Controller for a switched mode power converter, a switched mode power converter and method of controlling the same

摘要

A method of controlling a switched mode converter is disclosed in which the switching frequency varies in proportion to the square of the sine of the phase of the input AC supply. Thus the switching frequency is a maximum, and the respective on period of the switch is a minimum, when the mains voltage is a maximum. Conversely, the switching frequency is reduced, and the respective on time of the switch is increased, when the mains voltage is reduced. Such a switching method provides for a high power factor. Implementation by means of a phase locked loop and a comparator may prevent the need for complex circuitry, and may provide for direct use of a digital controller or digital signal processing through a counter output in the phase locked loop.;A controller configured to operate such a method, together with an AC/DC converter embodying such a controller are also disclosed.

主权项

1. A controller for use in an AC-DC switched mode power converter for converting an alternating current supply having a phase Φ relative to a zero-crossing of the alternating currently supply and having a switch operable at a switching frequency fs, configured to control the switching frequency such that it is proportional to the square of the sine of the phase, over at least a part of an alternating current half-cycle, which half-cycle commences at a zero-crossing of the alternating current supply, with a proportionality constant Fmax, according to:
fs(Φ)=Fmax*sin2 (Φ).