bridge driver ICs. IR's new chip set solution consists of six MOSFETs (four in the primary and two in the secondary side) and a single IC, yielding a 46% reduction in power-semiconductor part count. In addition, isolated bus-converter DC-DC applications made with this chip set achieve 29% reduced board space and operate with as much as 1.5% better efficiency.

The IRF6646 80V MOSFET has a maximum on-state resistance of 9.5milliohms while the IRF6635 30V MOSFET has a maximum on-state resistance of 1.8milliohms and is optimised for secondary-side synchronous rectification. This MOSFET pair combines with the recently introduced IR2086S full-bridge DC bus-converter IC and the existing IRF6608 30V DirectFET MOSFET, used as a secondary-side gate clamp.

International Rectifier also introduced a series of high voltage IGBT control ICs with a sophisticated set of protection functions at PCIM. In addition to these advanced functions, these devices feature high noise immunity with up to 30% fewer components in half the footprint compared to discrete opto-coupler- or transformer-based solutions.

The series consists of 1200V and 600V gate driver ICs and current-sense interface ICs for a variety of applications, including inverterised motor drives, general-purpose inverter circuits, switch-mode power supplies (SMPSs) and uninterruptible power supplies (UPSs).

Power stages using IGBTs or MOSFETs must be protected from failures such as short circuits, overcurrent conditions, and ground faults. In addition to protection circuits, the fault conditions must be detected, or sensed, in order to enable the protection functions. IR's new line of driver ICs and sensor ICs fill this requirement, while reducing component count and simplifying circuits, claims the company

YOKOGAWA PRECISION POWER ANALYSER Japanese instrumentation company featured its precision power analyser at the PCIM exhibition. The analyser combines high accuracy (±0.02% of reading +0.04% of range) with a wide frequency range (DC, 0.1 Hz to 1 MHz) even for power measurements, says Yokogawa. The new WT3000 can carry out up to four power measurements simultaneously, has direct keys operation, features a variety of display formats on an 8.4in colour TFT, includes integrator functions as standard, and offers a range of options to enhance application-specific measurements.

Two versions of the WT3000 are available. The standard model is suited to high-accuracy measurements of the input/output efficiency of invertors. A dedicated motor version has facilities for measuring torque and speed and converting measurements into mechanical parameters, with a data update speed from 50 ms to 20 sec.

Measurements can be made over seven current ranges from 0.5 to 30 A rms and eight voltage ranges from 15 to 1000 V rms. Guaranteed accuracy for AC voltage, current, and power is between 1% and 130% of input range. The continuous maximum common-mode voltage of 1000 V rms at 50Hz/60Hz enables precision power measurements in the evaluation of invertor and motor efficiency and characteristics. In addition, the low power-factor error (0.03% of apparent power) enables precision power-loss measurements, especially in the evaluation of transformer characteristics.

In addition to offering direct keys to access the most important measurement functions, the WT3000 allows the user to set nine different display item patterns in advance, and change between them at will. The display can be configured to show numerical, waveform, trend, or (optionally) harmonic bar-graph data.

The WT3000 offers new functions for apparent power and reactive power.

An optional delta calculation function enables the user to calculate individual phase voltages from the line voltage measured in a 3-phase/3-wire system. This makes it possible to determine the phase voltage in motors and other items under test where no neutral lines are present.

The harmonic measurement option allows the instrument to handle both normal and harmonic measurement data simultaneously.

Also available as an option is a 20-channel digital/analogue converter output, which allows measured values to be output as ±5 V (full-scale) DC voltages from a connector on the rear panel. Measured parameters can be output on up to 20 channels simultaneously.

PHILIPS THERMAL MODELS Royal Philips Electronics supplied details at the PCIM conference on how it will provide thermal models of its power semiconductors to help customers accurately predict the thermal performance of their devices—in a fraction of the time it takes to build and test prototypes.

Philips believes that manufacturers are increasingly turning to thermal modeling software to simulate the thermal performance of their devices and solve design issues associated with thermal management before building prototypes. This saves manufacturers considerable time—a typical "real" prototype could take up to two weeks to build and test, while simulating with thermal models takes only two days.

Philips' thermal models run on Flotherm thermal modeling software and are available free to existing users of the software. The models have features such as the device die, the die attachment and internal lead frame.

TOSHIBA UNVEILS DTMOS MOSFET Moving on to MOSFETs, Toshiba Electronics Europe and its parent Toshiba Corp. released details about a new power MOSFET called DTMOS. It employs a new superjunction structure that enables a reduction in power consumption, caused by on-state resistance (RDS-ON), to approximately 40% of the value typically achieved with conventional MOSFETs.

