Although the high-tech spotlight rarely shines on power connectors, they're crucial to the performance of many advanced electronic systems. Without the interface they provide between power supply and load, it would be difficult to create scalable power designs. After system configuration, it would also be a time-consuming, laborious operation to replace a failing power-supply module. Naturally, the system would need to be powered down, as hot-swapping would be impossible.
Of course, modularity is at the heart of many high-performance applications. Numerous examples can be found in the telecom and networking areas, where systems rely on modular designs to provide both configurability and very high reliability. Due to their stringent demands for reliable power, telecom and networking applications are driving many of the developments in power interconnects. This requires development of the connectors that interface to the power supply, as well as the associated backplanes, wiring harnesses, and bus bars that provide power distribution throughout the system.
The ruggedness of power connectors, as well as their current- and voltage-handling abilities, distinguish them from their signal-routing cousins. Power connectors are available in a number of mechanical styles, including circular, rectangular, and D-subminiature. They attach to boards and wires via soldered, crimped, or press-fit connections.
The term "power connector" might refer to any component that mates to a supply line. In this context, it means those interconnect devices that can handle several amps or more of current.
Beyond the high-current ratings, the connectors discussed here are designed to allow blindmating and hot-swapping of power supplies.
Power Interconnect Requirements
Given the weight of the power supply they're attached to, power connectors must withstand relatively high mating forces when used in blindmating designs. The power-supply module in blindmating systems is inserted along guides. These lead the unit back in the rack until its connector mates with its counterpart on a backplane or bus bar. Evidence of proper mating may be tactile feedback or the illumination of an indicator.
The force required to mate the two power connectors is typically much higher than that of two signal connectors. For example, it's not uncommon to have 25 lbs of insertion force exerted on a power connector during mating. In contrast, mating two SCSI connectors only takes about 5 lbs of force.
Blindmating imposes a few requirements on the connector. First, the connector housing must serve as a guide that allows for some tolerance in the alignment of the connectors. Also, due to the weight of the power supplies and the forces applied to them during insertion, the connector must be mechanically rugged. Durability is not only needed to protect the connector, but also to safeguard other assemblies. So, the connector's housing should be designed to absorb as much insertion force as possible to prevent damage to backplanes and other assemblies. In addition, closed-entry contacts can help prevent damage to the connection interface.
Naturally, there are tradeoffs in de-signing connectors for blindmating. A connector's ruggedness and tolerance for misalignment affect its size, for instance. In other words, enlarging a connector increases its suitability for blindmating. So, demands for blindmating conflict with the ever-present demands for smaller connectors that have higher pin and current density. Consider two blindmating power connectors offered by Positronic Industries. A 30-contact power connector designed to take up 1 mm of misalignment measures 2.4 (l) by 0.8 (h) in., while a similar connector built for 7 mm of alignment error is 3 by 1 in.
Demand for blindmating, in turn, has created demand for mixed-signal and power connectors. To implement blindmating, designers in many cases have moved from multiple connector arrangements (power in, power out, and signals) to a single connector. Gino Nanninga, vice president of sales at Positronic, says this has led to connectors with an assortment of different size contacts and contact spacings.
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