Implementing the Negative SMPS for the AC Switch Control


Almost every appliance require a power supply for converting 220-240 or 100-130 V AC mains voltage to 5 or 3.3 V DC voltage. This is needed for the supply board electronics. The regulation to ECO conception directive, and applicable for all energy using products, specifies that maximum off mode power consumption or standby mode must be within one or two W. This came into effect first in the year 2010, and then in 2013.


Home appliances like washing machines and refrigerators use huge quantities of AC loads like motors, heating resistors or valves. As these loads are powered by mains in the on or off mode, these are generally controlled by ACS. These devices are inexpensive to operate.


A new regulation has pushed the designers of appliance electronics to new techniques of implementation. They implement the switched mode power supplies or what is colloquially known as SMPS. The SMPS circuits are frequently utilized to offer positive outlet voltage. It is clear that negative power supplies could be more desirable. This is particularly so when the AC switches like Snubberless Triacs and ACST along with ACS devices can be controlled via the electronics board.