Universal power supply 2-12 volts 1 amp. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Power Supplies
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The use of the KR142EN12A (B) microcircuit and the TPP255-220-50 unified transformer makes it possible to manufacture a simple and reliable power source for various household devices.
The output voltage of the source can be smoothly adjusted from 2 to 12 V. The maximum load current is 1 A, while the amplitude of the output voltage ripple does not exceed 2 mV.
Rice. 5.3 (click to enlarge)
The electrical circuit of the device is shown in fig. 5.3. The unit is assembled according to a typical scheme of a serial compensation voltage regulator. In order not to dissipate too much thermal power on the DA1 chip, the stabilizer provides discrete switching of the outputs of the secondary windings of the transformer by section S2.1 of the switch. At the same time, the resistors R4 ... R7 of the feedback dividers are also switched to set the limit for adjusting the output voltage. On each of the subranges, the desired voltage can be set with a variable resistor R3. The switch provides setting of output voltage ranges 2...5, 5...7, 7...9, 9...12 V.
Chip DA1 has internal overload protection. The source operation indicator is the HL1 LED.
For ease of use, the circuit can be supplemented with a pointer measuring voltmeter.
In the design of the power supply, the transformer can be replaced with a more powerful one from the same series: TPP276-220-50, TPP292-220-50, TPP319-220-50 (the numbering of the winding connection terminals does not change, but the dimensions and weight of the device will increase).
The microcircuit is designed to work with a heat sink, and it must be mounted on a radiator, while the radiator should not have electrical contact with the structure case.
For the convenience of setting the boundary of the output voltage ranges, it is better to use tuning resistors R4 ... R7 multi-turn, for example, type SP5-2 or SP5-14. Capacitors used: C1, C3 type K50-29; C2.C4-K73-17.
Publication: cxem.net
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