Understanding Forced-Air Cooling

Understanding Forced-Air Cooling

Forced air cooling can make a significant difference to thermal management, improving the heatsink-to-air thermal resistance by as much as an order of magnitude with the right combination of hardware. Making the right choices, however, means interpreting and matching the convection data for both the heatsink and the fan. The first step is to calculate the maximum heatsink-to-air thermal resistance for the system: next, the operating airflow through the heatsink is determined. Airflow from the fan, expressed in cubic feet per minute (CFM), is plotted against the curve for pressure drop, shown in inches...

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Input Source Impedance and its Effects on DC-DC Converters

Understanding input source impedance in DC-DC converter designs helps to ensure correct damping and stable operation. A detailed examination of the input impedance of a switch-mode DC-DC converter reveals why it is common practice to use a large electrolytic capacitor across the input to a DC-DC converter, and make input source impedance smaller than the input impedance to the converter. Read full article (PDF)

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Vicor Modules Power On-Board Railway CCTV

Vicor Modules Power On-Board Railway CCTV

Vicor VE-200 DC-DC converters are being used at the heart of the power block for a major new on-board CCTV system, installed by Portugal Rail, to increase passenger safety. The power modules are one of the most crucial components in the main ‘CCTV System for Transportation Systems and Passenger Transportation’ project. The design needed a nominal input of 72VDC, with outputs to 12VDC and 24VDC, both supplying 100W. Using the 12V VE-241-CW and 24V VE-243-CU DC-DC converters, and working with Vicor distributor Arrow Iberia, the design team followed Vicor guidelines to create an active...

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New 28V Micro DC-DC Converters for Commercial or MIL-COTS Power

The addition of eight new wide-input 28V quarter-brick Micro DC-DC converters from Vicor provide more choice for power designers in commercial, industrial or MIL-COTS applications. With efficiency up to 82%, these new converters operate from 28V nominal input with an input range of 9 to 36V. They offer nominal output voltages from 3.3 to 48VDC with a wide nominal output voltage trim range of 10% to 110%. The maximum power rating for the 12 to 48V output modules is 100W, whilst the 3.3V and 5.0V versions are rated for 50W maximum power. Four environmental...

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Meeting Military Aircraft Electrical Specifications

Meeting Military Aircraft Electrical Specifications

MIL-STD-704* came into being to standardize aircraft electrical requirements for the armed services. Since 1959 there have been a number of modifications to this basic specification, with the latest, MIL-STD-704F, being introduced in 2004. Initially MIL-STD-704 limited itself to two basic voltage buses, a three-phase 115Vac (typically 400Hz) supply with limited single-phase loading and a 28V DC system. Over the years there have been many changes in the surge and transient withstand levels, particularly for the 28Vdc rail and the introduction of a 270Vdc bus. Vicor manufactures parts to meet most of these requirements....

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Paralleling Outputs

Paralleling Outputs

Vicor’s Maxi, Mini and Micro modules support paralleling of identical converters to expand the output power. A PR signal is communicated to all modules within the parallel array to synchronize switching frequency. Current sharing is inherent due to the matched power trains of the converters, even under conditions of dynamic loading. In a parallel array, the PR pin function allows only one module to be the Driver; all other modules will automatically become Boosters. Care should be taken by choosing a proper PR-connection. The following application note discusses different ways to connect the PR...

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Battery Charger Design Uses Unique Converter Control

Battery Charger Design Uses Unique Converter Control

A unique converter control scheme for a battery charger uses features on Vicor DC-DC modules to achieve small size and high-efficiency, plus the flexibility to adapt the charger for every input voltage range, battery voltage, and capacity. The design also maximises battery operating life and minimises maintenance costs for offline battery charging off lead-acid batteries. An offline battery charger, based on a Vicor DC-DC converter module and controller IC, provides the flexibility to adapt the design for every input voltage range, battery voltage, and capacity. The design also achieves high efficiency as well as...

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