Purpose of Voltage Regulators

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Purpose of Voltage Regulators

• A voltage regulator is an electrical
  regulator designed to automatically maintain a
  constant voltage level. A voltage regulator may
  be a simple "feed-forward" design or may include
  negative feedback. It may use an
  electromechanical mechanism, or electronic
  components. Depending on the design, it may be
  used to regulate AC or DC voltages.
• Electronic voltage regulators are found in
  devices such as computer power supplies where
  they stabilize the DC voltages used by the
  processor and other elements. In automobile,
  alternator and central power station generator
  plants, voltage regulators control the output of
  the plant. In an electric power distribution
  system, voltage regulators may be installed at a
  substation or along distribution lines so that
  all customers receive steady voltage independent
  of how much power is drawn from the line.

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Electromechanical regulator
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Voltage sources

• Voltage sources provide constant voltage as
  long as the amount of current drawn from the
  source is within the source's capabilities, its
  output voltage stays constant. An ideal voltage
  source provides no energy when it is loaded by
  an open circuit (i.e. an infinite impedance), but
  approaches infinite power and current when
  the load resistance approaches zero (a short
  circuit).

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CONSTANT CURRENT SOURCE

• a current source provides a constant current, as
  long as the load connected to the source
  terminals has sufficiently low impedance. An
  ideal current source would provide no energy to a
  short circuit and approach infinite energy and
  voltage as the load resistance approaches
  infinity (an open circuit).

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LM 317-CONSTANT CURRENT SOURCE
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The regulator is set up as a constant-current
source. (As opposed to a constant-voltage source,
which is how linear regulators are used most
often.) An LM317 style regulator strives to
always keep the voltage drop from OUT to ADJ
equal to 1.25V. If you put a resistor between the
two (R1), the regulator puts out whatever current
is required to keep the voltage 1.25V while
satisfying Ohm's LawI 1.25 / R2
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LM317-PARAMETERS

• Parameters / Values LM317
• Output Current 500, 1000, 1500 mA
• Input Min Voltage 4.2 Volt
• Input Max Voltage 40, 37 Volt
• Volt Adjustable Output Yes
• On/Off Pin No
• Power Good / Error Flag No
• Temperature Min -40, 0 deg C
• Temperature Max 125 deg C
• Reg Type Linear Regulator