Diagram Guide

The schema diagram shows the over voltage protection as a feature of LM317 linear voltage regulator.Over voltages come from several source or factors which are usually in the form of transients. Transients are represented in spikes which are short and fast disturbance or change in the voltage and current component.

It only occurs in diagram containing conductance and capacitance. The causes are typically from power outages, short diagram, tripped schema breakers, lightning spikes, inductive spikes and other malfunctions from power company.

 As an example using a 12V battery source, the LM317 voltage regulator can be used to obtain 6 Volts. To protect any device from over voltage, there are ways such as adding relays or a zener diode. A relay switch functions by opening or closing under the command of another schema. But finding a relay that would limit the output from 6 V to 12 V is not easy.

Fortunately, zener diodes are more abundant. A 6.2V zener diode rating can be used to surpass any excessive voltage set by the voltage regulator, to prevent more damage to the schema. The components will be as follows:

ZD1 – 6.2 Volts
R1 – 1K ohms
R2 – 1K ohms
T1 – NPN Transistor (low power)
T2 – NPN Transistor (acts as a switch)

Every schema design needs to be tested carefully as to avoid further damage to the equipment that will be connected. The trial can be done by using a multimeter, and gradually increasing the schema voltage. Once the schema turns off the supplied voltage, take note of the reading which will signify the threshold voltage of the zener diode.

Build a 1.2-36V 5A Adjustable Power Supply schema diagram with LM317. This schema is a simple power supply schema. 1.2 - 36V adjustable bench power supply with 5A of output current. Max input voltage is 37V and output is adjustable via potentiometer between 1.2 up to 36 volts. TIP147 PNP darlington transistor boosts the current of LM317 from 100mA to 5A. LM317 is the most useful and inexpensive adjustable regulator and for this schema you can also use LM317 L that can give 100mA, thats enough for transistor bias. 

 D1 and D2 are protection diodes because when you turn the schema off the output capacitors are discharging and can damage the transistor or regulator. 100nf capacitors are in parallel with electrolytic capacitors to remove high frequency noise because large value electrolytic have large ESR and ESL and cant remove high frequency noise.