Początkujący: "Który schemat mam wybrać, doradzajcie&qu

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Let us assume that for a given output of several volts, P2 is set so that the input of the IC is kept at 1 V. If the load is increased the output voltage will be kept constant by the voltage amplifier section of the circuit and the presence of R7 in series with the output will have a negligible effect because of its low value and because of its location outside the feedback loop of the voltage control circuit. While the load is kept constant and the output voltage is not changed the circuit is stable. If the load is increased so that the voltage drop across R7 is greater than 1 V, IC3 is forced into action and the circuit is shifted into the constant current mode. The output of U3 is coupled to the non inverting input of U2 by D9. U2 is responsible for the voltage control and as U3 is coupled to its input the latter can effectively override its function. What happens is that the voltage across R7 is monitored and is not allowed to increase above the preset value (1 V in our example) by reducing the output voltage of the circuit.

Cytat:

You almost got it all. If you want your Power Supply to provide up to 5A at any output voltage from 0V (dead short) to 30V, then I will update and correct your list:
1) Transformer: 30VAC, 7.5A, 225VA.
2) R2 & R3 = 1/2W.
R7 = 0.27 ohms, 15 or 20W.
R1 = 3 or 4W.
R14 = 1.2K (new discovery).
R15 = 100 ohms.
3) C1 = 10,000uf minimum, 50V.
4) D1 to D4 = 8 to 10A rectifier bridge module bolted to the chassis or to a medium heatsink.
5) P1: If you use a multi-turn pot, then you can't see its setting and won't know what the output voltage will be at power-up. Therefore perhaps having a single-turn 10K "coarse" pot with its dial marked in Volts, in series with a 1K "fine" pot is best.
6) U1 to U3 = OPA445AP.
7) Q1 = TIP31A (new discovery). It has a different pin-out. It doesn't need a heatsink. Connect its emitter to 0V, instead of the negative end of C1 (new discovery). See the other post "Projects Q/A" for an explanation.
Q2 = TIP31A. It has a different pin-out. Bolt it to the metal chassis with an insulator and thermal grease, or to a medium heatsink.
Q3 = Stays the same as a BC557 or BC327.
Q4 = Three 2N3055 transistors in parallel with a 0.1 ohm/1W emitter resistor for each. Use a huge heatsink/and-or forced air cooling with a fan.
Cool Q2 = TO-220 case.
Q4 = 2N3055s have a TO-3 case. Don't use a TO-220 case version.

Cytat:

Czyli wartość maksymalnego prądu ustala R7, wystarczy zwiększyć jego wartość ( np. dwukrotnie ) oraz moc do 10W. Wartość potrzebną policz sobie z prawa Ohma Smile

Cytat:

A tak już ogólnie mówiąc czyli wymiana diod, połączenie dwóch tranzystorów mocy, i wymiana tego jednego rezystora R7 i można cieszyć się z 8A? Nie za proste to jakieś? Spodziewałem się wielkich problemów i przeróbek.

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Jeśli miałbyś dwa takie to świetnie, jeśli jeden to troszkę mniej świetnie, dodałbym wentylator na jego radiator.

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Jeżeli chodzi o regulację ograniczenia prądowego to aby pokrywała zakres do 5A trzeba zmienić wartość rezystora R18. Przy zastosowaniu potencjometrów o takich wartościach jak podane na spisie elementów obliczyłem, że dla 5A rezystor R18 należy zmienić na wartość około 33k.