Showing posts with label lm317. Show all posts
Showing posts with label lm317. Show all posts

Thursday, April 11, 2013

LM317 Circuit

Introduction
The LM317 is AN adjustable three terminal transformer that is capable of supply 1.2 to 37 volts with a secure 1.5A output current. The LM317 is prepackaged terribly} normal electronic transistor package that makes it very simple to mount in your circuits. 
 
Schematic


Overview
The LM317 series of adjustable 3-terminal positive voltage regulators is capable of supply in more than 1.5A over a 1.2V to 37V output vary. theyre exceptionally simple to use and need solely 2 external resistors to line the output voltage. Further, each line and cargo regulation square measure higher than normal mounted regulators.

In addition to higher performance than mounted regulators, the LM317 series offers full overload protection out there solely in ICs. enclosed on the chip square measure current limit, thermal overload protection and safe space protection.

The LM317 makes AN particularly easy adjustable change regulator, a programmable output regulator, or by connecting a set electrical device between the adjustment pin and output, the LM317 may be used as a preciseness current regulator. provides with electronic conclusion may be achieved by clamping the adjustment terminal to ground that programs the output to one.2V wherever most masses draw very little current.

Pinout

Options


Specifications

  • Guaranteed 1% output voltage tolerance (LM317A)
  • Guaranteed max. 0.01%/V line regulation (LM317A)
  • Guaranteed max. 0.3% load regulation (LM117)
  • Guaranteed 1.5A output current
  • Adjustable output down to 1.2V
  • Current limit constant with temperature
  • P + Product Enhancement tested
  • 80 dB ripple rejection
  • Output is short-circuit protected
Output Formula
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Wednesday, April 10, 2013

High Current Regulated Supply Circuit Using LM317

The high current regulator circuit is built uses an additional winding or a separate transformer to supply power for the LM317 regulator so that the pass transistors can operate closer to saturation and improve efficiency. For good efficiency the voltage at the collectors of the two parallel 2N3055 pass transistors should be close to the output voltage. The operation of this circuit is explained like this.


The LM317 requires a couple extra volts on the input side, plus the emitter/base drop of the 3055s, plus whatever is lost across the (0.1 ohm) equalizing resistors (1volt at 10 amps), so a separate transformer and rectifier/filter circuit is used that is a few volts higher than the output voltage. The LM317 will provide over 1 amp of current to drive the bases of the pass transistors and assumption a gain of 10 the combination should deliver 15 amps or more.

The LM317 always operates with a voltage difference of 1.2 between the output terminal and adjustment terminal and requires a minimum load of 10mA, so a 75 ohm resistor was chosen which will draw (1.2/75 = 16mA). This same current flows through the emitter resistor of the 2N3904 which produces about a 1 volt drop across the 62 ohm resistor and 1.7 volts at the base. The output voltage is set with the voltage divider (1K/560) so that 1.7 volts is applied to the 3904 base when the output is 5 volts. For 13 volt operation, the 1K resistor could be adjusted to around 3.6K. The regulator has no output short circuit protection so the output probably should be fused.

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