Various diagram

5V Regulated Power Supply Circuit Diagram is a small +5V power supply, which is useful when experimenting with digital electronics. Small inexpensive wall tranformers with variable output voltage are available from any electronics shop and supermarket. Those transformers are easily available, but usually their voltage regulation is very poor, which makes then not very usable for digital circuit experimenter unless a better regulation can be achieved in some way.

The following circuit is the answer to the problem. This circuit can give +5V output at about 150 mA current, but it can be increased to 1 A when good cooling is added to 7805 regulator chip. The circuit has overload and thermal protection. The capacitors must have enough high voltage rating to safely handle the input voltage feed to circuit. The circuit is very easy to build for example into a piece of veroboard.

If you need other voltages than +5V, you can modify the circuit by replacing the 7805 chips with another regulator with different output voltage from regulator 78xx chip family. The last numbers in the the chip code tells the output voltage. Remember that the input voltage muts be at least 3V greater than regulator output voltage ot otherwise the regulator does not work well.

The accepted cesspool of the regulator is minute compared with that of, say, a 78L05: at an ascribe voltage of 9 V and open-circuit output, it is aloof beneath 50 µA. The ambit consists of a aboveboard bandgap advertence based on T1 and IC1, followed by an amplifier formed by IC2 and T1. The advertence voltage is about 1.22 V, which is aloft by IC2 to 5 V. The achievement voltage can be set to absolutely 5 V with P1. The ascribe voltage may lie amid 6.5 V and 30 V. The best achievement accepted with the present agreement and basic ethics as defined is about 10 mA. For optimum performance, T1a and T1b charge to be identical, which is why a bifold transtor Type MAT02 is used. Other types that may be acclimated are the MAT01, SSM2210 or LM394. In principle, two accepted BC transistors may be used, provided they are called for identical beginning voltage. Circuits IC1 and IC2 are programmable op amps Type OP22. In the case of IC2 this has the account that the aiguille achievement accepted can be set readily by altering the accumulation accepted to the op amp with R9. The akin of the accepted may be amid 500 nA and 400 µA.

Bear in apperception that a beyond achievement accepted requires the use of a added awful rated achievement transistor. Filter R6-C1 prevents any affected pulses extensive the ascribe of IC2. Capacitor C2 improves the adherence of the regulator, decidedly with best beating loading. Note that the ambit has a aerial resistance, so that it is appropriate to abode it in a buried asylum to anticipate causeless alluring and electromagnetic arrest actuality accompanying to the circuit. The regulator was activated with a absolute amount accepted of 1 mA on which was superimposed a square-wave accepted of 10 mA. The analysis after-effects are abbreviated in the table, in which Ig represents the accepted fatigued by the circuit.

A 4-cell pack is a convenient, popular battery size. Alkaline manganese batteries are sold in retail stores in packs of four, which usually provide sufficient energy to keep battery replacement frequency at a reasonable level. Generating 5 V from four batteries is, however, a bit tricky. A fresh set of four batteries has a terminal voltage of 6.4 V, but at the end of their life, this voltage is down to 3.2 V. Therefore, the voltage needs to be stepped up or down, depending on the state of the batteries. A flyback topology with a costly, custom designed transformer could be used, but the circuit in the diagram gets around the problem by using a flying capacitor together with a second inductor.

Circuit diagram:

The circuit also isolates the input from the output, allowing the output to go to 0 V during shutdown. The circuit can be divided conceptually into boost and buck sections. Inductor L1 and switch IC1 comprise the boost or step-up section, and inductor L2, diode D1 and capacitor C3 form the buck or step-down section. Capacitor C2 is charged to the input voltage, Vin, and acts as a level shift between the two sections. The switch toggles between ground and Vin+Vout , while the junction of L2, C2 and D1 toggles between –Vin and Vout +Vd1. Efficiency is directly related to the quality of the capacitors and inductors used.

Better quality capacitors are more expensive. Better quality inductors need not cost more, but normally take up more space. The Sanyo capacitors used in the prototype (C1–C3) specify a maximum ESR (effective series resistance) of 0.045 ½ and a maximum ripple current rating of 2.1 A. The inductors used specify a maximum DCR (direct current resistance) of 0.058 ½. Worst-case r.m.s. current through capacitor C2 occurs at minimum input voltage, that is, 400 mA at full load with an input voltage of 3 V. 

Simple Low-Drop 5V Regulator  Circuit diagram:

The schema also isolates the input from the output, allowing the output to go to 0 V during shutdown. The schema can be divided conceptually into boost and buck sections. Inductor L1 and switch IC1 comprise the boost or step-up section, and inductor L2, diode D1 and capacitor C3 form the buck or step-down section. Capacitor C2 is charged to the input voltage, Vin, and acts as a level shift between the two sections. The switch toggles between ground and Vin+Vout , while the junction of L2, C2 and D1 toggles between –Vin and Vout +Vd1. Efficiency is directly related to the quality of the capacitors and inductors used.

Better quality capacitors are more expensive. Better quality inductors need not cost more, but normally take up more space. The Sanyo capacitors used in the prototype (C1–C3) specify a maximum ESR (effective series resistance) of 0.045 ½ and a maximum ripple current rating of 2.1 A. The inductors used specify a maximum DCR (direct current resistance) of 0.058 ½. Worst-case r.m.s. current through capacitor C2 occurs at minimum input voltage, that is, 400 mA at full load with an input voltage of 3 V.