LM2574 Switch-Mode Power Supply Circuit


The LM2574 is a switching regulator IC that converts an input voltage to a regulated output voltage using pulse-width modulation (PWM) techniques. It operates in the range between 4.5V to 40V of input voltage and can provide a maximum output current of 500mA. It comes in a TO-220 or TO-263 package and is easy to integrate into circuit design. In this article, we will discuss the use of the LM2574 in designing a Switch-Mode Power Supply that is tailored for high efficiency and precision regulation.

The LM2574 includes a precision reference voltage, an error amplifier, an oscillator, and a PWM control block. These internal building blocks allow it to operate in a self-contained feedback loop that precisely regulates the output voltage. The feedback loop compares the reference voltage and the output voltage and adjusts the duty cycle of the PWM signal to keep the output voltage constant, even in the face of input voltage and output load variations.

Circuit Diagram of LM2574 Switch-Mode Power Supply

The LM2574 Switch-Mode Power Supply can be designed using a few basic components. The circuit diagram of this project is shown below.

LM2574 Switch-Mode Power Supply Circuit Diagram
LM2574 Switch-Mode Power Supply Circuit Diagram

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Working Explanation

of LM2574 Switch-Mode Power Supply

Advantages of the LM2574

The LM2574 SMPS circuit presents several advantages, including:

• High efficiency: As an SMPS, the LM2574 operates by rapidly switching the input voltage on and off, storing energy in an inductor and output capacitor. This results in higher efficiency compared to a linear regulator, which dissipates excess power as heat.

• Low noise: The switching frequency of the LM2574 typically ranges between 100kHz and 250kHz, which is much higher than the audio frequency range. Thus, its switching noise is typically beyond the audible range.

• Simple external components: The LM2574 requires only a handful of external components, typically including an input capacitor, an output capacitor, and an inductor in switch-mode power supply designs.

Applications of the LM2574

The LM2574 is well-suited for numerous low-power applications that require high efficiency and precision regulation such as:

• Battery-powered systems: The wide input voltage range of the LM2574 makes it an excellent choice for battery-powered systems. For example, it can be used to generate regulated output voltages for sensors or microcontrollers that operate from a battery.

• LED lighting: Due to the high efficiency of the LM2574, it is used to power LED lighting applications.

• Automotive electronics: The LM2574 can regulate the input voltage to electronics subsystems within an automobile. It is used to power instrument clusters, infotainment systems, and other subsystems.


The LM2574 is a versatile, low-power switching regulator IC that is tailored for high efficiency and precision regulation. Its self-contained feedback loop, high switching frequency, and small external component requirements make it an ideal choice for low-power applications. The LM2574 is also available in various package types, which means it can be easily integrated into the design of a wide range of applications. Therefore, it is a common choice for designers looking for efficient and reliable power supply solutions.

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LM2574 Switch-Mode Power Supply Circuit Diagram
LM2574 Switch-Mode Power Supply Circuit Diagram
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