Home » , , » Switching Power Supplies-Overview

Switching Power Supplies-Overview

EMI filter: to prevent the conducted EMI into the 50Hz AC input
Input rectifier + filter: to convert 50Hz AC voltage to unregulated DC voltage
Switching converter: to convert DC voltage to high-frequency (HF) AC voltage
HF power transformer: to step-up or step-down the HF AC voltage and to be used for electrical isolation
Output rectifier + filter: to convert HF AC voltage to DC voltage
Error amplifier: to compare the output voltage Vo to a reference voltage Vo,ref and produce an output voltage
PWM controller: to control its output pulse-width according to the output voltage of the error amplifier
HF signal transformer: to be used for electrical isolation
Gate/base drive circuit: to drive the power switches in the switching converterswitching power supplies
  1. The power supply output voltage Vo is regulated by means of the feedback control circuit.
  2. The HF signal transformer can be replaced by an optocoupler.
  3. The power processor is a cascading of AC-DC, DC-AC and ACDC converters with a HF transformer for electrical isolation.
  1. The switching devices in the switching converter operate as a switch (either completely on or completely off). Therefore, only switching losses are involved. This results the conversion efficiency is in 70 - 90% range. Furthermore, a switching element operating in switch-mode has a much larger power-handling capacity compared to its linear mode (refer to SOA).
  2. Since a high-frequency isolation transformer is used, the size and weight of switching supplies can be significantly reduced.
Switching supply circuits are more complex
Switching supply circuits produce EMI due to high-frequency switching.
previous Linear Power Supplies
next DC-DC converters with electrical isolation
Share this article :


Post a Comment

Please wait for approval of your comment .......