Controlling an adapter transformer voltage

摘要

An adapter for electrical power that includes a rectifier coupled to a transformer with a primary coil and a secondary coil. The secondary coil includes a first end tap, a second end tap, and a center tap. A first switch is coupled between the first end tap and a primary side ground. A second switch is coupled between the second end tap and the primary side ground. A controller is coupled to the first switch and to the second switch so that during one or more intervals, the first switch and the second switch are alternately open and closed a predetermined number of times, wherein the initial switch closed each interval alternates between the first switch and the second switch, and after the predetermined number of times, both the first switch and the second switch are opened for a predetermined time period.

主权项

1. An adapter for electrical power, comprising:
a rectifier with an input and an output; a transformer with a primary coil and a secondary coil, wherein the primary coil includes a center tap coupled to the output of the rectifier, and a first end tap and a second end tap; a first switch coupled between the first end tap and a primary side ground; a second switch coupled between the second end tap and the primary side ground; and a controller coupled to the first switch and to the second switch and configured to control the first switch and the second switch so that during each of one or more intervals,
the first switch and the second switch are alternately open and closed a predetermined number of times, wherein at each interval an initial switch that is closed at the beginning of the interval alternates between the first switch and the second switch, and wherein after the predetermined number of times, both the first switch and the second switch are opened for a predetermined time period, wherein the controller is further configured so that a duration that the initial switch is closed during a first of the predetermined number of times is equal to a duration that a switch is closed during a last of the predetermined number of times, and the duration that the initial switch is closed during the first of the predetermined number of times is equal to one half of a duration that a switch is closed during a second of the predetermined number of times.