Bipolar power supply for battery equipment, 20 volts 50 milliamps. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Power Supplies
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Many devices and devices made on operational amplifiers require a bipolar power supply with a relatively large potential difference. This imposes significant restrictions on the use of such equipment in the field, or it is required to use other circuit solutions, often at the expense of quality.
Here is a description of a simple bipolar converter, which makes it possible to obtain a stable bipolar voltage of +6 V from a 20 V battery source, with a load current of up to 50 mA for each pole, the efficiency of the converter is more than 60%.
(click to enlarge)
On the D1 chip (CD4047), a generator of symmetrical antiphase pulses is made. The CD4047 microcircuit is a combination of inverter elements for building a multivibrator and a trigger-shaper of antiphase signals of the correct symmetrical shape. As far as I know, the domestic industry does not produce CD4047 analogues in the K561 or K176 series. Although, maybe I'm wrong.
So, D1 generates anti-phase pulses with a frequency of about 80 kHz, the frequency is set by the R1-C1 circuit. Anti-phase pulses are taken from pins 10 and 11 of D1 and fed to keys on low-power field-effect transistors VT1 and VT2 (they have cases like KT3102).
In the drain circuits VT1 and VT2, the primary windings 5-6 and 7-8 of the pulse transformer T1 are included. Conclusions 6 and 7 of these windings connected together are connected to a power source. - to the plus of the battery with a voltage of 6 V (the battery is not shown in the diagram). From the secondary windings 1-2 and 3-4, an alternating voltage is removed to the rectifier VD3-VD6. The middle point of the secondary windings 2-3 is connected to a common minus.
The circuit can be made in two versions - with a common negative conductor for primary and secondary circuits (as shown in the diagram) or with galvanically independent primary and secondary circuits.
In the second case, all circuits of the common wire to the right of the transformer (according to the diagram) are not connected to the circuits of the common wire shown in the diagram to the left of T1.
Coils L1 and L2 suppress RF interference. Capacitors C4 and C5 suppress ripple.
Simple parametric stabilizers are made on transistors VT3 and VT4. The output voltages are equal to the stabilization voltages VD7 and VD8.
Transformer T1 is wound on a ferrite ring with an outer diameter of 23 mm. First, the secondary winding is wound 40 + 40 turns of PEV 0,43 wire. Then, a primary winding of 6 + 6 turns of PEV 0,96 is wound on its surface. Windings can be done by winding in two wires. Parts of the transformer windings are connected in series (the end of winding 1-2 is connected to the beginning of 3-4, the end of 5-6 is connected to the beginning of winding 7-8).
Coils L1 and L2 are wound on ferrite rings with a diameter of 7 mm. They contain 30 turns of PEV 0,43 wire.
Author: Toropov V.A.
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