Bipolar voltage from unipolar. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Bipolar voltage from unipolar. Encyclopedia of radio electronics and electrical engineering

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

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When designing various devices, radio amateurs often face the problem of the lack of a bipolar power source.

The scheme shown in fig. 8.4, allows you to get a bipolar supply from an ordinary power supply, in addition, it is a stabilizer in itself. Both AC and DC voltage can be applied to the input, in the latter case, the VD1 ... VD4 diodes can be excluded, but the polarity will have to be observed when connecting.

Bipolar voltage from unipolar

Consider the operation of the device. The circuit consists of three simple voltage stabilizers. When connected to a power source, +2 V is supplied to the collector of the transistor VT27, a stabilized voltage of +12 V is removed from its emitter relative to the minus, therefore, the voltage difference between the collector and emitter of VT2 is 15 V. It is this voltage that the transistor VT1 uses, on its emitter relative to the emitter VT2 is also stabilized +12 V, and relative to the minus voltage is +24 V.

However, in the event of a short circuit of the output of the upper arm according to the scheme, the emitter of the transistor VT2 will be closed with the emitter VT1, the voltage on the common wire will be +24 V relative to the minus, in other words, on the lower arm of the relative "common" wire according to the scheme, it will be -24 V. This can lead to the destruction of the powered equipment. To prevent this from happening, a minus stabilizer, assembled on VT3, is installed.

All parts of the stabilizer, except for transistors, are mounted on a printed circuit board (Fig. 8.5) made of one-sided foil textolite 35x95 mm in size.

Bipolar voltage from unipolar

The transistors are mounted on duralumin heat sinks and connected to the printed circuit board with stranded wire segments. Capacitor and resistor values can be changed by 20...25%. If all the details are in good order, a properly assembled circuit does not need to be adjusted and starts working immediately.

Author: Semyan A.P.

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