LM2596 DC-DC Converter Module Testing

According to TI’s website, these LM2596 step-down (buck) regulators are sold for $1.8 each for a quantity of a thousand. So how a finished converter could be sold for just above a dollar each is quite a mystery to me. Anyway, the picture below is the board I received. It appears that there are a few variations to this design (slightly different inductor size or capacitor size/voltage rating, etc.) but they all are largely based on the reference design.
LM2596 DC-DC Converter Module Testing
Below is the reverse engineered circuit diagram of this particular converter board I have (key components are also marked in the picture above for reference). The inclusion of a polarity protection diode (D2) is certainly a nice feature. It will prevent you from damaging the regulator should the input voltage be reversed. Of course, if the input power supply has very low output impedance and high current capability this tiny diode might not be able to save the board in an input voltage reversal situation. Also, not all variants of this step-down DC-DC converter have this diode. Although LM2596 can handle input voltages up to 45V, the input and output capacitors used are both rated for 35V only so in practice input voltage should stay below 30V for long term uses.
For LM2596, the output voltage is determined by the equation below. Given the component values used in this module the output voltage can be adjusted between 1.23V to 25V.

Vo=123R1R2+1 

Although LM2596 is rated for a maximum current of 3A in continuous operation, the tiny surface area of the ground plane on this board is not sufficient to dissipate the amount of heat generated over the entire operation range of the converter. And the efficiency of this converter varies quite a bit depending on the input voltage, output voltage and the load current. The efficiency can range from 60% to 90% depending on the operating conditions. As you can see in the video later, a heatsink is a must if continuous operation at over 1A is required.
For more detail: LM2596 DC-DC Converter Module Testing


About The Author

Ibrar Ayyub

I am an experienced technical writer holding a Master's degree in computer science from BZU Multan, Pakistan University. With a background spanning various industries, particularly in home automation and engineering, I have honed my skills in crafting clear and concise content. Proficient in leveraging infographics and diagrams, I strive to simplify complex concepts for readers. My strength lies in thorough research and presenting information in a structured and logical format.

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