Project Analog - December 2007 - (Page 16)

sured remaining fuel level. Although this would only be useful for systems where a fuel cartridge can be removed and reinserted. Other than the fuel cartridge fuel level, there are other parameters that need to be monitored regarding the fuel cell. These include temperature, fuel input rate, voltage output, and current output. These are used to calculate the present efficiency of the fuel cell. Using temperature you can determine if the fuel cell is running in an optimal state. The dc supply and system-load power data also should be measured to complete the data set. With this data and that from both of the monitoring subsystems, the values for total available energy and peak available energy can be generated. The available runtime of the end equipment is a function of these four factors. The nature of the fuel cell power output response capability and the battery size also raises a problem when it comes to the end of power shutdown. This needs additional understanding. predIctIng hpS run tIme The battery and fuel-cell-monitoring subsystems can provide total and peak energy to the host system, and allow the host system to determine the various pieces of user data that it requires. In this example architecture we have a power controller that can provide several advantages. The main one is that it can manage the data and subsystems, enabling the hybrid power source to be used as if it were any other standard battery power source. The power controller takes the monitored data and manages the use of the battery, maximizing its capabilities over the expected lifetime of the HPS. This can be beneficial in two specific areas: 1. Ensuring that peak available energy is at an optimal level by allowing the fuel cell to charge the battery, even when no dc supply is present. 2. Managing the state-of-charge (SOC) battery so that it has maximum usability within this architecture. Contents Viewpoint Charging lithium-ion batteries New trends in battery-powered portable devices Low power design: LDO thermal considerations Analog news Microchip analog page Battery charger overview Sample center microchipDIRECT Reference designs/ app notes Technical training fig. 2 EnErgy usagE comParison 16 · prOject AnALOg · Dec 07 http://www.microchip.com http://www.microchip.com/analog http://www.microchip.com/analog http://www.microchip.com/batterychargers http://www.microchip.com/batterychargers http://sample.microchip.com/Default.aspx?testCookies=true http://www.microchipdirect.com/catalogselection.aspx?returnURL=default.aspx http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1469&filter1=function&redirects=appnotes http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1469&filter1=function&redirects=appnotes http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1423

Table of Contents Feed for the Digital Edition of Project Analog - December 2007

Project Analog - December 2007 Contents Viewpoint About Project Analog Sponsor4 Charging Lithium-Ion Batteries: System Considerations New Trends In Battery-Powered Portable Devices Low Power Design: LDO Thermal Considerations Runtime Measurements for a Hybrid Power Source Battery-Powered System Design Considerations Analog News—Analog News from Multiple Sources Enter to Win an iPhone Contact Project Analog Sponsor Mindi™ Battery & Power Circuit Simulator Microchip Advanced Parts Selector (MAPS)

Project Analog - December 2007

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