In conventional power supplies a linear regulator provides the desired output voltage by dissipating excess electric power in form of heat, and hence its maximum power efficiency is given by the ratio of input to output voltage.
A Switch Mode Power Supply (SMPS) regulates its output voltage by switching energy storage elements such as inductors, by means of a transistor changing “on” and “off” states at high frequencies. In this mode of operation, the transistor has a very low resistance in its “on” state, thus enabling the converters to operate with high efficiency. The PWM duty cycle of the transistor is controlled by an integrated circuit ensuring proper output voltage regulation.
For mains input Switch Mode Power Supplies the necessary isolation is achieved by the built-in transformer which also acts as a mutual inductor for energy storage. Due to the high switching frequency this transformer can be of a much smaller size compared to 50/60Hz iron core types. This results in compact and light weight supplies, enabling applications with high power density.
Switch Mode Power Supplies come in various topologies, all with their specific advantages for certain applications and output power ranges. In the low to medium output power range, Flyback Switch Mode Power Supplies provide a solid and cost-effective solution for a wide array of demands.