Controller for a Power Converter and Method of Operating the Same
A controller, power converter and method of controlling a power switch therein to improve power conversion efficiency at low output current. In one embodiment, the power converter includes a power switch coupled to a source of electrical power, and a controller coupled to a control terminal of the power switch and to an output of the power converter. The controller is configured to control a conductivity of the power switch at a selected switching frequency from a set of discrete switching frequencies as a function of an output characteristic of the power converter.
1 . A controller, coupled to a control terminal of a power switch and to an output of a power converter, configured to control a conductivity of said power switch at a selected switching frequency from a set of discrete switching frequencies as a function of an output characteristic of said power converter.
2 . The controller as recited in claim 1 wherein said output characteristic is an unregulated output characteristic.
3 . The controller as recited in claim 1 wherein said set of discrete switching frequencies include four switching frequencies that span a frequency range of eight to one.
4 . The controller as recited in claim 1 wherein said selected switching frequency is reduced in discrete steps as said output characteristic increases.
5 . The controller as recited in claim 1 wherein said selected switching frequency is dependent on a ratio of an output voltage to an input voltage of said power converter.
6 . The controller as recited in claim 1 wherein controller includes at least one frequency divider to produce said set of discrete switching frequencies.
7 . A power converter, comprising:
a power switch coupled to a source of electrical power; and
a controller, coupled to a control terminal of said power switch and to an output of said power converter, configured to control a conductivity of said power switch at a selected switching frequency from a set of discrete switching frequencies as a function of an output characteristic of said power converter.
8 . The power converter as recited in claim 7 wherein said output characteristic is an unregulated output characteristic.
9 . The power converter as recited in claim 7 wherein said set of discrete switching frequencies include four switching frequencies that span a frequency range of eight to one.
10 . The power converter as recited in claim 7 wherein said selected switching frequency is reduced in discrete steps as said output characteristic increases.
11 . The power converter as recited in claim 7 wherein said selected switching frequency is dependent on a ratio of an output voltage to an input voltage of said power converter.
12 . The power converter as recited in claim 7 wherein controller includes at least one frequency divider to produce said set of discrete switching frequencies.
13 . The power converter as recited in claim 7 wherein said power converter is a switched-capacitor power converter.
14 . A method of operating a power converter, comprising:
coupling a power switch to a source of electrical power;
controlling a conductivity of said power switch at a selected switching frequency from a set of discrete switching frequencies as a function of an output characteristic of said power converter.
15 . The method as recited in claim 14 wherein said output characteristic is an unregulated output characteristic.
16 . The method as recited in claim 14 wherein said set of discrete switching frequencies include four switching frequencies that span a frequency range of eight to one.
17 . The method as recited in claim 14 wherein said selected switching frequency is reduced in discrete steps as said output characteristic increases.
18 . The method as recited in claim 14 wherein said selected switching frequency is dependent on a ratio of an output voltage to an input voltage of said power converter.
19 . The method as recited in claim 14 wherein said set of discrete switching frequencies are produced with at least one frequency divider.
20 . The method as recited in claim 14 wherein said power converter is a switched-capacitor power converter.