DIY

Stabilized preamplifier power supply ± 15V

Hello homemade radio amateurs!
 Stabilized preamplifier power supply ± 15V

Some circuits, in particular, audio devices: various equalizers, preamplifiers, mixers require high-quality stabilized power supply without ripple, which, moreover, often requires a bipolar one. To do this, you can assemble an adjustable bipolar power supply, for example, on the LM317 and LM337 microcircuits, however, adjustment is often not required and it is enough just to get a stable voltage of 15V for each shoulder – this voltage is often suitable for low-power audio devices. You can get it by collecting the diagram below.
Stabilized preamplifier power supply & plusmn; 15V In essence, the circuit is a parametric voltage regulator with two arms, positive and negative, to obtain a bipolar voltage at the output. Zener diodes are used as a reference voltage source – the output voltage will depend on their stabilization voltage. The diagram shows zener diodes 1N4744A, designed for 15V, however, you can put others instead, depending on the required output voltage. With a significant deviation of the required voltage from 15V, it is necessary to recalculate the value of the resistors R1 and R2 so that the current through the zener diode remains at the level required for it. The power elements in the circuit are TIP41C and TIP42C transistors, note that they have a different structure, since they are located in the negative and positive arms of the circuit, respectively. Using these transistors, the maximum output current of the circuit is 150-200 mA, which is quite enough to power low-power devices. According to the documentation, the maximum permissible current of these transistors is 6A, however, in this circuit, the maximum current output is limited by their low gain. In order to increase the power output of the circuit, you can use composite transistors, they are also Darlington transistors. Due to the fact that two transistors are enclosed in one package, the gain is significantly increased. Their designation is shown below.
Stabilized preamplifier power supply ± 15V There is a step-down transformer at the input of the circuit, it must have either two identical windings, or have one, but with a tap from the middle – this is a prerequisite for the operation of this circuit, since a bipolar voltage is obtained at its output. Accordingly, each arm is powered by its own transformer winding. The voltage of each winding must be no less than the stabilization voltage of each arm. But you also should not take a transformer with too high an output voltage, because all the voltage difference from the input and output of the circuit is dissipated in the form of heat on the transistors. The best option would be if the transformer voltage is 2-5V higher than the stabilization voltage. The power of the transformer should be 10-30W, depending on the power of the connected load. The diode bridge VD1-VD4 rectifies alternating voltage, capacitors C2, C4 smooth out ripple, filter capacitors play an important role, given that the circuit is supposed to power audio devices. The rest of the circuit does not have any peculiarities, does not require tuning, and has excellent reliability. To create a normal thermal regime for transistors, it is recommended to put them on small radiators, for example, from an aluminum or copper strip. Happy build!
Stabilized power supply preamplifier & plusmn; 15V

Source:

usamodelkina.ru

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