Lab3 - L303-3.R23 Drexel University Electrical and Computer...

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L303-3.R23 Drexel University Electrical and Computer Engr. Dept. Electrical Engineering Laboratory III, ECEL-303 E. L. Gerber DC  VOLTAGE  SUPPLIES  and  REGULATION Object The objects of this experiment  are to introduce  you to a voltage regulator  system,  voltage regulator  concepts, and  the voltage regulator  integrated  circuit chip (IC).  You will  learn how  to calculate voltage regulation  and  how  to design  a voltage regulator  IC system.  Also you will learn how  to convert AC line voltage to a regulated  DC voltage. Introduction All electronic systems require a good  quality (regulated) DC voltage source to  operate.  Radios, TVs, CD players, boom-boxes, and  computers  all require a very stable DC  voltage.  Batteries are a possible source of power  for these systems, but they have limited   power  and  are expensive.  Most home and  laboratory  systems utilize the 115 V-AC power   line for power.  The problem  is this voltage is the wrong  type (AC) and  is too large (115 V- RMS).  Most electronic devices use low DC voltages ranging  from 5 to 24 volts. The first step in the process of converting  the line voltage to a lower level DC is to  reduce the level of the AC voltage with  a step-down  transformer; a 10:1 transformer  will  output  11.5 V-RMS.  The second  step is to convert the AC sine wave to a full-wave rectified  sine wave (no negative content).  The third  step is to convert the varying  rectified DC wave  to a constant  (flat) DC function.  The final step is regulation, which keeps the DC level from  changing  if either the power  line changes or the load  connected  to this DC power  supply   changes. 3-1
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L303-3.R23 Theory 1 - Rectification: A PN junction diode  has the property  of allowing  current to flow in only one direction, and   almost no current in the other direction.  Fig. 1 depicts the output  of a full-wave bridge  rectifier circuit fed from a 10:1 step-down  transformer. Fig. 1. Bridge Rectifier and Full-Wave Sine Output Voltage The four diodes permit the sine wave current to flow in only one direction through  R C .  The  output  of the rectifier circuit shown  as V L  . The period  of the output  is T = 1/2f = 1/120 sec.  The peak value is V P  =  V R MS  =  12 volts, and  it has a DC (average) value V DC  = 2V P / , π   but it is not a constant  DC, see Fig. 1. 2 - Filters:
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This note was uploaded on 04/05/2010 for the course ECEC 303 taught by Professor Gerber during the Spring '10 term at Drexel.

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Lab3 - L303-3.R23 Drexel University Electrical and Computer...

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