Invisible power supplies. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Invisible power supplies. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Power Supplies

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Most of all, we value those devices that work, but are invisible themselves. It also happens to be convenient to “hide” power supplies in the body of a large device, in which there is enough free space.

Figure 1 shows a diagram of the installation of a voltage stabilizer in the case of a tube TV with a direct voltage output to the antenna jack. The power stabilizer circuit can be selected from those published by the author in "Electric" in 2000. It is only important that there is an incandescent lamp of minimum power in the break of the mains wire, which is sufficient for the operation of the powered device, and the stabilizer is performed according to the sequential stabilization scheme (in this case, removing the load leads to to the minimum current consumption from the network by the stabilizer circuit).

Invisible power supplies

Inductor L1 and capacitor (ceramic) C1 are installed to "decouple" DC and high-frequency signal. Resistors R1 ... R3, included in the "triangle", are needed to match the wave impedances of cables converging into one node. To ensure the passage of direct current, the resistor R1 has a winding similar to the choke L1.

From the side of the antenna, capacitor C2 is connected to the central core of the cable. If a Polish amplifier is installed on the antenna, then this capacitor is not needed: the power supply will provide voltage for the operation of the antenna amplifier.

To connector X2 (antenna plug) you can connect both a portable TV without a power cord (for example, in the kitchen), and a transistor receiver also without a power cord and a power stabilizer.

The antenna socket has a decoupling similar to that connected to the power supply with the addition of a diode (KD226 or others) connected in series with the inductor so that the diode conducts from the + 12 V antenna socket to the portable TV circuit, and in the opposite direction (from the portable power supply TV to the antenna jack) the current could not pass. This must be done, because the stabilized power supply was originally designed for heavy-duty operation, and the power supply of a portable TV can be quickly disabled by the "normal" shorting of the antenna jack or cable core to the braid!

If you connect a transistor receiver instead of a portable TV, you need to install an antenna TV jack on its body, to the central output of which connect only the elements that provide power (inductor and diode).

The practice of many years of operation has confirmed the convenience of such a scheme for the user: a thin TV cable with a plug "enters the kitchen", which can be hidden, or you can power a small transistor TV, radio, etc. from it.

The protective incandescent lamp (Fig. 2) must be installed so that it is convenient to observe its glow.

Invisible power supplies

It is necessary to turn off the power of the built-in unit regardless of the scheme of the TV, in the case of which the PSU is built.

In addition to powering the load, the circuit can be used to test transistor devices, New Year's garlands or "running lights". If there is no “ringing” at hand, you can, by observing the glow of the protective lamp, check the cable cores (after all, the power supply is not afraid of short circuits).

To make all such connections, you need to have an antenna jack with red and blue wires soldered to it (the colors indicate the polarity of the voltage).

The inductor is wound on a resistor BC-0,5 with a resistance above 30 kOhm with a thin wire in sections: 4; 8; 16; 32; 64; 128 turns. For the MV range, four sections with a large number of turns can be used, for the UHF - four sections with a small number of turns. You can fix the sections with strips of paint or nail polish.

A section with a smaller number of turns is mounted to the antenna socket.

Figure 2 shows a diagram of a power stabilizer that has been tested for many years inside a tube TV case.

The circuit (including the network transformer) is mounted on an aluminum sheet, which is a radiator for the control transistor. Mount the sheet in the lower part of the TV case with screws to the wooden planks, so that the common wire of the circuit (minus) is connected to the TV circuit only at the point of connection to the antenna jack. The transformer is taken at 20 W, the control transistor can withstand the same power. The HL1 lamp, included in the break in the mains wire, has a power of 6 W - the smallest of the "network" lamps with a large base. It is clear that with such a selection of parts at the end of the operation of the TV, the circuit can be dismantled and transferred to a new one.

Author: N.P. Goreiko

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