Protection Diode Lm317

Posted by Jack C. Cook in Protection
Protection Diode Lm317 - overvoltage protection for lm317 as well as 3 moreover zener diode protection overvoltage moreover reverse voltage protection circuit as well as stabilizator elektronika moreover zener diode reverse polarity protection. furthermore
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Protection Diode Lm317

Protection Diode Lm317, furthermore overvoltage protection for lm317 as well as 3 moreover zener diode protection overvoltage moreover reverse voltage protection circuit as well as stabilizator elektronika moreover zener diode reverse polarity protection. Overvoltage Protection For Lm317 together with Zener Diode Reverse Polarity Protection together with Reverse Voltage Protection Circuit additionally 3 additionally Stabilizator elektronika.
Protection Diode Lm317, Overvoltage Protection For Lm317 together with Zener Diode Reverse Polarity Protection together with Reverse Voltage Protection Circuit additionally 3 additionally Stabilizator elektronika. furthermore overvoltage protection for lm317 as well as 3 moreover zener diode protection overvoltage moreover reverse voltage protection circuit as well as stabilizator elektronika moreover zener diode reverse polarity protection.
When external capacitors are used with the LM317, sometimes it becomes essential to add protection diodes to prevent the capacitors from discharging through low current points into the regulator. However, there is no need to use diodes for output capacitors of 25 mF or less. Thus, protection diodes are included for use with output voltage more than 25 V and higher values of output capacitance. 16.6.9 Three Terminals Adjustable Negative Voltage Regulators The LM337 series of Derive the expression for the output voltage for LM317 adjustable voltage regulator. 25. What is the advantage of input, output capacitors and protecting diode ? Draw the voltage regidator circuit using LM317 showing all the capacitors and the protecting diodes.

26..Determine the regulated output voltage available from LM317 regulator if R2 is set to 1.8 k£l. Assume R, = 24CQ and IAD, as WO \iA. (Ans. : 10.81 V) 27. Design the adjustable using LM317 which will satisfy, Output 39V, 1W +100 V in LM317 out adj 4.7K +Vin 27K Iprog GND + 10uF 150V +400V 12 1N5242 10uF + 450V = 116uA GND 5.6 V 500mW Figure 2–8 A high voltage floating linear regulator. 12K 12K 3W Other methods such as a bootstrap Zener diode can also be used in order to shunt the voltage around the pass transistor, but only when the input voltage itself is switched on and off to activate the power supply. Also Protection diodes are usually used for this purpose. One last Example 8.4 An LM317 regulator shown in Fig. 8.13

has.Rl = 240Q and R2 = 2kil If IAD, = 50 uA and V ref 8.14, design an adjustable positive voltage regulator using LM317 for an output voltage V0 varying from 4 to 12 V and an output current I0 of 1A. Solution Maximum IADJ for LM317 = 100 |O.A Assume a Since the output voltage is less than 25V, the protection diode between input and output terminals is not required. If the regulator is placed closer to output filter capacitor of the The program resistor Rj is generally 240 £2 . Generally no capacitors are required. But if LM317 is located far from the power supply filter then the capacitors Q and C2 are required. The input capacitor C\ is generally 0.1 uF disc or 1 |aF tantalum while the output capacitor C2 is in the range of 1 to

1000.nF. To get high ripple rejection, the capacitor C3 is used. To avoid the discharging of the capacitors through low current points into the regulator, the protecting diodes are used. The Fig.Protection diodes are usually used for this purpose. One last caution is the littleknown breakdown voltage of common resistors. If the output voltage exceeds 200V, more than one sensing resistor must be placed in series in order to avoid the 250V breakdown characteristic of 1/4W resistors. A common lowvoltage positive floating regulator is the LM317 (the negative regulator complementary part is the LM337). The MC1723 can also be used to create a floating linear regulator, but Although the LM317 is stable with no output capacitors, like any

feedback.circuit, certain values of external capacitance can cause excessive ringing. This occurs with values between 500pF and 5000pF. A l^F solid tantalum (or 2S\iV aluminium electrolytic) on the output swamps this effect and insures stability. When external capacitors are used with an IC regulator it is sometimes necessary to add protection diodes to prevent the capacitors from discharging through low current points  TableI. Moreover TableI has many mistakes. 3. In the circuit, IC1 is LM315L. Since this 1C has low current capacity, it must be LM317T or LM317. 4. A high value electrolytic capacitor UOuF to 1OOuF) must be used at the output of IC7 to provide improved transient response. 5. A 2200u, 50V capacitor should be used in

place.of C1 since more than LA current is required. 6. A low value capacitor (lOpF, 50V) may be used in place of C7. 7. A protection diode may be used between pins A basic LM317 circuit is shown in Fig. 17.10. Note the use of a reversebias protection diode as employed previously for the fixed regulator. Additionally, a larger capacitor is recommended at the output to improve stability caused by internal differences with the 78xx fixed regulator. The real difference is in the LM317's voltage adjustment mechanism. An internal circuit maintains a fixed 1.25 V between the output and adjustment pins, resulting in a current through Rl determined by its LM317 and LM337 are commercial, grade, three,terminal voltage regulators. The

LM317.provides an adjustable positive voltage output and the LM337 regulates variable negative voltage. They can supply 1.5 A with full overload protection. The easy,to,use lCs require only two external resistors, a protection diode, and Typical circuit arrangement for LM337 To .» Pt. A Edwin H. Hartz is electronics specialist. Applied Science Division, Charles Stewart Molt Community College. Flint 

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