Linear vs Switching Power Supply Comparison and SMPS Control

Transformer Primaries in Power Supplies

In a transformer power supply, how many primaries do we find? In a transformer, we can only find one primary, through which energy is applied from the network.

Linear Power Supply Schematic and Operation

The linear power supply schematic functions as follows: the voltage grid passes through a transformer that adapts the level of the network signal to the voltage needed to power the circuit. Both input and output are AC voltages. The signal then passes through a rectifier, which converts the alternating voltage into a pulsating type. Next, it goes through a filter charged with reducing the variations in the output voltage of the rectifier, so the signal adopts a more or less stable form. Finally, it passes through a stabilizer, which is responsible for maintaining the output voltage at the exact value needed to bias the circuit at all times. To achieve this, it regulates its internal resistance to neutralize fluctuations in the input voltage.

Advantages of Switching Power Supplies

What advantages does a switching power supply have compared to a linear one? Switching power supplies offer better energy efficiency, which allows them to run cooler while reducing their size and weight. Similarly, lower consumption means using less powerful components, which reduces circuit costs. Switching power supplies are also more secure than linear ones.

What advantages does a switching power supply have compared to a linear one? Switching power supplies have better energy efficiency that makes them run cooler, while reducing their size and weight. Similarly, lower consumption means using less powerful components, reducing circuit costs. Switching power supplies are more secure than linear ones.

SMPS Control Techniques and Stand-by Mode

Techniques used in SMPS control include:

• Varying the frequency of the signal: If we apply a variable frequency signal to the switch, it will change the amount of energy that is injected into the transformer.
• Varying pulse duration: This involves varying the duty cycle of the control signal switch. Although the frequency does not change, if we keep the pulse at a high level for a longer time, more current will pass through the primary.

Regarding the role of the stand-by power supply: in stand-by mode, the device is inactive for most of its functions but allows recovery through remote control. This mode of operation requires that the power supply always remains in operation, since it must supply power to the control system functions to detect the entry of data from the remote receiver. The source must be able to disconnect any non-essential circuits, thus reducing power consumption during the idle state. These operations are achieved through the transistor Q1, which, polarized through the resistors R1 and R4, acts as an electronic switch working between cutoff and saturation states.