Power Electronics

Converter Taps Microcontroller to Minimize Components

Tapping the benefits of an eight-bit micro-controller with on-board analog-to-digital converter (ADC) and memory, power supply maker Datel Inc. (Mansfield, Mass.) has readied a nonisolated dc-dc converter with unprecedented transient protection features and supervisory/monitoring functions. The high-performance triple-output MAPC-104 can withstand input transient voltages, as per SAE automotive transient protection standards J1455 and J1211. Thus, the MAPC-104 can handle a load dump of 122 V at 0.4-Ω source impedance, which results in 305-A peak current — 305-A peak current × 80-V maximum clamping voltage results in 24,400 VA of peak power to be clamped. With this level of protection, a vehicle can have its alternator recharging the battery. Furthermore, if the battery cable is removed, the MAPC-104 can safely protect itself from 24 kVA.

“Mobile network applications are the driving force, and Datel developed this product as part of Cisco's Partner/System Integration program,” says Datel's Bob Leonard. In fact, the MAPC-104 power supply is designed to power the Cisco 3200 mobile access router and meets the PC/104 plus mechanical and electrical specifications.

As seen in Fig. 1, it employs a buck/boost synchronous-rectification topology to convert the vehicles' standard battery voltage of 12 V or 24 V to three fully regulated outputs of 3.3 V, 5.1 V and 12 V, with up to a total output power of 46 W. The converter's input voltage range is 9 V to 32 V. Unlike others, each output has its own independent regulation. Also, the buck/boost synchronous-rectification topology enables the maker to achieve 92.5%, thereby enabling full-power operation to ambient temperatures as high as 85°C with 100-lfm airflow. Thus, there is no derating to 85°C and 100-lfm airflow (Fig. 2).

Additional features include multilevel overtemperature protection, input undervoltage lockout, input overvoltage protection, power-on sequencing, 12-V monitor for 12-V Power Good signal, output crowbar for power-down sequence, retry functions for shorted outputs, and even a hierarchy for dual fault conditions. The operating temperature range is -40°C to 105°C. Presently, it's programmed to offer three thresholds. When the board temperature reaches 115°C, it gives warning for 30 sec before shutting down. There is an immediate shutdown when the temperature reaches 125°C. The board temperature must drop to 110°C before the dc-dc converter starts functioning again. If needed, the microcontroller permits these thresholds to be modified by software.

The MAPC-104 offers ±1% (max) line and load regulation, a step response of 200 µs, and 25-mVp-p ripple and noise output. It also provides stable no-load operation. Because the microcontroller-based design minimizes external component count, the unit's open-frame construction measures only 3.775 in. × 3.55 in. × 0.60 in. Pricing is $121 in quantities of 10,000.

Datel Inc., Mansfield, Mass.; www.datel.com CIRCLE 349 on Reader Service Card

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