The first device in the DTMOS family, TK15A60S, is for use in power supplies in television sets, home appliances, AC adapters, and ballast lighting.

The superjunction structure, which has vertical paths to allow electrical current to flow through easily on a silicon substrate, realises lower RDS-ON than the theoretical limit of silicon. By applying this superjunction structure and optimising the total device, the RDS-ON for the same area in Toshiba's DTMOS device achieves a 60% reduction and its gate charge (Qg ) achieves a 40% reduction compared with Toshiba's conventional MOSFETs.

Consequently, RDS-ON * Qg, a characteristic that is one important performance index for MOSFETs (in which smaller is better), is one quarter the value of the company's conventional MOSFETs.

With this announcement, Toshiba is combining a superjunction structure with the company's original Deep Trench MOSFET technology. Toshiba believes it is the first to combine a superjunction structure with deep trench.

The company also unveiled its first trench-gate-based 4.5kV Press Pack IEGT (Injection Enhancement Gate Transistor). The new PPI module is claimed to improve the performance and efficiency of high-power applications including high-end motor drives, transportation systems, and power-distribution schemes.

Until now, Toshiba's 4.5kV PPI modules have used conventional planar semiconductor technologies. Moving to a trench-gate semiconductor process delivers a reduction in saturation voltage (VCE(SAT)) of between 0.6V and 0.7V, and an increase in current-handling capability when compared to the conventional planar solution.

In tests at 2100A, the saturation voltage of the new PPI module ranges from 2.3V to 2.8V, depending on turn-off conditions. Under the same test conditions, the conventional planar-based module operates with saturation voltages ranging from 2.9V to 3.4V. Tests have also shown that the increase in current-handling capability when compared to previous planar PPIs is in the region of 20%.

The new 4.5kV trench module combines multiple trench-based IEGT chips in a press-pack module with a contact diameter of 125mm. No wire bonds or solder contacts are used in the PPI module, leading to high levels of resilience to thermal cycling. In addition, thermal management is simplified by the fact that the press-pack packaging allows for cooling on both sides of the module.

FAIRCHILD MOTION SMART MODULESMotion-Smart Power Modules (Motion-SPMs) that offer an integrated solution for low-power (below 100W), brushless dc (BLDC) motor applications, have been developed by Fairchild Semiconductor. The Motion-SPM devices integrate multiple functions in a single compact package, offering a simplified motor drive solution to speed engineering design, reduce pc board space, and enable energy-efficient and reliable designs in home appliances. Motion-SPM multichip modules combine six fast-recovery MOSFETs (FRFET) and three half-bridge high-voltage ICs (HVIC) in one thermally efficient, ultra-compact (29 mm x 12 mm), Tiny-DIP package designed for BLDC motors with built-in control.

Each Motion-SPM uses advanced FRFET and HVIC to simplify motor inverter designs. The Motion-SPMs' FRFETs are said to lower switching and conduction losses during low-current conditions. For ruggedness, they provide a wider reverse bias safe operating area (RBSOA) than IGBTs of similar ratings. By using the MOSFETs' body diodes as freewheeling diodes, Motion-SPMs eliminate the need for additional components, improving the efficiency and noise immunity. The gate-driver ICs increase reliability through high-isolation, 5 V CMOS/TTL interface and undervoltage-lockout (UVLO) protection features.

The 500V FSB50250 and FSB50450 (2A- and 3A-rated, respectively) are each housed in a 23-lead DIP. These products are lead-free (Pb-free).

SEMIX RECTIFIER MODULES Semikron SEMiX rectifier modules for up to 300A are now available in the same design as the new IGBT generation. They have a low case height of 17mm, screw connections, and an interconnection on the same level between IGBT and input bridge rectifier.

The SEMiX rectifier modules in combination with SEMiX IGBT modules have been optimised for use in drives (AC/DC drives: 15kW -110 kW) and power-supply systems.

The modules have SEMICELL, Semikron glass-passivated thyristor and diode chips. All of the rectifiers are available in two topologies: uncontrolled (diode/diode) and half-controlled (diode/thyristor), for currents up to 300A and reverse voltages up to 1800V. They come in SEMiX1 and SEMiX2 cases, or as three phase bridge rectifiers in SEMiX13 cases.

