Fractional-brick and modular dc/dc converters reach new highs in efficiency

-- EDN, 11/23/2000

Several families of half-brick, quarter-brick, and modular dc/dc converters from Ericsson Microelectronics use synchronous rectification to achieve high conversion efficiency at low output voltages (Picture). The half-brick PKJ 4000 family, for example, attains 91% efficiency at 3.3V output. The series uses a thermal design that keeps the temperature of the output MOSFETs to less than 10°C above the baseplate temperature. The family accepts input voltages in the telecommunications range of 36 to 75V and is available with output voltages of 1.8, 2.5, and 3.3V at 40A output current. Unlike some high-efficiency designs that display reverse-conduction phenomena when connected in parallel, the PKJ 4000 series requires no series diode for such operation. The converter costs $124 (500).

Another half-brick family, the PKL 4000 series, operates from the telecomm-standard 36 to 75V and delivers 60A output current. Ericsson has added two new 2.5V-output models to the family: the 60A PKL 4119 API and the 50A PKL 4119 PI. The converters attain 89% efficiency and 52W/in.³ power-conversion density. The 60 and 50A models cost $154 and $144 (500), respectively.

Eight new quarter-brick models from Ericsson offer 15 and 20A output currents and output voltages of 1.5, 1.8, 2.5, 3.3, and 5V. The PKM 4000 family operates from telecomm-level rails of 36 to 75V and attains efficiencies as high as 91%. The series uses a double-sided assembly that separates the power and signal circuitry. The converters cost $94 (500). A new family of modular dc/dc converters, the 13W MacroDens PKF 4110B series, also operates from telecomm levels of 36 to 75V and delivers 3.3V at 4A. Less than 8 mm high, the modules attain 85% efficiency at rated output. The converters are optimized for free-air convection cooling and operate over 45 to 100°C. Ericsson performs extensive power burn-in and life testing on all its converter families. The respective MTBF figures for the PKJ 4000, PKL 4000, PKM 4000, and PKF 4110B converters are 2.2, 2.2, 2.8, and 4.9 million hours.

Ericsson Microelectronics, www.ericsson.com/microe.

at www.rscahners.ims.ca/ednmag/.

-by Bill Travis