© aydindurdu dreamstime.com Application Notes | January 02, 2017
Active bridge rectifiers reduce heat dissipation within PoE security cameras
Power over Ethernet (PoE) has been embraced by the video surveillance industry as a solution to an age-old problem: complicated cabling.
This is a product release announcement by Linear Technology Corporation. The issuer is solely responsible for its content.
For instance, a basic, traditional fixed-view security camera requires two cables: one for power (10W to 15W from a 24V AC or 12V DC), and a separate, coax cable for the video signal. With PoE, a single Ethernet cable carries both video data and power. Everything is simplified. Right? Not quite. To meet compatibility with existing systems, camera manufacturers must produce PoE-enabled cameras that are also compatible with legacy power sources—they must accept PoE 37V to 57V DC from an RJ-45 jack or 24V AC, +12V DC, or –12V DC from an auxiliary power connector. The Old Way Loses Power Figure 1 shows the power architecture used by many PoE camera manufacturers to solve this problem. A full-bridge diode rectifier after the auxiliary (old-school) input produces positive DC power from either 24V AC, +12V DC or –12V DC. The resulting DC power and the PoE inputs are diode-ORed with the winning supply fed to a wide input voltage isolated switching power supply, which in turn powers the camera electronics. Figure 1. Auxiliary Input and PoE Power Architecture This power architecture presents a few challenges. When the camera is powered from the auxiliary input, three diodes (circled in Figure 1) fall into the power path. In addition to the inefficiency of this design and possible heat problems from the power dissipated by the diodes, the three diodes lead to a significant voltage drop at the input to the switching power supply. With a 10W to 15W camera, these challenges are easily surmountable, but the latest security cameras have doubled this power consumption. Features like pan/ tilt/zoom (PTZ) and camera lens heaters for outdoor operation have made this power architecture unsuitable for this new wave of cameras. To illustrate the architecture’s deficiencies, consider a 26W camera. For a 12V DC auxiliary input (assumed to actually be 9V DC due to use of unregulated wall warts/ AC adapters) and three 0.5V drop Schottky diodes, the input voltage of the switching power supply is 7.5V (9V – 3 • 0.5V). The input current for this camera is approximately 3.5A (26W/7.5V). The resultant power dissipation of the three Schottky diodes in the power path is 5.2W (3.5A • 3 • 0.5V). This power dissipation leads to higher temperature within the camera, which is difficult, time consuming and expensive to mitigate. Figure 2. Improved Power Architecture with No Diode Drops in Power Path Improve Performance with Ideal Diodes Figure 2 shows a way to counter this shortcoming. Here, the two diodes of the full-bridge rectifier are replaced by ideal diodes, circled (black) in Figure 2. Ideal diodes are simply MOSFETs controlled to behave like regular diodes. The advantage of an ideal diode is that one can use MOSFETs with low channel resistance (RDS(ON)), thus reducing the forward voltage drop (IDS • RDS(ON)) to much less than a Schottky diode drop. The LT4320 ideal diode bridge controller enables the control of four MOSFETs in a full-bridge configuration. The third diode drop due to the diode-OR in Figure 1 is eliminated by the LT4275 LTPoE++™/PoE+/PoE PD controller. Its topology allows the use of a few small-signal diodes, circled together (red) in Figure 2, for auxiliary input sensing. These diodes are not in the power path as in the traditional architecture, so they do not contribute any additional voltage drop or heat issues. Results The power architecture shown in Figure 2 significantly reduces overall power losses when compared to that of Figure 1. To quantify, the LT4320 combined with low channel resistance MOSFETs results in a 20mV drop across each ideal diode bridge MOSFET. This produces an input at the isolated supply of 8.96V (9V – 2 • 20mV). The higher input voltage drops the required input current to only 2.9A (26W/8.96V) versus the original 3.5A. The resulting power dissipation of the improved architecture is now a scant 116mW (2.9A • 2 • 20mV), versus 5.2W for the original architecture—a 45× reduction! Additionally, the lower input current further reduces power dissipation in the isolated power supply’s power components (i.e., input filter inductor, power transformer and switching MOSFETs) due to the reduction of their I2R power losses. A simple calculation puts this reduction at 31% (100% – 2.9A2/3.5A2). Conclusion Adding the LT4320 and LT4275 to the auxiliary and PoE inputs of a PoE-enabled security camera recovers more than 5W (5.2W – 116mW) of power dissipation over traditional full-bridge/diode-OR designs. This reduction of power eases the thermal design time and complexity of PoE security cameras. ----- Author: By Ryan Huff, PoE Applications Engineer, © Linear Technology Corp.
Vicor ink global distribution agreement with Arrow Vicor Corporation has expanded its Europe, Middle East and Africa relationship with Arrow Electronics, Inc. to a global distribution agreement.
Hemlock Semiconductor acquires DuPont TCS business The Michigan-based provider of ultra-pure polycrystalline silicon announces its acquisition of a DuPont business that makes trichlorosilane (TCS), the primary raw material used in producing the ultra-pure polysilicon HSC supplies to the semiconductor and solar industries.
Huawei opens 5G test centre in Serbia The company has officially opened its latest European centre for innovation and digital development and 5G test lab in Belgrade, Serbia.
