Laboratory power supply, 220/12,5 volts 5 amps. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Laboratory power supply, 220/12,5 volts 5 amps. Encyclopedia of radio electronics and electrical engineering

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For a radio amateur laboratory, when a stabilized power supply (SP) with an output voltage of 12.5 V and a current of up to 5 A is required, the proposed device is suitable. IP allows not only to power a powerful load, but also to simultaneously recharge the battery (AB).

Laboratory power supply, 220/12,5 volts 5 amps

The voltage regulator is made on transistors VT1 VT4. The source of the reference voltage is the Zener diodes VD9 and VD10. The output voltage of the source depends on their parameters. Diodes VD5...VD8 are used for thermal compensation and adjustment of the reference voltage. Resistor R9 sets the current through the zener diodes, resistors R6 ... R8 equalize the currents of transistors VT2 .. VT4. Capacitor C3 eliminates self-excitation of the stabilizer. Capacitors C5 and C6 perform the functions of the output filter of the stabilizer. The source is powered by a 220 V network through a step-down transformer T1.

The mains voltage is supplied to the primary winding of the transformer through the fuse FU1, switch SA1 and radio interference filter C1. From the secondary winding of the transformer, voltage is supplied to the rectifier diode bridge VD1 ... VD4 and the diode VD11. Capacitors C2, C4 are used to reduce the amplitude of the AC voltage at the input of the stabilizer. In order to obtain a higher stabilization coefficient, a circuit was used to supply voltage to the input of the stabilizer with a voltage boost.

The IP provides, if necessary, the connection of emergency power supply (AB with a voltage of 12 V). In the author's version, a 55ST type battery with a maximum current of 55 A is used for this. To connect a backup battery, an electronic key on transistors VT5 and VT6 is used. Resistors R1 and R10 set the current through the LED indicators HL1 and HL2. LED HL1 indicates the presence of mains voltage, and HL2 - the inclusion of emergency power. Power for recharging the battery is turned on using SA2

Details. Switches SA1, SA2 (P2K with latching) can be replaced with any similar switches rated for current up to 6 A. for example. PKN-125. PKN-41.PG2-22-2P8NVK Capacitor C1 - type K73-9 for an operating voltage of at least 300 V. Oxide capacitors C2, C4 and C5 - type K50-3S or similar for an operating voltage of at least 25 V. Other capacitors, except C1 - type K10-17. MBM, K76-3, KT4-23 or similar Resistors R6. R8-B3R C5-5-5W, C5-16B-5BT. the rest - MLT-0,5. LEDs HL1, HL2 - AL310A, AL311A. AL336A, AL307A. L63SRC Transistor VT1 is replaced by KT601, KT605 with any letter index, VT2 ... VT4 - by KT819. VT5...VT6 - on KT818. Diodes VD1 ... VD4 - type KD258, D245. D231, D112-16 with indices B...G, KD2996V. KD2997; VD5...VD8 - D220. KD519, KD513 with any letter index. Zener diodes VD9, VD10 provide a reference voltage that determines the output voltage of the stabilizer. They can be replaced by KS213B, D814D. Transformer T1 can be replaced with a similar one, given that the output voltage on winding II under load should be 15 ... 17 V. Winding III has an output voltage of 15 V. If the source is calculated for a load with a current consumption of less than 2 A, T1 can be replaced with a transformer TC-26-1 with appropriate winding connection.

Transistors VT2...VT4 are installed on isolated heat sinks with a cooling area of at least 120 cm2 each. In the off-load and battery mode, the quiescent current of the output transistors is negligible. The operating temperature of transistor heat sinks at maximum load (5 A) can reach 60...70°C. VD1...VD4HVD11 diodes are also installed on isolated heat sinks with a cooling area of at least 60 cm2. All elements of the device are fixed inside any suitable case, for example, from a charger for car batteries.

Author: A.Kashkarov, St. Petersburg

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