Power supply of low-voltage radio equipment from the network. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Power supply of low-voltage radio equipment from the network. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Power Supplies

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Modern portable and pocket radios, especially imported ones, as a rule, are powered by two batteries or accumulators and can be powered under stationary conditions from any source with a stabilized voltage of 3 V and a permissible current of up to 0,2 A. The same voltage is also necessary for powering electronic games such as "Just WAIT" and many other devices. The necessary power supply, if you try, can be found in commercial stores, but imported and at an unreasonably high price, and the domestic industry produces few such power supplies. In addition, they usually do not have output voltage stabilization, which leads to listening to the network background.

Collecting the necessary source is within the power of anyone who knows how to use a soldering iron, and this will not require much time and high costs.

Here are two options for building such a scheme, assembled on different elements, and you can choose the specific one yourself, having become acquainted with their features and based on your capabilities.

On fig. 1 shows a simple circuit of a 3 V power supply (load current 200 mA) with automatic electronic overload protection (Iz \u250d 8 mA). The level of output voltage ripple does not exceed XNUMX mV.

Power supply of low-voltage radio equipment from the network
Ris.1

For normal operation of the stabilizer, the voltage after the rectifier (on diodes VD1 ... VD4) can be from 4,5 to 10 V, but it is better if it is 5 ... 6 V - less source power is lost to heat dissipation by the transistor VT1 during operation stabilizer.

The circuit uses the HL1 LED and diodes VD5, VD6 as a reference voltage source. The LED is also an indicator of the operation of the power supply.

Transistor VT1 is mounted on a heat-dissipating plate. Transformer T1 can be purchased from any unified TN series, but it is better to use the smallest TI1-127/220-50 or TN2-127/220-50. Many other types of transformers with a secondary winding of 5 ... 6 V are also suitable. Capacitors C1 ... C3 - type K50-35.

The second circuit (Fig. 2) uses the integral regulator DA1, but unlike the transistor regulator shown in fig. 1, for the normal operation of the microcircuit, it is necessary that the input voltage exceed the output voltage by at least 3,5 V. This reduces the efficiency of the stabilizer due to heat dissipation on the microcircuit - at a low output voltage, the power lost in the power supply will exceed that given to the load.

Power supply of low-voltage radio equipment from the network
Ris.2

The required output voltage is set by the trimming resistor R2. The microcircuit is installed on the radiator.

The integral stabilizer provides a lower level of output voltage ripple (1 mV), and also allows the use of smaller capacitances.

See other articles Section Power Supplies.

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