Voltage Regulation in DC Adapters

Typically power adapters do not have active regulation. As the adapter label states, the voltage will be X when the current is Y. This is an area of confusion for many engineers, thinking that a 12 volt, 1 amp power supply can be substituted for a 12 volt 500 mA power supply. While this may be true, the voltage at 500 mA will be higher than the voltage at 1 amp. How much this varies depends on the load line of the transformer. Keep in mind, cheaper transformers have fewer windings, and therefore wilder voltage swings with load.

Another problem is the line regulation. In a simple adapter as the input (or line) is varied, the adapter also varies the voltage proportionally. Since line voltage in the U.S. varies between 105 and 125 volts, your 115 volt nominal input power adapter output will vary by 10 % (12 volts varies between 13.2 and 10.8 volts) depending on proximity to the main transformer and the level of current others in your neighborhood are drawing.

Active regulation of power adapters solves the dual problems of regulation and ripple.

Switching power supplies are always regulated. System Connection offers regulation as an option in all our OEM power supplies, linear or switching. In transformer based wall mount power adapters regulation is accomplished with a diode chain, a zener diode, a zener plus a bipolar transistor, or a three terminal regulator, depending on the price of components and the output current required