Linear stabilizers with high efficiency. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Surge Protectors
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The main disadvantage of linear stabilizers of medium and high power is low efficiency, and the lower the output voltage of the power source, the lower its efficiency. This is due to the fact that in the stabilization mode, the regulating transistor of the power source is usually connected in series with the load, and for the normal operation of such a stabilizer, the collector-emitter voltage (Uke) must drop at least 3 ... 5 V on the regulating transistor.
At currents of more than 1 A, significant power losses are obtained due to the thermal energy dissipated on the power transistor. This leads to the need to increase the area of the heat sink or use a fan for forced cooling. Widespread integrated linear voltage regulators based on 142EN5...142EN14 series microcircuits have the same drawback.
The microcircuits of the "LOW DROP" series (SD, DV, LT 1083/1084/1085) that appeared on sale can operate at a reduced voltage between the input and output (up to 1 ... 1.3 V) and provide a stabilized voltage at the output in the range of 1,25 . ..30 V at a load current of 7,5/5/3 A, respectively. The closest domestic analog KR142EN22 has a maximum stabilization current of 5 A. At the maximum output current, the stabilization mode is guaranteed at an input-output voltage of at least 1,5 V. The microcircuits have built-in protection against overcurrent in the load and thermal protection against overheating of the case.
These stabilizers provide output voltage instability of 0,05%/V, output voltage instability when the output current changes from 10 mA to the maximum value no worse than 0,1%/V. A typical scheme for switching on stabilizers is shown in fig. 1.
Capacitors C2 ... C4 should be located close to the microcircuit and it is better if they are tantalum Capacitor C1 is selected from the condition of 2000 microfarads per 1 A of output current.
Microcircuits are produced in three types of package design, shown in fig. 2.
The hull type is determined by the last letters in the designation. It is advisable to use such voltage stabilizers at a load current of more than 1 A, as well as in case of a lack of space in the structure.
Information sources
- cilyradio.narod.ru
- kazus.info
Author: V.Novikov
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