Power supply 1,5-25 volts with pre-regulator. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Power Supplies
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A microcircuit can be used as a regulated source KR142EN12 (analogue - LM317) - at load current up to 2A; or LT1083/84/85 at current up to 7/5/3A; or a stabilizer on discrete elements.
(click to enlarge)
We select the capacitance of capacitor C3 at the rate of 2000 microfarads per 1 A of output current.
Resistor P9 is used as a current sensor for an ammeter, and may be of a different value. Typically, such a resistor is connected at the output of the stabilizer, and increases its output resistance. To avoid this, a resistor is included at the input of the stabilizer. The measurement error in this case is very small, and is equal to the own current consumption of the stabilizer circuit.
All other elements are a pre-regulator of the voltage that appears on the stabilizer. Its function is to maintain a voltage difference between the input and output of approximately 5 ... 6 V (see the oscillograms in the diagram).
In fact, the thyristor does not pass all half-waves of the rectified voltage, but some of them, depending on the output voltage and load current. This makes it possible to significantly reduce the power dissipated in the control element, especially at low output voltages and high currents.
The parameters of the inductor are not critical, its purpose is to reduce the amplitude of the current through the transformer when the thyristor is opened. At load currents less than 2A, you can do without a choke.
The prototype of the circuit was taken from the collection of amateur radio designs of the GDR, which was released 20 years ago, I repeatedly repeated it, but I never got to the Internet and other collections of amateur designs, although the circuit is not bad.
If desired, I can find a prototype, but the description is in German, and the pre-regulator is only part of the original circuit.
Publication: cxem.net
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