Semikron also introduced the improved power electronics platform SEMIKUBE B6CI, now with SKYPERPRO and a driver adapter board. This system for forced air-cooled inverters is now also available for lower power ratings.

In addition to the embedded functions of SKYPERPRO, such as soft turn-off and external error input, the SEMIKUBE platform now has AC current, heatsink temperature, and DC voltage analog outputs (galvanic isolation to 4 kV between primary and secondary); overcurrent and overtemperature protection, over DC-voltage protection, and current imbalance monitoring between the paralleled modules.

SEMIKUBE's footprint is 154 x 306mm, and it comes in six sizes for forced air-cooled inverters from 160A to 1550A.

ON EXPANSION FOR SMART HOTPLUG FAMILY During the PCIM conference, ON Semiconductor was telling visitors about the expansion of its SMART HotPlug family with the introduction of the NIS5102 high-side, hot-swap protection IC with built-in charge pump and accurate temperature sensing circuitry. Designed for computing and telecom applications, it combines a MOSFET with control circuitry and thermal protection.

This integrated approach simplifies implementation of hot-swap protection in high-availability +12V systems, and is targeted at distributed power systems, servers, disk arrays, and powered board insertion applications.

According to ON Semiconductor, the NIS5102 is the only device available with a low 10milliohm, 18V-rated integrated smart MOSFET. By integrating a smart MOSFET with a current mirror into the NIS5102—specifically a SenseFET—only a fraction of the load current is sensed across the sense resistor. This eliminates the need for a larger and more expensive external power sense resistor.

An adjustable current-limiting feature enables the designer to set the maximum inrush current from 20A to less than 1A. Undervoltage and overvoltage lockouts prevent the load from "seeing" a potentially unsafe operating voltage.

ON says that by the end of 2005, three additional SMART HotPlug devices will be launched.

NAT SEMI ENERGY SAVER New at the show for National Semiconudctor was the LM5021, a high-performance AC-DC PWM current-mode controller that's designed to save energy in power supplies. The device contains the features needed to build energy-efficient, single-ended flyback and forward AC-DC converters for telecomms, networking equipment power systems, and high-end industrial and consumer power supplies.

National claims this controller is the first that can be used as either a secondary-side post regulator (SSPR) or as a stand-alone buck regulator. It enables designers to develop synchronised, multiple-output DC-DC power supplies. Applications include multi-output DC-DC power modules and wide-input-range DC-DC power sources for industrial and consumer electronic products.

CPS ALUMINIUM SILICON CARBIDE A specialist in the design and production of aluminium silicon carbide (AlSiC), the CPS Corporation was telling visitors to the PCIM exhibition about the benefits of metal matrix composite. AlSiC provides a reliable and cost-effective thermal management solution for power electronics, including base plates for IGBTs, says the company.

Unlike traditional packaging materials, AlSiC enables a tailored coefficient of thermal expansion (CTE), offering compatibility with various electronic devices and assemblies. The isotropic CTE value of AlSiC can be adjusted for specific applications by modifying the Al-metal/SiC-particulate ratio. AlSiC's CTE matching capabilities eliminate the need for thermal interface stacking, increasing reliability in the field.

AlSiC also exhibits a high thermal conductivity that results in extremely efficient thermal dissipation. Coupled with its superior CTE matching, AlSiC's high thermal conductivity prevents the bowing and flexing of packaging and substrate material that can lead to failure. Traditional packaging materials with lower thermal dissipation can cause delamination, leading to air gaps and poor reliability.

ZETEX DC MOTOR CONTROL The latest in its range of motor pre-driver ICs, as well as a completely new technique for improving the efficiency and reducing the acoustic noise and cost of brushless DC motor controller circuits, were presented by Zetex.

Demonstrated for the first time, the ZXBM1015 pre-driver provides variable- or fixed-speed control of single-phase brushless DC fans, blowers, and pumps. With an integral current monitoring circuit, the pre-driver keeps supply current on start-up and stall within the most stringent OEM power supply specifications.

Making use of existing PWM circuitry in half- and full-bridge brushless DC motor controllers is a novel technique developed by Zetex for reducing the excessive currents present at the end of a commutation period, a cause of undesirable back EMF.

MAGNETEC'S COOL BLUE CORES Making its show debut were the new Cool Blue range of cores that completes MAGNETEC's series of high-performance toroids.

Made from the nano-crystalline material NANOPERM, the cores feature improved high-frequency performance due to a high permeability level. They are being used increasingly to reduce damaging bearing currents in modern wind energy generators.

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