Power Supply

Update date:2018-05-30 Source:MAXGE

Power Supply

1, 3 - 25V voltage adjustable voltage regulator circuit

The adjustable range of the power supply can be arbitrarily adjusted between 3.5V and 25V, and the output current is large. The adjustable stabilizing tube circuit is used to obtain a satisfactory and stable output voltage.

Working principle: After the rectifier filter, the DC voltage is supplied by R1 to the base of the adjustment tube to make the adjustment tube conduct. When V1 is turned on, the voltage passes through RP and R2 to make V2 conduct, and then V3 also conducts. At this time, V1 The emitter and collector voltages of V2 and V3 no longer change (it acts exactly like a Zener). Adjust the RP to obtain a smooth output voltage. The ratio of R1, RP, R2, and R3 determines the voltage value output by the circuit.

Components Selection: Transformer T choose 80W - 100W, input AC220V, output dual winding AC28V. FU1 selects 1A, and FU2 selects 3A-5A. VD1, VD2 use 6A02. RP selects about 1W ordinary potentiometer, the resistance value is 250K- 330K, C1 selects 3300μF/35V electrolytic capacitor, C2, C3 selects 0.1μF monolithic capacitance, C4 selects 470μF/35V electrolytic capacitor. R1 selects 180 – 220Ω/0.1W – 1W, R2, R4, R5 selects 10KΩ, 1/8W. V1 selects 2N3055, V2 selects 3DG180 or 2SC3953, V3 selects 3CG12 or 3CG80

3 - 25V voltage adjustable voltage regulator circuit

2, 10A3 - 15V regulator adjustable power supply circuit

No matter whether the maintenance of computers or electronic production are inseparable from the power supply, the following describes a DC voltage from 3V to 15V continuously adjustable power supply, the maximum current up to 10A, the circuit uses a temperature compensation characteristics, high precision The standard voltage source integrated circuit TL431 makes the regulation accuracy higher. If there is no special requirement, it can basically meet the normal maintenance and use. The circuit is shown in the figure below.

10A3 - 15V regulator adjustable power supply circuit

Its working principle is divided into two parts. The first part is a fixed 5V 1.5A power supply circuit. The second part is another high-precision large-current steady voltage circuit that is continuously adjustable from 3 to 15V. The circuit of the first circuit is very simple. After the secondary 8V AC voltage of the transformer is rectified by the silicon bridge QL1, the DC voltage is filtered by the C1 electrolytic capacitor, and then the 5V three-terminal regulator block LM7805 can be used at the output without any adjustment. Fixed 5V1A regulated power supply. This power supply can be used as an internal power supply when servicing the computer board.

The second part is basically the same as an ordinary series-type regulated power supply. The difference is that a high-precision standard voltage source integrated circuit TL431 with temperature compensation characteristics is used, so the circuit is simplified, the cost is reduced, and the voltage regulation performance is high. . Resistor R4, voltage regulator TL431, and potentiometer R3 form a continuous adjustable constant voltage source to provide a reference voltage for the base of BG2. The voltage regulator value of the voltage regulator TL431 is continuously adjustable. This voltage regulation value determines the stability. Press the power supply's maximum output voltage. If you want to expand the adjustable voltage range, you can change the resistance of R4 and R3. Of course, the secondary voltage of the transformer must also be increased. The power of the transformer can be flexibly controlled based on the output current and the secondary voltage is about 15V.

The bridge rectifier rectifier QL uses a 15--20A silicon bridge, which has a compact structure and fixed screws in the middle. It can be directly fixed on the aluminum plate of the chassis, which is advantageous for heat dissipation. Adjust the tube with a large current NPN metal shell silicon tube, because of its large heat, if the chassis allows, try to buy a large heat sink, expand the cooling area, if you do not need a large current, you can also use a smaller power Silicon tube, this can be made smaller.

Filtering with 50V4700uF electrolytic capacitors C5 and C7 respectively with three parallel connection, so that the high current output is more stable, in addition to this capacitor to buy a relatively large volume, those smaller size the same marked 50V4700uF try not to use, when encountered frequent voltage fluctuations, or Long time no use, easy to failure. Finally, talk about the power transformer, if you do not have the ability to self-winding, you can not buy ready-made, you can buy a ready-made more than 200W switching power supply instead of the transformer, so that the voltage regulator performance can be further improved, the production cost is not too bad, There are no special requirements for other electronic components. After the installation is completed, it can work normally without too much adjustment.

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