Adjustable DC stabilized power supply circuit diagram

The DC regulated power supply circuit introduced in this example has a maximum output power of 15OW and a maximum output current of lA. The output voltage has two sets of fixed DC voltages of 5V and I2V and two sets of adjustable DC voltages of 3-36V and 108-130V. This regulated power supply can not only be used as a DC power supply for home appliance maintenance, but also can charge nickel-cadmium batteries and small-capacity lead-acid batteries (using 3-36V DC voltage).

How the circuit works

The DC regulated power supply circuit consists of a step-down rectifier circuit and a regulated output circuit, as shown in Figure 5-17.

The step-down rectifier circuit is composed of a power switch S, a power transformer T and a rectifier bridge stack UR1-UR3.

The regulated output circuit is composed of a 5V regulated circuit, a 12V regulated circuit, a 0-36V regulated output circuit and a 108-130V regulated output circuit.

The I2V voltage stabilizing circuit consists of filter capacitors Cl, C2 and a three-terminal voltage stabilizing integrated circuit ICl.

The 5V voltage stabilizing circuit consists of a resistor Rl and a three-terminal voltage stabilizing integrated circuit IC2.

The 3-36V stabilized voltage output circuit is composed of capacitors C3-C5, three-terminal voltage stabilizing integrated circuits R2, R3, potentiometer RPl, diodes VDl, VD2 and voltmeter PVl.

The 108-130V regulated output circuit consists of transistor V, capacitors C6-C9, resistors R4-R7, potentiometer RP2, Zener diode VS, three-terminal voltage stabilizing integrated circuit IC4, diode VD3 and voltmeter PV2.

After the power switch S is turned on, the AC 220V voltage is applied to both ends of the primary winding Wl of the power transformer T, and the 14V and 24V phase 13.5V AC voltages are generated on the secondary windings W2, W3 and W4 of T respectively.

The AC 14V voltage on winding W2 is rectified by UR1, filtered by Cl and stabilized by ICl to produce a +12V output voltage. This voltage is also filtered by C2, current limited by Rl and stabilized by IC2 to produce an output voltage of +5V.

The AC 38V (l4V+24V) voltage generated on windings W2 and W3 is output after rectification by UR2, filtering by C3 and C4, and voltage stabilization by IC3. Adjusting the resistance of RPl can make the output voltage change between 3-36V.

The AC 108V voltage on winding W4 is regulated by the UR3 rectifier and voltage stabilizing output circuit to generate a DC voltage of 108-130V. Adjusting the resistance of RP2 can change the DC output voltage.

Component selection

Rl uses 2W metal film resistors; R2, R4 and R5 all use 1W metal film resistors; R3, R6 and R7 all use 1/2W metal film resistors.

Both RPl and RP2 use 2W synthetic membrane potentiometers.

Cl-C3, C5, C6, C8 and C9 all use CDll aluminum electrolytic capacitors. The withstand voltage value of Cl is 25V, the withstand voltage value of C2 is 16V, the withstand voltage value of C3 and C5 is 5OV, and the withstand voltage value of C6 is 2OOV, the withstand voltage value of C8 and C9 is 160V; C4 uses a monolithic capacitor with a withstand voltage value of 63V; C7 uses a polyester capacitor with a withstand voltage value of 250V.

VDl and VD3 use 1N4004 or 1N4007 silicon rectifier diodes; VD2 uses lN5401 or lN5404 silicon rectifier diodes.

VS uses 1/2W, 6V Zener diode.

URl uses a 2A, 5OV rectifier bridge stack; UR2 uses a 2A, 2OOV rectifier bridge stack; UR3 uses a 2A, 400V rectifier bridge stack.

V selects 2N3055 or 3DD3055 silicon NPN transistor.

ICl selects LM7812 or CW7812 three-terminal voltage stabilizing integrated circuit; IC2 selects LM7805 or CW7805 three-terminal voltage stabilizing integrated circuit; IC3 and 1C4 both select LM317 three-terminal adjustable voltage stabilizing integrated circuit.

T is wound using a 150-2OOW transformer core: winding Wl is wound with 880 turns of φO.5lmm enameled wire;

W2 is wound with 56 turns of φ0.68mm enameled wire; winding W3 is wound with 96 turns of φ0.68-φ0.8lmm enameled wire; winding W4 is wound with 540 turns of φ0.68-φ0.8lmm enameled wire.

PA uses lA DC ammeter.

PVl uses a 0-5OV DC voltmeter; PV2 uses a 0-15Omm voltmeter.