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and provide around-the-clock care, they become more vulnerable to a wide array of security risks. While industry guide- lines mandate a growing reliance on security under its ‘Environment of Care’ standards, it is the responsibility of each individual hospital and healthcare organisation to decide on the right tools to meet their needs for protecting patients, visitors, staff and intellectual property.
Camera deployment To get complete surveillance coverage in most sites, several hundred cameras could be required. One of the most popular ways to monitor and manage a multiple location facility utilises Internet Protocol (IP) cameras with Power over Ethernet (PoE) capabilities.
Video security benefits from No-Opto Flyback DC/DC Controller
Bruce Haug, Senior Product Marketing Engineer, Power Products at Linear Technology explores the evolving video security market and how it is benefiting from a No-Opto Flyback DC/DC Controller
ven before heightened awareness brought on by threats of terrorism, many public and private institu- tions had already begun incorpo- rating video security into critical infrastructure. Video security provides the visual images necessary to improve situation awareness, deter vandalism, theft or other crime, accelerate response and management decisions and increase overall staff and public safety. From air- ports to bridges, refineries to pipelines, seaports to highways, all have benefited from incorporating video security equip- ment in their ‘preparedness’ plans. The first line of defence in airport security is fences, barriers and walls. Especially sensitive areas such as fuel depots, passenger terminals, even bag- gage handling facilities are more secure with security checkpoints. All of these areas and most locations inside an air- port are usually monitored with surveil- lance cameras.
E
One of the most demanding video secu- rity installations is a casino, where the sleight of hand and the quickest of move- ments must be captured, reviewed and archived to meet stringent regulations. The strategic placement of ‘Eye in the
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Sky’ cameras supplements a security staff's physical presence, helping to better manage crowds and deploy personnel in a timely and effective manner. High-quality video of gaming areas provides security professionals with the detailed information needed to prevent cheating, as well as catching any cheaters.
Retail stores benefit from video surveillance systems by serving as a visual deterrent to potential criminal acts and provide managers and security professionals with tools for dealing with liability claims, employee theft or other related issues. As a result, shoplifting and employee theft can be dealt with more easily when the perpetrator is caught in the act on video. Furthermore, slips, falls and liability claims can be more accurately understood and processed when caught on video, too. Contraband, violence, inmate and officer safety are just a few of the issues that must be dealt with on a routine basis in the management of today's correctional facilities. And so, video security has never played a more important role in maintaining order and ensuring a safe working environment.
As healthcare facilities grow larger
Linear Technology's LT3748 isolated flyback controller, ideal for video security
applications
This type of implementation can significantly simplify and reduce the cost of camera installations since data and power are transferred on the same cable and cameras do not need to be installed near a power source. However, care must be taken with regards to the maximum amount of power that can be drawn from an Ethernet cable. For more information on the maximum allowable power from a PoE interface, see the IEEE 802.3af (PoE) or IEEE 802.3at (PoE+) specifications. Surveillance cameras typically operate from a 24V DC or 12V DC supply voltage at power levels up to 25 Watts. A PoE connection will provide 48V which needs to be stepped down and isolated from its input to output for safety and fault reasons, making the power supply more complicated. However, recent advances in power conversion technol- ogy have made low to medium power isolated converters much simpler and easier to design.
Flyback converters have been widely used in isolated DC/DC applications for many years, but are not necessarily a designer's first choice. Power supply designers grudgingly choose a flyback out of necessity for lower power isolated requirements, not because they are easier to design.
The flyback converter has stability issues due to the well-known right-half- plane zero in the control loop that is further complicated by the propagation delay, aging and gain variation of an opto- coupler. Furthermore, a flyback converter requires a significant amount of time devoted to the design of the transformer, a task further complicated by the nor- mally limited selection of off-the-shelf transformers and the possible necessity for a custom transformer. However, Linear Tech nology's LT3748 isolated flyback controller solves many of these flyback converter design challenges.
New Flyback IC simplifies design First of all, this controller eliminates the
JUNE 2012 Electronics
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