LPS vs SMPS: Comparison
What are the advantages & Disadvantages of Linear Power Supply?
The linear power supply has the following three major advantages.
Advantages of Linear Power Supply:
One can purchase an entire linear regulator in a package and simply add two filter capacitors for storage and stability. Even if a Design Engineer plans to design a linear regulator from scratch, with the help of design books and some little effort, he can achieve it.
Quiet Operation & Load-handling Capability:
The linear regulator generates a negligible amount of electrical noise on its output. It's dynamic load response time (The time power supply takes to respond to changes in the load current) is very short.
For output power of less than 10W, linear power supply's component costs and manufacturing costs are less than the comparable switching power supply's cost.
Disadvantages of Linear Power Supply
Range of application:
It can be used only as a step down regulator. In case of AC-DC power supplies, a transformer with rectification and filtering must be placed before the linear power supply. This pre-power conditioning increases the cost.
Number of Outputs:
It has only one output voltage. To get additional output voltage, an entire separate linear regulator must be added. It increases system cost.
Normally linear regulators have 30% to 60% efficiency. It means for every watt delivered to the load, more than one watt is lost within the supply. This loss is called headroom loss. It occurs in the pass-transistor. Heat sink is required over the transistor for the heat dissipation. It occupies space and increase in system cost.
What are the advantages & Disadvantages of Switch Mode Power Supply?
Advantages of Switching Power Supply:
Switching Power supplies have efficiency of 68% to 90% regardless of the input voltage. Thus drastically reducing heat sink size, cost. The power transistors within the switching supply operate at their most efficient points of operation; saturation and cutoff. It means that the power transistors can deliver many times their power rating to the load and less expensive, lower power packages can be used.
Since the input voltage is chopped into an AC waveform and placed into a magnetic element, additional windings can be added to provide for more than one output voltage.
For tansformer-isolated switching power supplies, the output voltages are independent of the input voltage. ie, the input voltage can vary above and/or below the level of output voltages without affecting the operation of the supply.
Low cost and size:
Frequency of operation of magnetic components (Inductors, Capacitors) are very much greater than line frequency. It reduces the size and cost of components particularly at high power levels.
Disadvantages of Switching Power Supply:
The design is more complicated and time-consuming.
Applications of Linear and Switching Power Supplies:
Linear regulators are chosen for low power, board level regulation where the power distribution system within the product is highly variable and load's supply voltage needs are restricted.
They are uses in circuits where a quiet supply voltage is necessary, such as analog, audio, or interface circuits.
They are also used where a low overhead cost is required and heat generation is not a problem.
Switching power supplies are used in situations where a high supply efficiency is necessary and the handheld applications where battery life and internal external temperatures are important.