Voltage converter for powering portable radio stations. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Voltage converters, rectifiers, inverters

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A device that converts the viscous voltage of the battery into a high voltage necessary to power the anode-screen lamp circuits can be used not only for RBM radio stations of various modifications, but also for other similar low-power portable radio stations.

The schematic diagram of the converter is shown in fig. 1. The primary current source can be a battery with a voltage of 4,5-6,2 V. When operating in transmission, the converter consumes a current of 2,5-8 A from the battery and develops an output voltage of 200-220 V at a current of 30-50 mA . When working for reception, the converter consumes a current of about 1 A and develops an output voltage of 80-90 V at a current of 10-20 mA.

Fig.1 (click to enlarge)

The rated power of the converter is 10-15 W, the conversion frequency is 400-500 Hz. The efficiency of the converter during transmission is about 80%. When working at the reception, the efficiency is much less. To increase the efficiency of the converter when working on reception, separate power supply for the transmitter and receiver is required, as will be discussed below.

Details. For power transformer Tp1, you can use a core with a core section of about 3 cm² and a window area of ​​4 cm². Winding I consists of two sections of 19 turns of PEV-2 1,0 wire in each section. Winding II contains 20 turns of wire PEV-2 0,4 with a tap from the middle; winding III - 1100 turns of wire PEV-1 0,2; winding IV - 440 turns of wire PEV-1 0,14. Winding III is wound on the frame first, winding IV is the second. The wire in these windings is laid in even rows, turn to turn, laying transformer paper between the rows (you can use thin paper impregnated with transformer oil). Next, one section of the winding I is wound, on top of it - the winding II and then the second section of the winding I.

Choke Dr1 has two windings of 50 turns of PELSHO 1,0 wire wound on a transformer steel core with a core core cross-sectional area of ​​3 cm². Both windings of the inductor are wound simultaneously with two wires. The PELSHO wire can be replaced with a PBD wire, after soaking it with transformer oil.

Inductors Dr2 and Dr3 are low-frequency chokes from broadcasting or television receivers, but the inductor Dr2 must be wound with a wire with a diameter of 0,2-0,3 mm.

The converter uses P214V transistors - each arm has two transistors connected in parallel. You can use other low-frequency transistors with a rated output power of 8-10 W, for example, types P213, P215, P605, P609, or more powerful types P210B, P210V (in this case, parallel connection is not required).

Rectifiers B1 and B2 can be assembled on planar diodes D226D, or selenium bridges of the type ABC-80-240, ABC-120-270, designed for rectifiers of broadcasting receivers, can be used for them.

Resistor R1 is wire-wound, wound on the body of a resistor type BC-2. Resistor R2 type PEV-10X or PEV-15X with a moving contact or other wire variable resistor (from television receivers).

The design of the converter is arbitrary. But it is desirable to place the converter in a metal box, and separate the inductor Dr1 and capacitor C1 from other parts with a metal partition 1,5-2 mm thick.

Establishment. Starting to establish the converter, the slider of the resistor R2 should be set to the middle position. Connect a resistor with a resistance of 200-4,5 kΩ with a power of 5-15 W and a voltmeter with a measurement range of 20 V to the output of the converter "+300 V", and connect an ammeter for a current of up to 3 A to the power circuit.

If the installation is done correctly, then when the power is turned on, clicks or a sound with a frequency of several hundred hertz will be heard in the transformer, and the voltmeter will show voltage from a few volts to 200 volts. When the resistance of the resistor R2 changes, the frequency of sound (transformation) should change. If the converter does not work, then the conductors soldered to the extreme terminals of the winding II of the transformer Tr1 should be swapped.

In principle, the conversion frequency is determined by the cross section of the transformer core, the number of turns of the primary (I) winding and a number of other parameters, but in practice it also depends on the operating mode of the transistors, which is regulated by the resistor R2. Thus, it is possible, with the help of resistor R2, to regulate the conversion frequency with significant deviations from the data of the transformer core and other parameters, while maintaining a satisfactory transistor mode.

The conversion frequency must be set such that the voltmeter will show the maximum voltage, and the ammeter - the minimum current. After that, it is necessary to determine the efficiency of the converter, and if it is not lower than 80%, then the adjustment ends there.

If the conversion frequency is below 400 Hz, and the efficiency is very low, then you should reduce the number of transformer core plates by hammering wooden wedges instead, and adjust the conversion frequency with resistor R2. With a successful selection of the cross section of the transformer core and the conversion frequency, which can vary from 400 to 3000 Hz and higher, it is possible to obtain a converter efficiency of more than 80%.

Separate transmitter and receiver power supply

For separate power supply of the transmitter and receiver, two converters are needed, built according to the circuit shown in fig. 1, but with some changes: in the converter for the transmitter, there is no need for an 80 V rectifier (winding IV, rectifier B2, inductor Dr3 and capacitors C6 and C7), and in the converter for the receiver - in a 200 V rectifier with all its details.

The power transformer Tp1 for the receiver converter must be wound on a core with a cross-sectional area of ​​​​1,4-1,5 cm². Its winding I should contain 20x2 turns of wire PEV-2 0,5, and winding II - 12X2 turns of wire PEV-2 0,3. The converter uses two transistors - one in each arm. Resistor R2, as in the first converter, is wire-wound, but with a resistance of 500 ohms.

High Power Converter

If it becomes necessary to manufacture a converter for a power of more than 15 W, then a slightly modified converter of the portable version of the R-104M radio station can be recommended.

A schematic diagram of such a converter is shown in fig. 2. Here, the collectors of transistors T1 and T2 are connected to the minus of the primary current source, which allows low-frequency transistors, in which the collectors are connected to the case, to be mounted directly on the chassis, and it will act as a heat sink. The converter is designed for power up to 100 watts.

(click to enlarge)

Power transformer data:

cross-sectional area of ​​the core - about 6 cm²; winding I - 26X2 turns of wire PEV-2 1,56; winding II - 40X2 turns of wire PEV-2 0,44;

winding III-1320 turns of wire PEV-1 0,23; winding IV-640 turns of wire PEV-1 0,27.

Choke Dr1 contains 19 turns wound on an oxyfer ring 2000NM with a diameter of 30 mm with PBD 2,02 wire. Chokes Dr2 and Dr3 are low-frequency chokes from television receivers, wound with a wire with a diameter of at least 0,2 mm.

In rectifier bridges, diodes of the D226D type can be used. In each arm of the rectifier B1 there should be four diodes (total 16 pcs.), and in each arm of the rectifier B2, two such diodes (total 8 pcs.). In a 750 V circuit, both rectifiers are connected in series.

Transistors T1 and T2 - four P214V type transistors connected in parallel (other transistors with a rated power of 10 W can be used). The converter is powered by a 12 V DC source, consuming a current of 10-13 A from it at full load. The conversion frequency (800-1000 Hz) is regulated by resistors R2 and R3.

With a full load of the converter (up to 100 W), transistors must be placed on heat sinks. If the power consumed from the inverter is less than 50W, only the metal chassis can be used as a heat sink.

Author: S. Ronzhin; Publication: N. Bolshakov, rf.atnn.ru

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