Design and production of adjustable voltage-stabilized power supply circuit based on LM2576

The LM2576 series is a 3A current output step-down switch integrated voltage regulator circuit produced by National Semiconductor Corporation. It contains a fixed frequency oscillator (52kHz) and a reference voltage regulator (1.23V), and has a complete protection circuit, including current limiting and thermal shutdown circuits. This device only requires a few peripheral devices to form an efficient voltage regulator circuit. The maximum input voltage of LM257-adj is 37V, and the output voltage is 1.23V-36V.

The circuit schematic is shown below. The LM2576-adj circuit is very simple and only requires a few external components. During the production process, it is necessary to pay attention to the voltage resistance of the Cl and C3 aluminum electrolytic capacitors. The author selected 63V voltage resistance aluminum electrolytic. C2 and C4 use 0805 ceramic capacitors at the minimum, and the voltage resistance is generally 50v. The FB pin voltage of the LM2576 is fixed at 1.23V inside the chip. The output voltage value of VOUT can be adjusted by adjusting the resistance value of Rl. The relationship between VOUT and Rl is as follows: VOUT=1.23x(1+R1/R2)(V) In order to facilitate voltage adjustment. Rl uses a B50K flower axis potentiometer, and the inductor uses a CD100 (10mmx10mm) packaged chip power inductor with an inductance of 33uH, which can pass a maximum current of 2A. Add a voltmeter to indicate the output voltage.
The circuit board is welded using a perforated board.
The efficiency of LM2576 is relatively high. The typical value is 77% when outputting 5V3A. No external heat sink is required when the power output is low. The actual test shows that when the output is 15W (15V, 1A), there is no obvious heat generation in the circuit after 10 minutes.