The first models of automatic washing machines used transformer power supplies to power the control modules. In modern models, they are almost completely replaced by impulse ones. The only exceptions are LG manufacturers, they are in no hurry to introduce impulse sources into their devices, probably due to their low reliability.
The transformer power supply is a classic, the electrical transformer was invented at the end of the 19th century, and the entire 20th century was its era. In the modern world in consumer electronics, the transformer is losing its former glory, but still new solutions are inferior to it in reliability.
The power supply of the electronic module of the washing machine reduces the mains voltage to the required values, usually 12 or 24 volts.
At the first stage, the mains alternating voltage is applied to the primary winding of the transformer. Under the influence of electromagnetic induction, formed in the metal core, an alternating, lower voltage is induced on the secondary winding, it is this voltage that serves as a power supply for the elements of the module.
The next stage, the alternating voltage from the secondary winding of the transformer passes through the diode rectifier and becomes constant.
Then it passes through a capacitor filter.
At the last stage, the voltage is stabilized or converted to other values using special circuits or integrated elements.
The simplicity and reliability of transformer power supplies will ensure their use for many years to come. On the contrary, bulkiness and low efficiency play into the hands of competitors and leave chances for manufacturers of more efficient devices.