What is Switched-Mode Power Supply (SMPS)

Like other types of power supply, an SMPS power supply transfers power from an AC outlet to a DC device. However, what distinguishes the SMPS is its capability to regulate the output voltage. It has the ability to adjust the output voltage to ensure a consistent output, regardless of any fluctuations in the load.

Switched-mode power supplies (SMPS), also known as switch mode power supplies, are widely used in electrical systems for efficient power conversion. They take an AC input from the mains voltage and convert it to a low voltage DC output.

SMPS can be categorized into two types, which are non-isolated converters and isolated converters, based on their circuit topology.

In general, an SMPS functions by converting the AC source voltage into a DC voltage through a rectifier and an input filter. Afterward, a chopper is used to “chop up” the DC voltage, resulting in a series of square-wave high-frequency pulses (ranging from 20 kHz to 10 MHz) at the input of the transformer primary winding.

The primary purpose of a Switched Mode Power Supply (SMPS) is to convert unregulated AC or DC voltage into regulated DC voltage that is suitable for electronic devices such as computers. This conversion is necessary because computers and other electronic items require a stable and efficient power supply.

Dirt and foreign substances, such as cigarette smoke and house dust, can cause damage to an SMPS. Additionally, overheating and ventilation failures are common reasons for SMPS failure. To prevent this, it is important to ensure that the ventilation is clear of dust and clutter. It is also advisable to avoid keeping the CPU in an enclosed desk.

While voltage measurement can be done easily with the help of an isolation transformer, a more effective method is to utilize a differential probe for high-voltage measurements. Differential probes are equipped with two inputs and are specifically designed to measure the voltage difference between these inputs.

An SMPS distinguishes itself from a linear power supply by its method of converting the primary AC voltage into the output DC voltage. Instead of relying on a linear approach, the SMPS employs a power transistor to generate a high-frequency voltage that is subsequently passed through a compact transformer and filtered to eliminate any AC noise.

In SMPS, the inverter utilizes the PWM technique. The inverter’s output is then converted to dc through the use of a diode rectifier. Since the inverter operates at a high frequency, the ripples on the dc output voltage can be easily filtered out using small filter components.

Like other power supplies, an SMPS transfers power from a DC or AC source (often mains power), to DC loads, such as a personal computer, while converting voltage and current characteristics. It utilizes a high-frequency switching converter that converts DC to DC.