Method and system for controlling the power factor of a power converter
An apparatus for controlling a power converter includes a controller configured to detect an error in an output voltage of the power converter at a zero-crossing of a cyclically varying input signal and a compensator coupled to the controller and the power converter and configured to regulate the output voltage of the power converter in response to the error.
1. An apparatus for controlling a power converter, the apparatus comprising:
a controller configured to detect an error in an output voltage of the power converter at a zero-crossing of a cyclically varying input signal;
a compensator coupled to the controller and the power converter and configured to regulate the output voltage of the power converter in response to the error; and
an on-time generator coupled to the power converter and the compensator, wherein the compensator is further configured to provide one of a plurality of operation levels to the on-time generator.
2. The apparatus of claim 1 wherein the plurality of operation levels comprises a constant on-time control signal.
3. The apparatus of claim 1 wherein the plurality of operation levels comprises a continuous conduction mode control signal.
4. The apparatus of claim 1 wherein the power converter comprises a bridgeless power supply circuit.
5. The apparatus of claim 1 wherein the power converter comprises a diode bridge power supply circuit.
6. A method for controlling a power factor of a power converter, the method comprising:
detecting an error in an output voltage of the power converter at a zero-crossing of a cyclically varying input signal, wherein detecting the error in the output voltage comprises determining whether the output voltage is within a first predetermined range; and
regulating the output voltage of the power converter in response to the error, wherein regulating the output voltage comprises:
selecting a linear, discrete-time operation level when the output voltage is within the first predetermined range; and
selecting a nonlinear, discrete-time operation level when the output voltage is not within the first predetermined range.
7. The method of claim 6 wherein regulating the output voltage comprises selecting one of a plurality of operation levels comprising a first operation level of operation, a second operation level of operation, and a third operation level of operation.
8. The method of claim 6 further comprising:
setting a flag; and
stopping the nonlinear, discrete-time operation level when detecting a third zero crossing of the output voltage.
9. The method of claim 8 wherein the nonlinear, discrete-time operation level comprises adjusting a width of an adaptive on-time pulse of an on-time generator by a first predetermined amount of time in a first half-cycle of the cyclically varying input signal adjacent to the zero-crossing of the cyclically varying input signal.
10. The method of claim 9 wherein the nonlinear, discrete-time operation level further comprises:
adjusting the width of the adaptive on-time pulse of the on-time generator in a second half-cycle immediately following the first half-cycle by a second predetermined amount of time smaller than the first predetermined amount of time; and
resetting the flag.
11. A method for controlling a power factor of a power converter, the method comprising:
detecting an error in an output voltage of the power converter at a zero-crossing of a cyclically varying input signal;
regulating the output voltage of the power converter in response to the error;
determining a status of a flag:
when the flag is not set, determining whether the output voltage is within a first predetermined range;
selecting a linear, discrete-time operation level when the output voltage is within the first predetermined range; and
stopping the linear, discrete-time operation level when detecting a second zero crossing of the output voltage.
12. The method of claim 11 further comprising:
selecting a nonlinear, discrete-time operation level when the output voltage is not within the first predetermined range;
setting the flag; and
stopping the nonlinear, discrete-time operation level when detecting a third zero crossing of the output voltage.
13. The method of claim 12 wherein the nonlinear, discrete-time operation level comprises adjusting a width of an adaptive on-time pulse of an on-time generator by a first predetermined amount of time in a first half-cycle of the cyclically varying input signal adjacent to the zero-crossing of the cyclically varying input signal.
14. The method of claim 13 wherein the nonlinear, discrete-time operation level further comprises:
adjusting the width of the adaptive on-time pulse of the on-time generator in a second half-cycle immediately following the first half-cycle by a second predetermined amount of time smaller than the first predetermined amount of time; and
resetting the flag.
15. The method of claim 11 wherein regulating the output voltage comprises selecting one of a plurality of operation levels comprising a first operation level of the operation, a second operation level of the operation, and a third operation level of the operation.