The 3-pin regulator IC as a 78xx numbers have get very popular. I also like it because it is convenient and affordable. Although it is a short circuit within it. But very often, it would have been damaged when a short circuit. I think that should be a good short-circuit protection circuit.As an example, I would suggest a two circuit. We use a simple technique. The more secure without having to change the IC-regulator frequently.
Fuse electronic for ic regulator
Power supply, plus the ground, using current up to 1 Amp.Normally used, IC Regulator no. 78XX. When used to power circuits.And the short circuit that occurred.If no fuse various equipment will be damaged.But if there is an electronic fuse circuit for IC number 78XX.Then when the, short-circuit.This circuit will act to stop paying current and voltage immediately.Thus preventing the loss.
When entering the input voltage, the circuit Q1 and Q2 at the circuit, a bi stable multivibrator circuit.The Q1 Q2 will start but will not work.Because, C1 connected to the base pin of Q1.Then, the charging.Therefore, the voltage at Pin Collector ‘s Q1, to bias the base pin of Q3.Through R4, so the Q3 conduct. And Q4 will conduct with.As a result, voltage input to pin 1 of IC1.Cause the output voltage Implemented.If there is a short circuit when? D1 has served as a ground to stand Q2 base pressure of about 0.3 volts, resulting in a loss Q2 stopped. Bi stable circuit has changed the operating environment to run Q1.
Making Q3, Q4 and IC78XX not work. There is no voltage at the output of the circuit.If you want to IC1 output voltage again, switch S1. To reset the circuit to return to work.Or the bi stable multibrator circuit changes state to work again, sure enough Q4 work.
TTL Power Supply with Crowbar protection by 7805 and SCR
Power supplies that are intended to be used with TTL logic circuitry must guard against over-voltage, which can destroy TTL chips very rapidly. The duration of over-voltage that can destroy TTL chips is much too brief to trigger any conventional fuse, so that only other semiconductor circuits can play any useful part in protecting a circuit against the type of failure of a stabilizer that leads to excessive voltage. As it happens, this is the most common type of stabilizer failure, so that the protection is necessary for any TTL circuit of any significance. Many modern digital circuits make extensive use of MOS devices, which are less susceptible to damage from over-voltage, but it is unusual to find a large digital circuit, which does not contain at least one or more TTL devices.
In the circuit shown below, if the voltage at the output terminals rises above 6.2V, zener conducts charging capacitor C4. This voltage will fire the silicon-controlled rectifier (SCR), which quickly shorts-or puts a crowbar across the supply rails blowing the fuse.
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