L1 is a switching transformer, which can be replaced by a 25 or 29-inch power filter coil. And the large capacitor can easily cause vibration to stop. The small capacitor has a high switching frequency, but the voltage is unstable. C2 is the energy storage timing capacitor. When it is below 15V, it is higher than the no-load value, and when it is above 15V, it is lower than the no-load value, and the error is within 2V.Ĭ1 and C3 are filter capacitors, generally the larger the better. (2) The output voltage of the power supply cannot be adjusted from 1.25V. The temperature of LM317 increased sharply. When the capacity of C2 exceeds 47μF, the circuit is difficult to oscillate and becomes a series-regulated power supply. (1) The switching frequency of the circuit varies greatly, which is related to the load current, output voltage and C2 capacity. The circuit has the following characteristics: The circuit can work almost without debugging. In this cycle, LM317 is set to switch working states. Until the output voltage of LM317 is lower than the set value, LM317 turns on again. The energy in C2 is also released outward. The magnetic field stored in the L1 inductor supplies power to the load through its secondary coil and D1. When the voltage on C2 reaches the set value, LM317 will show high internal resistance and disconnect. At the same time, the current flowing through the primary coil of inductance L1 creates a magnetic field in LI. The voltage on the energy storage capacitor C2 starts to rise. When the circuit starts working, LM317 has not yet established working conditions, so its input voltage is higher than the output. Overload protection remains functional even if the ADJUST terminal is disconnected. It includes current limiting, thermal overload protection, and safe operating area protection. The device features a typical line regulation of 0.01% and typical load regulation of 0.1%. The output voltage can be set with the use of two resistors. The LM317 device is an adjustable three-terminal positive-voltage regulator capable of supplying more than 1.5 A over an output-voltage range of 1.25 V to 37V. This article introduces the switched-mode power supply based on LM317. Their advantages compared to the linear power supplies are small overall dimensions, low weight, high efficiency and output, and low price. Switched-mode power supplies have replaced the traditional linear power supply and are currently the most popular and the largest group of power supplies. A switched-mode power supply (SMPS) is an electronic power supply that incorporates a switching regulator to convert electrical power efficiently.
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