Linear Power Supply and. Switching Power Supply
Key Takeaways
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Switch Mode Power Supplies (SMPS) offer higher efficiency, smaller size, and less heat generation.
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Linear Power Supplies are favored in applications requiring minimal noise and are simpler in design and more cost-effective despite their lower efficiency and larger size.
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The choice between SMPS and Linear Power Supplies depends on the specific requirements of the application, including efficiency, size, heat generation, and noise sensitivity.
A DC power supply is also a linear power supply.
A switching power supply rapidly switches a power transistor between saturation (full-on) and cutoff (full-off) states, converting an input voltage to a high-frequency alternating current (AC). It is then transformed to the desired output voltage using a smaller transformer, and finally rectified and filtered to produce a stable output DC voltage.
Linear power supplies first transform the input AC voltage into a lower level using a transformer, then rectify it to DC, and finally regulate this voltage using a series pass transistor or a voltage regulator in a linear mode of operation to produce a stable output voltage. Read on as we explore linear power supply vs. switching power supply.
Linear Power Supply and. Switching Power Supply Basic Overview
|
Feature |
Switch Mode Power Supply (SMPS) |
Linear Power Supply |
|
Operating Principle |
Power transistor switches rapidly between on and off states, converting input DC voltage to high-frequency AC, then to the desired output voltage |
Transforms input AC voltage to a lower level, rectifies it to DC, and regulates voltage in a linear mode by heat dissipation |
|
Efficiency |
High (about 80% or higher) due to switching states |
Lower (about 60%), as it continuously dissipates power as heat |
|
Size and Weight |
Smaller and lighter |
Larger and heavier due to heat sinks |
|
Heat Generation |
More heat due to lower efficiency requires heat sinks to dissipate this energy |
|
|
Complexity and Cost |
More complex in design, with higher initial costs offset by efficiency and component size |
Simpler and potentially more cost-effective in design and manufacturing |
|
Output Noise and Ripple |
More electrical noise and ripple, requiring additional filtering for sensitive electronics |
Produces cleaner output with less noise and ripple, preferred in sensitive audio and analog applications |
|
Applications |
Preferred for applications requiring high efficiency, compact size, and a wide input voltage range |
Favored in applications requiring minimal noise and less sensitivity to size and efficiency |
Linear Power Supply and Switching Power Supply In Depth
Linear power supplies are also called linear regulators (LRs), and have numerous advantages. Below we’ve condensed important information about each type into a more detailed table.
|
Factor |
Switch Mode Power Supply (SMPS) |
Linear Power Supply (LPS) |
|
Input Voltage Range |
Flexible input voltage range, accommodating a wider variety of power sources and conditions |
Limited by design to specific input voltages, requiring precise input voltage levels for optimal operation. Ideal for low power applications |
|
Noise |
Can generate electrical noise (EMI/RFI) due to high-frequency operation, which may require additional filtering in sensitive applications |
Produces minimal electrical noise, making them ideal for sensitive applications such as audio and video equipment |
|
Reliability |
Potentially lower reliability due to complexity and higher component count; improving with technological advancements |
Higher reliability attributed to simplicity and fewer components, leading to fewer potential points of failure |
|
Output Voltage Ripple |
Higher ripple voltage and noise potential, requiring careful filtering; modern designs have greatly improved output quality |
Very low ripple voltage and cleaner output, beneficial for sensitive electronic applications |
|
Response to Changes |
Faster response to changes, advantageous in applications requiring quick adjustments to load or input variations |
Slower response to load or input voltage changes, which might be a limitation in dynamic applications |
|
Suitability for Power Levels |
More efficient and practical for high-power applications due to better power handling and efficiency |
More suited for low-power applications due to limitations in efficiency and heat dissipation |
There are other factors to consider, like load voltage and dropout voltage, when assessing a linear power supply for your design. Typically, when evaluating power supplies for a particular application, one must consider all factors, not just cost, efficiency, and size. In summary, the disadvantages of linear power supplies are higher heat loss, a larger size, and being less efficient in comparison to the SMPS.
Efficiency and Noise Quality Comparison
In regards to linear power supply vs. switching power supply when discussing efficiency, a switch mode power supply (SMPS) is more efficient and affords better performance. However, if you scrutinize the electronics landscape, you will see the widespread use of linear power supplies in applications that require strict noise mitigation. For this reason, one such area where we see linear power supplies is in the field of audio and video, which includes amplifiers. Since the linear power supply does not produce the noise and switching spikes of an SMPS, it makes it ideal for these types of sensitive applications.
The linear power supply possesses a longer historical track record versus the SMPS. However, the linear power supply is not without its flaws. Overall, the application requirements will generally dictate which power supply best fits your individual needs.
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