View Single Post
  #15   Spotlight this post!  
Unread 26-10-2011, 14:25
Unsung FIRST Hero
Al Skierkiewicz Al Skierkiewicz is offline
Broadcast Eng/Chief Robot Inspector
AKA: Big Al WFFA 2005
FRC #0111 (WildStang)
Team Role: Engineer
 
Join Date: Jun 2001
Rookie Year: 1996
Location: Wheeling, IL
Posts: 10,770
Al Skierkiewicz has a reputation beyond reputeAl Skierkiewicz has a reputation beyond reputeAl Skierkiewicz has a reputation beyond reputeAl Skierkiewicz has a reputation beyond reputeAl Skierkiewicz has a reputation beyond reputeAl Skierkiewicz has a reputation beyond reputeAl Skierkiewicz has a reputation beyond reputeAl Skierkiewicz has a reputation beyond reputeAl Skierkiewicz has a reputation beyond reputeAl Skierkiewicz has a reputation beyond reputeAl Skierkiewicz has a reputation beyond repute
Re: 12 volt to 24 volt

My answer was directed at Peggy and her team.
For everyone else, the inductor, used in this implementation, dumps charge into the output capacitor(s) when the MOSFET turns off and the magnetic field collapses. During the collapse time, the voltage developed across the inductor adds to that stored in the output capacitors. When the voltage across the inductor added to the battery voltage decays to the sum of the voltage in the output caps plus the diode drop, current ceases to flow to the output capacitors. (Vin + Vinductor</= Vout + Vdiode) The diode in series with the output capacitors prevents the caps from discharging into the power supply circuits and/or robot circuitry. The length of time that the MOSFET is turned on is set by a resistor chosen by the designer for a specific output voltage. During the time that the MOSFET is on, current flows through the inductor establishing a magnetic field. When the FET is turned off, the current that is induced in the inductor as the field collapses has only one path to flow, through the diode. The amount of available load current is also set by choosing a resistor on the supply IC. A full description is available by searching the data sheet for an LM3478.
Please see the linked documentation above on page 7 "24V 1A Boost Supply, 4.5-15V Input".
__________________
Good Luck All. Learn something new, everyday!
Al
WB9UVJ
www.wildstang.org
________________________
Storming the Tower since 1996.
Reply With Quote