Voltage polarity inverter, 12 volts 0,1 amps. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Voltage converters, rectifiers, inverters
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In the process of improving any finished device, it is often necessary to introduce one or two operational amplifiers into it, which forces you to immediately decide on the issue of their power supply - after all, most common op-amps require a bipolar power supply. In such cases, a way out can be a so-called polarity inverter - a device whose DC output voltage is equal to the input voltage, but with reverse polarity. Thus, the existing conventional power source together with the polarity inverter is replaced with a bipolar one.
A diagram of one of the variants of the polarity inverter is shown in fig. 4.28.
(click to enlarge)
A special feature of the device is the use of the K174UN7 (DA1) microcircuit - an AF power amplifier. Due to the strong positive feedback on alternating voltage through capacitor C2, the microcircuit operates in the mode of generating rectangular pulses with a frequency of approximately 20 kHz. The amplitude of the pulses at the output of the microcircuit is about 10 V. These pulses are fed to the input of a voltage multiplier assembled on diodes VD1...VD4 and capacitors C4...C7. The output voltage of the multiplier stabilizes the parametric stabilizer R2, VD5 with a current amplifier on transistor VT1.
The inverter provides an output current of up to 100 mA, while the current consumption is approximately 200 mA. In this mode, the microcircuit can operate without a heat sink. When the inverter input voltage decreases to 10 V, the maximum output current decreases to 40 mA. . In addition to those indicated, transistors KT814B...KT814G, KT816A...KT816G can be used in the inverter; rectifier diodes KD510A, KD212A; Zener diodes KS512A, KS213B, KS213E. Capacitors - K50-6 or K50-16, K53-1 (C1, C4...C8), the rest - KLS, KM; resistors - BC, MLT.
When setting up, the generation frequency is set within 20...25 kHz by selecting capacitor C2, and the required output voltage is set by zener diode VD5. The printed circuit board of the device is shown in Fig. 4.29.
Author: Semyan A.P.
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