Power supplies benefit from digital control

Paul Boughton
Claiming to take digital control to the next level, TDK-Lambda's innovative EFE series of embedded frontend power supplies are said to deliver industry-leading power density, high efficiency and enhanced reliability. The first products in the range are the 300W EFE-300 and the 400W EFE-400 single-output supplies that deliver 133 per cent peak power capability for 10 seconds and an efficiency of up to 90 per cent.

EFE series supplies employ an eight-bit microcontroller for full digital control of the output and to handle housekeeping routines. This brings a 25 per cent reduction in parts count to achieve a 45 per cent smaller and up to 56 per cent lighter design when compared to similar recently announced competitive products. Power densities of up to 22W/in3 are achieved under peak load conditions and 16.6W/in3 under continuous loading.

TDK-Lambda's European marketing director, Martin Southam comments: ''This is the breakthrough that marks a new inflexion point in the power supply industry. Our UK design team has created revolutionary core IP [intellectual property] that will spread rapidly across our product roadmap."

Compact dimensions and a 1U profile (the EFE-300 is only 127 x 76 x 34mm and the EFE-400 is only 152 x 76 x 34mm) enable the EFE series to be incorporated in designs where space is limited, so end equipment can be smaller, cooler and more feature-rich. Typical markets include broadcast, instrumentation and industrial, plus other applications, such as ATE, automation, routers, servers and security networks.

The new digitally controlled power supplies incorporate many innovative design features including an integrated magnetics transformer that increases efficiency by up to 1 per cent. The digital control allows the power supply's performance, such as current limit and start-up characteristics, to be optimised. A low-cost primary side control topology is used, supervised by the microcontroller. This results in fewer parts and higher efficiency without sacrificing load regulation performance. Furthermore, the need for an opto-isolator is eliminated – which helps to extend the power supply's life expectancy.

TDK-Lambda UK's advanced development manager, Andrew Skinner, comments: ''Many of the design features of the EFE series directly enhance reliability. For example, having precise control of abnormal situations through proprietary algorithms prevents device overstress. In addition, better circuit noise immunity is achieved compared to analogue designs, and the substantial parts count reduction allows for more optimised component spacing, leading to improved thermal performance."

The EFE-300 delivers 300W continuous power (400W peak for 10 seconds) with nominal outputs of 12V/25A or 24V/12.5A, and the EFE-400 delivers 400W continuous power (530W peak for 10 seconds) with nominal outputs of 12V/33.3A or 24V/16.7A. All models can be precisely factory programmed to accommodate non-standard system voltages. An additional 12V/0.25A fan supply is also available and all models operate from 90-264V AC input with dual fusing as standard. Active power factor correction ensures compliance with EN 61000-3-2. Other EMC improving design features, such as the use of SiC diodes, ensure curve B EMC performance with a significant margin.

The EFE Series is available in a variety of case options, either open-frame or enclosed. The use of low-profile output connectors allows good airflow for optimised cooling efficiency.

All products in TDK-Lambda's EFE Series are approved to IEC/EN/UL/CSA 60950-1 for general-purpose applications and IEC/EN 61010-1 for laboratory and process control applications. In addition, the units carry the CE mark according to the Low Voltage Directive and come with a three-year warranty.

EFE series