Transformerless power supply on KRENK, 220/12-22 volts. Scheme, description

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Transformerless power supply on KRENK, 220/12-22 volts. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Power Supplies

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When it is necessary to power some home device with a low current consumption (up to 150 mA) from the mains, which works autonomously (clock, night light, electronic thermometer, etc.) and has a plastic case (the risk of electric shock is excluded), it is advisable to use transformerless power supplies. In the proposed source, the KR142EN8 microcircuit is used as a stabilizer.

Transformerless power supply on KRENK, 220/12-22 volts

The source provides an output voltage of 12 V, which depends on the type of integrated regulator used. With a load current of up to 150 mA, the DA1 chip has a small voltage drop, i.e. the difference between the input and output voltage of DA1 is no more than 2,5 V. If adjustment of the output voltage is required, then pin 2 of DA1 is connected to a common wire through a variable resistor or zener diode. Then the output voltage can vary from 12 V to 22 V.

Any other integrated stabilizer with similar electrical characteristics can be used as DA1, for example, KR1212EN5, KR1157EN5A, KR5010EN5, KR1162EN5, KR1183EN5, etc.

Capacitor C1 acts as a ballast resistance, on which the excess mains voltage is "quenched". Resistor R1 reduces the initial inrush current when the device is turned on, R2 - discharges C1 when turned off. The Zener diode VD2 with a stabilization voltage of 22 ... 27 V protects the microcircuit from a voltage surge at the moment the source is turned on. Capacitor C3 reduces high frequency noise.

The operating voltage C1 must be at least 300 V. You can take capacitor types. K76-3, K73-17 or similar. Resistors R1, R2 - MLT-0,5 Instead of the VD1 diode bridge, individual diodes of the KD105B ... KD105G, KD103A, KD103B, KD202E types are suitable.

Attention! During the operation of the source, you must not touch not only its elements, but also the non-insulated parts of the device that is connected to it.

Author: A.Kashkarov, St. Petersburg

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a guest
very good site Thank you [up]

a guest
The article is not bad, but the presented power supply has a low output power. In my opinion, it is more expedient to use ROLLS with transistors that power them.

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