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Difference Between SMPS and Linear Power Supply
In electronic devices like computers, laptops, and more, power supplies are one of the most important components. Power supplies are essential for efficient and reliable functioning of the electronic devices.
In most electronic devices, two types of power supplies are very common namely, SMPS (Switch Mode Power Supply) and LPS (Linear Power Supply). The primary function of both SMPS and linear power supply is the same, i.e. to convert a high voltage AC supply in a low voltage DC supply using an assembly of transformer and rectifier. But they are completely different from each other.
The fundamental difference between SMPS (Switch Mode Power Supply) and linear power supply is in their operating components, i.e. SMPS consists of high-frequency switching circuits along with transformer and rectifier, while linear power supply consists of linear voltage regulators to reduce the voltage.
In this article, we will explore all the important Differences between SMPS (Switch Mode Power Supply) and Linear Power Supply. But before discussing the differences, let us first have a look into the basics of SMPS and linear power supply individually.
What is an SMPS?
SMPS stands for Switch Mode Power Supply. It is an electronic circuit that converts high voltage AC power into low voltage DC power. For this purpose, it employs transformer and rectifier along with high-frequency switching circuit. Transformer reduces the voltage level to the desirable level and rectifier converts the AC (Alternating Current) into DC (Direct Current) power. In addition to rectifier, it also consists of filter circuit to remove the ripples from the output DC voltage.
SMPS is widely used in various modern electronic devices, such as computers, laptops, communication equipment, medical equipment, industrial machinery, and more.
What is a Linear Power Supply?
A type of power supply which consists of linear voltage regulators to reduce the input AC voltage to the desired output DC voltage is known as a linear power supply. Linear power supplies work by dissipated extra voltage in the form of heat by using linear voltage regulators. Therefore, they are better suited for low-power applications.
Linear power supplies are simple to design, as they have a simple electronic circuit to directly convert the high voltage into low voltage. In comparison to SMPS, linear power supplies are less efficient due to high power generation.
Linear power supplies are commonly used in applications, such as lab instruments, analog electronic circuits, audio amplifiers, and many other low power electronic devices.
After getting an overview of SMPS and linear power supply. Let us now discuss the important differences between them.
Difference between SMPS and Linear Power Supply
The following table highlights all the significant differences between switch mode power supply and linear power supply −
Parameter |
Switch Mode Power Supply (SMPS) |
Linear Power Supply (LPS) |
|---|---|---|
Basic |
SMPS is a type of power supply that converts input AC voltage into DC voltage and then reduces its magnitude to the desired level. |
LPS is a type of power supply that steps down AC voltage and then converts it into DC voltage. |
Main Electronic Components |
The main electronic components of SMPS include transformer, rectifier, and high frequency switching circuit. |
The main electronic components of linear power supply include linear voltage regulator and transformer. |
Voltage Regulation |
In SMPS, a feedback circuit is employed for voltage regulation. |
In linear power supply, voltage regulators are employed for voltage regulation |
Efficiency |
SMPS has relatively high efficiency, about 70% to 85%. |
Linear power supply has lower efficiency, typically about 40% to 60%, due to heat loss. |
Operation |
SMPS first converts high AC voltage input into a high-frequency AC voltage, then convert AC into DC using rectifiers and filter circuits to obtain the desired DC voltage. |
Linear power supply first reduces the input AC voltage and then converts it into DC voltage. |
Material of Core |
In SMPS, a ferrite core is used. |
In linear power supply, a steel alloy or CRGO core is used. |
Circuit Complexity |
SMPS has a relatively more complex electronic circuit. |
The electronic circuit of a linear power supply is less complex than SMPS. |
Voltage Range |
SMPS can handle a wider of voltages. |
Linear power supply has limit to the input voltage. |
Noise and Electromagnetic Interference |
SMPS produces more electronic noise and electromagnetic interference due to high frequency switching. Therefore, electromagnetic interference filters are required. |
Linear power supply produces relatively less electronic noise and electromagnetic interference. |
Pricing |
SMPS are relatively more expensive due to complex design and advanced features. |
Linear power supplies are less expensive due to their simple design. |
Start-up Time |
SMPS has a shorter start-up time than linear power supply. |
Linear power supply has longer start-up time, as it requires more time to stabilize its output voltage. |
Built-in PFC Unit |
SMPS has a built-in power factor correction (PFC) unit to improve its efficiency. |
Linear power supply generally does not have a built-in power factor correction unit. |
Heat Generation |
SMPS generates less heat during operation. |
Linear power supply generates more heat, hence proper cooling system is required. |
RF Interference |
SMPS produces radio frequency interference, hence proper shielding is required. |
In linear power supply, there is no problem of radio frequency interference. |
Weight and size |
SMPS has compact size and less weight, making it best suited for portable electronic devices. |
Linear power supply has larger size and more weight. Hence, they are less portable. |
Load Regulation |
In SMPS, the load regulation varies from 0.05% to 0.5%. |
In linear power supply, the load regulation varies from 0.005% to 0.2%. |
Ripple Voltage |
In SMPS, the ripple voltage ranges between 10 mV and 25 mV. |
In linear power supply, the ripple voltage lies between 0.25 mV to 1.5 mV. |
Operating Power Factor |
For SMPS, the operating power factor lies between 0.6 and 0.7 (without PFC), and greater than 0.95 (with PFC). |
The operating power factor of linear power supply lies between 0.6 to 0.7. |
Power Density |
SMPS provides high power density, i.e. smaller size can handle more power. |
Linear power supply provides low power density, i.e. large size is required to handle the same amount of power. |
Power to weight ratio |
SMPS has high power to weight ratio. |
Linear power supply has low power to weight ratio. |
Transient Response |
SMPS has slower transient response. |
Linear power supply has faster transient response than SMPS. |
Applications |
SMPS is used in high-power applications, such as computers, laptops, industrial and consumer electronic devices, etc. |
Linear power supply is used in low power applications, such as analog electronic circuits, audio amplifiers, lab instruments, etc. |
Conclusion
Both SMPS and LPS are two different types of power supplies used in various electronic devices to provide conversion of input voltage into the desirable output voltage. The most significant difference between SMPS and LPS is that SMPS employes high-frequency switching mechanism for high AC voltage to low DC voltage conversion, while linear power supply uses linear voltage regulators for this conversion. Based on their own advantages and disadvantages, SMPS and linear power supply are used in different applications.
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