Wednesday, October 31, 2012
Bipolar power supply from unipolar. Circuitry engineeringIn the process of construction of various electronic devices, there are often situations when a bipolar power supply is required to power them. In case there is a transformer with one step-down winding, it is not difficult to make a source with bipolar power supply. Moreover, some of the circuits are also constant-voltage regulators. Here is one of the examples of a bipolar constant-voltage regulator. The circuit consists of 3 simple voltage regulators. Alternating current voltage is applied on the diode bridge, the plus of which comes to the collector of the transistor VT2, from its emitter, relative to minus, the constant voltage of +12 V is removed. Consequently, the voltage difference between the collector and the emitter of the transistor VT2 is 15 V. Therefore, this voltage is used by the transistor VT1, and on its emitter, relative to the emitter of the transistor VT2, a constant voltage of +12 V is also received, and relative to the minus, the voltage is +24 V. Now we have a plus, total and a minus. But imagine a situation when there will occur a short circuit of the output of the circuit-wise high-side, in other words, when the emitter VT2 will be closed to the emitter VT1, namely, there will be +24 V on the common wire, relative to minus. This can result in the bringing out of operation the power supply system. To avoid this, a stabilizer is set according to the minus on the transistor VT3. The circuit has ...
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