Switching power supply, 8-40/5 volts 500 milliamps. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Power Supplies
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The switching power supply uses the LM2674 chip from National Semiconductor. Instead of LM2674, you can use the LM2671 chip. These chips use key MOSFETs made using LMDMOS technology, with a residual on-state resistance of not more than 0,12 ohms, which allows you to get high efficiency (under normal conditions, it is about 90%). The relatively high value of the operating frequency (up to 260 kHz) makes it possible to reduce the size and weight of the parts of the energy storage filter.
Chips LM2674 / 71 have protection against overcurrent and overheating. Voltage and current instability coefficients do not exceed 1,5...2%, operating temperature range - from -40 to +125°С. Available in TO-220, TO-263 and LLP cases.
ICs of this series are produced for fixed output voltages of 3,3; 5,0 and 12 V, as well as in an adjustable version (from 1,2 to 37 V). The above circuit provides an output voltage of 5 V and delivers current up to 500 mA. Schottky diode VD1 must withstand a reverse voltage of at least 45 V and a maximum forward current of 3 A.
The LM2671 provides additional features, in particular, a "soft" start and work with an external generator. The latter allows multiple converters to be synchronized, greatly reducing their interference and meeting stringent electromagnetic compatibility (EMC) requirements.
Switching to the standby mode is carried out by applying a high voltage level to the ON / OFF output (no more than +5 V). In this case, the current consumption of the IC is 50 μA.
Publication: rlocman.ru
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