First Sensor plans to sell its subsidiaries in USA and France to TE Connectivity Berlin-based First Sensor says it is planning to sell its US-based subsidiary in California, as well as its unit in Paris, France to TE Connectivity.
Sponsored content by Nordson ASYMTEKConformal Coating Results — When You Need Better Than Just "Good Enough" Conformal coating contributes to product quality and reliability, but it is typically viewed as a process that tolerates sufficient results, or "good enough." That view is changing as more advanced and diverse electronic products enter the consumer marketplace, from the Internet of Things to self-driving vehicles.
Silvaco acquires the assets of Coupling Wave Solutions S.A. EDA software and design IP supplier, Silvaco, has completed its acquisition of the assets of Coupling Wave Solutions S.A. (CWS), including IP, patents, and analysis technologies.
Nvidia / Arm deal dubbed as ‘disaster’ by Arm-cofounder The news that US-based Nvidia will acquire Arm from SoftBank Group in a USD 40 billion deal has already sparked some backlash within the industry. One of the vocal parties is Arm-cofounder, Hermann Hauser, who called the deal a disaster and said that it should be blocked.
Everlight criminally convicted for misappropriating Seoul Semi trade secrets LED technology supplier, Seoul Semiconductor, says that the Korean Suwon District Court convicted Everlight Electronics of criminal misappropriation of Seoul’s trade secrets.
It's official - NVIDIA to acquire Arm for $40 billion NVIDIA and SoftBank have entered into a definitive agreement under which NVIDIA will acquire Arm Limited from SoftBank in a transaction valued at USD 40 billion.
Tower Semi: 'all sites up and running following cyber attack' Tower Semiconductor says that all of its manufacturing sites are operational, and targeting full capability within the next few days, following the recovery from the cyber event a few days ago.
Jenoptik invests in new system from ClassOne Jenoptik has invested in a new Solstice LT electroplating system from semiconductor equipment manufacturer ClassOne Technology. The new system will be used for manufacturing semiconductor material for high-power diode lasers at Jenoptik's semiconductor production facility in Berlin-Adlershof, Germany.
MaxLinear acquires NanoSemi, Inc. MaxLinear, a provider of radio frequency (RF), analog, digital and mixed-signal integrated circuits, has completed the acquisition of NanoSemi, a provider of IP that utilises patented machine learning techniques to improve signal integrity and power efficiency in SoCs, ASICs, and FPGAs used in next-gen communication and AI systems.
Delphi secures major power electronics business win The provider of automotive propulsion systems announces that it has secured a major Original Equipment Manufacturer (OEM) electrification business, driving profitable long-term growth.
Yamaichi Electronics' new European factory Japan-based group Yamaichi Electronics has been producing in Frankfurt (Oder), the only manufacturing location of the group in Europe, for almost 15 years. Now production is running out of space.
SnapEDA launches new KiCad plugin to help engineers design electronics faster Today, SnapEDA - a company that helps engineers design electronics faster by removing barriers - is launching a new KiCad plugin, allowing designers to search and download its computer-aided design (CAD) models directly within the KiCad PCB design environment.
One final update from the Infineon site in Villach The shell of Infinion’s massive expansion in Villach, Austria now stands complete. Both the research and factory building are standing tall and the company is in full swing working on the facade as well as the interior.
Tower Semiconductor hit by cyber attack The semiconductor company says that it has taken measures to prevent the expansion of the event, but at this point there is no assessment as to the actual effect on the company.
SMIC responds to reports about a potential blacklist situation Chinese semiconductor foundry, Semiconductor Manufacturing International Corporation (SMIC), found itself in eye of the storm following reports of a potential U.S. ban, much like the one experienced by Huawei.
ON Semi CEO plans to retire ON Semiconductor's president and CEO, Keith D. Jackson, intends to retire from ON Semiconductor in May 2021.
YES partners with Link Fab in Singapore and Malaysia YES (Yield Engineering Systems, Inc.), a manufacturer of process equipment for the semiconductor advanced packaging, life sciences and AR/VR markets, says it has signed an agreement with Link Fab to provide sales and service for YES’s clean, coat and cure systems in Singapore and Malaysia.
Former Digi-Key executive to bring expertise to RS and Allied Electrocomponents has announced the appointment of Chris Beeson to the role of Group Senior Vice President Electronics. Chris will report directly to COO Mike England and will be based at the headquarters of Allied Electronics & Automation in Fort Worth, Texas, USA.
Siltronic ramps up GaN wafer activities with Aixtron system Siltronic AG strengthens its GaN on Silicon wafer activities with an AIX G5+ C system from Aixtron.
Osram went head to head with its contract manufacturer The Munich-based company says that it protects its know how and has concluded a settlement with Taiwanese contract manufacturer Lextar Electronics
Panasonic completes transfer of its semiconductor business Panasonic says it has completed the transfer of its semiconductor business to Nuvoton Technology Corporation, a Taiwan-based semiconductor company under the Winbond Electronics umbrella.
MagnaChip completes the sale of its foundry services and Fab 4 The designer and manufacturer has completed previously announced sale of the its Foundry Services Group and the factory in Cheongju (Fab 4) to Key Foundry Co., Ltd., for approximately USD 350.6 million.Load more news