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Protection device. 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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The device (patent DL-WR 82992), the circuit diagram of which is shown in the figure, can also be used with stabilized series-type rectifiers to protect the load from unacceptably high output voltage. Under normal conditions, the transistor T1 operates in a mode where the voltage between its collector and emitter is small and little power is dissipated on the transistor (the base current is determined by resistor R1). The resistance of the zener diode D2 in this case is large and the thyristor D3 is closed.

Protection device

When the voltage at the output of the device rises above a certain value, a current begins to flow through the zener diode, which leads to the opening of the thyristor. Transistor T1 closes and the voltage at the output of the device is close to zero.

The described device must be included in the stabilizers in the output circuit so that the feedback signal is supplied from the circuit located behind the protection system. At a rated output voltage of 12 V and a current of 1 A, transistors KT802A, thyristor KU201A - KU201K, zener diode D814B can be used in the device. The resistance of the resistor R1 should be 39 ohms (the power dissipation in the absence of an automation system that disconnects the stabilizer from the network is 10 W). R2 - 200 Ohm, R3 - 1 kOhm.

Publication: N. Bolshakov, rf.atnn.ru

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